Make all SSSD processes a member of sssd supplementary group.

Previously it was done only for 'sssd_nss' to allow it to write to
sssd:sssd owned mem-cache file while running under 'root'.

Let's use this approach for all other files to avoid using
CAP_DAC_OVERRIDE / CAP_CHOWN (in following patches).

Primarily rely on systemd to set group, but try to set it manually
if (required and) missing at runtime.

Makefile.am

@@ -103,12 +103,15 @@ condconfigexists = ConditionPathExists=\|/etc/sssd/sssd.conf\nConditionDirectory
 # originally then it's addition to CapabilityBoundingSet doesn't matter.
 if SSSD_NON_ROOT_USER
 additional_caps = CAP_DAC_OVERRIDE
+supplementary_groups = \# "SupplementaryGroups" is important to keep if service is configured to be run under "root"\nSupplementaryGroups=$(SSSD_USER)
+else
+supplementary_groups = \#\n\# Warning: SSSD package was built without support of running as non-privileged user
 endif
 else
 ifp_dbus_exec_comment = \# "sss_signal" is used to force SSSD monitor to trigger "sssd_ifp" reconnection to dbus
 ifp_dbus_exec_cmd = $(sssdlibexecdir)/sss_signal
 ifp_systemdservice =
-endif
+endif # HAVE_SYSTEMD_UNIT
 
 secdbpath = @secdbpath@
 
@@ -5260,7 +5263,8 @@ edit_cmd = $(SED) \
         -e 's|@prefix[@]|$(prefix)|g' \
         -e 's|@SSSD_USER[@]|$(SSSD_USER)|g' \
         -e 's|@condconfigexists[@]|$(condconfigexists)|g' \
-        -e 's|@additional_caps[@]|$(additional_caps)|g'
+        -e 's|@additional_caps[@]|$(additional_caps)|g' \
+        -e 's|@supplementary_groups[@]|$(supplementary_groups)|g'
 
 replace_script = \
     @rm -f $@ $@.tmp; \

src/monitor/monitor.c

@@ -1977,6 +1977,56 @@ static void monitor_restart_service(struct mt_svc *svc)
     }
 }
 
+#ifdef SSSD_NON_ROOT_USER
+/* returns: -1 on error, 0 - group not set, 1 - group set */
+static int check_supplementary_group(gid_t gid)
+{
+    int ret;
+    int size;
+    gid_t *supp_gids = NULL;
+
+    if (getegid() == gid) {
+        return 1;
+    }
+
+    size = getgroups(0, NULL);
+    if (size == -1) {
+        ret = errno;
+        DEBUG(SSSDBG_TRACE_FUNC, "Getgroups failed! (%d, %s)\n",
+              ret, sss_strerror(ret));
+        return -1;
+    }
+
+    if (size > 0) {
+        supp_gids = talloc_zero_array(NULL, gid_t, size);
+        if (supp_gids == NULL) {
+            DEBUG(SSSDBG_TRACE_FUNC, "Allocation failed!\n");
+            return -1;
+        }
+
+        size = getgroups(size, supp_gids);
+        if (size == -1) {
+            ret = errno;
+            DEBUG(SSSDBG_TRACE_FUNC, "Getgroups failed! (%d, %s)\n",
+                  ret, sss_strerror(ret));
+            talloc_free(supp_gids);
+            return -1;
+        }
+
+        for (int i = 0; i < size; i++) {
+            if (supp_gids[i] == gid) {
+                talloc_free(supp_gids);
+                return 1;
+            }
+        }
+
+        talloc_free(supp_gids);
+    }
+
+    return 0;
+}
+#endif /* SSSD_NON_ROOT_USER */
+
 int main(int argc, const char *argv[])
 {
     int opt;
@@ -2021,6 +2071,51 @@ int main(int argc, const char *argv[])
         POPT_TABLEEND
     };
 
