rtc_base/sha1.cc - src/webrtc - Git at Google

 /*
  * SHA-1 in C
  * By Steve Reid <sreid@sea-to-sky.net>
  * 100% Public Domain
  *
  * -----------------
  * Modified 7/98
  * By James H. Brown <jbrown@burgoyne.com>
  * Still 100% Public Domain
  *
  * Corrected a problem which generated improper hash values on 16 bit machines
  * Routine SHA1Update changed from
  *   void SHA1Update(SHA1_CTX* context, unsigned char* data, unsigned int
  * len)
  * to
  *   void SHA1Update(SHA1_CTX* context, unsigned char* data, unsigned
  * long len)
  *
  * The 'len' parameter was declared an int which works fine on 32 bit machines.
  * However, on 16 bit machines an int is too small for the shifts being done
  * against
  * it.  This caused the hash function to generate incorrect values if len was
  * greater than 8191 (8K - 1) due to the 'len << 3' on line 3 of SHA1Update().
  *
  * Since the file IO in main() reads 16K at a time, any file 8K or larger would
  * be guaranteed to generate the wrong hash (e.g. Test Vector #3, a million
  * "a"s).
  *
  * I also changed the declaration of variables i & j in SHA1Update to
  * unsigned long from unsigned int for the same reason.
  *
  * These changes should make no difference to any 32 bit implementations since
  * an
  * int and a long are the same size in those environments.
  *
  * --
  * I also corrected a few compiler warnings generated by Borland C.
  * 1. Added #include <process.h> for exit() prototype
  * 2. Removed unused variable 'j' in SHA1Final
  * 3. Changed exit(0) to return(0) at end of main.
  *
  * ALL changes I made can be located by searching for comments containing 'JHB'
  * -----------------
  * Modified 8/98
  * By Steve Reid <sreid@sea-to-sky.net>
  * Still 100% public domain
  *
  * 1- Removed #include <process.h> and used return() instead of exit()
  * 2- Fixed overwriting of finalcount in SHA1Final() (discovered by Chris Hall)
  * 3- Changed email address from steve@edmweb.com to sreid@sea-to-sky.net
  *
  * -----------------
  * Modified 4/01
  * By Saul Kravitz <Saul.Kravitz@celera.com>
  * Still 100% PD
  * Modified to run on Compaq Alpha hardware.
  *
  * -----------------
  * Modified 07/2002
  * By Ralph Giles <giles@ghostscript.com>
  * Still 100% public domain
  * modified for use with stdint types, autoconf
  * code cleanup, removed attribution comments
  * switched SHA1Final() argument order for consistency
  * use SHA1_ prefix for public api
  * move public api to sha1.h
  *
  * -----------------
  * Modified 02/2012
  * By Justin Uberti <juberti@google.com>
  * Remove underscore from SHA1 prefix to avoid conflict with OpenSSL
  * Remove test code
  * Untabify
  *
  * -----------------
  * Modified 03/2012
  * By Ronghua Wu <ronghuawu@google.com>
  * Change the typedef of uint32(8)_t to uint32(8). We need this because in the
  * chromium android build, the stdio.h will include stdint.h which already
  * defined uint32(8)_t.
  *
  * -----------------
  * Modified 04/2012
  * By Frank Barchard <fbarchard@google.com>
  * Ported to C++, Google style, change len to size_t, enable SHA1HANDSOFF
  *
  * Test Vectors (from FIPS PUB 180-1)
  * "abc"
  *   A9993E36 4706816A BA3E2571 7850C26C 9CD0D89D
  * "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
  *   84983E44 1C3BD26E BAAE4AA1 F95129E5 E54670F1
  * A million repetitions of "a"
  *   34AA973C D4C4DAA4 F61EEB2B DBAD2731 6534016F
  *
  * -----------------
  * Modified 05/2015
  * By Sergey Ulanov <sergeyu@chromium.org>
  * Removed static buffer to make computation thread-safe.
  *
  * -----------------
  * Modified 10/2015
  * By Peter Boström <pbos@webrtc.org>
  * Change uint32(8) back to uint32(8)_t (undoes (03/2012) change).
  */

 // Enabling SHA1HANDSOFF preserves the caller's data buffer.
 // Disabling SHA1HANDSOFF the buffer will be modified (end swapped).
 #define SHA1HANDSOFF

 #include "webrtc/rtc_base/sha1.h"

