Add ChaCha20 stream cipher

* cipher/Makefile.am: Add 'chacha20.c'.
* cipher/chacha20.c: New.
* cipher/cipher.c (cipher_list): Add ChaCha20.
* configure.ac: Add ChaCha20.
* doc/gcrypt.texi: Add ChaCha20.
* src/cipher.h (_gcry_cipher_spec_chacha20): New.
* src/gcrypt.h.in (GCRY_CIPHER_CHACHA20): Add new algo.
* tests/basic.c (MAX_DATA_LEN): Increase to 128 from 100.
(check_stream_cipher): Add ChaCha20 test-vectors.
(check_ciphers): Add ChaCha20.
--

Patch adds Bernstein's ChaCha20 cipher to libgcrypt. Implementation is based
on public domain implementations.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>

1 files changed, 504 insertions, 0 deletions

diff --git a/cipher/chacha20.c b/cipher/chacha20.c
new file mode 100644
index 00000000..ff0366d3
--- /dev/null
+++ b/cipher/chacha20.c
@@ -0,0 +1,504 @@
+/* chacha20.c  -  Bernstein's ChaCha20 cipher
+ * Copyright (C) 2014 Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser general Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * Libgcrypt 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * For a description of the algorithm, see:
+ *   http://cr.yp.to/chacha.html
+ */
+
+/* The code is based on salsa20.c and public-domain ChaCha implementations:
+ *  chacha-ref.c version 20080118
+ *  D. J. Bernstein
+ *  Public domain.
+ * and
+ *  Andrew Moon
+ *  https://github.com/floodyberry/chacha-opt
+ */
+
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "types.h"
+#include "g10lib.h"
+#include "cipher.h"
+#include "bufhelp.h"
+
+
+#define CHACHA20_MIN_KEY_SIZE 16        /* Bytes.  */
+#define CHACHA20_MAX_KEY_SIZE 32        /* Bytes.  */
+#define CHACHA20_BLOCK_SIZE   64        /* Bytes.  */
+#define CHACHA20_MIN_IV_SIZE   8        /* Bytes.  */
+#define CHACHA20_MAX_IV_SIZE  12        /* Bytes.  */
+#define CHACHA20_INPUT_LENGTH (CHACHA20_BLOCK_SIZE / 4)
+
+
+struct CHACHA20_context_s;
+
+
+typedef unsigned int (* chacha20_blocks_t)(u32 *state, const byte *src,
+                                           byte *dst, size_t bytes);
+
+typedef struct CHACHA20_context_s
+{
+  u32 input[CHACHA20_INPUT_LENGTH];
+  u32 pad[CHACHA20_INPUT_LENGTH];
+  chacha20_blocks_t blocks;
+  unsigned int unused; /* bytes in the pad.  */
+} CHACHA20_context_t;
+
+
+static void chacha20_setiv (void *context, const byte * iv, size_t ivlen);
+static const char *selftest (void);
+
+
+
+#define QROUND(a,b,c,d)         \
+  do {                          \
+    a += b; d = rol(d ^ a, 16); \
+    c += d; b = rol(b ^ c, 12); \
+    a += b; d = rol(d ^ a, 8);  \
+    c += d; b = rol(b ^ c, 7);  \
+  } while (0)
+
+#define QOUT(ai, bi, ci, di) \
+  DO_OUT(ai); DO_OUT(bi); DO_OUT(ci); DO_OUT(di)
+
+static unsigned int
+chacha20_blocks (u32 *state, const byte *src, byte *dst, size_t bytes)
+{
+  u32 pad[CHACHA20_INPUT_LENGTH];
+  u32 inp[CHACHA20_INPUT_LENGTH];
+  unsigned int i;
+
+  /* Note: 'bytes' must be multiple of 64 and not zero. */
+
+  inp[0] = state[0];
+  inp[1] = state[1];
+  inp[2] = state[2];
