Add SHA256 calculator

Based on the sha256c.c file from the FreeBSD project and ported to compile on
Linux, Mac OS, and Windows. The file is licensed under the simplified/2-clause
BSD license so the library is now MIT/BSD-licensed.

4 files changed, 546 insertions, 0 deletions

diff --git a/butl/buildfile b/butl/buildfile
index f075e30..a92f4a9 100644
--- a/butl/buildfile
+++ b/butl/buildfile
@@ -13,6 +13,7 @@ lib{butl}:                        \
 {hxx            }{ path-io      } \
 {hxx            }{ path-map     } \
 {hxx     txx    }{ prefix-map   } \
+{hxx         cxx}{ sha256       } \
 {hxx ixx     cxx}{ process      } \
 {hxx     txx    }{ string-table } \
 {hxx         cxx}{ timestamp    } \
diff --git a/butl/sha256 b/butl/sha256
new file mode 100644
index 0000000..3fc9e63
--- /dev/null
+++ b/butl/sha256
@@ -0,0 +1,76 @@
+// file      : butl/sha256 -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_SHA256
+#define BUTL_SHA256
+
+#include <string>
+#include <cstring> // strlen()
+#include <cstdint>
+#include <cstddef> // size_t
+
+namespace butl
+{
+  // SHA256 checksum calculator.
+  //
+  // For a single chunk of data a sum can be obtained in one line, for
+  // example:
+  //
+  // cerr << sha256 ("123").string () << endl;
+  //
+  class sha256
+  {
+  public:
+    sha256 ();
+    explicit sha256 (const std::string& s): sha256 () {append (s);}
+    explicit sha256 (const char* s): sha256 () {append (s);}
+    sha256 (const void* b, std::size_t n): sha256 () {append (b, n);}
+
+    // Append string (without the traling '\0').
+    //
+    void
+    append (const std::string& s) {append (s.c_str (), s.size ());}
+
+    // Append C-string (without the traling '\0').
+    //
+    void
+    append (const char* s) {append (s, std::strlen (s));}
+
+    // Append binary data.
+    //
+    void
+    append (const void*, std::size_t);
+
+    // Extract result. It can be obtained as either a 32-byte binary digest or
+    // as a 64- character hex-encoded C-string.
+    //
+    using digest_type = std::uint8_t[32];
+
+    const digest_type&
+    binary () const;
+
+    const char*
+    string () const;
+
+  public:
+    struct context
+    {
+      std::uint32_t state[8];
+      std::uint64_t count;
+      std::uint8_t buf[64];
+    };
+
+  private:
+    union
+    {
+      mutable context ctx_;
+      mutable char str_[65];
+    };
+
+    mutable digest_type bin_;
+    mutable bool done_;
+  };
+};
+
+#endif // BUTL_SHA256
diff --git a/butl/sha256.cxx b/butl/sha256.cxx
new file mode 100644
index 0000000..feca9a7
--- /dev/null
+++ b/butl/sha256.cxx
@@ -0,0 +1,76 @@
+// file      : butl/sha256.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <butl/sha256>
+
+// C interface for sha256c.
+//
+#include <stdint.h>
+#include <stddef.h> // size_t
+
+using SHA256_CTX = butl::sha256::context;
+
+extern "C"
+{
+  static void SHA256_Init (SHA256_CTX*);
+  static void SHA256_Update (SHA256_CTX*, const void*, size_t);
+  static void SHA256_Final (uint8_t[32], SHA256_CTX*);
+
+#include "sha256c.c"
+}
+
+using namespace std;
+
+namespace butl
+{
+  sha256::
+  sha256 ()
+      : done_ (false)
+  {
+    SHA256_Init (&ctx_);
+  }
+
+  void sha256::
+  append (const void* b, size_t n)
+  {
+    SHA256_Update (&ctx_, b, n);
+  }
+
+  const sha256::digest_type& sha256::
+  binary () const
+  {
+    if (!done_)
+    {
+      SHA256_Final (bin_, &ctx_);
+      done_ = true;
+      str_[0] = '\0'; // Indicate we haven't computed the string yet.
