Merge pull request #4989 from poettering/nss-einval

nss user/group name validation fixes

3 files changed, 25 insertions, 25 deletions

diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index 938533d2e7..c619dad527 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -46,6 +46,8 @@
 
 bool uid_is_valid(uid_t uid) {
 
+        /* Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, 3.436. */
+
         /* Some libc APIs use UID_INVALID as special placeholder */
         if (uid == (uid_t) UINT32_C(0xFFFFFFFF))
                 return false;
@@ -519,7 +521,15 @@ bool valid_user_group_name(const char *u) {
         const char *i;
         long sz;
 
-        /* Checks if the specified name is a valid user/group name. */
+        /* Checks if the specified name is a valid user/group name. Also see POSIX IEEE Std 1003.1-2008, 2016 Edition,
+         * 3.437. We are a bit stricter here however. Specifically we deviate from POSIX rules:
+         *
+         * - We don't allow any dots (this would break chown syntax which permits dots as user/group name separator)
+         * - We require that names fit into the appropriate utmp field
+         * - We don't allow empty user names
+         *
+         * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters.
+         */
 
         if (isempty(u))
                 return false;
diff --git a/src/nss-mymachines/nss-mymachines.c b/src/nss-mymachines/nss-mymachines.c
index 895f61c462..fac37faea5 100644
--- a/src/nss-mymachines/nss-mymachines.c
+++ b/src/nss-mymachines/nss-mymachines.c
@@ -512,10 +512,8 @@ enum nss_status _nss_mymachines_getpwuid_r(
 
         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
 
-        if (!uid_is_valid(uid)) {
-                r = -EINVAL;
-                goto fail;
-        }
+        if (!uid_is_valid(uid))
+                goto not_found;
 
         /* We consider all uids < 65536 host uids */
         if (uid < HOST_UID_LIMIT)
@@ -686,10 +684,8 @@ enum nss_status _nss_mymachines_getgrgid_r(
 
         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
 
-        if (!gid_is_valid(gid)) {
-                r = -EINVAL;
-                goto fail;
-        }
+        if (!gid_is_valid(gid))
+                goto not_found;
 
         /* We consider all gids < 65536 host gids */
         if (gid < HOST_GID_LIMIT)
diff --git a/src/nss-systemd/nss-systemd.c b/src/nss-systemd/nss-systemd.c
index c80972742b..fd5064c937 100644
--- a/src/nss-systemd/nss-systemd.c
+++ b/src/nss-systemd/nss-systemd.c
@@ -123,10 +123,10 @@ enum nss_status _nss_systemd_getpwnam_r(
         assert(name);
         assert(pwd);
 
-        if (!valid_user_group_name(name)) {
-                r = -EINVAL;
-                goto fail;
-        }
+        /* If the username is not valid, then we don't know it. Ideally libc would filter these for us anyway. We don't
+         * generate EINVAL here, because it isn't really out business to complain about invalid user names. */
+        if (!valid_user_group_name(name))
+                goto not_found;
 
         /* Synthesize entries for the root and nobody users, in case they are missing in /etc/passwd */
         if (streq(name, root_passwd.pw_name)) {
@@ -227,10 +227,8 @@ enum nss_status _nss_systemd_getpwuid_r(
 
         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
 
-        if (!uid_is_valid(uid)) {
-                r = -EINVAL;
-                goto fail;
-        }
+        if (!uid_is_valid(uid))
+                goto not_found;
 
         /* Synthesize data for the root user and for nobody in case they are missing from /etc/passwd */
         if (uid == root_passwd.pw_uid) {
@@ -329,10 +327,8 @@ enum nss_status _nss_systemd_getgrnam_r(
         assert(name);
         assert(gr);
 
-        if (!valid_user_group_name(name)) {
-                r = -EINVAL;
-                goto fail;
-        }
+        if (!valid_user_group_name(name))
+                goto not_found;
 
         /* Synthesize records for root and nobody, in case they are missing form /etc/group */
         if (streq(name, root_group.gr_name)) {
@@ -430,10 +426,8 @@ enum nss_status _nss_systemd_getgrgid_r(
 
         BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
 
-        if (!gid_is_valid(gid)) {
-                r = -EINVAL;
-                goto fail;
-        }
+        if (!gid_is_valid(gid))
+                goto not_found;
 
         /* Synthesize records for root and nobody, in case they are missing from /etc/group */
         if (gid == root_group.gr_gid) {