From: Heiko Schlittermann (HS12-RIPE) <hs@schlittermann.de>
Date: Mon, 29 Mar 2021 21:05:58 +0000 (+0200)
Subject: CVE-2020-28017: Integer overflow in receive_add_recipient()
X-Git-Tag: exim-4.94.1~17
X-Git-Url: https://git.exim.org/exim.git/commitdiff_plain/605716b999a4ca6c7d5777ab7463058e9b055dc2

CVE-2020-28017: Integer overflow in receive_add_recipient()

Based on Phil Pennock's commit e3b441f7.

(cherry picked from commit 18a19e18242edc5ab2082fa9c41cd6210d1b6087)
---

diff --git a/src/src/receive.c b/src/src/receive.c
index 5c6420286..cf3ef4b96 100644
--- a/src/src/receive.c
+++ b/src/src/receive.c
@@ -485,18 +485,18 @@ Returns:      nothing
 void
 receive_add_recipient(uschar *recipient, int pno)
 {
-/* XXX This is a math limit; we should consider a performance/sanity limit too. */
-const int safe_recipients_limit = INT_MAX / sizeof(recipient_item) - 1;
-
 if (recipients_count >= recipients_list_max)
   {
   recipient_item *oldlist = recipients_list;
   int oldmax = recipients_list_max;
-  recipients_list_max = recipients_list_max ? 2*recipients_list_max : 50;
-  if ((recipients_list_max >= safe_recipients_limit) || (recipients_list_max < 0))
+
+  const int safe_recipients_limit = INT_MAX / 2 / sizeof(recipient_item);
+  if (recipients_list_max < 0 || recipients_list_max >= safe_recipients_limit)
     {
-    log_write(0, LOG_MAIN|LOG_PANIC, "Too many recipients needed: %d not satisfiable", recipients_list_max);
+    log_write(0, LOG_MAIN|LOG_PANIC_DIE, "Too many recipients: %d", recipients_list_max);
     }
+
+  recipients_list_max = recipients_list_max ? 2*recipients_list_max : 50;
   recipients_list = store_get(recipients_list_max * sizeof(recipient_item), FALSE);
   if (oldlist != NULL)
     memcpy(recipients_list, oldlist, oldmax * sizeof(recipient_item));