+
+#ifdef SSSD_NON_ROOT_USER
+    /* In case SSSD is built with non-root user support,
+     * a number of files are sssd:sssd owned.
+     * Make sure all processes are added to sssd supplementary
+     * group to avoid the need for CAP_DAC_OVERRIDE / CAP_CHOWN.
+     * Don't bother to check if config says to change uid/gid later.
+     */
+    gid_t sssd_gid = 0;
+    if ((getuid() == 0) || (geteuid() == 0)) {
+        sss_sssd_user_uid_and_gid(NULL, &sssd_gid);
+        ret = check_supplementary_group(sssd_gid);
+        if (ret == -1) {
+            DEBUG(SSSDBG_FATAL_FAILURE, "Can't check supplementary groups\n");
+            return 1;
+        }
+        /* Expected outcome is 'ret == 1' since supplementary group should be set
+           by systemd service description. */
+        if (ret == 0) {
+            /* Probably non-systemd based system or service file was edited,
+               let's try to set group manually. */
+            sss_log(SSS_LOG_WARNING,
+                    "SSSD is built with support of 'run under non-root user' "
+                    "feature but started under 'root'. Trying to add process "
+                    "to SSSD supplementary group.");
+            ret = setgroups(1, &sssd_gid);
+            if (ret != 0) {
+                DEBUG(SSSDBG_CRIT_FAILURE,
+                      "Failed to add process to the sssd supplementary group.\n");
+                sss_log(SSS_LOG_CRIT,
+                        "Failed to add process to the sssd supplementary group. "
+                        "Either run under 'sssd' or make sure that run-under-root "
+                        "main SSSD process has CAP_SETGID.");
+                return 1;
+            }
+        }
+
+        /* And drop CAP_SET_GID capability afterwards. */
+        /* TODO
+         * sss_drop_cap(CAP_SETGID);
+         */
+    }
+#endif /* SSSD_NON_ROOT_USER */
+
+
     /* Set debug level to invalid value so we can decide if -d 0 was used. */
     debug_level = SSSDBG_INVALID;
 

src/responder/nss/nss_private.h

@@ -93,8 +93,6 @@ struct sss_nss_ctx {
     struct sss_mc_ctx *grp_mc_ctx;
     struct sss_mc_ctx *initgr_mc_ctx;
     struct sss_mc_ctx *sid_mc_ctx;
-    uid_t mc_uid;
-    gid_t mc_gid;
 };
 
 struct sss_cmd_table *get_sss_nss_cmds(void);

src/responder/nss/nsssrv.c

@@ -92,7 +92,7 @@ sss_nss_clear_memcache(TALLOC_CTX *mem_ctx,
     }
 
     DEBUG(SSSDBG_TRACE_FUNC, "Clearing memory caches.\n");
-    ret = sss_mmap_cache_reinit(nctx, nctx->mc_uid, nctx->mc_gid,
+    ret = sss_mmap_cache_reinit(nctx, -1, -1,
                                 -1, /* keep current size */
                                 (time_t) memcache_timeout,
                                 &nctx->pwd_mc_ctx);
@@ -102,7 +102,7 @@ sss_nss_clear_memcache(TALLOC_CTX *mem_ctx,
         goto done;
     }
 
-    ret = sss_mmap_cache_reinit(nctx, nctx->mc_uid, nctx->mc_gid,
+    ret = sss_mmap_cache_reinit(nctx, -1, -1,
                                 -1, /* keep current size */
                                 (time_t) memcache_timeout,
                                 &nctx->grp_mc_ctx);
@@ -112,7 +112,7 @@ sss_nss_clear_memcache(TALLOC_CTX *mem_ctx,
         goto done;
     }
 
-    ret = sss_mmap_cache_reinit(nctx, nctx->mc_uid, nctx->mc_gid,
+    ret = sss_mmap_cache_reinit(nctx, -1, -1,
                                 -1, /* keep current size */
                                 (time_t)memcache_timeout,
                                 &nctx->initgr_mc_ctx);
@@ -287,6 +287,10 @@ static int setup_memcaches(struct sss_nss_ctx *nctx)
     int mc_size_group;
     int mc_size_initgroups;
     int mc_size_sid;
+    uid_t uid;
+    gid_t gid;
+
+    sss_sssd_user_uid_and_gid(&uid, &gid);
 
     /* Remove the CLEAR_MC_FLAG file if exists. */
     ret = unlink(SSS_NSS_MCACHE_DIR"/"CLEAR_MC_FLAG);
@@ -361,7 +365,7 @@ static int setup_memcaches(struct sss_nss_ctx *nctx)
     /* Initialize the fast in-memory caches if they were not disabled */
 
     ret = sss_mmap_cache_init(nctx, "passwd",
-                              nctx->mc_uid, nctx->mc_gid,
+                              uid, gid,
                               SSS_MC_PASSWD,
                               mc_size_passwd * SSS_MC_CACHE_SLOTS_PER_MB,
                               (time_t)memcache_timeout,
@@ -373,7 +377,7 @@ static int setup_memcaches(struct sss_nss_ctx *nctx)
     }
 
