From: Matt Caswell Date: Fri, 1 Jul 2016 10:58:05 +0000 (+0100) Subject: Avoid an overflow in constructing the ServerKeyExchange message X-Git-Tag: OpenSSL_1_0_2i~119 X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=77857ddcca41e1ad34725715fe7b32adc4de7930;p=oweals%2Fopenssl.git Avoid an overflow in constructing the ServerKeyExchange message We calculate the size required for the ServerKeyExchange message and then call BUF_MEM_grow_clean() on the buffer. However we fail to take account of 2 bytes required for the signature algorithm and 2 bytes for the signature length, i.e. we could overflow by 4 bytes. In reality this won't happen because the buffer is pre-allocated to a large size that means it should be big enough anyway. Addresses an OCAP Audit issue. Reviewed-by: Rich Salz --- diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c index 0c43c493ed..299f85b2fb 100644 --- a/ssl/s3_srvr.c +++ b/ssl/s3_srvr.c @@ -1872,6 +1872,11 @@ int ssl3_send_server_key_exchange(SSL *s) goto f_err; } kn = EVP_PKEY_size(pkey); + /* Allow space for signature algorithm */ + if (SSL_USE_SIGALGS(s)) + kn += 2; + /* Allow space for signature length */ + kn += 2; } else { pkey = NULL; kn = 0;