 #include <stdio.h>
 #include <string.h>

 namespace rtc {

 namespace {

 #define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

 // blk0() and blk() perform the initial expand.
 // I got the idea of expanding during the round function from SSLeay
 // FIXME: can we do this in an endian-proof way?
 #ifdef RTC_ARCH_CPU_BIG_ENDIAN
 #define blk0(i) block->l[i]
 #else
 #define blk0(i) (block->l[i] = (rol(block->l[i], 24) & 0xFF00FF00) | \
     (rol(block->l[i], 8) & 0x00FF00FF))
 #endif
 #define blk(i) (block->l[i & 15] = rol(block->l[(i + 13) & 15] ^ \
     block->l[(i + 8) & 15] ^ block->l[(i + 2) & 15] ^ block->l[i & 15], 1))

 // (R0+R1), R2, R3, R4 are the different operations used in SHA1.
 #define R0(v, w, x, y, z, i) \
     z += ((w & (x ^ y)) ^ y) + blk0(i) + 0x5A827999 + rol(v, 5); \
     w = rol(w, 30);
 #define R1(v, w, x, y, z, i) \
     z += ((w & (x ^ y)) ^ y) + blk(i) + 0x5A827999 + rol(v, 5); \
     w = rol(w, 30);
 #define R2(v, w, x, y, z, i) \
     z += (w ^ x ^ y) + blk(i) + 0x6ED9EBA1 + rol(v, 5);\
     w = rol(w, 30);
 #define R3(v, w, x, y, z, i) \
     z += (((w | x) & y) | (w & x)) + blk(i) + 0x8F1BBCDC + rol(v, 5); \
     w = rol(w, 30);
 #define R4(v, w, x, y, z, i) \
     z += (w ^ x ^ y) + blk(i) + 0xCA62C1D6 + rol(v, 5); \
     w = rol(w, 30);

 #ifdef VERBOSE  // SAK
 void SHAPrintContext(SHA1_CTX *context, char *msg) {
   printf("%s (%d,%d) %x %x %x %x %x\n",
          msg,
          context->count[0], context->count[1],
          context->state[0],
          context->state[1],
          context->state[2],
          context->state[3],
          context->state[4]);
 }
 #endif /* VERBOSE */

 // Hash a single 512-bit block. This is the core of the algorithm.
 void SHA1Transform(uint32_t state[5], const uint8_t buffer[64]) {
   union CHAR64LONG16 {
     uint8_t c[64];
     uint32_t l[16];
   };
 #ifdef SHA1HANDSOFF
   uint8_t workspace[64];
   memcpy(workspace, buffer, 64);
   CHAR64LONG16* block = reinterpret_cast<CHAR64LONG16*>(workspace);
 #else
   // Note(fbarchard): This option does modify the user's data buffer.
   CHAR64LONG16* block = const_cast<CHAR64LONG16*>(
       reinterpret_cast<const CHAR64LONG16*>(buffer));
 #endif

   // Copy context->state[] to working vars.
   uint32_t a = state[0];
   uint32_t b = state[1];
   uint32_t c = state[2];
   uint32_t d = state[3];
   uint32_t e = state[4];

   // 4 rounds of 20 operations each. Loop unrolled.
   // Note(fbarchard): The following has lint warnings for multiple ; on
   // a line and no space after , but is left as-is to be similar to the
   // original code.
   R0(a,b,c,d,e,0); R0(e,a,b,c,d,1); R0(d,e,a,b,c,2); R0(c,d,e,a,b,3);
   R0(b,c,d,e,a,4); R0(a,b,c,d,e,5); R0(e,a,b,c,d,6); R0(d,e,a,b,c,7);
   R0(c,d,e,a,b,8); R0(b,c,d,e,a,9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
   R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
   R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
   R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
   R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
   R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
   R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
   R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
   R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
   R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
   R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
   R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
   R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
   R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
   R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
   R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
   R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
   R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);

   // Add the working vars back into context.state[].
   state[0] += a;
   state[1] += b;
   state[2] += c;
   state[3] += d;
   state[4] += e;
 }

 }  // namespace

 // SHA1Init - Initialize new context.
 void SHA1Init(SHA1_CTX* context) {
   // SHA1 initialization constants.
   context->state[0] = 0x67452301;
   context->state[1] = 0xEFCDAB89;
   context->state[2] = 0x98BADCFE;
   context->state[3] = 0x10325476;
   context->state[4] = 0xC3D2E1F0;
   context->count[0] = context->count[1] = 0;
 }

 // Run your data through this.
 void SHA1Update(SHA1_CTX* context, const uint8_t* data, size_t input_len) {
   size_t i = 0;

 #ifdef VERBOSE
   SHAPrintContext(context, "before");
 #endif

   // Compute number of bytes mod 64.
   size_t index = (context->count[0] >> 3) & 63;

