commit dc210178f916ce4c1b00eb0b4f2c95f9fa06f86d
author Simon Butcher <simon.butcher@arm.com> Wed Feb 01 23:22:18 2017 +0000
committer Simon Butcher <simon.butcher@arm.com> Wed Feb 01 23:22:18 2017 +0000
tree c5bcac1753e25278b342a893547537e6b2640fc2
parent d63adef08192a1c2b086cb2580d727aa1b06c6e2
parent 5718ebf45bbd3350e935cfde6b28c4ee6cc6ff88

Merge branch fix-base64-arithmetic-overflows

Fix potential integer overflows in the function mbedtls_base64_decode().
This overflow would mainly be exploitable in 32-bit systems and could
cause buffer bound checks to be bypassed.

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index d68082b..4c2b1a1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,12 @@
 = mbed TLS 2.x.x branch released xxxx-xx-xx
 
 Bugfix
+   * Fixed potential arithmetic overflow in mbedtls_ctr_drbg_reseed() that could
+     cause buffer bound checks to be bypassed. Found by Eyal Itkin.
+   * Fixed potential arithmetic overflows in mbedtls_cipher_update() that could
+     cause buffer bound checks to be bypassed. Found by Eyal Itkin.
+   * Fixed potential arithmetic overflow in mbedtls_md2_update() that could
+     cause buffer bound checks to be bypassed. Found by Eyal Itkin.
    * Fixed potential arithmetic overflow in mbedtls_base64_decode() that could
      cause buffer bound checks to be bypassed. Found by Eyal Itkin.
 

library/cipher.c

diff --git a/library/cipher.c b/library/cipher.c
index a883438..e9e0b22 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -326,9 +326,9 @@
          * If there is not enough data for a full block, cache it.
          */
         if( ( ctx->operation == MBEDTLS_DECRYPT &&
-                ilen + ctx->unprocessed_len <= block_size ) ||
+                ilen <= block_size - ctx->unprocessed_len ) ||
              ( ctx->operation == MBEDTLS_ENCRYPT &&
-                ilen + ctx->unprocessed_len < block_size ) )
+                ilen < block_size - ctx->unprocessed_len ) )
         {
             memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
                     ilen );

library/ctr_drbg.c

diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index 386f8ad..55612c7 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -290,7 +290,8 @@
     unsigned char seed[MBEDTLS_CTR_DRBG_MAX_SEED_INPUT];
     size_t seedlen = 0;
 
-    if( ctx->entropy_len + len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
+    if( ctx->entropy_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ||
+        len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - ctx->entropy_len )
         return( MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
 
     memset( seed, 0, MBEDTLS_CTR_DRBG_MAX_SEED_INPUT );

library/md2.c

diff --git a/library/md2.c b/library/md2.c
index 8976701..95cbcce 100644
--- a/library/md2.c
+++ b/library/md2.c
@@ -158,7 +158,7 @@
 
     while( ilen > 0 )
     {
-        if( ctx->left + ilen > 16 )
+        if( ilen > 16 - ctx->left )
             fill = 16 - ctx->left;
         else
             fill = ilen;

tests/suites/test_suite_ctr_drbg.function

diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index 3acfb8b..883cfe0 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -39,6 +39,11 @@
     TEST_ASSERT( mbedtls_ctr_drbg_reseed( &ctx, additional,
                         MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + 1 ) ==
                         MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
+
+    mbedtls_ctr_drbg_set_entropy_len( &ctx, ~0 );
+    TEST_ASSERT( mbedtls_ctr_drbg_reseed( &ctx, additional,
+                        MBEDTLS_CTR_DRBG_MAX_SEED_INPUT ) ==
+                        MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG );
 exit:
     mbedtls_ctr_drbg_free( &ctx );
 }