     ret = sss_mmap_cache_init(nctx, "group",
-                              nctx->mc_uid, nctx->mc_gid,
+                              uid, gid,
                               SSS_MC_GROUP,
                               mc_size_group * SSS_MC_CACHE_SLOTS_PER_MB,
                               (time_t)memcache_timeout,
@@ -385,7 +389,7 @@ static int setup_memcaches(struct sss_nss_ctx *nctx)
     }
 
     ret = sss_mmap_cache_init(nctx, "initgroups",
-                              nctx->mc_uid, nctx->mc_gid,
+                              uid, gid,
                               SSS_MC_INITGROUPS,
                               mc_size_initgroups * SSS_MC_CACHE_SLOTS_PER_MB,
                               (time_t)memcache_timeout,
@@ -397,7 +401,7 @@ static int setup_memcaches(struct sss_nss_ctx *nctx)
     }
 
     ret = sss_mmap_cache_init(nctx, "sid",
-                              nctx->mc_uid, nctx->mc_gid,
+                              uid, gid,
                               SSS_MC_SID,
                               mc_size_sid * SSS_MC_CACHE_SLOTS_PER_MB,
                               (time_t)memcache_timeout,
@@ -441,79 +445,6 @@ sss_nss_register_service_iface(struct sss_nss_ctx *nss_ctx,
     return ret;
 }
 
-static int sssd_supplementary_group(struct sss_nss_ctx *nss_ctx)
-{
-    errno_t ret;
-    int size;
-    gid_t *supp_gids = NULL;
-
-    /*
-     * We explicitly read the IDs of the SSSD user even though the server
-     * receives --uid and --gid by parameters to account for the case where
-     * the SSSD is compiled --with-sssd-user=sssd but the default of the
-     * user option is root (this is what RHEL does)
-     */
-    ret = sss_user_by_name_or_uid(SSSD_USER,
-                                  &nss_ctx->mc_uid,
-                                  &nss_ctx->mc_gid);
-    if (ret != EOK) {
-        DEBUG(SSSDBG_MINOR_FAILURE, "Cannot get info on "SSSD_USER);
-        return ret;
-    }
-
-    if (getgid() == nss_ctx->mc_gid) {
-        DEBUG(SSSDBG_TRACE_FUNC, "Already running as the sssd group\n");
-        return EOK;
-    }
-
-    size = getgroups(0, NULL);
-    if (size == -1) {
-        ret = errno;
-        DEBUG(SSSDBG_CRIT_FAILURE, "Getgroups failed! (%d, %s)\n",
-                                    ret, sss_strerror(ret));
-        return ret;
-    }
-
-    if (size > 0) {
-        supp_gids = talloc_zero_array(NULL, gid_t, size);
-        if (supp_gids == NULL) {
-            DEBUG(SSSDBG_CRIT_FAILURE, "Allocation failed!\n");
-            ret = ENOMEM;
-            goto done;
-        }
-
-        size = getgroups(size, supp_gids);
-        if (size == -1) {
-            ret = errno;
-            DEBUG(SSSDBG_CRIT_FAILURE, "Getgroups failed! (%d, %s)\n",
-                                        ret, sss_strerror(ret));
-            goto done;
-        }
-
-        for (int i = 0; i < size; i++) {
-            if (supp_gids[i] == nss_ctx->mc_gid) {
-                DEBUG(SSSDBG_TRACE_FUNC,
-                      "Already assigned to the SSSD supplementary group\n");
-                ret = EOK;
-                goto done;
-            }
-        }
-    }
-
-    ret = setgroups(1, &nss_ctx->mc_gid);
-    if (ret != EOK) {
-        ret = errno;
-        DEBUG(SSSDBG_OP_FAILURE,
-              "Cannot setgroups [%d]: %s\n", ret, sss_strerror(ret));
-        goto done;
-    }
-
-    ret = EOK;
-done:
-    talloc_free(supp_gids);
-    return ret;
-}
-
 int sss_nss_process_init(TALLOC_CTX *mem_ctx,
                          struct tevent_context *ev,
                          struct confdb_ctx *cdb)
@@ -613,19 +544,6 @@ int sss_nss_process_init(TALLOC_CTX *mem_ctx,
         goto fail;
     }
 