+  inp[3] = state[3];
+  inp[4] = state[4];
+  inp[5] = state[5];
+  inp[6] = state[6];
+  inp[7] = state[7];
+  inp[8] = state[8];
+  inp[9] = state[9];
+  inp[10] = state[10];
+  inp[11] = state[11];
+  inp[12] = state[12];
+  inp[13] = state[13];
+  inp[14] = state[14];
+  inp[15] = state[15];
+
+  do
+    {
+      /* First round. */
+      pad[0] = inp[0];
+      pad[4] = inp[4];
+      pad[8] = inp[8];
+      pad[12] = inp[12];
+      QROUND (pad[0], pad[4], pad[8], pad[12]);
+      pad[1] = inp[1];
+      pad[5] = inp[5];
+      pad[9] = inp[9];
+      pad[13] = inp[13];
+      QROUND (pad[1], pad[5], pad[9], pad[13]);
+      pad[2] = inp[2];
+      pad[6] = inp[6];
+      pad[10] = inp[10];
+      pad[14] = inp[14];
+      QROUND (pad[2], pad[6], pad[10], pad[14]);
+      pad[3] = inp[3];
+      pad[7] = inp[7];
+      pad[11] = inp[11];
+      pad[15] = inp[15];
+      QROUND (pad[3], pad[7], pad[11], pad[15]);
+
+      QROUND (pad[0], pad[5], pad[10], pad[15]);
+      QROUND (pad[1], pad[6], pad[11], pad[12]);
+      QROUND (pad[2], pad[7], pad[8], pad[13]);
+      QROUND (pad[3], pad[4], pad[9], pad[14]);
+
+      for (i = 2; i < 20 - 2; i += 2)
+      {
+        QROUND (pad[0], pad[4], pad[8], pad[12]);
+        QROUND (pad[1], pad[5], pad[9], pad[13]);
+        QROUND (pad[2], pad[6], pad[10], pad[14]);
+        QROUND (pad[3], pad[7], pad[11], pad[15]);
+
+        QROUND (pad[0], pad[5], pad[10], pad[15]);
+        QROUND (pad[1], pad[6], pad[11], pad[12]);
+        QROUND (pad[2], pad[7], pad[8], pad[13]);
+        QROUND (pad[3], pad[4], pad[9], pad[14]);
+      }
+
+      QROUND (pad[0], pad[4], pad[8], pad[12]);
+      QROUND (pad[1], pad[5], pad[9], pad[13]);
+      QROUND (pad[2], pad[6], pad[10], pad[14]);
+      QROUND (pad[3], pad[7], pad[11], pad[15]);
+
+      if (src)
+        {
+#define DO_OUT(idx) buf_put_le32(dst + (idx) * 4, \
+                                 (pad[idx] + inp[idx]) ^ \
+                                  buf_get_le32(src + (idx) * 4))
+          /* Last round. */
+          QROUND (pad[0], pad[5], pad[10], pad[15]);
+          QOUT(0, 5, 10, 15);
+          QROUND (pad[1], pad[6], pad[11], pad[12]);
+          QOUT(1, 6, 11, 12);
+          QROUND (pad[2], pad[7], pad[8], pad[13]);
+          QOUT(2, 7, 8, 13);
+          QROUND (pad[3], pad[4], pad[9], pad[14]);
+          QOUT(3, 4, 9, 14);
+#undef DO_OUT
+        }
+      else
+        {
+#define DO_OUT(idx) buf_put_le32(dst + (idx) * 4, pad[idx] + inp[idx])
+          /* Last round. */
+          QROUND (pad[0], pad[5], pad[10], pad[15]);
+          QOUT(0, 5, 10, 15);
+          QROUND (pad[1], pad[6], pad[11], pad[12]);
+          QOUT(1, 6, 11, 12);
+          QROUND (pad[2], pad[7], pad[8], pad[13]);
+          QOUT(2, 7, 8, 13);
+          QROUND (pad[3], pad[4], pad[9], pad[14]);
+          QOUT(3, 4, 9, 14);
+#undef DO_OUT
+        }
+
+      /* Update counter. */
+      inp[13] += (!++inp[12]);
+
+      bytes -= CHACHA20_BLOCK_SIZE;
