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Fix potential overflow in base64_encode

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Manuel Pégourié-Gonnard 2015-09-30 16:30:28 +02:00
parent 50a739f8c3
commit 0aa45c209a
3 changed files with 16 additions and 5 deletions
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7
ChangeLog
View File

@ -2,6 +2,13 @@ mbed TLS ChangeLog (Sorted per branch, date)
= mbed TLS 2.1.1 released 2015-09-17 = mbed TLS 2.1.1 released 2015-09-17
Security
* Fix possible heap buffer overflow in base64_encoded() when the input
buffer is 512MB or larger on 32-bit platforms.
Found by Guido Vranken. Not trigerrable remotely in TLS.
= mbed TLS 2.1.1 released 2015-09-17
Security Security
* Add countermeasure against Lenstra's RSA-CRT attack for PKCS#1 v1.5 * Add countermeasure against Lenstra's RSA-CRT attack for PKCS#1 v1.5
signatures. (Found by Florian Weimer, Red Hat.) signatures. (Found by Florian Weimer, Red Hat.)

3
include/mbedtls/base64.h
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@ -24,6 +24,7 @@
#define MBEDTLS_BASE64_H #define MBEDTLS_BASE64_H
#include <stddef.h> #include <stddef.h>
#include <limits.h>
#define MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL -0x002A /**< Output buffer too small. */ #define MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL -0x002A /**< Output buffer too small. */
#define MBEDTLS_ERR_BASE64_INVALID_CHARACTER -0x002C /**< Invalid character in input. */ #define MBEDTLS_ERR_BASE64_INVALID_CHARACTER -0x002C /**< Invalid character in input. */
@ -44,6 +45,8 @@ extern "C" {
* \return 0 if successful, or MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL. * \return 0 if successful, or MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL.
* *olen is always updated to reflect the amount * *olen is always updated to reflect the amount
* of data that has (or would have) been written. * of data that has (or would have) been written.
* If that length cannot be represented, then no data is
* written to the buffer and *olen is set to SIZE_T_MAX.
* *
* \note Call this function with dlen = 0 to obtain the * \note Call this function with dlen = 0 to obtain the
* required buffer size in *olen * required buffer size in *olen

11
library/base64.c
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@ -85,15 +85,16 @@ int mbedtls_base64_encode( unsigned char *dst, size_t dlen, size_t *olen,
return( 0 ); return( 0 );
} }
n = ( slen << 3 ) / 6; n = slen / 3 + ( slen % 3 != 0 );
switch( ( slen << 3 ) - ( n * 6 ) ) if( n > ( SIZE_T_MAX - 1 ) / 4 )
{ {
case 2: n += 3; break; *olen = SIZE_T_MAX;
case 4: n += 2; break; return( MBEDTLS_ERR_BASE64_BUFFER_TOO_SMALL );
default: break;
} }
n *= 4;
if( dlen < n + 1 ) if( dlen < n + 1 )
{ {
*olen = n + 1; *olen = n + 1;