From 5987d0dfe88ee6081b72857bc8085c7d2afd53a3 Mon Sep 17 00:00:00 2001 From: Qualys Security Advisory Date: Sun, 21 Feb 2021 19:17:32 -0800 Subject: [PATCH 04/29] CVE-2020-28010: Heap out-of-bounds write in main() Based on Phil Pennock's commit 0f57feb4. --- src/exim.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/src/exim.c b/src/exim.c index 83b5ef51f..a7dc48c4e 100644 --- a/src/exim.c +++ b/src/exim.c @@ -3664,6 +3664,9 @@ during readconf_main() some expansion takes place already. */ /* Store the initial cwd before we change directories. Can be NULL if the dir has already been unlinked. */ initial_cwd = os_getcwd(NULL, 0); +if (initial_cwd && strlen(CCS initial_cwd) >= BIG_BUFFER_SIZE) { + exim_fail("exim: initial cwd is far too long\n"); +} /* checking: -be[m] expansion test - @@ -3950,11 +3953,9 @@ if ( (debug_selector & D_any || LOGGING(arguments)) p += 13; else { - Ustrncpy(p + 4, initial_cwd, big_buffer_size-5); - p += 4 + Ustrlen(initial_cwd); - /* in case p is near the end and we don't provide enough space for - * string_format to be willing to write. */ - *p = '\0'; + p += 4; + snprintf(CS p, big_buffer_size - (p - big_buffer), "%s", CCS initial_cwd); + p += strlen(CCS p); } (void)string_format(p, big_buffer_size - (p - big_buffer), " %d args:", argc); -- 2.30.2