+      dst += CHACHA20_BLOCK_SIZE;
+      src += (src) ? CHACHA20_BLOCK_SIZE : 0;
+    }
+  while (bytes >= CHACHA20_BLOCK_SIZE);
+
+  state[12] = inp[12];
+  state[13] = inp[13];
+
+  /* burn_stack */
+  return (2 * CHACHA20_INPUT_LENGTH * sizeof(u32) + 6 * sizeof(void *));
+}
+
+#undef QROUND
+#undef QOUT
+
+
+static unsigned int
+chacha20_core(u32 *dst, struct CHACHA20_context_s *ctx)
+{
+  return ctx->blocks(ctx->input, NULL, (byte *)dst, CHACHA20_BLOCK_SIZE);
+}
+
+
+static void
+chacha20_keysetup (CHACHA20_context_t * ctx, const byte * key,
+                   unsigned int keylen)
+{
+  /* These constants are the little endian encoding of the string
+     "expand 32-byte k".  For the 128 bit variant, the "32" in that
+     string will be fixed up to "16".  */
+  ctx->input[0] = 0x61707865;        /* "apxe"  */
+  ctx->input[1] = 0x3320646e;        /* "3 dn"  */
+  ctx->input[2] = 0x79622d32;        /* "yb-2"  */
+  ctx->input[3] = 0x6b206574;        /* "k et"  */
+
+  ctx->input[4] = buf_get_le32 (key + 0);
+  ctx->input[5] = buf_get_le32 (key + 4);
+  ctx->input[6] = buf_get_le32 (key + 8);
+  ctx->input[7] = buf_get_le32 (key + 12);
+
+  if (keylen == CHACHA20_MAX_KEY_SIZE) /* 256 bits */
+    {
+      ctx->input[8] = buf_get_le32 (key + 16);
+      ctx->input[9] = buf_get_le32 (key + 20);
+      ctx->input[10] = buf_get_le32 (key + 24);
+      ctx->input[11] = buf_get_le32 (key + 28);
+    }
+  else /* 128 bits */
+    {
+      ctx->input[8] = ctx->input[4];
+      ctx->input[9] = ctx->input[5];
+      ctx->input[10] = ctx->input[6];
+      ctx->input[11] = ctx->input[7];
+
+      ctx->input[1] -= 0x02000000;        /* Change to "1 dn".  */
+      ctx->input[2] += 0x00000004;        /* Change to "yb-6".  */
+    }
+}
+
+
+static void
+chacha20_ivsetup (CHACHA20_context_t * ctx, const byte * iv, size_t ivlen)
+{
+  ctx->input[12] = 0;
+
+  if (ivlen == CHACHA20_MAX_IV_SIZE)
+    {
+      ctx->input[13] = buf_get_le32 (iv + 0);
+      ctx->input[14] = buf_get_le32 (iv + 4);
+      ctx->input[15] = buf_get_le32 (iv + 8);
+    }
+  else if (ivlen == CHACHA20_MIN_IV_SIZE)
+    {
+      ctx->input[13] = 0;
+      ctx->input[14] = buf_get_le32 (iv + 0);
+      ctx->input[15] = buf_get_le32 (iv + 4);
+    }
+  else
+    {
+      ctx->input[13] = 0;
+      ctx->input[14] = 0;
+      ctx->input[15] = 0;
+    }
+}
+
+
+static gcry_err_code_t
+chacha20_do_setkey (CHACHA20_context_t * ctx,
+                    const byte * key, unsigned int keylen)
+{
+  static int initialized;
+  static const char *selftest_failed;
+
+  if (!initialized)
+    {
+      initialized = 1;
+      selftest_failed = selftest ();
+      if (selftest_failed)
+        log_error ("CHACHA20 selftest failed (%s)\n", selftest_failed);
+    }
+  if (selftest_failed)
+    return GPG_ERR_SELFTEST_FAILED;
+
+  if (keylen != CHACHA20_MAX_KEY_SIZE && keylen != CHACHA20_MIN_KEY_SIZE)
+    return GPG_ERR_INV_KEYLEN;
+
+  ctx->blocks = chacha20_blocks;
+
+  chacha20_keysetup (ctx, key, keylen);
+
