From dceed8e099c8f9d5606fa7e5a0742fb5e023103b Mon Sep 17 00:00:00 2001 From: Tobias Brunner Date: Tue, 28 Sep 2021 19:38:22 +0200 Subject: [PATCH] cert-cache: Prevent crash due to integer overflow/sign change random() allocates values in the range [0, RAND_MAX], with RAND_MAX usually equaling INT_MAX = 2^31-1. Previously, values between 0 and 31 were added directly to that offset before applying`% CACHE_SIZE` to get an index into the cache array. If the random value was very high, this resulted in an integer overflow and a negative index value and, therefore, an out-of-bounds access of the array and in turn dereferencing invalid pointers when trying to acquire the read lock. This most likely results in a segmentation fault. Fixes: 764e8b2211ce ("reimplemented certificate cache") Fixes: CVE-2021-41991 --- src/libstrongswan/credentials/sets/cert_cache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/libstrongswan/credentials/sets/cert_cache.c b/src/libstrongswan/credentials/sets/cert_cache.c index f1579c60a..ceebb3843 100644 --- a/src/libstrongswan/credentials/sets/cert_cache.c +++ b/src/libstrongswan/credentials/sets/cert_cache.c @@ -151,7 +151,7 @@ static void cache(private_cert_cache_t *this, for (try = 0; try < REPLACE_TRIES; try++) { /* replace a random relation */ - offset = random(); + offset = random() % CACHE_SIZE; for (i = 0; i < CACHE_SIZE; i++) { rel = &this->relations[(i + offset) % CACHE_SIZE];