   // Update number of bits.
   // TODO: Use uint64_t instead of 2 uint32_t for count.
   // count[0] has low 29 bits for byte count + 3 pad 0's making 32 bits for
   // bit count.
   // Add bit count to low uint32_t
   context->count[0] += static_cast<uint32_t>(input_len << 3);
   if (context->count[0] < static_cast<uint32_t>(input_len << 3)) {
     ++context->count[1];  // if overlow (carry), add one to high word
   }
   context->count[1] += static_cast<uint32_t>(input_len >> 29);
   if ((index + input_len) > 63) {
     i = 64 - index;
     memcpy(&context->buffer[index], data, i);
     SHA1Transform(context->state, context->buffer);
     for (; i + 63 < input_len; i += 64) {
       SHA1Transform(context->state, data + i);
     }
     index = 0;
   }
   memcpy(&context->buffer[index], &data[i], input_len - i);

 #ifdef VERBOSE
   SHAPrintContext(context, "after ");
 #endif
 }

 // Add padding and return the message digest.
 void SHA1Final(SHA1_CTX* context, uint8_t digest[SHA1_DIGEST_SIZE]) {
   uint8_t finalcount[8];
   for (int i = 0; i < 8; ++i) {
     // Endian independent
     finalcount[i] = static_cast<uint8_t>(
         (context->count[(i >= 4 ? 0 : 1)] >> ((3 - (i & 3)) * 8)) & 255);
   }
   SHA1Update(context, reinterpret_cast<const uint8_t*>("\200"), 1);
   while ((context->count[0] & 504) != 448) {
     SHA1Update(context, reinterpret_cast<const uint8_t*>("\0"), 1);
   }
   SHA1Update(context, finalcount, 8);  // Should cause a SHA1Transform().
   for (int i = 0; i < SHA1_DIGEST_SIZE; ++i) {
     digest[i] = static_cast<uint8_t>(
         (context->state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
   }

   // Wipe variables.
   memset(context->buffer, 0, 64);
   memset(context->state, 0, 20);
   memset(context->count, 0, 8);
   memset(finalcount, 0, 8);   // SWR

 #ifdef SHA1HANDSOFF  // Make SHA1Transform overwrite its own static vars.
   SHA1Transform(context->state, context->buffer);
 #endif
 }

 }  // namespace rtc
	/*
	* SHA-1 in C
	* By Steve Reid <sreid@sea-to-sky.net>
	* 100% Public Domain
	*
	* -----------------
	* Modified 7/98
	* By James H. Brown <jbrown@burgoyne.com>
	* Still 100% Public Domain
	*
	* Corrected a problem which generated improper hash values on 16 bit machines
	* Routine SHA1Update changed from
	* void SHA1Update(SHA1_CTX* context, unsigned char* data, unsigned int
	* len)
	* to
	* void SHA1Update(SHA1_CTX* context, unsigned char* data, unsigned
	* long len)
	*
	* The 'len' parameter was declared an int which works fine on 32 bit machines.
	* However, on 16 bit machines an int is too small for the shifts being done
	* against
	* it. This caused the hash function to generate incorrect values if len was
	* greater than 8191 (8K - 1) due to the 'len << 3' on line 3 of SHA1Update().
	*
	* Since the file IO in main() reads 16K at a time, any file 8K or larger would
	* be guaranteed to generate the wrong hash (e.g. Test Vector #3, a million
	* "a"s).
	*
	* I also changed the declaration of variables i & j in SHA1Update to
	* unsigned long from unsigned int for the same reason.
	*
	* These changes should make no difference to any 32 bit implementations since
	* an
	* int and a long are the same size in those environments.
	*
	* --
	* I also corrected a few compiler warnings generated by Borland C.
	* 1. Added #include <process.h> for exit() prototype
	* 2. Removed unused variable 'j' in SHA1Final
	* 3. Changed exit(0) to return(0) at end of main.
	*
	* ALL changes I made can be located by searching for comments containing 'JHB'
	* -----------------
	* Modified 8/98
	* By Steve Reid <sreid@sea-to-sky.net>
	* Still 100% public domain
	*
	* 1- Removed #include <process.h> and used return() instead of exit()
	* 2- Fixed overwriting of finalcount in SHA1Final() (discovered by Chris Hall)
	* 3- Changed email address from steve@edmweb.com to sreid@sea-to-sky.net
	*
	* -----------------
	* Modified 4/01
	* By Saul Kravitz <Saul.Kravitz@celera.com>
	* Still 100% PD
	* Modified to run on Compaq Alpha hardware.
	*
	* -----------------
	* Modified 07/2002
	* By Ralph Giles <giles@ghostscript.com>
	* Still 100% public domain
	* modified for use with stdint types, autoconf
	* code cleanup, removed attribution comments
	* switched SHA1Final() argument order for consistency
	* use SHA1_ prefix for public api
	* move public api to sha1.h
	*
	* -----------------
	* Modified 02/2012
	* By Justin Uberti <juberti@google.com>
	* Remove underscore from SHA1 prefix to avoid conflict with OpenSSL
	* Remove test code
	* Untabify
	*
	* -----------------
	* Modified 03/2012
	* By Ronghua Wu <ronghuawu@google.com>
	* Change the typedef of uint32(8)_t to uint32(8). We need this because in the
	* chromium android build, the stdio.h will include stdint.h which already
	* defined uint32(8)_t.
	*
	* -----------------
	* Modified 04/2012
	* By Frank Barchard <fbarchard@google.com>
	* Ported to C++, Google style, change len to size_t, enable SHA1HANDSOFF
	*
	* Test Vectors (from FIPS PUB 180-1)
	* "abc"
	* A9993E36 4706816A BA3E2571 7850C26C 9CD0D89D
	* "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
	* 84983E44 1C3BD26E BAAE4AA1 F95129E5 E54670F1
	* A million repetitions of "a"
	* 34AA973C D4C4DAA4 F61EEB2B DBAD2731 6534016F
	*
	* -----------------
	* Modified 05/2015
	* By Sergey Ulanov <sergeyu@chromium.org>
	* Removed static buffer to make computation thread-safe.
	*
	* -----------------
	* Modified 10/2015
	* By Peter Boström <pbos@webrtc.org>
	* Change uint32(8) back to uint32(8)_t (undoes (03/2012) change).
	*/