-    /*
-     * Adding the NSS process to the SSSD supplementary group avoids
-     * dac_override AVC messages from SELinux in case sssd_nss runs
-     * as root and tries to write to memcache owned by sssd:sssd
-     */
-    ret = sssd_supplementary_group(nctx);
-    if (ret != EOK) {
-        DEBUG(SSSDBG_MINOR_FAILURE,
-              "Cannot add process to the sssd supplementary group [%d]: %s\n",
-              ret, sss_strerror(ret));
-        goto fail;
-    }
-
     ret = setup_memcaches(nctx);
     if (ret != EOK) {
         goto fail;

src/responder/nss/nsssrv_mmap_cache.c

@@ -1271,6 +1271,7 @@ static errno_t sss_mc_create_file(struct sss_mc_ctx *mc_ctx)
         return ret;
     }
 
+#ifdef SSSD_NON_ROOT_USER
     /* Make sure that the memory cache files are chowned to sssd.sssd even
      * if the nss responder runs as root. This is because the specfile
      * has the ownership recorded as sssd.sssd
@@ -1284,6 +1285,7 @@ static errno_t sss_mc_create_file(struct sss_mc_ctx *mc_ctx)
             return ret;
         }
     }
+#endif /* SSSD_NON_ROOT_USER */
 
     ret = sss_br_lock_file(mc_ctx->fd, 0, 1, retries, t);
     if (ret != EOK) {

src/sysv/systemd/sssd-autofs.service.in

@@ -16,3 +16,4 @@ ExecStart=@libexecdir@/sssd/sssd_autofs ${DEBUG_LOGGER} --socket-activated
 Restart=on-failure
 User=@SSSD_USER@
 Group=@SSSD_USER@
+@supplementary_groups@

src/sysv/systemd/sssd-ifp.service.in

@@ -18,3 +18,4 @@ CapabilityBoundingSet= @additional_caps@
 Restart=on-failure
 User=@SSSD_USER@
 Group=@SSSD_USER@
+@supplementary_groups@

src/sysv/systemd/sssd-kcm.service.in

@@ -15,3 +15,4 @@ ExecStart=@libexecdir@/sssd/sssd_kcm --uid 0 --gid 0 ${DEBUG_LOGGER}
 # ('User=' and 'Group=' defaults to 'root' for system services)
 # 'CapabilityBoundingSet' is used to limit privileges set:
 CapabilityBoundingSet= @additional_caps@ CAP_SETGID CAP_SETUID
+@supplementary_groups@

src/sysv/systemd/sssd-nss.service.in

@@ -16,3 +16,4 @@ Restart=on-failure
 # Currently SSSD NSS service ('sssd_nss') can't be started under 'sssd' user
 # via systemd due to NSS loop when systemd resolves getgrouplist(sssd).
 # Hence 'User=' and 'Group=' aren't set (defaults to root).
+@supplementary_groups@

src/sysv/systemd/sssd-pac.service.in

@@ -16,3 +16,4 @@ ExecStart=@libexecdir@/sssd/sssd_pac ${DEBUG_LOGGER} --socket-activated
 Restart=on-failure
 User=@SSSD_USER@
 Group=@SSSD_USER@
+@supplementary_groups@

src/sysv/systemd/sssd-pam.service.in

@@ -16,3 +16,4 @@ ExecStart=@libexecdir@/sssd/sssd_pam ${DEBUG_LOGGER} --socket-activated
 Restart=on-failure
 User=@SSSD_USER@
 Group=@SSSD_USER@
+@supplementary_groups@

src/sysv/systemd/sssd-ssh.service.in

@@ -16,3 +16,4 @@ ExecStart=@libexecdir@/sssd/sssd_ssh ${DEBUG_LOGGER} --socket-activated
 Restart=on-failure
 User=@SSSD_USER@
 Group=@SSSD_USER@
+@supplementary_groups@

src/sysv/systemd/sssd-sudo.service.in

@@ -16,3 +16,4 @@ ExecStart=@libexecdir@/sssd/sssd_sudo --socket-activated
 Restart=on-failure
 User=@SSSD_USER@
 Group=@SSSD_USER@
+@supplementary_groups@

src/sysv/systemd/sssd.service.in

@@ -19,6 +19,7 @@ PIDFile=@pidpath@/sssd.pid
 # 'CapabilityBoundingSet' is used to limit privileges set:
 CapabilityBoundingSet= @additional_caps@ CAP_CHOWN CAP_KILL CAP_SETGID CAP_SETUID
 Restart=on-abnormal
+@supplementary_groups@
 
 [Install]
 WantedBy=multi-user.target