From: Fabian Groffen <grobian@gentoo.org>
Date: Tue, 10 Dec 2019 17:32:12 +0000 (+0000)
Subject: PAM: fix crash in the pam expansion condition.  Bug 2489
X-Git-Url: https://git.exim.org/users/heiko/exim.git/commitdiff_plain/dcbfbadac2f557dc73bbcf2b26aadf50f8414ca1?ds=sidebyside

PAM: fix crash in the pam expansion condition.  Bug 2489

Broken-by: f3ebb786e4
---

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 9f8775f0f..6a06e440f 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -24,6 +24,10 @@ JH/05 Regard command-line receipients as tainted.
 
 JH/06 Bug 340: Remove the daemon pid file on exit, whe due to SIGTERM.
 
+JH/07 Bug 2489: Fix crash in the "pam" expansion condition.  It seems that the
+      PAM library frees one of the arguments given to it, despite the
+      documentation.  Therefore a plain malloc must be used.
+
 
 Exim version 4.93
 -----------------
diff --git a/src/src/auths/call_pam.c b/src/src/auths/call_pam.c
index 9a46b6b63..c96e146d1 100644
--- a/src/src/auths/call_pam.c
+++ b/src/src/auths/call_pam.c
@@ -69,9 +69,11 @@ pam_converse (int num_msg, PAM_CONVERSE_ARG2_TYPE **msg,
 int sep = 0;
 struct pam_response *reply;
 
-if (pam_arg_ended) return PAM_CONV_ERR;
+/* It seems that PAM frees reply[] */
 
-reply = store_get(sizeof(struct pam_response) * num_msg, FALSE);
+if (  pam_arg_ended
+   || !(reply = malloc(sizeof(struct pam_response) * num_msg)))
+  return PAM_CONV_ERR;
 
 for (int i = 0; i < num_msg; i++)
   {
@@ -80,25 +82,26 @@ for (int i = 0; i < num_msg; i++)
     {
     case PAM_PROMPT_ECHO_ON:
     case PAM_PROMPT_ECHO_OFF:
-    arg = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
-    if (arg == NULL)
-      {
-      arg = US"";
-      pam_arg_ended = TRUE;
-      }
-    reply[i].resp = CS string_copy_perm(arg, FALSE); /* PAM frees resp */
-    reply[i].resp_retcode = PAM_SUCCESS;
-    break;
+      arg = string_nextinlist(&pam_args, &sep, big_buffer, big_buffer_size);
+      if (!arg)
+	{
+	arg = US"";
+	pam_arg_ended = TRUE;
+	}
+      reply[i].resp = CS string_copy_malloc(arg); /* PAM frees resp */
+      reply[i].resp_retcode = PAM_SUCCESS;
+      break;
 
     case PAM_TEXT_INFO:    /* Just acknowledge messages */
     case PAM_ERROR_MSG:
-    reply[i].resp_retcode = PAM_SUCCESS;
-    reply[i].resp = NULL;
-    break;
+      reply[i].resp_retcode = PAM_SUCCESS;
+      reply[i].resp = NULL;
+      break;
 
     default:  /* Must be an error of some sort... */
-    pam_conv_had_error = TRUE;
-    return PAM_CONV_ERR;
+      free(reply);
+      pam_conv_had_error = TRUE;
+      return PAM_CONV_ERR;
     }
   }