sysusers: move various user credential validity checks to src/basic/

This way we can reuse them for validating User=/Group= settings in unit files
(to be added in a later commit).

Also, add some tests for them.

2 files changed, 98 insertions, 0 deletions

diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index e9d668ddfc..122d9a0c7c 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -29,6 +29,7 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <utmp.h>
 
 #include "missing.h"
 #include "alloc-util.h"
@@ -39,6 +40,7 @@
 #include "path-util.h"
 #include "string-util.h"
 #include "user-util.h"
+#include "utf8.h"
 
 bool uid_is_valid(uid_t uid) {
 
@@ -479,3 +481,94 @@ int take_etc_passwd_lock(const char *root) {
 
         return fd;
 }
+
+bool valid_user_group_name(const char *u) {
+        const char *i;
+        long sz;
+
+        /* Checks if the specified name is a valid user/group name. */
+
+        if (isempty(u))
+                return false;
+
+        if (!(u[0] >= 'a' && u[0] <= 'z') &&
+            !(u[0] >= 'A' && u[0] <= 'Z') &&
+            u[0] != '_')
+                return false;
+
+        for (i = u+1; *i; i++) {
+                if (!(*i >= 'a' && *i <= 'z') &&
+                    !(*i >= 'A' && *i <= 'Z') &&
+                    !(*i >= '0' && *i <= '9') &&
+                    *i != '_' &&
+                    *i != '-')
+                        return false;
+        }
+
+        sz = sysconf(_SC_LOGIN_NAME_MAX);
+        assert_se(sz > 0);
+
+        if ((size_t) (i-u) > (size_t) sz)
+                return false;
+
+        if ((size_t) (i-u) > UT_NAMESIZE - 1)
+                return false;
+
+        return true;
+}
+
+bool valid_user_group_name_or_id(const char *u) {
+
+        /* Similar as above, but is also fine with numeric UID/GID specifications, as long as they are in the right
+         * range, and not the invalid user ids. */
+
+        if (isempty(u))
+                return false;
+
+        if (valid_user_group_name(u))
+                return true;
+
+        return parse_uid(u, NULL) >= 0;
+}
+
+bool valid_gecos(const char *d) {
+
+        if (!d)
+                return false;
+
+        if (!utf8_is_valid(d))
+                return false;
+
+        if (string_has_cc(d, NULL))
+                return false;
+
+        /* Colons are used as field separators, and hence not OK */
+        if (strchr(d, ':'))
+                return false;
+
+        return true;
+}
+
+bool valid_home(const char *p) {
+
+        if (isempty(p))
+                return false;
+
+        if (!utf8_is_valid(p))
+                return false;
+
+        if (string_has_cc(p, NULL))
+                return false;
+
+        if (!path_is_absolute(p))
+                return false;
+
+        if (!path_is_safe(p))
+                return false;
+
+        /* Colons are used as field separators, and hence not OK */
+        if (strchr(p, ':'))
+                return false;
+
+        return true;
+}
diff --git a/src/basic/user-util.h b/src/basic/user-util.h
index 8026eca3f4..36f71fb004 100644
--- a/src/basic/user-util.h
+++ b/src/basic/user-util.h
@@ -68,3 +68,8 @@ int take_etc_passwd_lock(const char *root);
 static inline bool userns_supported(void) {
         return access("/proc/self/uid_map", F_OK) >= 0;
 }
+
+bool valid_user_group_name(const char *u);
+bool valid_user_group_name_or_id(const char *u);
+bool valid_gecos(const char *d);
+bool valid_home(const char *p);