| Message ID | 20171026084055.25482-1-mjg59@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 26 Oct 2017, Matthew Garrett wrote: > For IMA purposes, we want to be able to obtain the prepared secid in the > bprm structure before the credentials are committed. Add a cred_getsecid > hook that makes this possible. > > Signed-off-by: Matthew Garrett <mjg59@google.com> > Acked-by: Paul Moore <paul@paul-moore.com> Acked-by: James Morris <james.l.morris@oracle.com>
On 10/26/2017 1:40 AM, Matthew Garrett wrote: > For IMA purposes, we want to be able to obtain the prepared secid in the > bprm structure before the credentials are committed. Add a cred_getsecid > hook that makes this possible. > > Signed-off-by: Matthew Garrett <mjg59@google.com> > Acked-by: Paul Moore <paul@paul-moore.com> > Cc: Paul Moore <paul@paul-moore.com> > Cc: Stephen Smalley <sds@tycho.nsa.gov> > Cc: Eric Paris <eparis@parisplace.org> > Cc: selinux@tycho.nsa.gov > Cc: Casey Schaufler <casey@schaufler-ca.com> > Cc: linux-security-module@vger.kernel.org > Cc: Mimi Zohar <zohar@linux.vnet.ibm.com> > Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com> > Cc: linux-integrity@vger.kernel.org > --- > V3: Fix smack_cred_getsecid() Much better. Have you tried this with Smack? > > include/linux/lsm_hooks.h | 6 ++++++ > include/linux/security.h | 1 + > security/security.c | 7 +++++++ > security/selinux/hooks.c | 8 ++++++++ > security/smack/smack_lsm.c | 18 ++++++++++++++++++ > 5 files changed, 40 insertions(+) > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index c9258124e417..c28c6f8b65dc 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -554,6 +554,10 @@ > * @new points to the new credentials. > * @old points to the original credentials. > * Transfer data from original creds to new creds > + * @cred_getsecid: > + * Retrieve the security identifier of the cred structure @c > + * @c contains the credentials, secid will be placed into @secid. > + * In case of failure, @secid will be set to zero. > * @kernel_act_as: > * Set the credentials for a kernel service to act as (subjective context). > * @new points to the credentials to be modified. > @@ -1507,6 +1511,7 @@ union security_list_options { > int (*cred_prepare)(struct cred *new, const struct cred *old, > gfp_t gfp); > void (*cred_transfer)(struct cred *new, const struct cred *old); > + void (*cred_getsecid)(const struct cred *c, u32 *secid); > int (*kernel_act_as)(struct cred *new, u32 secid); > int (*kernel_create_files_as)(struct cred *new, struct inode *inode); > int (*kernel_module_request)(char *kmod_name); > @@ -1779,6 +1784,7 @@ struct security_hook_heads { > struct list_head cred_free; > struct list_head cred_prepare; > struct list_head cred_transfer; > + struct list_head cred_getsecid; > struct list_head kernel_act_as; > struct list_head kernel_create_files_as; > struct list_head kernel_read_file; > diff --git a/include/linux/security.h b/include/linux/security.h > index ce6265960d6c..14848fef8f62 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -324,6 +324,7 @@ int security_cred_alloc_blank(struct cred *cred, gfp_t gfp); > void security_cred_free(struct cred *cred); > int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp); > void security_transfer_creds(struct cred *new, const struct cred *old); > +void security_cred_getsecid(const struct cred *c, u32 *secid); > int security_kernel_act_as(struct cred *new, u32 secid); > int security_kernel_create_files_as(struct cred *new, struct inode *inode); > int security_kernel_module_request(char *kmod_name); > diff --git a/security/security.c b/security/security.c > index 4bf0f571b4ef..02d217597400 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -1004,6 +1004,13 @@ void security_transfer_creds(struct cred *new, const struct cred *old) > call_void_hook(cred_transfer, new, old); > } > > +void security_cred_getsecid(const struct cred *c, u32 *secid) > +{ > + *secid = 0; > + call_void_hook(cred_getsecid, c, secid); > +} > +EXPORT_SYMBOL(security_cred_getsecid); > + > int security_kernel_act_as(struct cred *new, u32 secid) > { > return call_int_hook(kernel_act_as, 0, new, secid); > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index f5d304736852..1d11679674a6 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -3836,6 +3836,13 @@ static void