agent: don't skip PAM setup outside of tests

We need the PAM setup to initialize environment for user session,
even if we do not actually change the user. Keep the simplified
behaviour to tests.

agent/qrexec-agent.c

@@ -164,12 +164,19 @@ void do_exec(char *cmd)
     signal(SIGCHLD, SIG_DFL);
     signal(SIGPIPE, SIG_DFL);
 
-    pw = getpwuid(geteuid());
-    if (!pw) {
-        perror("getpwuid");
-        exit(1);
-    }
-    if (!strcmp(pw->pw_name, user)) {
+    if (geteuid() != 0) {
+        /* We're not root, assume this is a testing environment. */
+
+        pw = getpwuid(geteuid());
+        if (!pw) {
+            perror("getpwuid");
+            exit(1);
+        }
+        if (strcmp(pw->pw_name, user)) {
+            fprintf(stderr, "requested user %s, but qrexec-agent is running as user %s\n",
+                    user, pw->pw_name);
+            exit(1);
+        }
         /* call QUBESRPC if requested */
         exec_qubes_rpc_if_requested(realcmd, environ);