| Message ID | 20190502040441.30372-2-jlee@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2,v2] efi: add a function to convert the status value to string | expand |
On Thu, 2 May 2019 at 06:04, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote: > > When loading certificates list from UEFI variable, the original error > message direct shows the efi status code from UEFI firmware. It looks > ugly: > > [ 2.335031] Couldn't get size: 0x800000000000000e > [ 2.335032] Couldn't get UEFI MokListRT > [ 2.339985] Couldn't get size: 0x800000000000000e > [ 2.339987] Couldn't get UEFI dbx list > > So, this patch shows the status string instead of status code. > > On the other hand, the "Couldn't get UEFI" message doesn't need > to be exposed when db/dbx/mok variable do not exist. So, this > patch set the message level to debug. > > v3. > - Print messages similar to db/mok when loading dbx hash to blacklist: > [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx > [ 1.501773] blacklist: Loaded blacklisting hash > 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' > > - Setting messages for the existence of db/mok/dbx lists to debug level. > > v2. > Setting the MODSIGN messages level to debug. > > Link: > https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 > Cc: James Morris <jmorris@namei.org> > Cc: Serge E. Hallyn" <serge@hallyn.com> > Cc: David Howells <dhowells@redhat.com> > Cc: Nayna Jain <nayna@linux.ibm.com> > Cc: Josh Boyer <jwboyer@fedoraproject.org> > Cc: Mimi Zohar <zohar@linux.ibm.com> > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > --- > certs/blacklist.c | 3 +- > security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- > 2 files changed, 31 insertions(+), 12 deletions(-) > > diff --git a/certs/blacklist.c b/certs/blacklist.c > index 3a507b9e2568..f91437e39e44 100644 > --- a/certs/blacklist.c > +++ b/certs/blacklist.c > @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) > if (IS_ERR(key)) { > pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); > return PTR_ERR(key); > - } > + } else > + pr_notice("Loaded blacklisting hash '%s'\n", hash); > return 0; > } > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > index 81b19c52832b..6b6996e5bc27 100644 > --- a/security/integrity/platform_certs/load_uefi.c > +++ b/security/integrity/platform_certs/load_uefi.c > @@ -1,5 +1,7 @@ > // SPDX-License-Identifier: GPL-2.0 > > +#define pr_fmt(fmt) "EFI: "fmt > + > #include <linux/kernel.h> > #include <linux/sched.h> > #include <linux/cred.h> > @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) > return status == EFI_SUCCESS; > } > > +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) > +{ > + int i = 0; > + > + while (str16[i] != '\0' && i < (str_size - 1)) { > + str[i] = str16[i]; > + i++; > + } > + > + str[i] = '\0'; > +} > + > /* > * Get a certificate list blob from the named EFI variable. > */ > @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > efi_status_t status; > unsigned long lsize = 4; > unsigned long tmpdb[4]; > + char namestr[16]; > void *db; > > + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); Please drop this (and the function above) - instead, just return NULL if the variable is not found (without reporting an error). > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); > if (status != EFI_BUFFER_TOO_SMALL) { > - pr_err("Couldn't get size: 0x%lx\n", status); > + if (status == EFI_NOT_FOUND) > + pr_debug("UEFI %s list doesn't exist\n", namestr); > + else > + pr_err("Couldn't get size for UEFI %s list: %s\n", > + namestr, efi_status_to_str(status)); > return NULL; > } > + pr_debug("UEFI %s list exists\n", namestr); > > db = kmalloc(lsize, GFP_KERNEL); > if (!db) > @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > status = efi.get_variable(name, guid, NULL, &lsize, db); > if (status != EFI_SUCCESS) { > kfree(db); > - pr_err("Error reading db var: 0x%lx\n", status); > + pr_err("Error reading UEFI %s list: %s\n", > + namestr, efi_status_to_str(status)); > return NULL; > } > > @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, > static __init void uefi_blacklist_x509_tbs(const char *source, > const void *data, size_t len) > { > + pr_info("Blacklisting X.509 TBS hash: %s\n", source); > uefi_blacklist_hash(source, data, len, "tbs:", 4); > } > > @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, > static __init void uefi_blacklist_binary(const char *source, > const void *data, size_t len) > { > + pr_info("Blacklisting hash of an executable: %s\n", source); > uefi_blacklist_hash(source, data, len, "bin:", 4); > } > These are separate changes - I don't have an opinion whether they are appropriate or not, but they should be in a separate patch. > @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) > */ > if (!uefi_check_ignore_db()) { > db = get_cert_list(L"db", &secure_var, &dbsize); > - if (!db) { > - pr_err("MODSIGN: Couldn't get UEFI db list\n"); > - } else { > + if (db) { > rc = parse_efi_signature_list("UEFI:db", > db, dbsize, get_handler_for_db); > if (rc) > @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) > } > > mok = get_cert_list(L"MokListRT", &mok_var, &moksize); > - if (!mok) { > - pr_info("Couldn't get UEFI MokListRT\n"); > - } else { > + if (mok) { > rc = parse_efi_signature_list("UEFI:MokListRT", > mok, moksize, get_handler_for_db); > if (rc) > @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) > } > > dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); > - if (!dbx) { > - pr_info("Couldn't get UEFI dbx list\n"); > - } else { > + if (dbx) { > rc = parse_efi_signature_list("UEFI:dbx", > dbx, dbxsize, > get_handler_for_dbx); > -- > 2.16.4 > I think we should consider carefully what it means if some of these variables don't exist: - if secure boot is enabled, db and dbx must exist, so if they don't, something is wrong - secure boot might be enabled but we may be booting without shim. - secure boot might be disabled. Tweaking the severity of error messages without having a clear idea of the policy we are aiming to implement is likely to cause trouble down the road, so perhaps someone could explain what this code does, and how it should behave in the above circumstances.
