core: merge branch 'th/getpwuid-cleanup'

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1771

src/core/nm-auth-utils.c

@@ -8,6 +8,7 @@
 #include "nm-auth-utils.h"
 
 #include "libnm-glib-aux/nm-c-list.h"
+#include "libnm-core-intern/nm-core-internal.h"
 #include "nm-setting-connection.h"
 #include "libnm-core-aux-intern/nm-auth-subject.h"
 #include "nm-auth-manager.h"
@@ -603,7 +604,6 @@ gboolean
 nm_auth_is_subject_in_acl(NMConnection *connection, NMAuthSubject *subject, char **out_error_desc)
 {
     NMSettingConnection *s_con;
-    gs_free char        *user = NULL;
     gulong               uid;
 
     g_return_val_if_fail(connection, FALSE);
@@ -621,13 +621,6 @@ nm_auth_is_subject_in_acl(NMConnection *connection, NMAuthSubject *subject, char
     if (0 == uid)
         return TRUE;
 
-    user = nm_utils_uid_to_name(uid);
-    if (!user) {
-        NM_SET_OUT(out_error_desc,
-                   g_strdup_printf("Could not determine username for uid %lu", uid));
-        return FALSE;
-    }
-
     s_con = nm_connection_get_setting_connection(connection);
     if (!s_con) {
         /* This can only happen when called from AddAndActivate, so we know
@@ -637,7 +630,7 @@ nm_auth_is_subject_in_acl(NMConnection *connection, NMAuthSubject *subject, char
     }
 
     /* Match the username returned by the session check to a user in the ACL */
-    if (!nm_setting_connection_permissions_user_allowed(s_con, user)) {
+    if (!nm_setting_connection_permissions_user_allowed_by_uid(s_con, uid)) {
         NM_SET_OUT(out_error_desc,
                    g_strdup_printf("uid %lu has no permission to perform this operation", uid));
         return FALSE;

src/libnm-core-impl/nm-setting-connection.c

@@ -355,19 +355,10 @@ invalid:
     return TRUE;
 }
 
-/**
- * nm_setting_connection_permissions_user_allowed:
- * @setting: the #NMSettingConnection
- * @uname: the user name to check permissions for
- *
- * Checks whether the given username is allowed to view/access this connection.
- *
- * Returns: %TRUE if the requested user is allowed to view this connection,
- * %FALSE if the given user is not allowed to view this connection
- */
-gboolean
-nm_setting_connection_permissions_user_allowed(NMSettingConnection *setting, const char *uname)
+static gboolean
+_permissions_user_allowed(NMSettingConnection *setting, const char *uname, gulong uid)
 {
+    gs_free struct passwd      *pw = NULL;
     NMSettingConnectionPrivate *priv;
     guint                       i;
 
@@ -384,13 +375,52 @@ nm_setting_connection_permissions_user_allowed(NMSettingConnection *setting, con
     for (i = 0; i < priv->permissions->len; i++) {
         const Permission *permission = &nm_g_array_index(priv->permissions, Permission, i);
 
-        if (permission->ptype == PERM_TYPE_USER && nm_streq(permission->item, uname))
+        if (permission->ptype != PERM_TYPE_USER)
+            continue;
+
+        if (!uname) {
+            if (uid != G_MAXULONG) {
+                pw    = nm_getpwuid(uid);
+                uname = nm_passwd_name(pw);
+            }
+            if (!uname)
+                return FALSE;
+        }
+
+        if (nm_streq(permission->item, uname))
             return TRUE;
     }
 
     return FALSE;
 }
 
+/**
+ * nm_setting_connection_permissions_user_allowed:
+ * @setting: the #NMSettingConnection
+ * @uname: the user name to check permissions for
+ *
+ * Checks whether the given username is allowed to view/access this connection.
+ *
+ * Returns: %TRUE if the requested user is allowed to view this connection,
+ * %FALSE if the given user is not allowed to view this connection
+ */
+gboolean
+nm_setting_connection_permissions_user_allowed(NMSettingConnection *setting, const char *uname)
+{
+    g_return_val_if_fail(NM_IS_SETTING_CONNECTION(setting), FALSE);
+    g_return_val_if_fail(uname != NULL, FALSE);
+
+    return _permissions_user_allowed(setting, uname, G_MAXULONG);
+}
+
+gboolean
+nm_setting_connection_permissions_user_allowed_by_uid(NMSettingConnection *setting, gulong uid)
+{
+    g_return_val_if_fail(NM_IS_SETTING_CONNECTION(setting), FALSE);
+
+    return _permissions_user_allowed(setting, NULL, uid);
+}
+
 /**
  * nm_setting_connection_add_permission:
  * @setting: the #NMSettingConnection

src/libnm-core-intern/nm-core-internal.h

@@ -533,6 +533,9 @@ GPtrArray *_nm_setting_bridge_port_get_vlans(NMSettingBridgePort *setting);
 
 GArray *_nm_setting_connection_get_secondaries(NMSettingConnection *setting);
 
+gboolean nm_setting_connection_permissions_user_allowed_by_uid(NMSettingConnection *setting,
+                                                               gulong               uid);
+
 /*****************************************************************************/
 
 NMSettingBluetooth *_nm_connection_get_setting_bluetooth_for_nap(NMConnection *connection);

src/libnm-glib-aux/nm-shared-utils.c

@@ -5771,40 +5771,81 @@ nm_utils_is_specific_hostname(const char *name)
 