+  /* We default to a zero nonce.  */
+  chacha20_setiv (ctx, NULL, 0);
+
+  return 0;
+}
+
+
+static gcry_err_code_t
+chacha20_setkey (void *context, const byte * key, unsigned int keylen)
+{
+  CHACHA20_context_t *ctx = (CHACHA20_context_t *) context;
+  gcry_err_code_t rc = chacha20_do_setkey (ctx, key, keylen);
+  _gcry_burn_stack (4 + sizeof (void *) + 4 * sizeof (void *));
+  return rc;
+}
+
+
+static void
+chacha20_setiv (void *context, const byte * iv, size_t ivlen)
+{
+  CHACHA20_context_t *ctx = (CHACHA20_context_t *) context;
+
+  /* draft-nir-cfrg-chacha20-poly1305-02 defines 96-bit and 64-bit nonce. */
+  if (iv && ivlen != CHACHA20_MAX_IV_SIZE && ivlen != CHACHA20_MIN_IV_SIZE)
+    log_info ("WARNING: chacha20_setiv: bad ivlen=%u\n", (u32) ivlen);
+
+  if (iv && (ivlen == CHACHA20_MAX_IV_SIZE || ivlen == CHACHA20_MIN_IV_SIZE))
+    chacha20_ivsetup (ctx, iv, ivlen);
+  else
+    chacha20_ivsetup (ctx, NULL, 0);
+
+  /* Reset the unused pad bytes counter.  */
+  ctx->unused = 0;
+}
+
+
+
+/* Note: This function requires LENGTH > 0.  */
+static void
+chacha20_do_encrypt_stream (CHACHA20_context_t * ctx,
+                            byte * outbuf, const byte * inbuf, size_t length)
+{
+  unsigned int nburn, burn = 0;
+
+  if (ctx->unused)
+    {
+      unsigned char *p = (void *) ctx->pad;
+      size_t n;
+
+      gcry_assert (ctx->unused < CHACHA20_BLOCK_SIZE);
+
+      n = ctx->unused;
+      if (n > length)
+        n = length;
+      buf_xor (outbuf, inbuf, p + CHACHA20_BLOCK_SIZE - ctx->unused, n);
+      length -= n;
+      outbuf += n;
+      inbuf += n;
+      ctx->unused -= n;
+      if (!length)
+        return;
+      gcry_assert (!ctx->unused);
+    }
+
+  if (length >= CHACHA20_BLOCK_SIZE)
+    {
+      size_t nblocks = length / CHACHA20_BLOCK_SIZE;
+      size_t bytes = nblocks * CHACHA20_BLOCK_SIZE;
+      burn = ctx->blocks(ctx->input, inbuf, outbuf, bytes);
+      length -= bytes;
+      outbuf += bytes;
+      inbuf  += bytes;
+    }
+
+  if (length > 0)
+    {
+      nburn = chacha20_core (ctx->pad, ctx);
+      burn = nburn > burn ? nburn : burn;
+
+      buf_xor (outbuf, inbuf, ctx->pad, length);
+      ctx->unused = CHACHA20_BLOCK_SIZE - length;
+    }
+
+  _gcry_burn_stack (burn);
+}
+
+
+static void
+chacha20_encrypt_stream (void *context, byte * outbuf, const byte * inbuf,
+                         size_t length)
+{
+  CHACHA20_context_t *ctx = (CHACHA20_context_t *) context;
+
+  if (length)
+    chacha20_do_encrypt_stream (ctx, outbuf, inbuf, length);
+}
+
+
+static const char *
+selftest (void)
+{
+  CHACHA20_context_t ctx;
+  byte scratch[127 + 1];
+  byte buf[256 + 64 + 4];
+  int i;
+
+  /* From draft-strombergson-chacha-test-vectors */
+  static byte key_1[] = {
+    0xc4, 0x6e, 0xc1, 0xb1, 0x8c, 0xe8, 0xa8, 0x78,
+    0x72, 0x5a, 0x37, 0xe7, 0x80, 0xdf, 0xb7, 0x35,
+    0x1f, 0x68, 0xed, 0x2e, 0x19, 0x4c, 0x79, 0xfb,
+    0xc6, 0xae, 0xbe, 0xe1, 0xa6, 0x67, 0x97, 0x5d
+  };
+  static const byte nonce_1[] =