+    }
+
+    return bin_;
+  }
+
+  static const char hex_map[16] = {
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+    'a', 'b', 'c', 'd', 'e', 'f'};
+
+  const char* sha256::
+  string () const
+  {
+    if (!done_)
+      binary ();
+
+    if (str_[0] == '\0')
+    {
+      for (size_t i (0); i != 32; ++i)
+      {
+        str_[i * 2]     = hex_map[bin_[i] >> 4];
+        str_[i * 2 + 1] = hex_map[bin_[i] & 0x0f];
+      }
+
+      str_[64] = '\0';
+    }
+
+    return str_;
+  }
+}
diff --git a/butl/sha256c.c b/butl/sha256c.c
new file mode 100644
index 0000000..3a6b8eb
--- /dev/null
+++ b/butl/sha256c.c
@@ -0,0 +1,393 @@
+/*-
+ * Copyright 2005 Colin Percival
+ * Copyright 2016 Code Synthesis Ltd
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stddef.h> /* size_t */
+
+#ifdef SHA256_TEST_DRIVER
+
+struct context
+{
+  uint32_t state[8];
+  uint64_t count;
+  uint8_t buf[64];
+};
+
+typedef struct context SHA256_CTX;
+
+static void SHA256_Init (SHA256_CTX*);
+static void SHA256_Update (SHA256_CTX*, const void*, size_t);
+static void SHA256_Final (uint8_t[32], SHA256_CTX*);
+
+#include <string.h>
+#include <assert.h>
+
+int
+main ()
+{
+  SHA256_CTX c;
+  uint8_t r[32];
+
+  /* ""    e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 */
+  SHA256_Init (&c);
+  SHA256_Final (r, &c);
+  assert (r[0] == 0xe3 && r[31] == 0x55);
+
+  /* "123" a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3 */
+  SHA256_Init (&c);
+  SHA256_Update (&c, "123", 3);
+  SHA256_Final (r, &c);
+  assert (r[0] == 0xa6 && r[31] == 0xe3);
+
+  return 0;
+}
+
+#endif /* SHA256_TEST_DRIVER */
+
+#ifdef __FreeBSD__
+#  include <sys/endian.h> /* BYTE_ORDER, be32dec(), be32enc(), be64enc */
+#else
+#  if defined(_WIN32)
+#    ifndef BYTE_ORDER
+#      define BIG_ENDIAN    4321
+#      define LITTLE_ENDIAN 1234
+#      define BYTE_ORDER    LITTLE_ENDIAN
+#    endif
+#  else
+#    include <sys/param.h>  /* BYTE_ORDER/__BYTE_ORDER */
+#    ifndef BYTE_ORDER
+#      ifdef __BYTE_ORDER
+#        define BYTE_ORDER    __BYTE_ORDER
+#        define BIG_ENDIAN    __BIG_ENDIAN
+#        define LITTLE_ENDIAN __LITTLE_ENDIAN
+#      else
+#        error no BYTE_ORDER/__BYTE_ORDER define
+#      endif
+#    endif
+#  endif
+
+static uint32_t
+be32dec(const void *pp)
+{
+	unsigned char const *p = (unsigned char const *)pp;
+
+	return ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
+}
+
+static void
+be32enc(void *pp, uint32_t u)
+{
+	unsigned char *p = (unsigned char *)pp;
+
+	p[0] = (u >> 24) & 0xff;
+	p[1] = (u >> 16) & 0xff;
+	p[2] = (u >> 8) & 0xff;
+	p[3] = u & 0xff;
+}
+
+static void
+be64enc(void *pp, uint64_t u)
+{
+	unsigned char *p = (unsigned char *)pp;
+
+        p[0] = (u >> 56) & 0xff;
+	p[1] = (u >> 48) & 0xff;
+	p[2] = (u >> 40) & 0xff;
+        p[3] = (u >> 32) & 0xff;
+        p[4] = (u >> 24) & 0xff;
+	p[5] = (u >> 16) & 0xff;
+	p[6] = (u >> 8) & 0xff;
+	p[7] = u & 0xff;
+}
+#endif
+
+/* The rest is the unmodified (except for a few explicit casts to make it
+   compilable in C++), latest implementation from FreeBSD. */
+
+#include <string.h>
+
+#if BYTE_ORDER == BIG_ENDIAN
+
+/* Copy a vector of big-endian uint32_t into a vector of bytes */
+#define be32enc_vect(dst, src, len)	\
+	memcpy((void *)dst, (const void *)src, (size_t)len)
+
+/* Copy a vector of bytes into a vector of big-endian uint32_t */
+#define be32dec_vect(dst, src, len)	\
+	memcpy((void *)dst, (const void *)src, (size_t)len)
+
+#else /* BYTE_ORDER != BIG_ENDIAN */
+
+/*
+ * Encode a length len/4 vector of (uint32_t) into a length len vector of
+ * (unsigned char) in big-endian form.  Assumes len is a multiple of 4.
+ */
+static void
+be32enc_vect(unsigned char *dst, const uint32_t *src, size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len / 4; i++)
+		be32enc(dst + i * 4, src[i]);
+}
+
+/*
+ * Decode a big-endian length len vector of (unsigned char) into a length
+ * len/4 vector of (uint32_t).  Assumes len is a multiple of 4.
