From: Jeremy Harris <jgh146exb@wizmail.org>
Date: Thu, 12 Dec 2019 23:43:10 +0000 (+0000)
Subject: Fix taint issue with retry records.  Bug 2492
X-Git-Url: https://git.exim.org/users/jgh/exim.git/commitdiff_plain/5fae29d5b430d6a5f58c6c02cdefbbf307e258a9?ds=inline

Fix taint issue with retry records.  Bug 2492
---

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 1cc3d63c8..f9a939d72 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -35,6 +35,10 @@ JH/08 Bug 2491: Use tainted buffers for the transport smtp context.  Previously
 JH/09 Bug 2493: Harden ARC verify against Outlook, whick has been seen to mix
       the ordering of its ARC headers.  This caused a crash.
 
+JH/10 Bug 2492: Use tainted memory for retry record when needed.  Previously when
+      a new record was being constructed with information from the peer, a trap
+      was taken.
+
 
 Exim version 4.93
 -----------------
diff --git a/src/src/retry.c b/src/src/retry.c
index d068f547d..175da216e 100644
--- a/src/src/retry.c
+++ b/src/src/retry.c
@@ -659,7 +659,8 @@ for (int i = 0; i < 3; i++)
         /* Read a retry record from the database or construct a new one.
         Ignore an old one if it is too old since it was last updated. */
 
-        retry_record = dbfn_read(dbm_file, rti->key);
+        retry_record = dbfn_read_with_length(dbm_file, rti->key,
+					      &message_space);
         if (  retry_record
 	   && now - retry_record->time_stamp > retry_data_expire)
           retry_record = NULL;
@@ -675,7 +676,7 @@ for (int i = 0; i < 3; i++)
           retry_record->expired = FALSE;
           retry_record->text[0] = 0;      /* just in case */
           }
-        else message_space = Ustrlen(retry_record->text);
+	else message_space -= sizeof(dbdata_retry);
 
         /* Compute how long this destination has been failing */
 
@@ -806,15 +807,17 @@ for (int i = 0; i < 3; i++)
         if (next_try - now > retry_interval_max)
           next_try = now + retry_interval_max;
 
-        /* If the new message length is greater than the previous one, we
-        have to copy the record first. */
-
-        if (message_length > message_space)
-          {
-          dbdata_retry *newr = store_get(sizeof(dbdata_retry) + message_length, FALSE);
-          memcpy(newr, retry_record, sizeof(dbdata_retry));
-          retry_record = newr;
-          }
+        /* If the new message length is greater than the previous one, we have
+	to copy the record first.  If we're using an old one, the read used
+	tainted memory so we're ok to write into it. */
+
+	if (message_length > message_space)
+	  {
+	  dbdata_retry * newr =
+	    store_get(sizeof(dbdata_retry) + message_length, is_tainted(message));
+	  memcpy(newr, retry_record, sizeof(dbdata_retry));
+	  retry_record = newr;
+	  }
 
         /* Set up the retry record; message_length may be less than the string
         length for very long error strings. */