 /*****************************************************************************/
 
-/* taken from systemd's uid_to_name(). */
-char *
-nm_utils_uid_to_name(uid_t uid)
-{
-    gs_free char *buf_heap = NULL;
-    char          buf_stack[4096];
-    gsize         bufsize;
-    char         *buf;
+typedef struct {
+    struct passwd pw;
+    _nm_alignas(max_align_t) char buf[];
+} GetPwuidData;
 
-    bufsize = sizeof(buf_stack);
-    buf     = buf_stack;
+/**
+ * nm_getpwuid:
+ * uid: the user Id to look up
+ *
+ * Calls getpwuid_r() to lookup the passwd entry. See the manual.
+ * Allocates and returns a suitable buffer.
+ *
+ * The returned buffer is likely much large than required. You don't want to
+ * keep this buffer around for longer than necessary.
+ *
+ * Returns: (transfer full): the passwd entry, if found or NULL on error
+ *   or if the entry was not found.
+ */
+struct passwd *
+nm_getpwuid(uid_t uid)
+{
+    gs_free GetPwuidData *data = NULL;
+    gsize                 bufsize;
+    const gsize           OFFSET = G_STRUCT_OFFSET(GetPwuidData, buf);
+    long int              size_max;
+
+    size_max = sysconf(_SC_GETPW_R_SIZE_MAX);
+    if (size_max > 0 && ((unsigned long int) size_max < G_MAXSIZE - OFFSET))
+        bufsize = size_max;
+    else
+        bufsize = 4096;
 
     for (;;) {
-        struct passwd  pwbuf;
         struct passwd *pw = NULL;
         int            r;
 
-        r = getpwuid_r(uid, &pwbuf, buf, bufsize, &pw);
-        if (r == 0 && pw)
-            return nm_strdup_not_empty(pw->pw_name);
+        if (bufsize >= G_MAXSIZE - OFFSET)
+            return NULL;
+
+        nm_clear_g_free(&data);
+        data = g_malloc(OFFSET + bufsize);
+
+        r = getpwuid_r(uid, &data->pw, data->buf, bufsize, &pw);
+        if (r == 0) {
+            if (!pw)
+                return NULL;
+            nm_assert(pw == (gpointer) data);
+            return (gpointer) g_steal_pointer(&data);
+        }
 
         if (r != ERANGE)
             return NULL;
 
         if (bufsize > G_MAXSIZE / 2u)
             return NULL;
-
         bufsize *= 2u;
-        g_free(buf_heap);
-        buf_heap = g_malloc(bufsize);
-        buf      = buf_heap;
     }
 }
 
+const char *
+nm_passwd_name(const struct passwd *pw)
+{
+    /* Normalize "pw->pw_name" and return it. */
+    return pw ? nm_str_not_empty(pw->pw_name) : NULL;
+}
+
+char *
+nm_utils_uid_to_name(uid_t uid)
+{
+    gs_free struct passwd *pw = NULL;
+
+    pw = nm_getpwuid(uid);
+    return g_strdup(nm_passwd_name(pw));
+}
+
 /* taken from systemd's nss_user_record_by_name() */
 gboolean
 nm_utils_name_to_uid(const char *name, uid_t *out_uid)

src/libnm-glib-aux/nm-shared-utils.h

@@ -3196,6 +3196,12 @@ gboolean nm_utils_is_localhost(const char *name);
 
 gboolean nm_utils_is_specific_hostname(const char *name);
 
+struct passwd;
+
+struct passwd *nm_getpwuid(uid_t uid);
+
+const char *nm_passwd_name(const struct passwd *pw);
+
 char    *nm_utils_uid_to_name(uid_t uid);
 gboolean nm_utils_name_to_uid(const char *name, uid_t *out_uid);
 

src/libnm-glib-aux/tests/test-shared-general.c

@@ -5,6 +5,8 @@
 
 #include "libnm-glib-aux/nm-default-glib-i18n-prog.h"
 
+#include <pwd.h>
+
 #include "libnm-std-aux/unaligned.h"
 #include "libnm-glib-aux/nm-random-utils.h"
 #include "libnm-glib-aux/nm-str-buf.h"
@@ -2580,6 +2582,40 @@ test_nm_prioq(void)
 
 /*****************************************************************************/
 
+static const char *
+_getpwuid_name(uid_t uid)
+{
+    static struct passwd *pw;
+
+    pw = getpwuid(uid);
+    return pw ? nm_str_not_empty(pw->pw_name) : NULL;
+}
+
+static void
+test_uid_to_name(void)
+{
+    int i;
+
+    for (i = 0; i < 20; i++) {
+        gs_free char          *name = NULL;
+        gs_free struct passwd *pw   = NULL;
+        uid_t                  uid;
+
+        if (i < 5)
+            uid = i;
+        else
+            uid = nmtst_get_rand_uint32() % 2000u;
+
+        name = nm_utils_uid_to_name(uid);
+        g_assert_cmpstr(name, ==, _getpwuid_name(uid));
+
+        pw = nm_getpwuid(uid);
+        g_assert_cmpstr(name, ==, nm_passwd_name(pw));
+    }
+}
+
+/*****************************************************************************/
+
 NMTST_DEFINE();
 
 int
@@ -2630,6 +2666,7 @@ main(int argc, char **argv)
     g_test_add_func("/general/test_garray", test_garray);
     g_test_add_func("/general/test_nm_prioq", test_nm_prioq);
     g_test_add_func("/general/test_nm_random", test_nm_random);
+    g_test_add_func("/general/test_uid_to_name", test_uid_to_name);
 
     return g_test_run();
 }