acl-util: beef up add_acls_for_user()

Let's add support for controlling r/w/x bits separetely. This is useful
for using it to control access to directories, where r + x shall be
enabled.

src/coredump/coredump.c

@@ -186,7 +186,7 @@ static int fix_acl(int fd, uid_t uid) {
                 return 0;
 
         /* Make sure normal users can read (but not write or delete) their own coredumps */
-        r = add_acls_for_user(fd, uid);
+        r = fd_add_uid_acl_permission(fd, uid, /* read = */ true, /* write = */ false, /* execute = */ false);
         if (r < 0)
                 return log_error_errno(r, "Failed to adjust ACL of coredump: %m");
 #endif

src/journal/journald-server.c

@@ -256,7 +256,7 @@ static void server_add_acls(JournalFile *f, uid_t uid) {
         if (uid_for_system_journal(uid))
                 return;
 
-        r = add_acls_for_user(f->fd, uid);
+        r = fd_add_uid_acl_permission(f->fd, uid, /* read = */ true, /* write = */ false, /* execute = */ false);
         if (r < 0)
                 log_warning_errno(r, "Failed to set ACL on %s, ignoring: %m", f->path);
 #endif

src/shared/acl-util.c

@@ -378,12 +378,21 @@ int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl) {
         return 0;
 }
 
-int add_acls_for_user(int fd, uid_t uid) {
+int fd_add_uid_acl_permission(
+                int fd,
+                uid_t uid,
+                bool rd,
+                bool wr,
+                bool ex) {
+
         _cleanup_(acl_freep) acl_t acl = NULL;
         acl_permset_t permset;
         acl_entry_t entry;
         int r;
 
+        /* Adds an ACL entry for the specified file to allow the indicated access to the specified
+         * user. Operates purely incrementally. */
+
         assert(fd >= 0);
         assert(uid_is_valid(uid));
 
@@ -399,10 +408,14 @@ int add_acls_for_user(int fd, uid_t uid) {
                         return -errno;
         }
 
-        /* We do not recalculate the mask unconditionally here, so that the fchmod() mask above stays
-         * intact. */
-        if (acl_get_permset(entry, &permset) < 0 ||
-            acl_add_perm(permset, ACL_READ) < 0)
+        if (acl_get_permset(entry, &permset) < 0)
+                return -errno;
+
+        if (rd && acl_add_perm(permset, ACL_READ) < 0)
+                return -errno;
+        if (wr && acl_add_perm(permset, ACL_WRITE) < 0)
+                return -errno;
+        if (ex && acl_add_perm(permset, ACL_EXECUTE) < 0)
                 return -errno;
 
         r = calc_acl_mask_if_needed(&acl);

src/shared/acl-util.h

@@ -15,7 +15,7 @@ int add_base_acls_if_needed(acl_t *acl_p, const char *path);
 int acl_search_groups(const char* path, char ***ret_groups);
 int parse_acl(const char *text, acl_t *acl_access, acl_t *acl_default, bool want_mask);
 int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl);
-int add_acls_for_user(int fd, uid_t uid);
+int fd_add_uid_acl_permission(int fd, uid_t uid, bool rd, bool wr, bool ex);
 
 /* acl_free takes multiple argument types.
  * Multiple cleanup functions are necessary. */

src/test/test-acl-util.c

@@ -41,8 +41,8 @@ static void test_add_acls_for_user(void) {
         } else
                 uid = getuid();
 
-        r = add_acls_for_user(fd, uid);
-        log_info_errno(r, "add_acls_for_user(%d, "UID_FMT"): %m", fd, uid);
+        r = fd_add_uid_acl_permission(fd, uid, true, false, false);
+        log_info_errno(r, "fd_add_uid_acl_permission(%i, "UID_FMT", true, false, false): %m", fd, uid);
         assert_se(r >= 0);
 
         cmd = strjoina("ls -l ", fn);
@@ -53,7 +53,7 @@ static void test_add_acls_for_user(void) {
 
         /* set the acls again */
 
-        r = add_acls_for_user(fd, uid);
+        r = fd_add_uid_acl_permission(fd, uid, true, false, false);
         assert_se(r >= 0);
 
         cmd = strjoina("ls -l ", fn);