Hi Ard, On Thu, May 02, 2019 at 11:04:34AM +0200, Ard Biesheuvel wrote: > On Thu, 2 May 2019 at 06:04, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote: > > > > When loading certificates list from UEFI variable, the original error > > message direct shows the efi status code from UEFI firmware. It looks > > ugly: > > > > [ 2.335031] Couldn't get size: 0x800000000000000e > > [ 2.335032] Couldn't get UEFI MokListRT > > [ 2.339985] Couldn't get size: 0x800000000000000e > > [ 2.339987] Couldn't get UEFI dbx list > > > > So, this patch shows the status string instead of status code. > > > > On the other hand, the "Couldn't get UEFI" message doesn't need > > to be exposed when db/dbx/mok variable do not exist. So, this > > patch set the message level to debug. > > > > v3. > > - Print messages similar to db/mok when loading dbx hash to blacklist: > > [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx > > [ 1.501773] blacklist: Loaded blacklisting hash > > 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' > > > > - Setting messages for the existence of db/mok/dbx lists to debug level. > > > > v2. > > Setting the MODSIGN messages level to debug. > > > > Link: > > https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 > > Cc: James Morris <jmorris@namei.org> > > Cc: Serge E. Hallyn" <serge@hallyn.com> > > Cc: David Howells <dhowells@redhat.com> > > Cc: Nayna Jain <nayna@linux.ibm.com> > > Cc: Josh Boyer <jwboyer@fedoraproject.org> > > Cc: Mimi Zohar <zohar@linux.ibm.com> > > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > > --- > > certs/blacklist.c | 3 +- > > security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- > > 2 files changed, 31 insertions(+), 12 deletions(-) > > > > diff --git a/certs/blacklist.c b/certs/blacklist.c > > index 3a507b9e2568..f91437e39e44 100644 > > --- a/certs/blacklist.c > > +++ b/certs/blacklist.c > > @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) > > if (IS_ERR(key)) { > > pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); > > return PTR_ERR(key); > > - } > > + } else > > + pr_notice("Loaded blacklisting hash '%s'\n", hash); > > return 0; > > } > > > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > > index 81b19c52832b..6b6996e5bc27 100644 > > --- a/security/integrity/platform_certs/load_uefi.c > > +++ b/security/integrity/platform_certs/load_uefi.c > > @@ -1,5 +1,7 @@ > > // SPDX-License-Identifier: GPL-2.0 > > > > +#define pr_fmt(fmt) "EFI: "fmt > > + > > #include <linux/kernel.h> > > #include <linux/sched.h> > > #include <linux/cred.h> > > @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) > > return status == EFI_SUCCESS; > > } > > > > +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) > > +{ > > + int i = 0; > > + > > + while (str16[i] != '\0' && i < (str_size - 1)) { > > + str[i] = str16[i]; > > + i++; > > + } > > + > > + str[i] = '\0'; > > +} > > + > > /* > > * Get a certificate list blob from the named EFI variable. > > */ > > @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > efi_status_t status; > > unsigned long lsize = 4; > > unsigned long tmpdb[4]; > > + char namestr[16]; > > void *db; > > > > + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); > > Please drop this (and the function above) - instead, just return NULL > if the variable is not found (without reporting an error). > This name string is for printing debug level message, not error message. This function already returns NULL when EFI_NOT_FOUND be returned by firmware. > > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); > > if (status != EFI_BUFFER_TOO_SMALL) { > > - pr_err("Couldn't get size: 0x%lx\n", status); > > + if (status == EFI_NOT_FOUND) > > + pr_debug("UEFI %s list doesn't exist\n", namestr); > > + else > > + pr_err("Couldn't get size for UEFI %s list: %s\n", > > + namestr, efi_status_to_str(status)); > > return NULL; here returns NULL when EFI_NOT_FOUND. The message of existence is for debugging. > > } > > + pr_debug("UEFI %s list exists\n", namestr); > > > > db = kmalloc(lsize, GFP_KERNEL); > > if (!db) > > @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > status = efi.get_variable(name, guid, NULL, &lsize, db); > > if (status != EFI_SUCCESS) { > > kfree(db); > > - pr_err("Error reading db var: 0x%lx\n", status); > > + pr_err("Error reading UEFI %s list: %s\n", > > + namestr, efi_status_to_str(status)); > > return NULL; > > } > > > > @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, > > static __init void uefi_blacklist_x509_tbs(const char *source, > > const void *data, size_t len) > > { > > + pr_info("Blacklisting X.509 TBS hash: %s\n", source); > > uefi_blacklist_hash(source, data, len, "tbs:", 4); > > } > > > > @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, > > static __init void uefi_blacklist_binary(const char *source, > > const void *data, size_t len) > > { > > + pr_info("Blacklisting hash of an executable: %s\n", source); > > uefi_blacklist_hash(source, data, len, "bin:", 4); > > } > > > > These are separate changes - I don't have an opinion whether they are > appropriate or not, but they should be in a separate patch. > I will move the message of blacklising hash to other patch. Thanks! > > @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) > > */ > > if (!uefi_check_ignore_db()) { > > db = get_cert_list(L"db", &secure_var, &dbsize); > > - if (!db) { > > - pr_err("MODSIGN: Couldn't get UEFI db list\n"); > > - } else { > > + if (db) { > > rc = parse_efi_signature_list("UEFI:db", > > db, dbsize, get_handler_for_db); > > if (rc) > > @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) > > } > > > > mok = get_cert_list(L"MokListRT", &mok_var, &moksize); > > - if (!mok) { > > - pr_info("Couldn't get UEFI MokListRT\n"); > > - } else { > > + if (mok) { > > rc = parse_efi_signature_list("UEFI:MokListRT", > > mok, moksize, get_handler_for_db); > > if (rc) > > @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) > > } > > > > dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); > > - if (!dbx) { > > - pr_info("Couldn't get UEFI dbx list\n"); > > - } else { > > + if (dbx) { > > rc = parse_efi_signature_list("UEFI:dbx", > > dbx, dbxsize, > > get_handler_for_dbx); > > -- > > 2.16.4 > > > > I think we should consider carefully what it means if some of these > variables don't exist: > - if secure boot is enabled, db and dbx must exist, so if they don't, > something is wrong The existence of db/dbx is not related to secure boot. If manufacturer/user enrolled certificate/hash to db or dbx, then the variable will be created. If user didn't enroll anything to db/dbx, then variables will not show up. > - secure boot might be enabled but we may be booting without shim. Shim always creates MokListRT no matter secure boot enabled or disabled. > - secure boot might be disabled. > It's not about secure boot, db/dbx/MokListRT are always available at runtime if user was enrolled something to those list. > Tweaking the severity of error messages without having a clear idea of > the policy we are aiming to implement is likely to cause trouble down > the road, so perhaps someone could explain what this code does, and > how it should behave in the above circumstances. Thanks Joey Lee
