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Check for errors in BN_bn2dec()

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If an oversize BIGNUM is presented to BN_bn2dec() it can cause
BN_div_word() to fail and not reduce the value of 't' resulting
in OOB writes to the bn_data buffer and eventually crashing.

Fix by checking return value of BN_div_word() and checking writes
don't overflow buffer.

Thanks to Shi Lei for reporting this bug.

CVE-2016-2182

Reviewed-by: Tim Hudson <tjh@openssl.org>
This commit is contained in:
Dr. Stephen Henson 2016-08-05 14:26:03 +01:00
parent 40c60b0d73
commit 07bed46f33
1 changed files with 7 additions and 1 deletions
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8
crypto/bn/bn_print.c
View file

@ -62,6 +62,7 @@ char *BN_bn2dec(const BIGNUM *a)
char *p;
BIGNUM *t = NULL;
BN_ULONG *bn_data = NULL, *lp;
int bn_data_num;
/*-
* get an upper bound for the length of the decimal integer
@ -71,7 +72,8 @@ char *BN_bn2dec(const BIGNUM *a)
*/
i = BN_num_bits(a) * 3;
num = (i / 10 + i / 1000 + 1) + 1;
bn_data = OPENSSL_malloc((num / BN_DEC_NUM + 1) * sizeof(BN_ULONG));
bn_data_num = num / BN_DEC_NUM + 1;
bn_data = OPENSSL_malloc(bn_data_num * sizeof(BN_ULONG));
buf = OPENSSL_malloc(num + 3);
if ((buf == NULL) || (bn_data == NULL)) {
BNerr(BN_F_BN_BN2DEC, ERR_R_MALLOC_FAILURE);
@ -93,7 +95,11 @@ char *BN_bn2dec(const BIGNUM *a)
i = 0;
while (!BN_is_zero(t)) {
*lp = BN_div_word(t, BN_DEC_CONV);
if (*lp == (BN_ULONG)-1)
goto err;
lp++;
if (lp - bn_data >= bn_data_num)
goto err;
}
lp--;
/*