master: Require auth source and destination processes to use different UIDs.

--HG--
branch : HEAD

diff --git a/src/master/service-process.c b/src/master/service-process.c
index 465b6b5128c7a52d51c43fa3b9c8b3994a4b1f51..63687334377376962514a2b1881dea99ceecca90 100644 (file)
--- a/src/master/service-process.c
+++ b/src/master/service-process.c
@@ -155,14 +155,31 @@ service_dup_fds(struct service *service, int auth_fd, int std_fd,
        env_put(t_strdup_printf("SSL_SOCKET_COUNT=%d", ssl_socket_count));
 }
 
-static void validate_uid_gid(struct master_settings *set, uid_t uid, gid_t gid,
-                            const char *user)
+static void
+validate_uid_gid(struct master_settings *set,
+                uid_t uid, gid_t gid, const char *user,
+                const struct service_process_auth_request *request)
 {
+       struct service_process *request_process =
+               request == NULL ? NULL : &request->process->process;
+
        if (uid == 0) {
                i_fatal("User %s not allowed to log in using UNIX UID 0 "
                        "(root logins are never allowed)", user);
        }
 
+       if (request != NULL && request_process->service->uid == uid &&
+           master_uid != uid) {
+               struct passwd *pw;
+
+               pw = getpwuid(uid);
+               i_fatal("User %s not allowed to log in using %s's "
+                       "UNIX UID %s%s (see http://wiki.dovecot.org/UserIds)",
+                       user, request_process->service->set->name,
+                       dec2str(uid), pw == NULL ? "" :
+                       t_strdup_printf("(%s)", pw->pw_name));
+       }
+
        if (uid < (uid_t)set->first_valid_uid ||
            (set->last_valid_uid != 0 && uid > (uid_t)set->last_valid_uid)) {
                struct passwd *pw;
@@ -315,8 +332,9 @@ static void chdir_to_home(const struct restrict_access_settings *rset,
        }
 }
 
-static void drop_privileges(struct service *service,
-                           const char *const *auth_args)
+static void
+drop_privileges(struct service *service, const char *const *auth_args,
+               const struct service_process_auth_request *request)
 {
        struct master_settings *master_set = service->set->master_set;
        struct restrict_access_settings rset;
@@ -351,7 +369,8 @@ static void drop_privileges(struct service *service,
                auth_success_write();
                auth_args_apply(auth_args + 1, &rset, &home);
 
-               validate_uid_gid(master_set, rset.uid, rset.gid, user);
+               validate_uid_gid(master_set, rset.uid, rset.gid, user,
+                                request);
        }
 
        if (home != NULL)
@@ -495,7 +514,7 @@ service_process_create(struct service *service, const char *const *auth_args,
                handle_request(request);
                service_dup_fds(service, fd[1], request == NULL ? -1 :
                                request->fd, auth_args != NULL);
-               drop_privileges(service, auth_args);
+               drop_privileges(service, auth_args, request);
                process_exec(service->executable, NULL);
        }