On Fri, 3 May 2019 at 09:18, joeyli <jlee@suse.com> wrote: > > Hi Ard, > > On Thu, May 02, 2019 at 11:04:34AM +0200, Ard Biesheuvel wrote: > > On Thu, 2 May 2019 at 06:04, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote: > > > > > > When loading certificates list from UEFI variable, the original error > > > message direct shows the efi status code from UEFI firmware. It looks > > > ugly: > > > > > > [ 2.335031] Couldn't get size: 0x800000000000000e > > > [ 2.335032] Couldn't get UEFI MokListRT > > > [ 2.339985] Couldn't get size: 0x800000000000000e > > > [ 2.339987] Couldn't get UEFI dbx list > > > > > > So, this patch shows the status string instead of status code. > > > > > > On the other hand, the "Couldn't get UEFI" message doesn't need > > > to be exposed when db/dbx/mok variable do not exist. So, this > > > patch set the message level to debug. > > > > > > v3. > > > - Print messages similar to db/mok when loading dbx hash to blacklist: > > > [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx > > > [ 1.501773] blacklist: Loaded blacklisting hash > > > 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' > > > > > > - Setting messages for the existence of db/mok/dbx lists to debug level. > > > > > > v2. > > > Setting the MODSIGN messages level to debug. > > > > > > Link: > > > https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 > > > Cc: James Morris <jmorris@namei.org> > > > Cc: Serge E. Hallyn" <serge@hallyn.com> > > > Cc: David Howells <dhowells@redhat.com> > > > Cc: Nayna Jain <nayna@linux.ibm.com> > > > Cc: Josh Boyer <jwboyer@fedoraproject.org> > > > Cc: Mimi Zohar <zohar@linux.ibm.com> > > > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > > > --- > > > certs/blacklist.c | 3 +- > > > security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- > > > 2 files changed, 31 insertions(+), 12 deletions(-) > > > > > > diff --git a/certs/blacklist.c b/certs/blacklist.c > > > index 3a507b9e2568..f91437e39e44 100644 > > > --- a/certs/blacklist.c > > > +++ b/certs/blacklist.c > > > @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) > > > if (IS_ERR(key)) { > > > pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); > > > return PTR_ERR(key); > > > - } > > > + } else > > > + pr_notice("Loaded blacklisting hash '%s'\n", hash); > > > return 0; > > > } > > > > > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > > > index 81b19c52832b..6b6996e5bc27 100644 > > > --- a/security/integrity/platform_certs/load_uefi.c > > > +++ b/security/integrity/platform_certs/load_uefi.c > > > @@ -1,5 +1,7 @@ > > > // SPDX-License-Identifier: GPL-2.0 > > > > > > +#define pr_fmt(fmt) "EFI: "fmt > > > + > > > #include <linux/kernel.h> > > > #include <linux/sched.h> > > > #include <linux/cred.h> > > > @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) > > > return status == EFI_SUCCESS; > > > } > > > > > > +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) > > > +{ > > > + int i = 0; > > > + > > > + while (str16[i] != '\0' && i < (str_size - 1)) { > > > + str[i] = str16[i]; > > > + i++; > > > + } > > > + > > > + str[i] = '\0'; > > > +} > > > + > > > /* > > > * Get a certificate list blob from the named EFI variable. > > > */ > > > @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > efi_status_t status; > > > unsigned long lsize = 4; > > > unsigned long tmpdb[4]; > > > + char namestr[16]; > > > void *db; > > > > > > + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); > > > > Please drop this (and the function above) - instead, just return NULL > > if the variable is not found (without reporting an error). > > > > This name string is for printing debug level message, not error message. > This function already returns NULL when EFI_NOT_FOUND be returned by > firmware. > > > > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); > > > if (status != EFI_BUFFER_TOO_SMALL) { > > > - pr_err("Couldn't get size: 0x%lx\n", status); > > > + if (status == EFI_NOT_FOUND) > > > + pr_debug("UEFI %s list doesn't exist\n", namestr); > > > + else > > > + pr_err("Couldn't get size for UEFI %s list: %s\n", > > > + namestr, efi_status_to_str(status)); > > > return NULL; > > here returns NULL when EFI_NOT_FOUND. The message of existence is for > debugging. > I understand that. But I don't think we need it. > > > } > > > + pr_debug("UEFI %s list exists\n", namestr); > > > > > > db = kmalloc(lsize, GFP_KERNEL); > > > if (!db) > > > @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > status = efi.get_variable(name, guid, NULL, &lsize, db); > > > if (status != EFI_SUCCESS) { > > > kfree(db); > > > - pr_err("Error reading db var: 0x%lx\n", status); > > > + pr_err("Error reading UEFI %s list: %s\n", > > > + namestr, efi_status_to_str(status)); > > > return NULL; > > > } > > > > > > @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, > > > static __init void uefi_blacklist_x509_tbs(const char *source, > > > const void *data, size_t len) > > > { > > > + pr_info("Blacklisting X.509 TBS hash: %s\n", source); > > > uefi_blacklist_hash(source, data, len, "tbs:", 4); > > > } > > > > > > @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, > > > static __init void uefi_blacklist_binary(const char *source, > > > const void *data, size_t len) > > > { > > > + pr_info("Blacklisting hash of an executable: %s\n", source); > > > uefi_blacklist_hash(source, data, len, "bin:", 4); > > > } > > > > > > > These are separate changes - I don't have an opinion whether they are > > appropriate or not, but they should be in a separate patch. > > > > I will move the message of blacklising hash to other patch. Thanks! > > > > @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) > > > */ > > > if (!uefi_check_ignore_db()) { > > > db = get_cert_list(L"db", &secure_var, &dbsize); > > > - if (!db) { > > > - pr_err("MODSIGN: Couldn't get UEFI db list\n"); > > > - } else { > > > + if (db) { > > > rc = parse_efi_signature_list("UEFI:db", > > > db, dbsize, get_handler_for_db); > > > if (rc) > > > @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) > > > } > > > > > > mok = get_cert_list(L"MokListRT", &mok_var, &moksize); > > > - if (!mok) { > > > - pr_info("Couldn't get UEFI MokListRT\n"); > > > - } else { > > > + if (mok) { > > > rc = parse_efi_signature_list("UEFI:MokListRT", > > > mok, moksize, get_handler_for_db); > > > if (rc) > > > @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) > > > } > > > > > > dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); > > > - if (!dbx) { > > > - pr_info("Couldn't get UEFI dbx list\n"); > > > - } else { > > > + if (dbx) { > > > rc = parse_efi_signature_list("UEFI:dbx", > > > dbx, dbxsize, > > > get_handler_for_dbx); > > > -- > > > 2.16.4 > > > > > > > I think we should consider carefully what it means if some of these > > variables don't exist: > > - if secure boot is enabled, db and dbx must exist, so if they don't, > > something is wrong > > The existence of db/dbx is not related to secure boot. If manufacturer/user > enrolled certificate/hash to db or dbx, then the variable will be created. > If user didn't enroll anything to db/dbx, then variables will not show up. > Yes, but if secure boot is enabled and db is empty, how could you have booted in the first place? And what about the converse case: if secure boot is not enabled, why should we trust the contents of db? > > - secure boot might be enabled but we may be booting without shim. > > Shim always creates MokListRT no matter secure boot enabled or disabled. > That is not my point. What happens if you booted with secure boot enabled but without the help of shim? > > - secure boot might be disabled. > > > > It's not about secure boot, db/dbx/MokListRT are always available at > runtime if user was enrolled something to those list. > Yes, but again, depending on whether shim was involved, and/or whether secure boot was enabled or not, the way we interpret these things may be very different. I want the reasoning to be sound before merging any patches that deal with these variables.