selinux_cred_transfer(struct cred *new, const struct cred *old) > *tsec = *old_tsec; > } > > +static void selinux_cred_getsecid(const struct cred *c, u32 *secid) > +{ > + rcu_read_lock(); > + *secid = cred_sid(c); > + rcu_read_unlock(); > +} > + > /* > * set the security data for a kernel service > * - all the creation contexts are set to unlabelled > @@ -6338,6 +6345,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { > LSM_HOOK_INIT(cred_free, selinux_cred_free), > LSM_HOOK_INIT(cred_prepare, selinux_cred_prepare), > LSM_HOOK_INIT(cred_transfer, selinux_cred_transfer), > + LSM_HOOK_INIT(cred_getsecid, selinux_cred_getsecid), > LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as), > LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as), > LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request), > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 286171a16ed2..37c35aaa6955 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -2049,6 +2049,23 @@ static void smack_cred_transfer(struct cred *new, const struct cred *old) > /* cbs copy rule list */ > } > > +/** > + * smack_cred_getsecid - get the secid corresponding to a creds structure > + * @c: the object creds > + * @secid: where to put the result > + * > + * Sets the secid to contain a u32 version of the smack label. > + */ > +static void smack_cred_getsecid(const struct cred *c, u32 *secid) > +{ > + struct smack_known *skp; > + > + rcu_read_lock(); > + skp = smk_of_task(c->security); > + *secid = skp->smk_secid; > + rcu_read_unlock(); > +} > + > /** > * smack_kernel_act_as - Set the subjective context in a set of credentials > * @new: points to the set of credentials to be modified. > @@ -4651,6 +4668,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = { > LSM_HOOK_INIT(cred_free, smack_cred_free), > LSM_HOOK_INIT(cred_prepare, smack_cred_prepare), > LSM_HOOK_INIT(cred_transfer, smack_cred_transfer), > + LSM_HOOK_INIT(cred_getsecid, smack_cred_getsecid), > LSM_HOOK_INIT(kernel_act_as, smack_kernel_act_as), > LSM_HOOK_INIT(kernel_create_files_as, smack_kernel_create_files_as), > LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),
On Thu, 2017-10-26 at 01:40 -0700, Matthew Garrett via Selinux wrote: > For IMA purposes, we want to be able to obtain the prepared secid in > the > bprm structure before the credentials are committed. Add a > cred_getsecid > hook that makes this possible. > > Signed-off-by: Matthew Garrett <mjg59@google.com> > Acked-by: Paul Moore <paul@paul-moore.com> > Cc: Paul Moore <paul@paul-moore.com> > Cc: Stephen Smalley <sds@tycho.nsa.gov> > Cc: Eric Paris <eparis@parisplace.org> > Cc: selinux@tycho.nsa.gov > Cc: Casey Schaufler <casey@schaufler-ca.com> > Cc: linux-security-module@vger.kernel.org > Cc: Mimi Zohar <zohar@linux.vnet.ibm.com> > Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com> > Cc: linux-integrity@vger.kernel.org > --- > V3: Fix smack_cred_getsecid() > > include/linux/lsm_hooks.h | 6 ++++++ > include/linux/security.h | 1 + > security/security.c | 7 +++++++ > security/selinux/hooks.c | 8 ++++++++ > security/smack/smack_lsm.c | 18 ++++++++++++++++++ > 5 files changed, 40 insertions(+) > > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index c9258124e417..c28c6f8b65dc 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -554,6 +554,10 @@ > * @new points to the new credentials. > * @old points to the original credentials. > * Transfer data from original creds to new creds > + * @cred_getsecid: > + * Retrieve the security identifier of the cred structure @c > + * @c contains the credentials, secid will be placed into > @secid. > + * In case of failure, @secid will be set to zero. > * @kernel_act_as: > * Set the credentials for a kernel service to act as > (subjective context). > * @new points to the credentials to be modified. > @@ -1507,6 +1511,7 @@ union security_list_options { > int (*cred_prepare)(struct cred *new, const struct cred > *old, > gfp_t gfp); > void (*cred_transfer)(struct cred *new, const struct cred > *old); > + void (*cred_getsecid)(const struct cred *c, u32 *secid); > int (*kernel_act_as)(struct cred *new, u32 secid); > int (*kernel_create_files_as)(struct cred *new, struct inode > *inode); > int (*kernel_module_request)(char *kmod_name); > @@ -1779,6 +1784,7 @@ struct security_hook_heads { > struct list_head cred_free; > struct