| Message ID | 1365605450-3009-1-git-send-email-simo@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 2013-04-10 at 10:50 -0400, Simo Sorce wrote: > This way all applications that need access to krb5 protected shares do not need > to be taught how to initiate crdentials on their own, nor they need to be > wrapped in additional init scripts like k5start or use wasteful cronjobs to > keep credentials fresh. All is needed is to drop a keytab with the right keys > in a special location on the system and gss-proxy will do the rest. Can you explain further? Will this for instance work with Active Directory servers as well as MIT and Heimdal?
On Wed, 2013-04-10 at 15:06 +0000, Myklebust, Trond wrote: > On Wed, 2013-04-10 at 10:50 -0400, Simo Sorce wrote: > > > This way all applications that need access to krb5 protected shares do not need > > to be taught how to initiate crdentials on their own, nor they need to be > > wrapped in additional init scripts like k5start or use wasteful cronjobs to > > keep credentials fresh. All is needed is to drop a keytab with the right keys > > in a special location on the system and gss-proxy will do the rest. > > Can you explain further? Will this for instance work with Active > Directory servers as well as MIT and Heimdal? GSS-Proxy on the client works only with MIT 1.11 as explained, but the patch itself does not depend on GSS-Proxy so it is safe from rpc.gssd to include it. GSS-Proxy doesn't really care what it the Kerberos infrastructure is used on the KDC, so it will work with any KDC, be it MIT, Heimdal or Active Directory. Simo.
On Wed, 2013-04-10 at 12:09 -0400, Simo Sorce wrote: > On Wed, 2013-04-10 at 15:06 +0000, Myklebust, Trond wrote: > > On Wed, 2013-04-10 at 10:50 -0400, Simo Sorce wrote: > > > > > This way all applications that need access to krb5 protected shares do not need > > > to be taught how to initiate crdentials on their own, nor they need to be > > > wrapped in additional init scripts like k5start or use wasteful cronjobs to > > > keep credentials fresh. All is needed is to drop a keytab with the right keys > > > in a special location on the system and gss-proxy will do the rest. > > > > Can you explain further? Will this for instance work with Active > > Directory servers as well as MIT and Heimdal? > > GSS-Proxy on the client works only with MIT 1.11 as explained, but the > patch itself does not depend on GSS-Proxy so it is safe from rpc.gssd to > include it. OK. > GSS-Proxy doesn't really care what it the Kerberos infrastructure is > used on the KDC, so it will work with any KDC, be it MIT, Heimdal or > Active Directory. So what kind of privileges do the keys in this keytab need in order to allow gss-proxy to perform automatic renewal of gss sessions?
On Wed, 2013-04-10 at 16:29 +0000, Myklebust, Trond wrote: > On Wed, 2013-04-10 at 12:09 -0400, Simo Sorce wrote: > > On Wed, 2013-04-10 at 15:06 +0000, Myklebust, Trond wrote: > > > On Wed, 2013-04-10 at 10:50 -0400, Simo Sorce wrote: > > > > > > > This way all applications that need access to krb5 protected shares do not need > > > > to be taught how to initiate crdentials on their own, nor they need to be > > > > wrapped in additional init scripts like k5start or use wasteful cronjobs to > > > > keep credentials fresh. All is needed is to drop a keytab with the right keys > > > > in a special location on the system and gss-proxy will do the rest. > > > > > > Can you explain further? Will this for instance work with Active > > > Directory servers as well as MIT and Heimdal? > > > > GSS-Proxy on the client works only with MIT 1.11 as explained, but the > > patch itself does not depend on GSS-Proxy so it is safe from rpc.gssd to > > include it. > > OK. > > > GSS-Proxy doesn't really care what it the Kerberos infrastructure is > > used on the KDC, so it will work with any KDC, be it MIT, Heimdal or > > Active Directory. > > So what kind of privileges do the keys in this keytab need in order to > allow gss-proxy to perform automatic renewal of gss sessions? Sorry I am not sure I understand the question. Let me make an example that may answer your question though. Assume you have a cronjob that runs as the user 'apache' (assume uid 1234) that needs access to a nfs share to write some backup. All you need to do is obtain a keytab for apache@EXAMPLE.COM and place it in /var/lib/gssproxy/clients/1234.keytab and gss-proxy will use this keytab to get a ticket for the principal apache@EXAMPLE.COM when the user apache walks into the nfs mountpoint and triggers a gss auth request via rpc.gssd Note that the principal name do not really need to match the local user name, all is needed is that the principal in the client keytab is allowed access by nfs server to the directory the local user is walking in. Simo.
