Generalize _ctr_crypt16, so it can be used also for gcm.

ChangeLog

+2018-02-01  Niels Möller  <nisse@lysator.liu.se>
+
+	Based on a patch contributed by Nikos Mavrogiannopoulos.
+	* ctr16.c (_ctr_crypt16): New file, renamed and generalized
+	function. New function pointer argument, used to fill a block with
+	counter values. Use nettle_block16 * as the type for the buffer to
+	be filled. Always process any final and partial block, and return
+	no value.
+	* ctr.c (ctr_crypt): ... previous, replaced, function.
+	(ctr_fill16): Updated to new argument type.
+	(ctr_crypt): Return immediately after using _ctr_crypt16.
+
+	* ctr-internal.h: New file, declaring _ctr_crypt16.
+	(nettle_fill16_func): New function typedef.
+
+	* Makefile.in (nettle_SOURCES): Added ctr16.c.
+	(DISTFILES): Added ctr-internal.h.
+
 2018-01-30  Niels Möller  <nisse@lysator.liu.se>
 
 	* Makefile.in (clean-here): Don't delete desdata.stamp.

Makefile.in

@@ -92,7 +92,7 @@ nettle_SOURCES = aes-decrypt-internal.c aes-decrypt.c \
 		 chacha-crypt.c chacha-core-internal.c \
 		 chacha-poly1305.c chacha-poly1305-meta.c \
 		 chacha-set-key.c chacha-set-nonce.c \
-		 ctr.c des.c des3.c des-compat.c \
+		 ctr.c ctr16.c des.c des3.c des-compat.c \
 		 eax.c eax-aes128.c eax-aes128-meta.c \
 		 gcm.c gcm-aes.c \
 		 gcm-aes128.c gcm-aes128-meta.c \
@@ -225,6 +225,7 @@ DISTFILES = $(SOURCES) $(HEADERS) getopt.h getopt_int.h \
 	aes-internal.h camellia-internal.h serpent-internal.h \
 	cast128_sboxes.h desinfo.h desCode.h \
 	memxor-internal.h nettle-internal.h nettle-write.h \
+	ctr-internal.h \
 	gmp-glue.h ecc-internal.h fat-setup.h \
 	mini-gmp.h asm.m4 \
 	nettle.texinfo nettle.info nettle.html nettle.pdf sha-example.c

ctr-internal.h

+/* ctr-internal.h
+
+   Copyright (C) 2018 Niels Möller
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#ifndef NETTLE_CTR_INTERNAL_H_INCLUDED
+#define NETTLE_CTR_INTERNAL_H_INCLUDED
+
+#include "nettle-types.h"
+
+/* Name mangling */
+#define _ctr_crypt16 _nettle_ctr_crypt16
+
+/* Size limit for temporary stack buffers. */
+#define CTR_BUFFER_LIMIT 512
+
+/* Fill BUFFER (n blocks) with incrementing CTR values. It would be
+   nice if CTR was always 64-bit aligned, but it isn't when called
+   from ctr_crypt. */
+typedef void
+nettle_fill16_func(uint8_t *ctr, size_t n, union nettle_block16 *buffer);
+
+void
+_ctr_crypt16(const void *ctx, nettle_cipher_func *f,
+	     nettle_fill16_func *fill, uint8_t *ctr,
+	     size_t length, uint8_t *dst,
+	     const uint8_t *src);
+
+
+#endif /* NETTLE_CTR_INTERNAL_H_INCLUDED */

ctr.c

@@ -41,13 +41,11 @@
 
 #include "ctr.h"
 
+#include "ctr-internal.h"
 #include "macros.h"
 #include "memxor.h"
 #include "nettle-internal.h"
 
-/* Don't allocate any more space than this on the stack */
-#define CTR_BUFFER_LIMIT 512
-
 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
 
 static size_t
@@ -64,17 +62,19 @@ ctr_fill (size_t block_size, uint8_t *ctr, size_t length, uint8_t *buffer)
 