On Fri, May 03, 2019 at 10:07:59AM +0200, Ard Biesheuvel wrote: > On Fri, 3 May 2019 at 09:18, joeyli <jlee@suse.com> wrote: > > > > Hi Ard, > > > > On Thu, May 02, 2019 at 11:04:34AM +0200, Ard Biesheuvel wrote: > > > On Thu, 2 May 2019 at 06:04, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote: > > > > > > > > When loading certificates list from UEFI variable, the original error > > > > message direct shows the efi status code from UEFI firmware. It looks > > > > ugly: > > > > > > > > [ 2.335031] Couldn't get size: 0x800000000000000e > > > > [ 2.335032] Couldn't get UEFI MokListRT > > > > [ 2.339985] Couldn't get size: 0x800000000000000e > > > > [ 2.339987] Couldn't get UEFI dbx list > > > > > > > > So, this patch shows the status string instead of status code. > > > > > > > > On the other hand, the "Couldn't get UEFI" message doesn't need > > > > to be exposed when db/dbx/mok variable do not exist. So, this > > > > patch set the message level to debug. > > > > > > > > v3. > > > > - Print messages similar to db/mok when loading dbx hash to blacklist: > > > > [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx > > > > [ 1.501773] blacklist: Loaded blacklisting hash > > > > 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' > > > > > > > > - Setting messages for the existence of db/mok/dbx lists to debug level. > > > > > > > > v2. > > > > Setting the MODSIGN messages level to debug. > > > > > > > > Link: > > > > https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 > > > > Cc: James Morris <jmorris@namei.org> > > > > Cc: Serge E. Hallyn" <serge@hallyn.com> > > > > Cc: David Howells <dhowells@redhat.com> > > > > Cc: Nayna Jain <nayna@linux.ibm.com> > > > > Cc: Josh Boyer <jwboyer@fedoraproject.org> > > > > Cc: Mimi Zohar <zohar@linux.ibm.com> > > > > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > > > > --- > > > > certs/blacklist.c | 3 +- > > > > security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- > > > > 2 files changed, 31 insertions(+), 12 deletions(-) > > > > > > > > diff --git a/certs/blacklist.c b/certs/blacklist.c > > > > index 3a507b9e2568..f91437e39e44 100644 > > > > --- a/certs/blacklist.c > > > > +++ b/certs/blacklist.c > > > > @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) > > > > if (IS_ERR(key)) { > > > > pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); > > > > return PTR_ERR(key); > > > > - } > > > > + } else > > > > + pr_notice("Loaded blacklisting hash '%s'\n", hash); > > > > return 0; > > > > } > > > > > > > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > > > > index 81b19c52832b..6b6996e5bc27 100644 > > > > --- a/security/integrity/platform_certs/load_uefi.c > > > > +++ b/security/integrity/platform_certs/load_uefi.c > > > > @@ -1,5 +1,7 @@ > > > > // SPDX-License-Identifier: GPL-2.0 > > > > > > > > +#define pr_fmt(fmt) "EFI: "fmt > > > > + > > > > #include <linux/kernel.h> > > > > #include <linux/sched.h> > > > > #include <linux/cred.h> > > > > @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) > > > > return status == EFI_SUCCESS; > > > > } > > > > > > > > +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) > > > > +{ > > > > + int i = 0; > > > > + > > > > + while (str16[i] != '\0' && i < (str_size - 1)) { > > > > + str[i] = str16[i]; > > > > + i++; > > > > + } > > > > + > > > > + str[i] = '\0'; > > > > +} > > > > + > > > > /* > > > > * Get a certificate list blob from the named EFI variable. > > > > */ > > > > @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > > efi_status_t status; > > > > unsigned long lsize = 4; > > > > unsigned long tmpdb[4]; > > > > + char namestr[16]; > > > > void *db; > > > > > > > > + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); > > > > > > Please drop this (and the function above) - instead, just return NULL > > > if the variable is not found (without reporting an error). > > > > > > > This name string is for printing debug level message, not error message. > > This function already returns NULL when EFI_NOT_FOUND be returned by > > firmware. > > > > > > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); > > > > if (status != EFI_BUFFER_TOO_SMALL) { > > > > - pr_err("Couldn't get size: 0x%lx\n", status); > > > > + if (status == EFI_NOT_FOUND) > > > > + pr_debug("UEFI %s list doesn't exist\n", namestr); > > > > + else > > > > + pr_err("Couldn't get size for UEFI %s list: %s\n", > > > > + namestr, efi_status_to_str(status)); > > > > return NULL; > > > > here returns NULL when EFI_NOT_FOUND. The message of existence is for > > debugging. > > > > I understand that. But I don't think we need it. > OK. I will remove the debug message. > > > > } > > > > + pr_debug("UEFI %s list exists\n", namestr); > > > > > > > > db = kmalloc(lsize, GFP_KERNEL); > > > > if (!db) > > > > @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > > status = efi.get_variable(name, guid, NULL, &lsize, db); > > > > if (status != EFI_SUCCESS) { > > > > kfree(db); > > > > - pr_err("Error reading db var: 0x%lx\n", status); > > > > + pr_err("Error reading UEFI %s list: %s\n", > > > > + namestr, efi_status_to_str(status)); > > > > return NULL; > > > > } > > > > > > > > @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, > > > > static __init void uefi_blacklist_x509_tbs(const char *source, > > > > const void *data, size_t len) > > > > { > > > > + pr_info("Blacklisting X.509 TBS hash: %s\n", source); > > > > uefi_blacklist_hash(source, data, len, "tbs:", 4); > > > > } > > > > > > > > @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, > > > > static __init void uefi_blacklist_binary(const char *source, > > > > const void *data, size_t len) > > > > { > > > > + pr_info("Blacklisting hash of an executable: %s\n", source); > > > > uefi_blacklist_hash(source, data, len, "bin:", 4); > > > > } > > > > > > > > > > These are separate changes - I don't have an opinion whether they are > > > appropriate or not, but they should be in a separate patch. > > > > > > > I will move the message of blacklising hash to other patch. Thanks! > > > > > > @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) > > > > */ > > > > if (!uefi_check_ignore_db()) { > > > > db = get_cert_list(L"db", &secure_var, &dbsize); > > > > - if (!db) { > > > > - pr_err("MODSIGN: Couldn't get UEFI db list\n"); > > > > - } else { > > > > + if (db) { > > > > rc = parse_efi_signature_list("UEFI:db", > > > > db, dbsize, get_handler_for_db); > > > > if (rc) > > > > @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) > > > > } > > > > > > > > mok = get_cert_list(L"MokListRT", &mok_var, &moksize); > > > > - if (!mok) { > > > > - pr_info("Couldn't get UEFI MokListRT\n"); > > > > - } else { > > > > + if (mok) { > > > > rc = parse_efi_signature_list("UEFI:MokListRT", > > > > mok, moksize, get_handler_for_db); > > > > if (rc) > > > > @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) > > > > } > > > > > > > > dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); > > > > - if (!dbx) { > > > > - pr_info("Couldn't get UEFI dbx list\n"); > > > > - } else { > > > > + if (dbx) { > > > > rc = parse_efi_signature_list("UEFI:dbx", > > > > dbx, dbxsize, > > > > get_handler_for_dbx); > > > > -- > > > > 2.16.4 > > > > > > > > > > I think we should consider carefully what it means if some of these > > > variables don't exist: > > > - if secure boot is enabled, db and dbx must exist, so if they don't, > > > something is wrong > > > > The existence of db/dbx is not related to secure boot. If manufacturer/user > > enrolled certificate/hash to db or dbx, then the variable will be created. > > If user didn't enroll anything to db/dbx, then variables will not show up. > > > > Yes, but if secure boot is enabled and db is empty, how could you have > booted in the first place? > I agree. When secure boot enabled, kernel can not be booted without db. > And what about the converse case: if secure boot is not enabled, why > should we trust the contents of db? > The db and dbx are authenticated variables that it protected by KEK. So it can be trusted even secure boot is disabled. Unless manufacturer or user's KEK is leaked. > > > - secure boot might be enabled but we may be booting without shim. > > > > Shim always creates MokListRT no matter secure boot enabled or disabled. > > > > That is not my point. What happens if you booted with secure boot > enabled but without the help of shim? > Without shim, the signed EFI stub can still be booted by EFI boot manager. But the MokListRT will not be created for runtime. So MOK signed kernel module can not be verified. (or IMA can not verify MOK signed kernel image for kexec...) > > > - secure boot might be disabled. > > > > > > > It's not about secure boot, db/dbx/MokListRT are always available at > > runtime if user was enrolled something to those list. > > > > Yes, but again, depending on whether shim was involved, and/or whether > secure boot was enabled or not, the way we interpret these things may > be very different. > > I want the reasoning to be sound before merging any patches that deal > with these variables. Here is a simple summary: When secure boot is enabled: - db/dbx: Can be trusted because they are authenticated variables. (unless end user doesn't want to trust db/dbx) - MokListRT: - with shim: MokListRT will be created. It can be trusted. - without shim: MokListRT will not be created. MOK protected kernel module or file can not be verified. When secure boot is disabled: - db/dbx: Can be trusted because they are authenticated variables. (unless end user doesn't want to trust db/dbx) - MokListRT: - with shim: MokListRT will be created. But it can not be trusted. MOK protected kernel module or file can not be verified. - without shim: MokListRT will not be created. MOK protected kernel module or file can not be verified. Thanks a lot! Joey Lee
On Fri, 3 May 2019 at 10:59, joeyli <jlee@suse.com> wrote: > > On Fri, May 03, 2019 at 10:07:59AM +0200, Ard Biesheuvel wrote: > > On Fri, 3 May 2019 at 09:18, joeyli <jlee@suse.com> wrote: > > > > > > Hi Ard, > > > > > > On Thu, May 02, 2019 at 11:04:34AM +0200, Ard Biesheuvel wrote: > > > > On Thu, 2 May 2019 at 06:04, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote: > > > > > > > > > > When loading certificates list from UEFI variable, the original error > > > > > message direct shows the efi status code from UEFI firmware. It looks > > > > > ugly: > > > > > > > > > > [ 2.335031] Couldn't get size: 0x800000000000000e > > > > > [ 2.335032] Couldn't get UEFI MokListRT > > > > > [ 2.339985] Couldn't get size: 0x800000000000000e > > > > > [ 2.339987] Couldn't get UEFI dbx list > > > > > > > > > > So, this patch shows the status string instead of status code. > > > > > > > > > > On the other hand, the "Couldn't get UEFI" message doesn't need > > > > > to be exposed when db/dbx/mok variable do not exist. So, this > > > > > patch set the message level to debug. > > > > > > > > > > v3. > > > > > - Print messages similar to db/mok when loading dbx hash to blacklist: > > > > > [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx > > > > > [ 1.501773] blacklist: Loaded blacklisting hash > > > > > 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' > > > > > > > > > > - Setting messages for the existence of db/mok/dbx lists to debug level. > > > > > > > > > > v2. > > > > > Setting the MODSIGN messages level to debug. > > > > > > > > > > Link: > > > > > https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 > > > > > Cc: James Morris <jmorris@namei.org> > > > > > Cc: Serge E. Hallyn" <serge@hallyn.com> > > > > > Cc: David Howells <dhowells@redhat.com> > > > > > Cc: Nayna Jain <nayna@linux.ibm.com> > > > > > Cc: Josh Boyer <jwboyer@fedoraproject.org> > > > > > Cc: Mimi Zohar <zohar@linux.ibm.com> > > > > > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > > > > > --- > > > > > certs/blacklist.c | 3 +- > > > > > security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- > > > > > 2 files changed, 31 insertions(+), 12 deletions(-) > > > > > > > > > > diff --git a/certs/blacklist.c b/certs/blacklist.c > > > > > index 3a507b9e2568..f91437e39e44 100644 > > > > > --- a/certs/blacklist.c > > > > > +++ b/certs/blacklist.c > > > > > @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) > > > > > if (IS_ERR(key)) { > > > > > pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); > > > > > return PTR_ERR(key); > > > > > - } > > > > > + } else > > > > > + pr_notice("Loaded blacklisting hash '%s'\n", hash); > > > > > return 0; > > > > > } > > > > > > > > > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > > > > > index 81b19c52832b..6b6996e5bc27 100644 > > > > > --- a/security/integrity/platform_certs/load_uefi.c > > > > > +++ b/security/integrity/platform_certs/load_uefi.c > > > > > @@ -1,5 +1,7 @@ > > > > > // SPDX-License-Identifier: GPL-2.0 > > > > > > > > > > +#define pr_fmt(fmt) "EFI: "fmt > > > > > + > > > > > #include <linux/kernel.h> > > > > > #include <linux/sched.h> > > > > > #include <linux/cred.h> > > > > > @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) > > > > > return status == EFI_SUCCESS; > > > > > } > > > > > > > > > > +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) > > > > > +{ > > > > > + int i = 0; > > > > > + > > > > > + while (str16[i] != '\0' && i < (str_size - 1)) { > > > > > + str[i] = str16[i]; > > > > > + i++; > > > > > + } > > > > > + > > > > > + str[i] = '\0'; > > > > > +} > > > > > + > > > > > /* > > > > > * Get a certificate list blob from the named EFI variable. > > > > > */ > > > > > @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > > > efi_status_t status; > > > > > unsigned long lsize = 4; > > > > > unsigned long tmpdb[4]; > > > > > + char namestr[16]; > > > > > void *db; > > > > > > > > > > + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); > > > > > > > > Please drop this (and the function above) - instead, just return NULL > > > > if the variable is not found (without reporting an error). > > > > > > > > > > This name string is for printing debug level message, not error message. > > > This function already returns NULL when EFI_NOT_FOUND be returned by > > > firmware. > > > > > > > > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); > > > > > if (status != EFI_BUFFER_TOO_SMALL) { > > > > > - pr_err("Couldn't get size: 0x%lx\n", status); > > > > > + if (status == EFI_NOT_FOUND) > > > > > + pr_debug("UEFI %s list doesn't exist\n", namestr); > > > > > + else > > > > > + pr_err("Couldn't get size for UEFI %s list: %s\n", > > > > > + namestr, efi_status_to_str(status)); > > > > > return NULL; > > > > > > here returns NULL when EFI_NOT_FOUND. The message of existence is for > > > debugging. > > > > > > > I understand that. But I don't think we need it. > > > > OK. I will remove the debug message. > > > > > > } > > > > > + pr_debug("UEFI %s list exists\n", namestr); > > > > > > > > > > db = kmalloc(lsize, GFP_KERNEL); > > > > > if (!db) > > > > > @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > > > status = efi.get_variable(name, guid, NULL, &lsize, db); > > > > > if (status != EFI_SUCCESS) { > > > > > kfree(db); > > > > > - pr_err("Error reading db var: 0x%lx\n", status); > > > > > + pr_err("Error reading UEFI %s list: %s\n", > > > > > + namestr, efi_status_to_str(status)); > > > > > return NULL; > > > > > } > > > > > > > > > > @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, > > > > > static __init void uefi_blacklist_x509_tbs(const char *source, > > > > > const void *data, size_t len) > > > > > { > > > > > + pr_info("Blacklisting X.509 TBS hash: %s\n", source); > > > > > uefi_blacklist_hash(source, data, len, "tbs:", 4); > > > > > } > > > > > > > > > > @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, > > > > > static __init void uefi_blacklist_binary(const char *source, > > > > > const void *data, size_t len) > > > > > { > > > > > + pr_info("Blacklisting hash of an executable: %s\n", source); > > > > > uefi_blacklist_hash(source, data, len, "bin:", 4); > > > > > } > > > > > > > > > > > > > These are separate changes - I don't have an opinion whether they are > > > > appropriate or not, but they should be in a separate patch. > > > > > > > > > > I will move the message of blacklising hash to other patch. Thanks! > > > > > > > > @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) > > > > > */ > > > > > if (!uefi_check_ignore_db()) { > > > > > db = get_cert_list(L"db", &secure_var, &dbsize); > > > > > - if (!db) { > > > > > - pr_err("MODSIGN: Couldn't get UEFI db list\n"); > > > > > - } else { > > > > > + if (db) { > > > > > rc = parse_efi_signature_list("UEFI:db", > > > > > db, dbsize, get_handler_for_db); > > > > > if (rc) > > > > > @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) > > > > > } > > > > > > > > > > mok = get_cert_list(L"MokListRT", &mok_var, &moksize); > > > > > - if (!mok) { > > > > > - pr_info("Couldn't get UEFI MokListRT\n"); > > > > > - } else { > > > > > + if (mok) { > > > > > rc = parse_efi_signature_list("UEFI:MokListRT", > > > > > mok, moksize, get_handler_for_db); > > > > > if (rc) > > > > > @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) > > > > > } > > > > > > > > > > dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); > > > > > - if (!dbx) { > > > > > - pr_info("Couldn't get UEFI dbx list\n"); > > > > > - } else { > > > > > + if (dbx) { > > > > > rc = parse_efi_signature_list("UEFI:dbx", > > > > > dbx, dbxsize, > > > > > get_handler_for_dbx); > > > > > -- > > > > > 2.16.4 > > > > > > > > > > > > > I think we should consider carefully what it means if some of these > > > > variables don't exist: > > > > - if secure boot is enabled, db and dbx must exist, so if they don't, > > > > something is wrong > > > > > > The existence of db/dbx is not related to secure boot. If manufacturer/user > > > enrolled certificate/hash to db or dbx, then the variable will be created. > > > If user didn't enroll anything to db/dbx, then variables will not show up. > > > > > > > Yes, but if secure boot is enabled and db is empty, how could you have > > booted in the first place? > > > > I agree. When secure boot enabled, kernel can not be booted without db. > > > And what about the converse case: if secure boot is not enabled, why > > should we trust the contents of db? > > > > The db and dbx are authenticated variables that it protected by KEK. > So it can be trusted even secure boot is disabled. Unless manufacturer > or user's KEK is leaked. > Is that true for non-secureboot capable firmware? Of course, in that case, we cannot be sure that the kernel itself is trusted, but we shouldn't open up another hole either. > > > > - secure boot might be enabled but we may be booting without shim. > > > > > > Shim always creates MokListRT no matter secure boot enabled or disabled. > > > > > > > That is not my point. What happens if you booted with secure boot > > enabled but without the help of shim? > > > > Without shim, the signed EFI stub can still be booted by EFI boot manager. > But the MokListRT will not be created for runtime. So MOK signed kernel > module can not be verified. (or IMA can not verify MOK signed kernel image > for kexec...) > So if we opt out of using shim, we lose kexec capability as well? That doesn't make any sense. In general, I am very uncomfortable with the way we have painted ourselves into a corner with shim. If I install Suse on a system that has the Suse cert in db or KEK, why would I need shim in the first place? > > > > - secure boot might be disabled. > > > > > > > > > > It's not about secure boot, db/dbx/MokListRT are always available at > > > runtime if user was enrolled something to those list. > > > > > > > Yes, but again, depending on whether shim was involved, and/or whether > > secure boot was enabled or not, the way we interpret these things may > > be very different. > > > > I want the reasoning to be sound before merging any patches that deal > > with these variables. > > Here is a simple summary: > > When secure boot is enabled: > - db/dbx: Can be trusted because they are authenticated variables. > (unless end user doesn't want to trust db/dbx) > - MokListRT: > - with shim: MokListRT will be created. It can be trusted. > - without shim: MokListRT will not be created. > MOK protected kernel module or file can not be > verified. > So who polices that MoKlistRT is not created? > When secure boot is disabled: > - db/dbx: Can be trusted because they are authenticated variables. > (unless end user doesn't want to trust db/dbx) Is this true? Does non-secure boot capable firmware still guarantee that db/dbx can't be created? > - MokListRT: > - with shim: MokListRT will be created. But it can not be trusted. > MOK protected kernel module or file can not be > verified. > - without shim: MokListRT will not be created. > MOK protected kernel module or file can not be > verified. > Enabling this securely involves more than connecting the dots when it comes to db, MokListRT etc. I would like for someone to convince me as a maintainer, as well as the IMA maintainers, that the security requirements are still met in all cases we care about. Just copying db and MokListRT into a kernel keychain doesn't appear to do that, and if it does, it needs more documentation to clarify that.
On Fri, May 03, 2019 at 04:23:51PM +0200, Ard Biesheuvel wrote: > On Fri, 3 May 2019 at 10:59, joeyli <jlee@suse.com> wrote: > > > > On Fri, May 03, 2019 at 10:07:59AM +0200, Ard Biesheuvel wrote: > > > On Fri, 3 May 2019 at 09:18, joeyli <jlee@suse.com> wrote: > > > > > > > > Hi Ard, > > > > > > > > On Thu, May 02, 2019 at 11:04:34AM +0200, Ard Biesheuvel wrote: > > > > > On Thu, 2 May 2019 at 06:04, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote: > > > > > > > > > > > > When loading certificates list from UEFI variable, the original error > > > > > > message direct shows the efi status code from UEFI firmware. It looks > > > > > > ugly: > > > > > > > > > > > > [ 2.335031] Couldn't get size: 0x800000000000000e > > > > > > [ 2.335032] Couldn't get UEFI MokListRT > > > > > > [ 2.339985] Couldn't get size: 0x800000000000000e > > > > > > [ 2.339987] Couldn't get UEFI dbx list > > > > > > > > > > > > So, this patch shows the status string instead of status code. > > > > > > > > > > > > On the other hand, the "Couldn't get UEFI" message doesn't need > > > > > > to be exposed when db/dbx/mok variable do not exist. So, this > > > > > > patch set the message level to debug. > > > > > > > > > > > > v3. > > > > > > - Print messages similar to db/mok when loading dbx hash to blacklist: > > > > > > [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx > > > > > > [ 1.501773] blacklist: Loaded blacklisting hash > > > > > > 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' > > > > > > > > > > > > - Setting messages for the existence of db/mok/dbx lists to debug level. > > > > > > > > > > > > v2. > > > > > > Setting the MODSIGN messages level to debug. > > > > > > > > > > > > Link: > > > > > > https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 > > > > > > Cc: James Morris <jmorris@namei.org> > > > > > > Cc: Serge E. Hallyn" <serge@hallyn.com> > > > > > > Cc: David Howells <dhowells@redhat.com> > > > > > > Cc: Nayna Jain <nayna@linux.ibm.com> > > > > > > Cc: Josh Boyer <jwboyer@fedoraproject.org> > > > > > > Cc: Mimi Zohar <zohar@linux.ibm.com> > > > > > > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> > > > > > > --- > > > > > > certs/blacklist.c | 3 +- > > > > > > security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- > > > > > > 2 files changed, 31 insertions(+), 12 deletions(-) > > > > > > > > > > > > diff --git a/certs/blacklist.c b/certs/blacklist.c > > > > > > index 3a507b9e2568..f91437e39e44 100644 > > > > > > --- a/certs/blacklist.c > > > > > > +++ b/certs/blacklist.c > > > > > > @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) > > > > > > if (IS_ERR(key)) { > > > > > > pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); > > > > > > return PTR_ERR(key); > > > > > > - } > > > > > > + } else > > > > > > + pr_notice("Loaded blacklisting hash '%s'\n", hash); > > > > > > return 0; > > > > > > } > > > > > > > > > > > > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c > > > > > > index 81b19c52832b..6b6996e5bc27 100644 > > > > > > --- a/security/integrity/platform_certs/load_uefi.c > > > > > > +++ b/security/integrity/platform_certs/load_uefi.c > > > > > > @@ -1,5 +1,7 @@ > > > > > > // SPDX-License-Identifier: GPL-2.0 > > > > > > > > > > > > +#define pr_fmt(fmt) "EFI: "fmt > > > > > > + > > > > > > #include <linux/kernel.h> > > > > > > #include <linux/sched.h> > > > > > > #include <linux/cred.h> > > > > > > @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) > > > > > > return status == EFI_SUCCESS; > > > > > > } > > > > > > > > > > > > +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) > > > > > > +{ > > > > > > + int i = 0; > > > > > > + > > > > > > + while (str16[i] != '\0' && i < (str_size - 1)) { > > > > > > + str[i] = str16[i]; > > > > > > + i++; > > > > > > + } > > > > > > + > > > > > > + str[i] = '\0'; > > > > > > +} > > > > > > + > > > > > > /* > > > > > > * Get a certificate list blob from the named EFI variable. > > > > > > */ > > > > > > @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > > > > efi_status_t status; > > > > > > unsigned long lsize = 4; > > > > > > unsigned long tmpdb[4]; > > > > > > + char namestr[16]; > > > > > > void *db; > > > > > > > > > > > > + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); > > > > > > > > > > Please drop this (and the function above) - instead, just return NULL > > > > > if the variable is not found (without reporting an error). > > > > > > > > > > > > > This name string is for printing debug level message, not error message. > > > > This function already returns NULL when EFI_NOT_FOUND be returned by > > > > firmware. > > > > > > > > > > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); > > > > > > if (status != EFI_BUFFER_TOO_SMALL) { > > > > > > - pr_err("Couldn't get size: 0x%lx\n", status); > > > > > > + if (status == EFI_NOT_FOUND) > > > > > > + pr_debug("UEFI %s list doesn't exist\n", namestr); > > > > > > + else > > > > > > + pr_err("Couldn't get size for UEFI %s list: %s\n", > > > > > > + namestr, efi_status_to_str(status)); > > > > > > return NULL; > > > > > > > > here returns NULL when EFI_NOT_FOUND. The message of existence is for > > > > debugging. > > > > > > > > > > I understand that. But I don't think we need it. > > > > > > > OK. I will remove the debug message. > > > > > > > > } > > > > > > + pr_debug("UEFI %s list exists\n", namestr); > > > > > > > > > > > > db = kmalloc(lsize, GFP_KERNEL); > > > > > > if (!db) > > > > > > @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, > > > > > > status = efi.get_variable(name, guid, NULL, &lsize, db); > > > > > > if (status != EFI_SUCCESS) { > > > > > > kfree(db); > > > > > > - pr_err("Error reading db var: 0x%lx\n", status); > > > > > > + pr_err("Error reading UEFI %s list: %s\n", > > > > > > + namestr, efi_status_to_str(status)); > > > > > > return NULL; > > > > > > } > > > > > > > > > > > > @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, > > > > > > static __init void uefi_blacklist_x509_tbs(const char *source, > > > > > > const void *data, size_t len) > > > > > > { > > > > > > + pr_info("Blacklisting X.509 TBS hash: %s\n", source); > > > > > > uefi_blacklist_hash(source, data, len, "tbs:", 4); > > > > > > } > > > > > > > > > > > > @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, > > > > > > static __init void uefi_blacklist_binary(const char *source, > > > > > > const void *data, size_t len) > > > > > > { > > > > > > + pr_info("Blacklisting hash of an executable: %s\n", source); > > > > > > uefi_blacklist_hash(source, data, len, "bin:", 4); > > > > > > } > > > > > > > > > > > > > > > > These are separate changes - I don't have an opinion whether they are > > > > > appropriate or not, but they should be in a separate patch. > > > > > > > > > > > > > I will move the message of blacklising hash to other patch. Thanks! > > > > > > > > > > @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) > > > > > > */ > > > > > > if (!uefi_check_ignore_db()) { > > > > > > db = get_cert_list(L"db", &secure_var, &dbsize); > > > > > > - if (!db) { > > > > > > - pr_err("MODSIGN: Couldn't get UEFI db list\n"); > > > > > > - } else { > > > > > > + if (db) { > > > > > > rc = parse_efi_signature_list("UEFI:db", > > > > > > db, dbsize, get_handler_for_db); > > > > > > if (rc) > > > > > > @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) > > > > > > } > > > > > > > > > > > > mok = get_cert_list(L"MokListRT", &mok_var, &moksize); > > > > > > - if (!mok) { > > > > > > - pr_info("Couldn't get UEFI MokListRT\n"); > > > > > > - } else { > > > > > > + if (mok) { > > > > > > rc = parse_efi_signature_list("UEFI:MokListRT", > > > > > > mok, moksize, get_handler_for_db); > > > > > > if (rc) > > > > > > @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) > > > > > > } > > > > > > > > > > > > dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); > > > > > > - if (!dbx) { > > > > > > - pr_info("Couldn't get UEFI dbx list\n"); > > > > > > - } else { > > > > > > + if (dbx) { > > > > > > rc = parse_efi_signature_list("UEFI:dbx", > > > > > > dbx, dbxsize, > > > > > > get_handler_for_dbx); > > > > > > -- > > > > > > 2.16.4 > > > > > > > > > > > > > > > > I think we should consider carefully what it means if some of these > > > > > variables don't exist: > > > > > - if secure boot is enabled, db and dbx must exist, so if they don't, > > > > > something is wrong > > > > > > > > The existence of db/dbx is not related to secure boot. If manufacturer/user > > > > enrolled certificate/hash to db or dbx, then the variable will be created. > > > > If user didn't enroll anything to db/dbx, then variables will not show up. > > > > > > > > > > Yes, but if secure boot is enabled and db is empty, how could you have > > > booted in the first place? > > > > > > > I agree. When secure boot enabled, kernel can not be booted without db. > > > > > And what about the converse case: if secure boot is not enabled, why > > > should we trust the contents of db? > > > > > > > The db and dbx are authenticated variables that it protected by KEK. > > So it can be trusted even secure boot is disabled. Unless manufacturer > > or user's KEK is leaked. > > > > Is that true for non-secureboot capable firmware? Of course, in that > case, we cannot be sure that the kernel itself is trusted, but we > shouldn't open up another hole either. > I agree with you that we should filer-out non-secureboot firmware. I think that we can check the existence of SecureBoot variable before loading db/dbx. On the other hand, the SetupMode should also be checked because db/dbx can be changed in setup mode. > > > > > - secure boot might be enabled but we may be booting without shim. > > > > > > > > Shim always creates MokListRT no matter secure boot enabled or disabled. > > > > > > > > > > That is not my point. What happens if you booted with secure boot > > > enabled but without the help of shim? > > > > > > > Without shim, the signed EFI stub can still be booted by EFI boot manager. > > But the MokListRT will not be created for runtime. So MOK signed kernel > > module can not be verified. (or IMA can not verify MOK signed kernel image > > for kexec...) > > > > So if we opt out of using shim, we lose kexec capability