list_head cred_prepare; > struct list_head cred_transfer; > + struct list_head cred_getsecid; > struct list_head kernel_act_as; > struct list_head kernel_create_files_as; > struct list_head kernel_read_file; > diff --git a/include/linux/security.h b/include/linux/security.h > index ce6265960d6c..14848fef8f62 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -324,6 +324,7 @@ int security_cred_alloc_blank(struct cred *cred, > gfp_t gfp); > void security_cred_free(struct cred *cred); > int security_prepare_creds(struct cred *new, const struct cred *old, > gfp_t gfp); > void security_transfer_creds(struct cred *new, const struct cred > *old); > +void security_cred_getsecid(const struct cred *c, u32 *secid); > int security_kernel_act_as(struct cred *new, u32 secid); > int security_kernel_create_files_as(struct cred *new, struct inode > *inode); > int security_kernel_module_request(char *kmod_name); > diff --git a/security/security.c b/security/security.c > index 4bf0f571b4ef..02d217597400 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -1004,6 +1004,13 @@ void security_transfer_creds(struct cred *new, > const struct cred *old) > call_void_hook(cred_transfer, new, old); > } > > +void security_cred_getsecid(const struct cred *c, u32 *secid) > +{ > + *secid = 0; > + call_void_hook(cred_getsecid, c, secid); > +} > +EXPORT_SYMBOL(security_cred_getsecid); > + > int security_kernel_act_as(struct cred *new, u32 secid) > { > return call_int_hook(kernel_act_as, 0, new, secid); > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index f5d304736852..1d11679674a6 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -3836,6 +3836,13 @@ static void selinux_cred_transfer(struct cred > *new, const struct cred *old) > *tsec = *old_tsec; > } > > +static void selinux_cred_getsecid(const struct cred *c, u32 *secid) > +{ > + rcu_read_lock(); > + *secid = cred_sid(c); > + rcu_read_unlock(); Is rcu_read_lock() necessary here? Seems like we use cred_sid() in many places without it. > +} > + > /* > * set the security data for a kernel service > * - all the creation contexts are set to unlabelled > @@ -6338,6 +6345,7 @@ static struct security_hook_list > selinux_hooks[] __lsm_ro_after_init = { > LSM_HOOK_INIT(cred_free, selinux_cred_free), > LSM_HOOK_INIT(cred_prepare, selinux_cred_prepare), > LSM_HOOK_INIT(cred_transfer, selinux_cred_transfer), > + LSM_HOOK_INIT(cred_getsecid, selinux_cred_getsecid), > LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as), > LSM_HOOK_INIT(kernel_create_files_as, > selinux_kernel_create_files_as), > LSM_HOOK_INIT(kernel_module_request, > selinux_kernel_module_request), > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 286171a16ed2..37c35aaa6955 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -2049,6 +2049,23 @@ static void smack_cred_transfer(struct cred > *new, const struct cred *old) > /* cbs copy rule list */ > } > > +/** > + * smack_cred_getsecid - get the secid corresponding to a creds > structure > + * @c: the object creds > + * @secid: where to put the result > + * > + * Sets the secid to contain a u32 version of the smack label. > + */ > +static void smack_cred_getsecid(const struct cred *c, u32 *secid) > +{ > + struct smack_known *skp; > + > + rcu_read_lock(); > + skp = smk_of_task(c->security); > + *secid = skp->smk_secid; > + rcu_read_unlock(); > +} > + > /** > * smack_kernel_act_as - Set the subjective context in a set of > credentials > * @new: points to the set of credentials to be modified. > @@ -4651,6 +4668,7 @@ static struct security_hook_list smack_hooks[] > __lsm_ro_after_init = { > LSM_HOOK_INIT(cred_free, smack_cred_free), > LSM_HOOK_INIT(cred_prepare, smack_cred_prepare), > LSM_HOOK_INIT(cred_transfer, smack_cred_transfer), > + LSM_HOOK_INIT(cred_getsecid, smack_cred_getsecid), > LSM_HOOK_INIT(kernel_act_as, smack_kernel_act_as), > LSM_HOOK_INIT(kernel_create_files_as, > smack_kernel_create_files_as), > LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),
On Thu, Oct 26, 2017 at 2:21 PM, Casey Schaufler <casey@schaufler-ca.com> wrote: > On 10/26/2017 1:40 AM, Matthew Garrett wrote: >> V3: Fix smack_cred_getsecid() > > Much better. Have you tried this with Smack? I'm afraid not - I have zero expertise with Smack and no easy way to set it up. I can do so later in the week if you like?