On 10/04/13 10:50, Simo Sorce wrote: > GSSAPI can be given a uid number as a special name, and then > gss_acquire_cred() can use the name to try to find credentials for > the user. > > Give GSSAPI a chance to do it on its own, then fallback to the classic > method of trolling through the file system to find a credential cache. > > This patch uses a little know feature of GSSAPI that permits to acquire > crdentials specifying the user's UID. Normally GSSAPI will simply perform > a getpwuid() call and use the user name to generate a principal name and > then see if it can find a TGT for that principal in the local ccache. > > This feature is vital to allow the GSS-Proxy to be able to initiate crdentials > on behalf of rpc.gssd using client keytabs stored in the filsystem. > > GSS-Proxy works through an interposer-type plugin (new feature in MIT 1.11) > that allows to intercept all GSSAPI requestes and relay them to a system > daemon via a socket. This daemon (GSS-Proxy) then can perform operations on > behalf of other applications with additional logic. > > In the rpc.gssd case the GSS-Proxy daemon allows applications running as > system users to properly access krb5 protected shares by creating a credential > cache on the fly when necessary. > > This way all applications that need access to krb5 protected shares do not need > to be taught how to initiate crdentials on their own, nor they need to be > wrapped in additional init scripts like k5start or use wasteful cronjobs to > keep credentials fresh. All is needed is to drop a keytab with the right keys > in a special location on the system and gss-proxy will do the rest. > > Signed-off-by: Simo Sorce <simo@redhat.com> Committed steved. > --- > utils/gssd/gssd_proc.c | 22 ++++++++++----- > utils/gssd/krb5_util.c | 77 +++++++++++++++++++++++++++++++++++++------------- > utils/gssd/krb5_util.h | 2 ++ > 3 files changed, 75 insertions(+), 26 deletions(-) > > diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c > index b1239785500f8e1bc601e4033a5f212c5b5b6c76..afc2076cde74e3cea6764408ec839a6f99b86ea4 100644 > --- a/utils/gssd/gssd_proc.c > +++ b/utils/gssd/gssd_proc.c > @@ -817,7 +817,8 @@ create_auth_rpc_client(struct clnt_info *clp, > CLIENT **clnt_return, > AUTH **auth_return, > uid_t uid, > - int authtype) > + int authtype, > + gss_cred_id_t cred) > { > CLIENT *rpc_clnt = NULL; > struct rpc_gss_sec sec; > @@ -843,7 +844,7 @@ create_auth_rpc_client(struct clnt_info *clp, > > sec.qop = GSS_C_QOP_DEFAULT; > sec.svc = RPCSEC_GSS_SVC_NONE; > - sec.cred = GSS_C_NO_CREDENTIAL; > + sec.cred = cred; > sec.req_flags = 0; > if (authtype == AUTHTYPE_KRB5) { > sec.mech = (gss_OID)&krb5oid; > @@ -968,6 +969,7 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname, > char **dirname; > int create_resp = -1; > int err, downcall_err = -EACCES; > + gss_cred_id_t gss_cred; > OM_uint32 maj_stat, min_stat, lifetime_rec; > > printerr(1, "handling krb5 upcall (%s)\n", clp->dirname); > @@ -1002,15 +1004,20 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname, > if (uid != 0 || (uid == 0 && root_uses_machine_creds == 0 && > service == NULL)) { > /* Tell krb5 gss which credentials cache to use */ > - for (dirname = ccachesearch; *dirname != NULL; dirname++) { > + /* Try first to acquire credentials directly via GSSAPI */ > + err = gssd_acquire_user_cred(uid, &gss_cred); > + if (!err) > + create_resp = create_auth_rpc_client(clp, &rpc_clnt, &auth, uid, > + AUTHTYPE_KRB5, gss_cred); > + /* if create_auth_rplc_client fails try the traditional method of > + * trolling for credentials */ > + for (dirname = ccachesearch; create_resp != 0 && *dirname != NULL; dirname++) { > err = gssd_setup_krb5_user_gss_ccache(uid, clp->servername, *dirname); > if (err == -EKEYEXPIRED) > downcall_err = -EKEYEXPIRED; > else if (!err) > create_resp = create_auth_rpc_client(clp, &rpc_clnt, &auth, uid, > - AUTHTYPE_KRB5); > - if (create_resp == 0) > - break; > + AUTHTYPE_KRB5, GSS_C_NO_CREDENTIAL); > } > } > if (create_resp != 0) { > @@ -1036,7 +1043,8 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname, > gssd_setup_krb5_machine_gss_ccache(*ccname); > if ((create_auth_rpc_client(clp, &rpc_clnt, > &auth, uid, > - AUTHTYPE_KRB5)) == 0) { > + AUTHTYPE_KRB5, > + GSS_C_NO_CREDENTIAL)) == 0) { > /* Success! */ > success++; > break; > diff --git a/utils/gssd/krb5_util.c b/utils/gssd/krb5_util.c > index 20b55b37c0f38405794be18f4bebd8ac089dccd2..6275dd8717c64c69939481444bc4b115a2a93a13 100644 > --- a/utils/gssd/krb5_util.c > +++ b/utils/gssd/krb5_util.c > @@ -1350,6 +1350,57 @@ gssd_k5_get_default_realm(char **def_realm) > krb5_free_context(context); > } > > +static int > +gssd_acquire_krb5_cred(gss_name_t name, gss_cred_id_t *gss_cred) > +{ > + OM_uint32 maj_stat, min_stat; > + gss_OID_set_desc desired_mechs = { 1, &krb5oid }; > + > + maj_stat = gss_acquire_cred(&min_stat, name, GSS_C_INDEFINITE, > + &desired_mechs, GSS_C_INITIATE, > + gss_cred, NULL, NULL); > + > + if (maj_stat != GSS_S_COMPLETE) { > + if (get_verbosity() > 0) > + pgsserr("gss_acquire_cred", > + maj_stat, min_stat, &krb5oid); > + return -1; > + } > + > + return 0; > +} > + > +int > +gssd_acquire_user_cred(uid_t uid, gss_cred_id_t *gss_cred) > +{ > + OM_uint32 maj_stat, min_stat; > + gss_buffer_desc name_buf; > + gss_name_t name; > + char buf[11]; > + int ret; > + > + ret = snprintf(buf, 11, "%u", uid); > + if (ret < 1 || ret > 10) { > + return -1; > + } > + name_buf.value = buf; > + name_buf.length = ret + 1; > + > + maj_stat = gss_import_name(&min_stat, &name_buf, > + GSS_C_NT_STRING_UID_NAME, &name); > + if (maj_stat != GSS_S_COMPLETE) { > + if (get_verbosity() > 0) > + pgsserr("gss_import_name", > + maj_stat, min_stat, &krb5oid); > + return -1; > + } > + > + ret = gssd_acquire_krb5_cred(name, gss_cred); > + > + maj_stat = gss_release_name(&min_stat, &name); > + return ret; > +} > + > #ifdef HAVE_SET_ALLOWABLE_ENCTYPES > /* > * this routine obtains a credentials handle via gss_acquire_cred() > @@ -1368,28 +1419,18 @@ int > limit_krb5_enctypes(struct rpc_gss_sec *sec) > { > u_int maj_stat, min_stat; > - gss_cred_id_t credh; > - gss_OID_set_desc desired_mechs; > krb5_enctype enctypes[] = { ENCTYPE_DES_CBC_CRC, > ENCTYPE_DES_CBC_MD5, > ENCTYPE_DES_CBC_MD4 }; > int num_enctypes = sizeof(enctypes) / sizeof(enctypes[0]); > extern int num_krb5_enctypes; > extern krb5_enctype *krb5_enctypes; > + int err = -1; > > - /* We only care