+    { 0x1a, 0xda, 0x31, 0xd5, 0xcf, 0x68, 0x82, 0x21 };
+  static const byte plaintext_1[127] = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  static const byte ciphertext_1[127] = {
+    0xf6, 0x3a, 0x89, 0xb7, 0x5c, 0x22, 0x71, 0xf9,
+    0x36, 0x88, 0x16, 0x54, 0x2b, 0xa5, 0x2f, 0x06,
+    0xed, 0x49, 0x24, 0x17, 0x92, 0x30, 0x2b, 0x00,
+    0xb5, 0xe8, 0xf8, 0x0a, 0xe9, 0xa4, 0x73, 0xaf,
+    0xc2, 0x5b, 0x21, 0x8f, 0x51, 0x9a, 0xf0, 0xfd,
+    0xd4, 0x06, 0x36, 0x2e, 0x8d, 0x69, 0xde, 0x7f,
+    0x54, 0xc6, 0x04, 0xa6, 0xe0, 0x0f, 0x35, 0x3f,
+    0x11, 0x0f, 0x77, 0x1b, 0xdc, 0xa8, 0xab, 0x92,
+    0xe5, 0xfb, 0xc3, 0x4e, 0x60, 0xa1, 0xd9, 0xa9,
+    0xdb, 0x17, 0x34, 0x5b, 0x0a, 0x40, 0x27, 0x36,
+    0x85, 0x3b, 0xf9, 0x10, 0xb0, 0x60, 0xbd, 0xf1,
+    0xf8, 0x97, 0xb6, 0x29, 0x0f, 0x01, 0xd1, 0x38,
+    0xae, 0x2c, 0x4c, 0x90, 0x22, 0x5b, 0xa9, 0xea,
+    0x14, 0xd5, 0x18, 0xf5, 0x59, 0x29, 0xde, 0xa0,
+    0x98, 0xca, 0x7a, 0x6c, 0xcf, 0xe6, 0x12, 0x27,
+    0x05, 0x3c, 0x84, 0xe4, 0x9a, 0x4a, 0x33
+  };
+
+  chacha20_setkey (&ctx, key_1, sizeof key_1);
+  chacha20_setiv (&ctx, nonce_1, sizeof nonce_1);
+  scratch[sizeof (scratch) - 1] = 0;
+  chacha20_encrypt_stream (&ctx, scratch, plaintext_1, sizeof plaintext_1);
+  if (memcmp (scratch, ciphertext_1, sizeof ciphertext_1))
+    return "ChaCha20 encryption test 1 failed.";
+  if (scratch[sizeof (scratch) - 1])
+    return "ChaCha20 wrote too much.";
+  chacha20_setkey (&ctx, key_1, sizeof (key_1));
+  chacha20_setiv (&ctx, nonce_1, sizeof nonce_1);
+  chacha20_encrypt_stream (&ctx, scratch, scratch, sizeof plaintext_1);
+  if (memcmp (scratch, plaintext_1, sizeof plaintext_1))
+    return "ChaCha20 decryption test 1 failed.";
+
+  for (i = 0; i < sizeof buf; i++)
+    buf[i] = i;
+  chacha20_setkey (&ctx, key_1, sizeof key_1);
+  chacha20_setiv (&ctx, nonce_1, sizeof nonce_1);
+  /*encrypt */
+  chacha20_encrypt_stream (&ctx, buf, buf, sizeof buf);
+  /*decrypt */
+  chacha20_setkey (&ctx, key_1, sizeof key_1);
+  chacha20_setiv (&ctx, nonce_1, sizeof nonce_1);
+  chacha20_encrypt_stream (&ctx, buf, buf, 1);
+  chacha20_encrypt_stream (&ctx, buf + 1, buf + 1, (sizeof buf) - 1 - 1);
+  chacha20_encrypt_stream (&ctx, buf + (sizeof buf) - 1,
+                           buf + (sizeof buf) - 1, 1);
+  for (i = 0; i < sizeof buf; i++)
+    if (buf[i] != (byte) i)
+      return "ChaCha20 encryption test 2 failed.";
+
+  return NULL;
+}
+
+
+gcry_cipher_spec_t _gcry_cipher_spec_chacha20 = {
+  GCRY_CIPHER_CHACHA20,
+  {0, 0},                       /* flags */
+  "CHACHA20",                   /* name */
+  NULL,                         /* aliases */
+  NULL,                         /* oids */
+  1,                            /* blocksize in bytes. */
+  CHACHA20_MAX_KEY_SIZE * 8,    /* standard key length in bits. */
+  sizeof (CHACHA20_context_t),
+  chacha20_setkey,
+  NULL,
+  NULL,
+  chacha20_encrypt_stream,
+  chacha20_encrypt_stream,
+  NULL,
+  NULL,
+  chacha20_setiv
+};