On Thu, Oct 26, 2017 at 3:20 PM, Stephen Smalley <sds@tycho.nsa.gov> wrote: > On Thu, 2017-10-26 at 01:40 -0700, Matthew Garrett via Selinux wrote: >> +static void selinux_cred_getsecid(const struct cred *c, u32 *secid) >> +{ >> + rcu_read_lock(); >> + *secid = cred_sid(c); >> + rcu_read_unlock(); > > Is rcu_read_lock() necessary here? Seems like we use cred_sid() in many > places without it. Ah, I thought it was based on task_sid(), but I guess that's actually protecting the __task_cred()?
On Mon, 2017-10-30 at 10:57 +0000, Matthew Garrett via Selinux wrote: > On Thu, Oct 26, 2017 at 3:20 PM, Stephen Smalley <sds@tycho.nsa.gov> > wrote: > > On Thu, 2017-10-26 at 01:40 -0700, Matthew Garrett via Selinux > > wrote: > > > +static void selinux_cred_getsecid(const struct cred *c, u32 > > > *secid) > > > +{ > > > + rcu_read_lock(); > > > + *secid = cred_sid(c); > > > + rcu_read_unlock(); > > > > Is rcu_read_lock() necessary here? Seems like we use cred_sid() in > > many > > places without it. > > Ah, I thought it was based on task_sid(), but I guess that's actually > protecting the __task_cred()? It appears to me that in all other cases, we are either dealing with the current cred, or something in the call chain of cred_sid() is holding a reference to the cred, or something in the call chain of cred_sid() has called rcu_read_lock() already. I might have missed something though, and I don't know how safe it is to assume that all future callers will do this. cc'd David for his thoughts.
On Mon, Oct 30, 2017 at 10:03 AM, Stephen Smalley <sds@tycho.nsa.gov> wrote: > On Mon, 2017-10-30 at 10:57 +0000, Matthew Garrett via Selinux wrote: >> On Thu, Oct 26, 2017 at 3:20 PM, Stephen Smalley <sds@tycho.nsa.gov> >> wrote: >> > On Thu, 2017-10-26 at 01:40 -0700, Matthew Garrett via Selinux >> > wrote: >> > > +static void selinux_cred_getsecid(const struct cred *c, u32 >> > > *secid) >> > > +{ >> > > + rcu_read_lock(); >> > > + *secid = cred_sid(c); >> > > + rcu_read_unlock(); >> > >> > Is rcu_read_lock() necessary here? Seems like we use cred_sid() in >> > many >> > places without it. >> >> Ah, I thought it was based on task_sid(), but I guess that's actually >> protecting the __task_cred()? > > It appears to me that in all other cases, we are either dealing with > the current cred, or something in the call chain of cred_sid() is > holding a reference to the cred, or something in the call chain of > cred_sid() has called rcu_read_lock() already. I might have missed > something though, and I don't know how safe it is to assume that all > future callers will do this. cc'd David for his thoughts. Hi David, Any opinion on this? Thanks!