 #if WORDS_BIGENDIAN
 # define USE_CTR_CRYPT16 1
+static nettle_fill16_func ctr_fill16;
 static void
-ctr_fill16(uint8_t *ctr, size_t blocks, uint64_t *buffer)
+ctr_fill16(uint8_t *ctr, size_t blocks, union nettle_block16 *buffer)
 {
   uint64_t hi, lo;
+  size_t i;
   hi = READ_UINT64(ctr);
   lo = READ_UINT64(ctr + 8);
 
-  while (blocks-- > 0)
+  for (i = 0; i < blocks; i++)
     {
-      *buffer++ = hi;
-      *buffer++ = lo;
+      buffer[i].u64[0] = hi;
+      buffer[i].u64[1] = lo;
       hi += !(++lo);
     }
   WRITE_UINT64(ctr, hi);
@@ -83,18 +83,20 @@ ctr_fill16(uint8_t *ctr, size_t blocks, uint64_t *buffer)
 #else /* !WORDS_BIGENDIAN */
 # if HAVE_BUILTIN_BSWAP64
 #  define USE_CTR_CRYPT16 1
+static nettle_fill16_func ctr_fill16;
 static void
-ctr_fill16(uint8_t *ctr, size_t blocks, uint64_t *buffer)
+ctr_fill16(uint8_t *ctr, size_t blocks, union nettle_block16 *buffer)
 {
   uint64_t hi, lo;
+  size_t i;
   /* Read hi in native endianness */
   hi = LE_READ_UINT64(ctr);
   lo = READ_UINT64(ctr + 8);
 
-  while (blocks-- > 0)
+  for (i = 0; i < blocks; i++)
     {
-      *buffer++ = hi;
-      *buffer++ = __builtin_bswap64(lo);
+      buffer[i].u64[0] = hi;
+      buffer[i].u64[1] = __builtin_bswap64(lo);
       if (!++lo)
 	hi = __builtin_bswap64(__builtin_bswap64(hi) + 1);
     }
@@ -106,53 +108,6 @@ ctr_fill16(uint8_t *ctr, size_t blocks, uint64_t *buffer)
 # endif
 #endif /* !WORDS_BIGENDIAN */
 
-#if USE_CTR_CRYPT16
-static size_t
-ctr_crypt16(const void *ctx, nettle_cipher_func *f,
-	    uint8_t *ctr,
-	    size_t length, uint8_t *dst,
-	    const uint8_t *src)
-{
-  if (dst != src && !((uintptr_t) dst % sizeof(uint64_t)))
-    {
-      size_t blocks = length / 16u;
-      ctr_fill16 (ctr, blocks, (uint64_t *) dst);
-      f(ctx, blocks * 16, dst, dst);
-      memxor (dst, src, blocks * 16);
-      return blocks * 16;
-    }
-  else
-    {
-      /* Construct an aligned buffer of consecutive counter values, of
-	 size at most CTR_BUFFER_LIMIT. */
-      TMP_DECL(buffer, union nettle_block16, CTR_BUFFER_LIMIT / 16);
-      size_t blocks = (length + 15) / 16u;
-      size_t i;
-      TMP_ALLOC(buffer, MIN(blocks, CTR_BUFFER_LIMIT / 16));
-
-      for (i = 0; blocks >= CTR_BUFFER_LIMIT / 16;
-	   i += CTR_BUFFER_LIMIT, blocks -= CTR_BUFFER_LIMIT / 16)
-	{
-	  ctr_fill16 (ctr, CTR_BUFFER_LIMIT / 16, buffer->u64);
-	  f(ctx, CTR_BUFFER_LIMIT, buffer->b, buffer->b);
-	  if (length - i < CTR_BUFFER_LIMIT)
-	    goto done;
-	  memxor3 (dst, src, buffer->b, CTR_BUFFER_LIMIT);
-	}
-
-      if (blocks > 0)
-	{
-	  assert (length - i < CTR_BUFFER_LIMIT);
-	  ctr_fill16 (ctr, blocks, buffer->u64);
-	  f(ctx, blocks * 16, buffer->b, buffer->b);
-	done:
-	  memxor3 (dst + i, src + i, buffer->b, length - i);
-      }
-      return length;
-    }
-}
-#endif /* USE_CTR_CRYPT16 */
-
 void
 ctr_crypt(const void *ctx, nettle_cipher_func *f,
 	  size_t block_size, uint8_t *ctr,
@@ -162,10 +117,8 @@ ctr_crypt(const void *ctx, nettle_cipher_func *f,
 #if USE_CTR_CRYPT16
   if (block_size == 16)
     {
-      size_t done = ctr_crypt16(ctx, f, ctr, length, dst, src);
-      length -= done;
-      src += done;
-      dst += done;
+      _ctr_crypt16(ctx, f, ctr_fill16, ctr, length, dst, src);
+      return;
     }
 #endif
 

