Attachment 7511 Details for Bug 40189

[patch] CVE-2016-0797.patch

CVE-2016-0797.patch (text/plain), 3.89 KB, created by Arvid Requate on 2016-03-01 16:53 CET

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Creator: Arvid Requate

Created: 2016-03-01 16:53 CET

Size: 3.89 KB

patch

obsolete

>commit 8f651326a5cbec5ca7cf0bad0205d4c87dc8c2d0
>Author: Matt Caswell <matt@openssl.org>
>Date:   Mon Feb 22 10:27:18 2016 +0000
>
>    Fix BN_hex2bn/BN_dec2bn NULL ptr/heap corruption
>    
>    In the BN_hex2bn function the number of hex digits is calculated using
>    an int value |i|. Later |bn_expand| is called with a value of |i * 4|.
>    For large values of |i| this can result in |bn_expand| not allocating any
>    memory because |i * 4| is negative. This leaves ret->d as NULL leading
>    to a subsequent NULL ptr deref. For very large values of |i|, the
>    calculation |i * 4| could be a positive value smaller than |i|. In this
>    case memory is allocated to ret->d, but it is insufficiently sized
>    leading to heap corruption. A similar issue exists in BN_dec2bn.
>    
>    This could have security consequences if BN_hex2bn/BN_dec2bn is ever
>    called by user applications with very large untrusted hex/dec data. This is
>    anticipated to be a rare occurrence.
>    
>    All OpenSSL internal usage of this function uses data that is not expected
>    to be untrusted, e.g. config file data or application command line
>    arguments. If user developed applications generate config file data based
>    on untrusted data then it is possible that this could also lead to security
>    consequences. This is also anticipated to be a rare.
>    
>    Issue reported by Guido Vranken.
>    
>    CVE-2016-0797
>    
>    Reviewed-by: Andy Polyakov <appro@openssl.org>
>    (cherry picked from commit c175308407858afff3fc8c2e5e085d94d12edc7d)
>
>diff --git a/crypto/bn/bn.h b/crypto/bn/bn.h
>index 47d8c71..b39258d 100644
>--- a/crypto/bn/bn.h
>+++ b/crypto/bn/bn.h
>@@ -125,6 +125,7 @@
> #ifndef HEADER_BN_H
> # define HEADER_BN_H
> 
>+# include <limits.h>
> # include <openssl/e_os2.h>
> # ifndef OPENSSL_NO_FP_API
> #  include <stdio.h>            /* FILE */
>@@ -739,8 +740,17 @@ const BIGNUM *BN_get0_nist_prime_521(void);
> 
> /* library internal functions */
> 
>-# define bn_expand(a,bits) ((((((bits+BN_BITS2-1))/BN_BITS2)) <= (a)->dmax)?\
>-        (a):bn_expand2((a),(bits+BN_BITS2-1)/BN_BITS2))
>+# define bn_expand(a,bits) \
>+    ( \
>+        bits > (INT_MAX - BN_BITS2 + 1) ? \
>+            NULL \
>+        : \
>+            (((bits+BN_BITS2-1)/BN_BITS2) <= (a)->dmax) ? \
>+                (a) \
>+            : \
>+                bn_expand2((a),(bits+BN_BITS2-1)/BN_BITS2) \
>+    )
>+
> # define bn_wexpand(a,words) (((words) <= (a)->dmax)?(a):bn_expand2((a),(words)))
> BIGNUM *bn_expand2(BIGNUM *a, int words);
> # ifndef OPENSSL_NO_DEPRECATED
>diff --git a/crypto/bn/bn_print.c b/crypto/bn/bn_print.c
>index ab10b95..bfa31ef 100644
>--- a/crypto/bn/bn_print.c
>+++ b/crypto/bn/bn_print.c
>@@ -58,6 +58,7 @@
> 
> #include <stdio.h>
> #include <ctype.h>
>+#include <limits.h>
> #include "cryptlib.h"
> #include <openssl/buffer.h>
> #include "bn_lcl.h"
>@@ -189,7 +190,11 @@ int BN_hex2bn(BIGNUM **bn, const char *a)
>         a++;
>     }
> 
>-    for (i = 0; isxdigit((unsigned char)a[i]); i++) ;
>+    for (i = 0; i <= (INT_MAX/4) && isxdigit((unsigned char)a[i]); i++)
>+        continue;
>+
>+    if (i > INT_MAX/4)
>+        goto err;
> 
>     num = i + neg;
>     if (bn == NULL)
>@@ -204,7 +209,7 @@ int BN_hex2bn(BIGNUM **bn, const char *a)
>         BN_zero(ret);
>     }
> 
>-    /* i is the number of hex digests; */
>+    /* i is the number of hex digits */
>     if (bn_expand(ret, i * 4) == NULL)
>         goto err;
> 
>@@ -260,7 +265,11 @@ int BN_dec2bn(BIGNUM **bn, const char *a)
>         a++;
>     }
> 
>-    for (i = 0; isdigit((unsigned char)a[i]); i++) ;
>+    for (i = 0; i <= (INT_MAX/4) && isdigit((unsigned char)a[i]); i++)
>+        continue;
>+
>+    if (i > INT_MAX/4)
>+        goto err;
> 
>     num = i + neg;
>     if (bn == NULL)
>@@ -278,7 +287,7 @@ int BN_dec2bn(BIGNUM **bn, const char *a)
>         BN_zero(ret);
>     }
> 
>-    /* i is the number of digests, a bit of an over expand; */
>+    /* i is the number of digits, a bit of an over expand */
>     if (bn_expand(ret, i * 4) == NULL)
>         goto err;
>

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