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index c9258124e417..c28c6f8b65dc 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -554,6 +554,10 @@ * @new points to the new credentials. * @old points to the original credentials. * Transfer data from original creds to new creds + * @cred_getsecid: + * Retrieve the security identifier of the cred structure @c + * @c contains the credentials, secid will be placed into @secid. + * In case of failure, @secid will be set to zero. * @kernel_act_as: * Set the credentials for a kernel service to act as (subjective context). * @new points to the credentials to be modified. @@ -1507,6 +1511,7 @@ union security_list_options { int (*cred_prepare)(struct cred *new, const struct cred *old, gfp_t gfp); void (*cred_transfer)(struct cred *new, const struct cred *old); + void (*cred_getsecid)(const struct cred *c, u32 *secid); int (*kernel_act_as)(struct cred *new, u32 secid); int (*kernel_create_files_as)(struct cred *new, struct inode *inode); int (*kernel_module_request)(char *kmod_name); @@ -1779,6 +1784,7 @@ struct security_hook_heads { struct list_head cred_free; struct list_head cred_prepare; struct list_head cred_transfer; + struct list_head cred_getsecid; struct list_head kernel_act_as; struct list_head kernel_create_files_as; struct list_head kernel_read_file; diff --git a/include/linux/security.h b/include/linux/security.h index ce6265960d6c..14848fef8f62 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -324,6 +324,7 @@ int security_cred_alloc_blank(struct cred *cred, gfp_t gfp); void security_cred_free(struct cred *cred); int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp); void security_transfer_creds(struct cred *new, const struct cred *old); +void security_cred_getsecid(const struct cred *c, u32 *secid); int security_kernel_act_as(struct cred *new, u32 secid); int security_kernel_create_files_as(struct cred *new, struct inode *inode); int security_kernel_module_request(char *kmod_name); diff --git a/security/security.c b/security/security.c index 4bf0f571b4ef..02d217597400 100644 --- a/security/security.c +++ b/security/security.c @@ -1004,6 +1004,13 @@ void security_transfer_creds(struct cred *new, const struct cred *old) call_void_hook(cred_transfer, new, old); } +void security_cred_getsecid(const struct cred *c, u32 *secid) +{ + *secid = 0; + call_void_hook(cred_getsecid, c, secid); +} +EXPORT_SYMBOL(security_cred_getsecid); + int security_kernel_act_as(struct cred *new, u32 secid) { return call_int_hook(kernel_act_as, 0, new, secid); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index f5d304736852..1d11679674a6 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3836,6 +3836,13 @@ static void selinux_cred_transfer(struct cred *new, const struct cred *old) *tsec = *old_tsec; } +static void selinux_cred_getsecid(const struct cred *c, u32 *secid) +{ + rcu_read_lock(); + *secid = cred_sid(c); + rcu_read_unlock(); +} + /* * set the security data for a kernel service * - all the creation contexts are set to unlabelled @@ -6338,6 +6345,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(cred_free, selinux_cred_free), LSM_HOOK_INIT(cred_prepare, selinux_cred_prepare), LSM_HOOK_INIT(cred_transfer, selinux_cred_transfer), + LSM_HOOK_INIT(cred_getsecid, selinux_cred_getsecid), LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as), LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as), LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request), diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 286171a16ed2..37c35aaa6955 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -2049,6 +2049,23 @@ static void smack_cred_transfer(struct cred *new, const struct cred *old) /* cbs copy rule list */ } +/** + * smack_cred_getsecid - get the secid corresponding to a creds structure + * @c: the object creds + * @secid: where to put the result + * + * Sets the secid to contain a u32 version of the smack label. + */ +static void smack_cred_getsecid(const struct cred *c, u32 *secid) +{ + struct smack_known *skp; + + rcu_read_lock(); + skp = smk_of_task(c->security); + *secid = skp->smk_secid; + rcu_read_unlock(); +} + /** * smack_kernel_act_as - Set the subjective context in a set of credentials * @new: points to the set of credentials to be modified. @@ -4651,6 +4668,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(cred_free, smack_cred_free), LSM_HOOK_INIT(cred_prepare, smack_cred_prepare), LSM_HOOK_INIT(cred_transfer, smack_cred_transfer), + LSM_HOOK_INIT(cred_getsecid, smack_cred_getsecid), LSM_HOOK_INIT(kernel_act_as, smack_kernel_act_as), LSM_HOOK_INIT(kernel_create_files_as, smack_kernel_create_files_as), LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),