ctr16.c

+/* ctr16.c
+
+   Cipher counter mode, optimized for 16-byte blocks.
+
+   Copyright (C) 2005-2018 Niels Möller
+   Copyright (C) 2018 Red Hat, Inc.
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <assert.h>
+
+#include "ctr.h"
+
+#include "ctr-internal.h"
+#include "memxor.h"
+#include "nettle-internal.h"
+
+#define MIN(a,b) (((a) < (b)) ? (a) : (b))
+
+void
+_ctr_crypt16(const void *ctx, nettle_cipher_func *f,
+	     nettle_fill16_func *fill, uint8_t *ctr,
+	     size_t length, uint8_t *dst,
+	     const uint8_t *src)
+{
+  if (dst != src && !((uintptr_t) dst % sizeof(uint64_t)))
+    {
+      size_t blocks = length / 16u;
+      size_t done;
+      fill (ctr, blocks, (union nettle_block16 *) dst);
+
+      done = blocks * 16;
+      f(ctx, done, dst, dst);
+      memxor (dst, src, done);
+
+      length -= done;
+      if (length > 0)
+	{ /* Left-over partial block */
+	  union nettle_block16 block;
+	  dst += done;
+	  src += done;
+	  assert (length < 16);
+	  /* Use fill, to update ctr value in the same way in all cases. */
+	  fill (ctr, 1, &block);
+	  f (ctx, 16, block.b, block.b);
+	  memxor3 (dst, src, block.b, length);
+	}
+    }
+  else
+    {
+      /* Construct an aligned buffer of consecutive counter values, of
+	 size at most CTR_BUFFER_LIMIT. */
+      TMP_DECL(buffer, union nettle_block16, CTR_BUFFER_LIMIT / 16);
+      size_t blocks = (length + 15) / 16u;
+      size_t i;
+      TMP_ALLOC(buffer, MIN(blocks, CTR_BUFFER_LIMIT / 16));
+
+      for (i = 0; blocks >= CTR_BUFFER_LIMIT / 16;
+	   i += CTR_BUFFER_LIMIT, blocks -= CTR_BUFFER_LIMIT / 16)
+	{
+	  fill (ctr, CTR_BUFFER_LIMIT / 16, buffer);
+	  f(ctx, CTR_BUFFER_LIMIT, buffer->b, buffer->b);
+	  if (length - i < CTR_BUFFER_LIMIT)
+	    goto done;
+	  memxor3 (dst, src, buffer->b, CTR_BUFFER_LIMIT);
+	}
+
+      if (blocks > 0)
+	{
+	  assert (length - i < CTR_BUFFER_LIMIT);
+	  fill (ctr, blocks, buffer);
+	  f(ctx, blocks * 16, buffer->b, buffer->b);
+	done:
+	  memxor3 (dst + i, src + i, buffer->b, length - i);
+	}
+    }
+}