as well? That > doesn't make any sense. > MOK is just one of options that it can be used to sign crash kernel image. We can also use the key in db or the kernel embedded keys. > In general, I am very uncomfortable with the way we have painted > ourselves into a corner with shim. If I install Suse on a system that > has the Suse cert in db or KEK, why would I need shim in the first > place? > Yes! We don't need MOK if distro's certificates are preloaded in most machines' db. Unfortunately it's not the case on most x86 machines. > > > > > - secure boot might be disabled. > > > > > > > > > > > > > It's not about secure boot, db/dbx/MokListRT are always available at > > > > runtime if user was enrolled something to those list. > > > > > > > > > > Yes, but again, depending on whether shim was involved, and/or whether > > > secure boot was enabled or not, the way we interpret these things may > > > be very different. > > > > > > I want the reasoning to be sound before merging any patches that deal > > > with these variables. > > > > Here is a simple summary: > > > > When secure boot is enabled: > > - db/dbx: Can be trusted because they are authenticated variables. > > (unless end user doesn't want to trust db/dbx) > > - MokListRT: > > - with shim: MokListRT will be created. It can be trusted. > > - without shim: MokListRT will not be created. > > MOK protected kernel module or file can not be > > verified. > > > > So who polices that MoKlistRT is not created? > At boot time, shim copies MokList (boot variable) to MokListRT (runtime variable). The MokListRT is a read-only runtime volatile variable. So, without shim, the MokListRT will not be created for runtime. > > When secure boot is disabled: > > - db/dbx: Can be trusted because they are authenticated variables. > > (unless end user doesn't want to trust db/dbx) > > Is this true? Does non-secure boot capable firmware still guarantee > that db/dbx can't be created? > I agree. So we should check the existence of SecureBoot variable as I mentioned above. > > - MokListRT: > > - with shim: MokListRT will be created. But it can not be trusted. > > MOK protected kernel module or file can not be > > verified. > > - without shim: MokListRT will not be created. > > MOK protected kernel module or file can not be > > verified. > > > > Enabling this securely involves more than connecting the dots when it > comes to db, MokListRT etc. I would like for someone to convince me as > a maintainer, as well as the IMA maintainers, that the security > requirements are still met in all cases we care about. Just copying db > and MokListRT into a kernel keychain doesn't appear to do that, and if > it does, it needs more documentation to clarify that. Welcome for more input from other maintainers. But I hope that my cosmetic can be accepted because current warning messages looks ugly. Thanks a lot! Joey Lee
diff --git a/certs/blacklist.c b/certs/blacklist.c index 3a507b9e2568..f91437e39e44 100644 --- a/certs/blacklist.c +++ b/certs/blacklist.c @@ -100,7 +100,8 @@ int mark_hash_blacklisted(const char *hash) if (IS_ERR(key)) { pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); return PTR_ERR(key); - } + } else + pr_notice("Loaded blacklisting hash '%s'\n", hash); return 0; } diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c index 81b19c52832b..6b6996e5bc27 100644 --- a/security/integrity/platform_certs/load_uefi.c +++ b/security/integrity/platform_certs/load_uefi.c @@ -1,5 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) "EFI: "fmt + #include <linux/kernel.h> #include <linux/sched.h> #include <linux/cred.h> @@ -35,6 +37,18 @@ static __init bool uefi_check_ignore_db(void) return status == EFI_SUCCESS; } +static void str16_to_str(efi_char16_t *str16, char *str, int str_size) +{ + int i = 0; + + while (str16[i] != '\0' && i < (str_size - 1)) { + str[i] = str16[i]; + i++; + } + + str[i] = '\0'; +} + /* * Get a certificate list blob from the named EFI variable. */ @@ -44,13 +58,20 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, efi_status_t status; unsigned long lsize = 4; unsigned long tmpdb[4]; + char namestr[16]; void *db; + str16_to_str(name, namestr, ARRAY_SIZE(namestr)); status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); if (status != EFI_BUFFER_TOO_SMALL) { - pr_err("Couldn't get size: 0x%lx\n", status); + if (status == EFI_NOT_FOUND) + pr_debug("UEFI %s list doesn't exist\n", namestr); + else + pr_err("Couldn't get size for UEFI %s list: %s\n", + namestr, efi_status_to_str(status)); return NULL; } + pr_debug("UEFI %s list exists\n", namestr); db = kmalloc(lsize, GFP_KERNEL); if (!db) @@ -59,7 +80,8 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, status = efi.get_variable(name, guid, NULL, &lsize, db); if (status != EFI_SUCCESS) { kfree(db); - pr_err("Error reading db var: 0x%lx\n", status); + pr_err("Error reading UEFI %s list: %s\n", + namestr, efi_status_to_str(status)); return NULL; } @@ -95,6 +117,7 @@ static __init void uefi_blacklist_hash(const char *source, const void *data, static __init void uefi_blacklist_x509_tbs(const char *source, const void *data, size_t len) { + pr_info("Blacklisting X.509 TBS hash: %s\n", source); uefi_blacklist_hash(source, data, len, "tbs:", 4); } @@ -104,6 +127,7 @@ static __init void uefi_blacklist_x509_tbs(const char *source, static __init void uefi_blacklist_binary(const char *source, const void *data, size_t len) { + pr_info("Blacklisting hash of an executable: %s\n", source); uefi_blacklist_hash(source, data, len, "bin:", 4); } @@ -154,9 +178,7 @@ static int __init load_uefi_certs(void) */ if (!uefi_check_ignore_db()) { db = get_cert_list(L"db", &secure_var, &dbsize); - if (!db) { - pr_err("MODSIGN: Couldn't get UEFI db list\n"); - } else { + if (db) { rc = parse_efi_signature_list("UEFI:db", db, dbsize, get_handler_for_db); if (rc) @@ -167,9 +189,7 @@ static int __init load_uefi_certs(void) } mok = get_cert_list(L"MokListRT", &mok_var, &moksize); - if (!mok) { - pr_info("Couldn't get UEFI MokListRT\n"); - } else { + if (mok) { rc = parse_efi_signature_list("UEFI:MokListRT", mok, moksize, get_handler_for_db); if (rc) @@ -178,9 +198,7 @@ static int __init load_uefi_certs(void) } dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); - if (!dbx) { - pr_info("Couldn't get UEFI dbx list\n"); - } else { + if (dbx) { rc = parse_efi_signature_list("UEFI:dbx", dbx, dbxsize, get_handler_for_dbx);
When loading certificates list from UEFI variable, the original error message direct shows the efi status code from UEFI firmware. It looks ugly: [ 2.335031] Couldn't get size: 0x800000000000000e [ 2.335032] Couldn't get UEFI MokListRT [ 2.339985] Couldn't get size: 0x800000000000000e [ 2.339987] Couldn't get UEFI dbx list So, this patch shows the status string instead of status code. On the other hand, the "Couldn't get UEFI" message doesn't need to be exposed when db/dbx/mok variable do not exist. So, this patch set the message level to debug. v3. - Print messages similar to db/mok when loading dbx hash to blacklist: [ 1.500952] EFI: Blacklisting hash of an executable: UEFI:dbx [ 1.501773] blacklist: Loaded blacklisting hash 'bin:80b4d96931bf0d02fd91a61e19d14f1da452e66db2408ca8604d411f92659f0a' - Setting messages for the existence of db/mok/dbx lists to debug level. v2. Setting the MODSIGN messages level to debug. Link: https://forums.opensuse.org/showthread.php/535324-MODSIGN-Couldn-t-get-UEFI-db-list?p=2897516#post2897516 Cc: James Morris <jmorris@namei.org> Cc: Serge E. Hallyn" <serge@hallyn.com> Cc: David Howells <dhowells@redhat.com> Cc: Nayna Jain <nayna@linux.ibm.com> Cc: Josh Boyer <jwboyer@fedoraproject.org> Cc: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com> --- certs/blacklist.c | 3 +- security/integrity/platform_certs/load_uefi.c | 40 +++++++++++++++++++-------- 2 files changed, 31 insertions(+), 12 deletions(-)