	// Enabling SHA1HANDSOFF preserves the caller's data buffer.
	// Disabling SHA1HANDSOFF the buffer will be modified (end swapped).
	#define SHA1HANDSOFF

	#include "webrtc/rtc_base/sha1.h"

	#include <stdio.h>
	#include <string.h>

	namespace rtc {

	namespace {

	#define rol(value, bits) (((value) << (bits)) \| ((value) >> (32 - (bits))))

	// blk0() and blk() perform the initial expand.
	// I got the idea of expanding during the round function from SSLeay
	// FIXME: can we do this in an endian-proof way?
	#ifdef RTC_ARCH_CPU_BIG_ENDIAN
	#define blk0(i) block->l[i]
	#else
	#define blk0(i) (block->l[i] = (rol(block->l[i], 24) & 0xFF00FF00) \| \
	(rol(block->l[i], 8) & 0x00FF00FF))
	#endif
	#define blk(i) (block->l[i & 15] = rol(block->l[(i + 13) & 15] ^ \
	block->l[(i + 8) & 15] ^ block->l[(i + 2) & 15] ^ block->l[i & 15], 1))

	// (R0+R1), R2, R3, R4 are the different operations used in SHA1.
	#define R0(v, w, x, y, z, i) \
	z += ((w & (x ^ y)) ^ y) + blk0(i) + 0x5A827999 + rol(v, 5); \
	w = rol(w, 30);
	#define R1(v, w, x, y, z, i) \
	z += ((w & (x ^ y)) ^ y) + blk(i) + 0x5A827999 + rol(v, 5); \
	w = rol(w, 30);
	#define R2(v, w, x, y, z, i) \
	z += (w ^ x ^ y) + blk(i) + 0x6ED9EBA1 + rol(v, 5);\
	w = rol(w, 30);
	#define R3(v, w, x, y, z, i) \
	z += (((w \| x) & y) \| (w & x)) + blk(i) + 0x8F1BBCDC + rol(v, 5); \
	w = rol(w, 30);
	#define R4(v, w, x, y, z, i) \
	z += (w ^ x ^ y) + blk(i) + 0xCA62C1D6 + rol(v, 5); \
	w = rol(w, 30);

	#ifdef VERBOSE // SAK
	void SHAPrintContext(SHA1_CTX context, char msg) {
	printf("%s (%d,%d) %x %x %x %x %x\n",
	msg,
	context->count[0], context->count[1],
	context->state[0],
	context->state[1],
	context->state[2],
	context->state[3],
	context->state[4]);
	}
	#endif /* VERBOSE */

