Add new options to override shell value

https://fedorahosted.org/sssd/ticket/742

3 files changed, 123 insertions, 1 deletions

diff --git a/src/responder/nss/nsssrv.c b/src/responder/nss/nsssrv.c
index a5323bd7..b9d548e4 100644
--- a/src/responder/nss/nsssrv.c
+++ b/src/responder/nss/nsssrv.c
@@ -48,6 +48,9 @@
 
 #define DEFAULT_PWFIELD "*"
 
+#define SHELL_REALLOC_INCREMENT 5
+#define SHELL_REALLOC_MAX       50
+
 struct sbus_method monitor_nss_methods[] = {
     { MON_CLI_METHOD_PING, monitor_common_pong },
     { MON_CLI_METHOD_RES_INIT, monitor_common_res_init },
@@ -63,6 +66,71 @@ struct sbus_interface monitor_nss_interface = {
     NULL
 };
 
+static errno_t nss_get_etc_shells(TALLOC_CTX *mem_ctx, char ***_shells)
+{
+    int i = 0;
+    char *sh;
+    char **shells = NULL;
+    TALLOC_CTX *tmp_ctx;
+    errno_t ret;
+    int size;
+
+    tmp_ctx = talloc_new(NULL);
+    if (!tmp_ctx) return ENOMEM;
+
+    shells = talloc_array(tmp_ctx, char *, SHELL_REALLOC_INCREMENT);
+    if (!shells) {
+        ret = ENOMEM;
+        goto done;
+    }
+    size = SHELL_REALLOC_INCREMENT;
+
+    setusershell();
+    while ((sh = getusershell())) {
+        shells[i] = talloc_strdup(shells, sh);
+        if (!shells[i]) {
+            endusershell();
+            ret = ENOMEM;
+            goto done;
+        }
+        DEBUG(6, ("Found shell %s in /etc/shells\n", shells[i]));
+        i++;
+
+        if (i == size) {
+            size += SHELL_REALLOC_INCREMENT;
+            if (size > SHELL_REALLOC_MAX) {
+                DEBUG(0, ("Reached maximum number of shells [%d]. "
+                          "Users may be denied access. "
+                          "Please check /etc/shells for sanity\n",
+                          SHELL_REALLOC_MAX));
+                break;
+            }
+            shells = talloc_realloc(NULL, shells, char *,
+                                    size);
+            if (!shells) {
+                ret = ENOMEM;
+                goto done;
+            }
+        }
+    }
+    endusershell();
+
+    if (i + 1 < size) {
+        shells = talloc_realloc(NULL, shells, char *, i + 1);
+        if (!shells) {
+            ret = ENOMEM;
+            goto done;
+        }
+    }
+    shells[i] = NULL;
+
+    *_shells = talloc_move(mem_ctx, &shells);
+    ret = EOK;
+done:
+    talloc_zfree(tmp_ctx);
+    return ret;
+}
+
 static int nss_get_config(struct nss_ctx *nctx,
                           struct resp_ctx *rctx,
                           struct confdb_ctx *cdb)
@@ -115,6 +183,20 @@ static int nss_get_config(struct nss_ctx *nctx,
                             &nctx->override_homedir);
     if (ret != EOK) goto done;
 
+    ret = confdb_get_string_as_list(cdb, nctx, CONFDB_NSS_CONF_ENTRY,
+                                    CONFDB_NSS_ALLOWED_SHELL,
+                                    &nctx->allowed_shells);
+    if (ret != EOK && ret != ENOENT) goto done;
+
+    ret = nss_get_etc_shells(nctx, &nctx->etc_shells);
+    if (ret != EOK) goto done;
+
+    ret = confdb_get_string(cdb, nctx, CONFDB_NSS_CONF_ENTRY,
+                            CONFDB_NSS_SHELL_FALLBACK,
+                            CONFDB_DEFAULT_SHELL_FALLBACK,
+                            &nctx->shell_fallback);
+    if (ret != EOK) goto done;
+
     ret = 0;
 done:
     talloc_free(tmpctx);
diff --git a/src/responder/nss/nsssrv.h b/src/responder/nss/nsssrv.h
index e3e774f9..f9aff566 100644
--- a/src/responder/nss/nsssrv.h
+++ b/src/responder/nss/nsssrv.h
@@ -59,6 +59,9 @@ struct nss_ctx {
     char *pwfield;
 
     char *override_homedir;
+    char **allowed_shells;
+    char **etc_shells;
+    char *shell_fallback;
 };
 
 struct nss_packet;
diff --git a/src/responder/nss/nsssrv_cmd.c b/src/responder/nss/nsssrv_cmd.c
index 4386da71..e698b5ec 100644
--- a/src/responder/nss/nsssrv_cmd.c
+++ b/src/responder/nss/nsssrv_cmd.c
@@ -305,6 +305,43 @@ static const char *get_homedir_override(TALLOC_CTX *mem_ctx,
             ldb_msg_find_attr_as_string(msg, SYSDB_HOMEDIR, NULL));
 }
 
+static const char *get_shell_override(TALLOC_CTX *mem_ctx,
+                                      struct ldb_message *msg,
+                                      struct nss_ctx *nctx)
+{
+    const char *user_shell;
+    int i;
+
+    user_shell = ldb_msg_find_attr_as_string(msg, SYSDB_SHELL, NULL);
+    if (!user_shell) return NULL;
+    if (!nctx->allowed_shells) return talloc_strdup(mem_ctx, user_shell);
+
+    for (i=0; nctx->etc_shells[i]; i++) {
+        if (strcmp(user_shell, nctx->etc_shells[i]) == 0) {
+            DEBUG(9, ("Shell %s found in /etc/shells\n",
+                      nctx->etc_shells[i]));
+            break;
+        }
+    }
+
+    if (nctx->etc_shells[i]) {
+        DEBUG(9, ("Using original shell '%s'\n", user_shell));
+        return talloc_strdup(mem_ctx, user_shell);
+    }
+
+    for (i=0; nctx->allowed_shells[i]; i++) {
+        if (strcmp(nctx->allowed_shells[i], user_shell) == 0) {
+            DEBUG(5, ("The shell '%s' is allowed but does not exist. "
+                      "Using fallback\n", user_shell));
+            return talloc_strdup(mem_ctx, nctx->shell_fallback);
+        }
+    }
+
+    DEBUG(5, ("The shell '%s' is not allowed and does not exist.\n",
+              user_shell));
+    return talloc_strdup(mem_ctx, NOLOGIN_SHELL);
+}
+
 static int fill_pwent(struct sss_packet *packet,
                       struct sss_domain_info *dom,
                       struct nss_ctx *nctx,
@@ -373,7 +410,7 @@ static int fill_pwent(struct sss_packet *packet,
 
         gecos = ldb_msg_find_attr_as_string(msg, SYSDB_GECOS, NULL);
         homedir = get_homedir_override(tmp_ctx, msg, nctx, dom, name, uid);
-        shell = ldb_msg_find_attr_as_string(msg, SYSDB_SHELL, NULL);
+        shell = get_shell_override(tmp_ctx, msg, nctx);
 
         if (!gecos) gecos = "";
         if (!homedir) homedir = "/";