+ */
+static void
+be32dec_vect(uint32_t *dst, const unsigned char *src, size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len / 4; i++)
+		dst[i] = be32dec(src + i * 4);
+}
+
+#endif /* BYTE_ORDER != BIG_ENDIAN */
+
+/* Elementary functions used by SHA256 */
+#define Ch(x, y, z)	((x & (y ^ z)) ^ z)
+#define Maj(x, y, z)	((x & (y | z)) | (y & z))
+#define SHR(x, n)	(x >> n)
+#define ROTR(x, n)	((x >> n) | (x << (32 - n)))
+#define S0(x)		(ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
+#define S1(x)		(ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))
+#define s0(x)		(ROTR(x, 7) ^ ROTR(x, 18) ^ SHR(x, 3))
+#define s1(x)		(ROTR(x, 17) ^ ROTR(x, 19) ^ SHR(x, 10))
+
+/* SHA256 round function */
+#define RND(a, b, c, d, e, f, g, h, k)			\
+	t0 = h + S1(e) + Ch(e, f, g) + k;		\
+	t1 = S0(a) + Maj(a, b, c);			\
+	d += t0;					\
+	h  = t0 + t1;
+
+/* Adjusted round function for rotating state */
+#define RNDr(S, W, i, k)			\
+	RND(S[(64 - i) % 8], S[(65 - i) % 8],	\
+	    S[(66 - i) % 8], S[(67 - i) % 8],	\
+	    S[(68 - i) % 8], S[(69 - i) % 8],	\
+	    S[(70 - i) % 8], S[(71 - i) % 8],	\
+	    W[i] + k)
+
+/*
+ * SHA256 block compression function.  The 256-bit state is transformed via
+ * the 512-bit input block to produce a new state.
+ */
+static void
+SHA256_Transform(uint32_t * state, const unsigned char block[64])
+{
+	uint32_t W[64];
+	uint32_t S[8];
+	uint32_t t0, t1;
+	int i;
+
+	/* 1. Prepare message schedule W. */
+	be32dec_vect(W, block, 64);
+	for (i = 16; i < 64; i++)
+		W[i] = s1(W[i - 2]) + W[i - 7] + s0(W[i - 15]) + W[i - 16];
+
+	/* 2. Initialize working variables. */
+	memcpy(S, state, 32);
+
+	/* 3. Mix. */
+	RNDr(S, W, 0, 0x428a2f98);
+	RNDr(S, W, 1, 0x71374491);
+	RNDr(S, W, 2, 0xb5c0fbcf);
+	RNDr(S, W, 3, 0xe9b5dba5);
+	RNDr(S, W, 4, 0x3956c25b);
+	RNDr(S, W, 5, 0x59f111f1);
+	RNDr(S, W, 6, 0x923f82a4);
+	RNDr(S, W, 7, 0xab1c5ed5);
+	RNDr(S, W, 8, 0xd807aa98);
+	RNDr(S, W, 9, 0x12835b01);
+	RNDr(S, W, 10, 0x243185be);
+	RNDr(S, W, 11, 0x550c7dc3);
+	RNDr(S, W, 12, 0x72be5d74);
+	RNDr(S, W, 13, 0x80deb1fe);
+	RNDr(S, W, 14, 0x9bdc06a7);
+	RNDr(S, W, 15, 0xc19bf174);
+	RNDr(S, W, 16, 0xe49b69c1);
+	RNDr(S, W, 17, 0xefbe4786);
+	RNDr(S, W, 18, 0x0fc19dc6);
+	RNDr(S, W, 19, 0x240ca1cc);
+	RNDr(S, W, 20, 0x2de92c6f);
+	RNDr(S, W, 21, 0x4a7484aa);
+	RNDr(S, W, 22, 0x5cb0a9dc);
+	RNDr(S, W, 23, 0x76f988da);
+	RNDr(S, W, 24, 0x983e5152);
+	RNDr(S, W, 25, 0xa831c66d);
+	RNDr(S, W, 26, 0xb00327c8);
+	RNDr(S, W, 27, 0xbf597fc7);
+	RNDr(S, W, 28, 0xc6e00bf3);
+	RNDr(S, W, 29, 0xd5a79147);
+	RNDr(S, W, 30, 0x06ca6351);
+	RNDr(S, W, 31, 0x14292967);
+	RNDr(S, W, 32, 0x27b70a85);
+	RNDr(S, W, 33, 0x2e1b2138);
+	RNDr(S, W, 34, 0x4d2c6dfc);
+	RNDr(S, W, 35, 0x53380d13);
+	RNDr(S, W, 36, 0x650a7354);
+	RNDr(S, W, 37, 0x766a0abb);
+	RNDr(S, W, 38, 0x81c2c92e);
+	RNDr(S, W, 39, 0x92722c85);
+	RNDr(S, W, 40, 0xa2bfe8a1);
+	RNDr(S, W, 41, 0xa81a664b);
+	RNDr(S, W, 42, 0xc24b8b70);
+	RNDr(S, W, 43, 0xc76c51a3);
+	RNDr(S, W, 44, 0xd192e819);
+	RNDr(S, W, 45, 0xd6990624);
