From efee575ad464bfb60bf72dcb73f9b51768f4b1a1 Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Tue, 19 May 2015 16:03:02 +0100 Subject: [PATCH] Fix off-by-one in BN_rand If BN_rand is called with |bits| set to 1 and |top| set to 1 then a 1 byte buffer overflow can occur. There are no such instances within the OpenSSL at the moment. Thanks to Mateusz Kocielski (LogicalTrust), Marek Kroemeke, Filip Palian for discovering and reporting this issue. Reviewed-by: Kurt Roeckx --- crypto/bn/bn_rand.c | 7 ++++++- doc/crypto/BN_rand.pod | 3 ++- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/crypto/bn/bn_rand.c b/crypto/bn/bn_rand.c index 4dd3f924a7..2764c8a307 100644 --- a/crypto/bn/bn_rand.c +++ b/crypto/bn/bn_rand.c @@ -122,6 +122,11 @@ static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom) int ret = 0, bit, bytes, mask; time_t tim; + if (bits < 0 || (bits == 1 && top > 0)) { + BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL); + return 0; + } + if (bits == 0) { BN_zero(rnd); return 1; @@ -168,7 +173,7 @@ static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom) } } - if (top != -1) { + if (top >= 0) { if (top) { if (bit == 0) { buf[0] = 1; diff --git a/doc/crypto/BN_rand.pod b/doc/crypto/BN_rand.pod index d6b975ccf6..bd6bc86323 100644 --- a/doc/crypto/BN_rand.pod +++ b/doc/crypto/BN_rand.pod @@ -24,7 +24,8 @@ most significant bit of the random number can be zero. If B is 0, it is set to 1, and if B is 1, the two most significant bits of the number will be set to 1, so that the product of two such random numbers will always have 2*B length. If B is true, the -number will be odd. +number will be odd. The value of B must be zero or greater. If B is +1 then B cannot also be 1. BN_pseudo_rand() does the same, but pseudo-random numbers generated by this function are not necessarily unpredictable. They can be used for -- GitLab