about getting a krb5 cred */ > - desired_mechs.count = 1; > - desired_mechs.elements = &krb5oid; > - > - maj_stat = gss_acquire_cred(&min_stat, NULL, 0, > - &desired_mechs, GSS_C_INITIATE, > - &credh, NULL, NULL); > - > - if (maj_stat != GSS_S_COMPLETE) { > - if (get_verbosity() > 0) > - pgsserr("gss_acquire_cred", > - maj_stat, min_stat, &krb5oid); > - return -1; > + if (sec->cred == GSS_C_NO_CREDENTIAL) { > + err = gssd_acquire_krb5_cred(GSS_C_NO_NAME, &sec->cred); > + if (err) > + return -1; > } > > /* > @@ -1397,19 +1438,17 @@ limit_krb5_enctypes(struct rpc_gss_sec *sec) > * list of supported enctypes, use local default here. > */ > if (krb5_enctypes == NULL || limit_to_legacy_enctypes) > - maj_stat = gss_set_allowable_enctypes(&min_stat, credh, > + maj_stat = gss_set_allowable_enctypes(&min_stat, sec->cred, > &krb5oid, num_enctypes, enctypes); > else > - maj_stat = gss_set_allowable_enctypes(&min_stat, credh, > + maj_stat = gss_set_allowable_enctypes(&min_stat, sec->cred, > &krb5oid, num_krb5_enctypes, krb5_enctypes); > > if (maj_stat != GSS_S_COMPLETE) { > pgsserr("gss_set_allowable_enctypes", > maj_stat, min_stat, &krb5oid); > - gss_release_cred(&min_stat, &credh); > return -1; > } > - sec->cred = credh; > > return 0; > } > diff --git a/utils/gssd/krb5_util.h b/utils/gssd/krb5_util.h > index 9f41625858fe136a63f08d757b4140508729423e..eed12944a73024c015d79f1c4aace2a9d31a1688 100644 > --- a/utils/gssd/krb5_util.h > +++ b/utils/gssd/krb5_util.h > @@ -36,6 +36,8 @@ int gssd_refresh_krb5_machine_credential(char *hostname, > char *gssd_k5_err_msg(krb5_context context, krb5_error_code code); > void gssd_k5_get_default_realm(char **def_realm); > > +int gssd_acquire_user_cred(uid_t uid, gss_cred_id_t *gss_cred); > + > #ifdef HAVE_SET_ALLOWABLE_ENCTYPES > extern int limit_to_legacy_enctypes; > int limit_krb5_enctypes(struct rpc_gss_sec *sec); > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c index b1239785500f8e1bc601e4033a5f212c5b5b6c76..afc2076cde74e3cea6764408ec839a6f99b86ea4 100644 --- a/utils/gssd/gssd_proc.c +++ b/utils/gssd/gssd_proc.c @@ -817,7 +817,8 @@ create_auth_rpc_client(struct clnt_info *clp, CLIENT **clnt_return, AUTH **auth_return, uid_t uid, - int authtype) + int authtype, + gss_cred_id_t cred) { CLIENT *rpc_clnt = NULL; struct rpc_gss_sec sec; @@ -843,7 +844,7 @@ create_auth_rpc_client(struct clnt_info *clp, sec.qop = GSS_C_QOP_DEFAULT; sec.svc = RPCSEC_GSS_SVC_NONE; - sec.cred = GSS_C_NO_CREDENTIAL; + sec.cred = cred; sec.req_flags = 0; if (authtype == AUTHTYPE_KRB5) { sec.mech = (gss_OID)&krb5oid; @@ -968,6 +969,7 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname, char **dirname; int create_resp = -1; int err, downcall_err = -EACCES; + gss_cred_id_t gss_cred; OM_uint32 maj_stat, min_stat, lifetime_rec; printerr(1, "handling krb5 upcall (%s)\n", clp->dirname); @@ -1002,15 +1004,20 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname, if (uid != 0 || (uid == 0 && root_uses_machine_creds == 0 && service == NULL)) { /* Tell krb5 gss which credentials cache to use */ - for (dirname = ccachesearch; *dirname != NULL; dirname++) { + /* Try first to acquire credentials directly via GSSAPI */ + err = gssd_acquire_user_cred(uid, &gss_cred); + if (!err) + create_resp = create_auth_rpc_client(clp, &rpc_clnt, &auth, uid, + AUTHTYPE_KRB5, gss_cred); + /* if create_auth_rplc_client fails try the traditional method of + * trolling for credentials */ + for (dirname = ccachesearch; create_resp != 0 && *dirname != NULL; dirname++) { err = gssd_setup_krb5_user_gss_ccache(uid, clp->servername, *dirname); if (err == -EKEYEXPIRED) downcall_err = -EKEYEXPIRED; else if (!err) create_resp = create_auth_rpc_client(clp, &rpc_clnt, &auth, uid, - AUTHTYPE_KRB5); - if (create_resp == 0) - break; + AUTHTYPE_KRB5, GSS_C_NO_CREDENTIAL); } } if (create_resp != 0) { @@ -1036,7 +1043,8 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname, gssd_setup_krb5_machine_gss_ccache(*ccname); if ((create_auth_rpc_client(clp, &rpc_clnt, &auth, uid, - AUTHTYPE_KRB5)) == 0) { + AUTHTYPE_KRB5, + GSS_C_NO_CREDENTIAL)) == 0) { /* Success! */ success++; break; diff --git a/utils/gssd/krb5_util.c b/utils/gssd/krb5_util.c index 20b55b37c0f38405794be18f4bebd8ac089dccd2..6275dd8717c64c69939481444bc4b115a2a93a13 100644 --- a/utils/gssd/krb5_util.c +++ b/utils/gssd/krb5_util.c @@ -1350,6 +1350,57 @@ gssd_k5_get_default_realm(char **def_realm) krb5_free_context(context); } +static int +gssd_acquire_krb5_cred(gss_name_t name, gss_cred_id_t *gss_cred) +{ + OM_uint32 maj_stat, min_stat; + gss_OID_set_desc desired_mechs = { 1, &krb5oid }; + + maj_stat = gss_acquire_cred(&min_stat, name, GSS_C_INDEFINITE, + &desired_mechs, GSS_C_INITIATE, + gss_cred, NULL, NULL); + + if (maj_stat != GSS_S_COMPLETE) { + if (get_verbosity() > 0) + pgsserr("gss_acquire_cred", + maj_stat, min_stat, &krb5oid); + return -1; + } + + return 0; +} + +int +gssd_acquire_user_cred(uid_t uid, gss_cred_id_t *gss_cred) +{ + OM_uint32 maj_stat, min_stat; + gss_buffer_desc name_buf; + gss_name_t name; + char buf[11]; + int ret; + + ret = snprintf(buf, 11, "%u", uid); + if (ret < 1 || ret > 10) { + return -1; + } + name_buf.value = buf; + name_buf.length = ret + 1; + + maj_stat = gss_import_name(&min_stat, &name_buf, + GSS_C_NT_STRING_UID_NAME, &name); + if (maj_stat != GSS_S_COMPLETE) { + if (get_verbosity() > 0) + pgsserr("gss_import_name", + maj_stat, min_stat, &krb5oid); + return -1; + } + + ret = gssd_acquire_krb5_cred(name, gss_cred); + + maj_stat = gss_release_name(&min_stat, &name); + return ret; +} + #ifdef HAVE_SET_ALLOWABLE_ENCTYPES /* * this routine obtains a credentials handle via gss_acquire_cred() @@ -1368,28 +1419,18 @@ int limit_krb5_enctypes(struct rpc_gss_sec *sec) { u_int maj_stat, min_stat; - gss_cred_id_t credh; - gss_OID_set_desc desired_mechs; krb5_enctype enctypes[] = { ENCTYPE_DES_CBC_CRC, ENCTYPE_DES_CBC_MD5, ENCTYPE_DES_CBC_MD4 }; int num_enctypes = sizeof(enctypes) / sizeof(enctypes[0]); extern int num_krb5_enctypes; extern krb5_enctype *krb5_enctypes; + int err = -1; - /* We only care about getting a krb5 cred */ - desired_mechs.count = 1; - desired_mechs.elements = &krb5oid; - - maj_stat = gss_acquire_cred(&min_stat, NULL, 0, - &desired_mechs, GSS_C_INITIATE, - &credh, NULL, NULL); - - if (maj_stat != GSS_S_COMPLETE) { - if (get_verbosity() > 0) - pgsserr("gss_acquire_cred", - maj_stat, min_stat, &krb5oid); - return -1; + if (sec->cred == GSS_C_NO_CREDENTIAL) { + err = gssd_acquire_krb5_cred(GSS_C_NO_NAME, &sec->cred); + if (err) + return -1; } /* @@ -1397,19 +1438,17 @@ limit_krb5_enctypes(struct rpc_gss_sec *sec) * list of supported enctypes, use local default here. */ if (krb5_enctypes == NULL || limit_to_legacy_enctypes) - maj_stat = gss_set_allowable_enctypes(&min_stat, credh, + maj_stat = gss_set_allowable_enctypes(&min_stat, sec->cred, &krb5oid, num_enctypes, enctypes); else - maj_stat = gss_set_allowable_enctypes(&min_stat, credh, + maj_stat = gss_set_allowable_enctypes(&min_stat, sec->cred, &krb5oid, num_krb5_enctypes, krb5_enctypes); if (maj_stat != GSS_S_COMPLETE) { pgsserr("gss_set_allowable_enctypes", maj_stat, min_stat, &krb5oid); - gss_release_cred(&min_stat, &credh); return -1; } - sec->cred = credh; return 0; } diff --git a/utils/gssd/krb5_util.h b/utils/gssd/krb5_util.h index 9f41625858fe136a63f08d757b4140508729423e..eed12944a73024c015d79f1c4aace2a9d31a1688 100644 --- a/utils/gssd/krb5_util.h +++ b/utils/gssd/krb5_util.h @@ -36,6 +36,8 @@ int gssd_refresh_krb5_machine_credential(char *hostname, char *gssd_k5_err_msg(krb5_context context, krb5_error_code code); void gssd_k5_get_default_realm(char **def_realm); +int gssd_acquire_user_cred(uid_t uid, gss_cred_id_t *gss_cred); + #ifdef HAVE_SET_ALLOWABLE_ENCTYPES extern int limit_to_legacy_enctypes; int limit_krb5_enctypes(struct rpc_gss_sec *sec);
GSSAPI can be given a uid number as a special name, and then gss_acquire_cred() can use the name to try to find credentials for the user. Give GSSAPI a chance to do it on its own, then fallback to the classic method of trolling through the file system to find a credential cache. This patch uses a little know feature of GSSAPI that permits to acquire crdentials specifying the user's UID. Normally GSSAPI will simply perform a getpwuid() call and use the user name to generate a principal name and then see if it can find a TGT for that principal in the local ccache. This feature is vital to allow the GSS-Proxy to be able to initiate crdentials on behalf of rpc.gssd using client keytabs stored in the filsystem. GSS-Proxy works through an interposer-type plugin (new feature in MIT 1.11) that allows to intercept all GSSAPI requestes and relay them to a system daemon via a socket. This daemon (GSS-Proxy) then can perform operations on behalf of other applications with additional logic. In the rpc.gssd case the GSS-Proxy daemon allows applications running as system users to properly access krb5 protected shares by creating a credential cache on the fly when necessary. This way all applications that need access to krb5 protected shares do not need to be taught how to initiate crdentials on their own, nor they need to be wrapped in additional init scripts like k5start or use wasteful cronjobs to keep credentials fresh. All is needed is to drop a keytab with the right keys in a special location on the system and gss-proxy will do the rest. Signed-off-by: Simo Sorce <simo@redhat.com> --- utils/gssd/gssd_proc.c | 22 ++++++++++----- utils/gssd/krb5_util.c | 77 +++++++++++++++++++++++++++++++++++++------------- utils/gssd/krb5_util.h | 2 ++ 3 files changed, 75 insertions(+), 26 deletions(-)