+	RNDr(S, W, 46, 0xf40e3585);
+	RNDr(S, W, 47, 0x106aa070);
+	RNDr(S, W, 48, 0x19a4c116);
+	RNDr(S, W, 49, 0x1e376c08);
+	RNDr(S, W, 50, 0x2748774c);
+	RNDr(S, W, 51, 0x34b0bcb5);
+	RNDr(S, W, 52, 0x391c0cb3);
+	RNDr(S, W, 53, 0x4ed8aa4a);
+	RNDr(S, W, 54, 0x5b9cca4f);
+	RNDr(S, W, 55, 0x682e6ff3);
+	RNDr(S, W, 56, 0x748f82ee);
+	RNDr(S, W, 57, 0x78a5636f);
+	RNDr(S, W, 58, 0x84c87814);
+	RNDr(S, W, 59, 0x8cc70208);
+	RNDr(S, W, 60, 0x90befffa);
+	RNDr(S, W, 61, 0xa4506ceb);
+	RNDr(S, W, 62, 0xbef9a3f7);
+	RNDr(S, W, 63, 0xc67178f2);
+
+	/* 4. Mix local working variables into global state */
+	for (i = 0; i < 8; i++)
+		state[i] += S[i];
+}
+
+static unsigned char PAD[64] = {
+	0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+};
+
+/* Add padding and terminating bit-count. */
+static void
+SHA256_Pad(SHA256_CTX * ctx)
+{
+	unsigned char len[8];
+	uint32_t r, plen;
+
+	/*
+	 * Convert length to a vector of bytes -- we do this now rather
+	 * than later because the length will change after we pad.
+	 */
+	be64enc(len, ctx->count);
+
+	/* Add 1--64 bytes so that the resulting length is 56 mod 64 */
+	r = (ctx->count >> 3) & 0x3f;
+	plen = (r < 56) ? (56 - r) : (120 - r);
+	SHA256_Update(ctx, PAD, (size_t)plen);
+
+	/* Add the terminating bit-count */
+	SHA256_Update(ctx, len, 8);
+}
+
+/* SHA-256 initialization.  Begins a SHA-256 operation. */
+void
+SHA256_Init(SHA256_CTX * ctx)
+{
+
+	/* Zero bits processed so far */
+	ctx->count = 0;
+
+	/* Magic initialization constants */
+	ctx->state[0] = 0x6A09E667;
+	ctx->state[1] = 0xBB67AE85;
+	ctx->state[2] = 0x3C6EF372;
+	ctx->state[3] = 0xA54FF53A;
+	ctx->state[4] = 0x510E527F;
+	ctx->state[5] = 0x9B05688C;
+	ctx->state[6] = 0x1F83D9AB;
+	ctx->state[7] = 0x5BE0CD19;
+}
+
+/* Add bytes into the hash */
+void
+SHA256_Update(SHA256_CTX * ctx, const void *in, size_t len)
+{
+	uint64_t bitlen;
+	uint32_t r;
+	const unsigned char *src = (const unsigned char *) (in);
+
+	/* Number of bytes left in the buffer from previous updates */
+	r = (ctx->count >> 3) & 0x3f;
+
+	/* Convert the length into a number of bits */
+	bitlen = len << 3;
+
+	/* Update number of bits */
+	ctx->count += bitlen;
+
+	/* Handle the case where we don't need to perform any transforms */
+	if (len < 64 - r) {
+		memcpy(&ctx->buf[r], src, len);
+		return;
+	}
+
+	/* Finish the current block */
+	memcpy(&ctx->buf[r], src, 64 - r);
+	SHA256_Transform(ctx->state, ctx->buf);
+	src += 64 - r;
+	len -= 64 - r;
+
+	/* Perform complete blocks */
+	while (len >= 64) {
+		SHA256_Transform(ctx->state, src);
+		src += 64;
+		len -= 64;
+	}
+
+	/* Copy left over data into buffer */
+	memcpy(ctx->buf, src, len);
+}
+
+/*
+ * SHA-256 finalization.  Pads the input data, exports the hash value,
+ * and clears the context state.
+ */
+void
+SHA256_Final(uint8_t digest[32], SHA256_CTX * ctx)
+{
+
+	/* Add padding */
+	SHA256_Pad(ctx);
+
+	/* Write the hash */
+	be32enc_vect(digest, ctx->state, 32);
+
+	/* Clear the context state */
+	memset((void *)ctx, 0, sizeof(*ctx));
+}