Re: incorrect large buffer handling in md5.c/sha1.c/sha256.c/sha512.c

[Paul Eggert]

On 05/18/2012 08:47 AM, Serge Belyshev wrote:

> http://sourceware.org/bugzilla/show_bug.cgi?id=14090

Thanks for the heads-up.  For gnulib I see the bug in
md4.c, md5.c, sha1.c, and sha256.c, so I installed the
following patch.  I don't see a bug in sha512.c, though;
could you please elaborate?  Thanks.

---
 ChangeLog    |   12 ++++++++++++
 lib/md4.c    |    6 +++---
 lib/md5.c    |    6 +++---
 lib/sha1.c   |    6 +++---
 lib/sha256.c |    6 +++---
 5 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index aeb3cf8..fbe9c1d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2012-05-18  Paul Eggert  <address@hidden>
+
+       crypto: fix bug in large buffer handling
+       Problem reported by Serge Belyshev for glibc in
+       <http://sourceware.org/bugzilla/show_bug.cgi?id=14090> and for gnulib in
+       <http://lists.gnu.org/archive/html/bug-gnulib/2012-05/msg00226.html>.
+       * lib/md4.c (md4_process_block):
+       * lib/md5.c (md5_process_block):
+       * lib/sha1.c (sha1_process_block):
+       * lib/sha256.c (sha256_process_block):
+       Don't assume the buffer length is less than 2**32.
+
 2012-05-15  Pádraig Brady  <address@hidden>
 
        fsusage: fix block size returned on older Linux 2.6
diff --git a/lib/md4.c b/lib/md4.c
index 6307b46..3d1c369 100644
--- a/lib/md4.c
+++ b/lib/md4.c
@@ -301,13 +301,13 @@ md4_process_block (const void *buffer, size_t len, struct 
md4_ctx *ctx)
   uint32_t B = ctx->B;
   uint32_t C = ctx->C;
   uint32_t D = ctx->D;
+  uint32_t lolen = len;
 
   /* First increment the byte count.  RFC 1320 specifies the possible
      length of the file up to 2^64 bits.  Here we only compute the
      number of bytes.  Do a double word increment.  */
-  ctx->total[0] += len;
-  if (ctx->total[0] < len)
-    ++ctx->total[1];
+  ctx->total[0] += lolen;
+  ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);
 
   /* Process all bytes in the buffer with 64 bytes in each round of
      the loop.  */
diff --git a/lib/md5.c b/lib/md5.c
index 498ac98..66ede23 100644
--- a/lib/md5.c
+++ b/lib/md5.c
@@ -312,13 +312,13 @@ md5_process_block (const void *buffer, size_t len, struct 
md5_ctx *ctx)
   uint32_t B = ctx->B;
   uint32_t C = ctx->C;
   uint32_t D = ctx->D;
+  uint32_t lolen = len;
 
   /* First increment the byte count.  RFC 1321 specifies the possible
      length of the file up to 2^64 bits.  Here we only compute the
      number of bytes.  Do a double word increment.  */
-  ctx->total[0] += len;
-  if (ctx->total[0] < len)
-    ++ctx->total[1];
+  ctx->total[0] += lolen;
+  ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);
 
   /* Process all bytes in the buffer with 64 bytes in each round of
      the loop.  */
diff --git a/lib/sha1.c b/lib/sha1.c
index 35870ee..db4ab42 100644
--- a/lib/sha1.c
+++ b/lib/sha1.c
@@ -305,13 +305,13 @@ sha1_process_block (const void *buffer, size_t len, 
struct sha1_ctx *ctx)
   uint32_t c = ctx->C;
   uint32_t d = ctx->D;
   uint32_t e = ctx->E;
+  uint32_t lolen = len;
 
   /* First increment the byte count.  RFC 1321 specifies the possible
      length of the file up to 2^64 bits.  Here we only compute the
      number of bytes.  Do a double word increment.  */
-  ctx->total[0] += len;
-  if (ctx->total[0] < len)
-    ++ctx->total[1];
+  ctx->total[0] += lolen;
+  ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);
 
 #define rol(x, n) (((x) << (n)) | ((uint32_t) (x) >> (32 - (n))))
 
diff --git a/lib/sha256.c b/lib/sha256.c
index c1482d3..a8d29da 100644
--- a/lib/sha256.c
+++ b/lib/sha256.c
@@ -454,13 +454,13 @@ sha256_process_block (const void *buffer, size_t len, 
struct sha256_ctx *ctx)
   uint32_t f = ctx->state[5];
   uint32_t g = ctx->state[6];
   uint32_t h = ctx->state[7];
+  uint32_t lolen = len;
 
   /* First increment the byte count.  FIPS PUB 180-2 specifies the possible
      length of the file up to 2^64 bits.  Here we only compute the
      number of bytes.  Do a double word increment.  */
-  ctx->total[0] += len;
-  if (ctx->total[0] < len)
-    ++ctx->total[1];
+  ctx->total[0] += lolen;
+  ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);
 
 #define rol(x, n) (((x) << (n)) | ((x) >> (32 - (n))))
 #define S0(x) (rol(x,25)^rol(x,14)^(x>>3))
-- 
1.7.6.5