Commit b484b040 authored by Matt Caswell's avatar Matt Caswell
Browse files

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: default avatarKurt Roeckx <kurt@openssl.org>
parent 726b5e71

crypto/bn/bn.h

+1 −0
Original line number Diff line number Diff line
@@ -934,6 +934,7 @@ void ERR_load_BN_strings(void); 
# define BN_R_ARG2_LT_ARG3                                100

# define BN_R_BAD_RECIPROCAL                              101

# define BN_R_BIGNUM_TOO_LONG                             114

# define BN_R_BITS_TOO_SMALL                              118

# define BN_R_CALLED_WITH_EVEN_MODULUS                    102

# define BN_R_DIV_BY_ZERO                                 103

# define BN_R_ENCODING_ERROR                              104

crypto/bn/bn_err.c

+2 −1
Original line number Diff line number Diff line 
/* crypto/bn/bn_err.c */

/* ====================================================================

 * Copyright (c) 1999-2007 The OpenSSL Project.  All rights reserved.

 * Copyright (c) 1999-2015 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions
@@ -119,6 +119,7 @@ static ERR_STRING_DATA BN_str_reasons[] = { 
    {ERR_REASON(BN_R_ARG2_LT_ARG3), "arg2 lt arg3"},

    {ERR_REASON(BN_R_BAD_RECIPROCAL), "bad reciprocal"},

    {ERR_REASON(BN_R_BIGNUM_TOO_LONG), "bignum too long"},

    {ERR_REASON(BN_R_BITS_TOO_SMALL), "bits too small"},

    {ERR_REASON(BN_R_CALLED_WITH_EVEN_MODULUS), "called with even modulus"},

    {ERR_REASON(BN_R_DIV_BY_ZERO), "div by zero"},

    {ERR_REASON(BN_R_ENCODING_ERROR), "encoding error"},

crypto/bn/bn_rand.c

+6 −1
Original line number Diff line number Diff line
@@ -121,6 +121,11 @@ 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;
@@ -169,7 +174,7 @@ static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom) 
    }

#endif



    if (top != -1) {

    if (top >= 0) {

        if (top) {

            if (bit == 0) {

                buf[0] = 1;

doc/crypto/BN_rand.pod

+2 −1
Original line number Diff line number Diff line
@@ -24,7 +24,8 @@ most significant bit of the random number can be zero. If B<top> is 0, 
it is set to 1, and if B<top> 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<bits> length.  If B<bottom> is true, the

number will be odd.

number will be odd. The value of B<bits> must be zero or greater. If B<bits> is

1 then B<top> 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