	// Hash a single 512-bit block. This is the core of the algorithm.
	void SHA1Transform(uint32_t state[5], const uint8_t buffer[64]) {
	union CHAR64LONG16 {
	uint8_t c[64];
	uint32_t l[16];
	};
	#ifdef SHA1HANDSOFF
	uint8_t workspace[64];
	memcpy(workspace, buffer, 64);
	CHAR64LONG16* block = reinterpret_cast<CHAR64LONG16*>(workspace);
	#else
	// Note(fbarchard): This option does modify the user's data buffer.
	CHAR64LONG16* block = const_cast<CHAR64LONG16*>(
	reinterpret_cast<const CHAR64LONG16*>(buffer));
	#endif

	// Copy context->state[] to working vars.
	uint32_t a = state[0];
	uint32_t b = state[1];
	uint32_t c = state[2];
	uint32_t d = state[3];
	uint32_t e = state[4];

	// 4 rounds of 20 operations each. Loop unrolled.
	// Note(fbarchard): The following has lint warnings for multiple ; on
	// a line and no space after , but is left as-is to be similar to the
	// original code.
	R0(a,b,c,d,e,0); R0(e,a,b,c,d,1); R0(d,e,a,b,c,2); R0(c,d,e,a,b,3);
	R0(b,c,d,e,a,4); R0(a,b,c,d,e,5); R0(e,a,b,c,d,6); R0(d,e,a,b,c,7);
	R0(c,d,e,a,b,8); R0(b,c,d,e,a,9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
	R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
	R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
	R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
	R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
	R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
	R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
	R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
	R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
	R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
	R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
	R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
	R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
	R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
	R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
	R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
	R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
	R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);

	// Add the working vars back into context.state[].
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
	state[4] += e;
	}

	} // namespace

	// SHA1Init - Initialize new context.
	void SHA1Init(SHA1_CTX* context) {
	// SHA1 initialization constants.
	context->state[0] = 0x67452301;
	context->state[1] = 0xEFCDAB89;
	context->state[2] = 0x98BADCFE;
	context->state[3] = 0x10325476;
	context->state[4] = 0xC3D2E1F0;
	context->count[0] = context->count[1] = 0;
	}

	// Run your data through this.
	void SHA1Update(SHA1_CTX* context, const uint8_t* data, size_t input_len) {
	size_t i = 0;

	#ifdef VERBOSE
	SHAPrintContext(context, "before");
	#endif

	// Compute number of bytes mod 64.
	size_t index = (context->count[0] >> 3) & 63;

	// Update number of bits.
	// TODO: Use uint64_t instead of 2 uint32_t for count.
	// count[0] has low 29 bits for byte count + 3 pad 0's making 32 bits for
	// bit count.
	// Add bit count to low uint32_t
	context->count[0] += static_cast<uint32_t>(input_len << 3);
	if (context->count[0] < static_cast<uint32_t>(input_len << 3)) {
	++context->count[1]; // if overlow (carry), add one to high word
	}
	context->count[1] += static_cast<uint32_t>(input_len >> 29);
	if ((index + input_len) > 63) {
	i = 64 - index;
	memcpy(&context->buffer[index], data, i);
	SHA1Transform(context->state, context->buffer);
	for (; i + 63 < input_len; i += 64) {
	SHA1Transform(context->state, data + i);
	}
	index = 0;
	}
	memcpy(&context->buffer[index], &data[i], input_len - i);

	#ifdef VERBOSE
	SHAPrintContext(context, "after ");
	#endif
	}

	// Add padding and return the message digest.
	void SHA1Final(SHA1_CTX* context, uint8_t digest[SHA1_DIGEST_SIZE]) {
	uint8_t finalcount[8];
	for (int i = 0; i < 8; ++i) {
	// Endian independent
	finalcount[i] = static_cast<uint8_t>(
	(context->count[(i >= 4 ? 0 : 1)] >> ((3 - (i & 3)) * 8)) & 255);
	}
	SHA1Update(context, reinterpret_cast<const uint8_t*>("\200"), 1);
	while ((context->count[0] & 504) != 448) {
	SHA1Update(context, reinterpret_cast<const uint8_t*>("\0"), 1);
	}
	SHA1Update(context, finalcount, 8); // Should cause a SHA1Transform().
	for (int i = 0; i < SHA1_DIGEST_SIZE; ++i) {
	digest[i] = static_cast<uint8_t>(
	(context->state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
	}

	// Wipe variables.
	memset(context->buffer, 0, 64);
	memset(context->state, 0, 20);
	memset(context->count, 0, 8);
	memset(finalcount, 0, 8); // SWR

	#ifdef SHA1HANDSOFF // Make SHA1Transform overwrite its own static vars.
	SHA1Transform(context->state, context->buffer);
	#endif
	}

	} // namespace rtc