winamp/Src/auth/sha2.c
2024-09-24 14:54:57 +02:00

610 lines
19 KiB
C

/*
* FILE: sha2.c
* AUTHOR: Aaron D. Gifford <me@aarongifford.com>
*
* Copyright (c) 2000-2001, Aaron D. Gifford
* 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.
* 3. Neither the name of the copyright holder nor the names of contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTOR(S) ``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 CONTRIBUTOR(S) 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 <string.h> /* memcpy()/memset() or bcopy()/bzero() */
#include <assert.h> /* assert() */
#include "sha2.h"
/*
* ASSERT NOTE:
* Some sanity checking code is included using assert(). On my FreeBSD
* system, this additional code can be removed by compiling with NDEBUG
* defined. Check your own systems manpage on assert() to see how to
* compile WITHOUT the sanity checking code on your system.
*
* UNROLLED TRANSFORM LOOP NOTE:
* You can define SHA2_UNROLL_TRANSFORM to use the unrolled transform
* loop version for the hash transform rounds (defined using macros
* later in this file). Either define on the command line, for example:
*
* cc -DSHA2_UNROLL_TRANSFORM -o sha2 sha2.c sha2prog.c
*
* or define below:
*
* #define SHA2_UNROLL_TRANSFORM
*
*/
/*** SHA-256/384/512 Machine Architecture Definitions *****************/
/*
* BYTE_ORDER NOTE:
*
* Please make sure that your system defines BYTE_ORDER. If your
* architecture is little-endian, make sure it also defines
* LITTLE_ENDIAN and that the two (BYTE_ORDER and LITTLE_ENDIAN) are
* equivilent.
*
* If your system does not define the above, then you can do so by
* hand like this:
*
* #define LITTLE_ENDIAN 1234
* #define BIG_ENDIAN 4321
*
* And for little-endian machines, add:
*
* #define BYTE_ORDER LITTLE_ENDIAN
*
* Or for big-endian machines:
*
* #define BYTE_ORDER BIG_ENDIAN
*
* The FreeBSD machine this was written on defines BYTE_ORDER
* appropriately by including <sys/types.h> (which in turn includes
* <machine/endian.h> where the appropriate definitions are actually
* made).
*/
#if !defined(BYTE_ORDER) || (BYTE_ORDER != LITTLE_ENDIAN && BYTE_ORDER != BIG_ENDIAN)
#error Define BYTE_ORDER to be equal to either LITTLE_ENDIAN or BIG_ENDIAN
#endif
/*
* Define the followingsha2_* types to types of the correct length on
* the native archtecture. Most BSD systems and Linux define u_intXX_t
* types. Machines with very recent ANSI C headers, can use the
* uintXX_t definintions from inttypes.h by defining SHA2_USE_INTTYPES_H
* during compile or in the sha.h header file.
*
* Machines that support neither u_intXX_t nor inttypes.h's uintXX_t
* will need to define these three typedefs below (and the appropriate
* ones in sha.h too) by hand according to their system architecture.
*
* Thank you, Jun-ichiro itojun Hagino, for suggesting using u_intXX_t
* types and pointing out recent ANSI C support for uintXX_t in inttypes.h.
*/
#ifdef SHA2_USE_INTTYPES_H
typedef uint8_t sha2_byte; /* Exactly 1 byte */
typedef uint32_t sha2_word32; /* Exactly 4 bytes */
typedef uint64_t sha2_word64; /* Exactly 8 bytes */
#else /* SHA2_USE_INTTYPES_H */
typedef u_int8_t sha2_byte; /* Exactly 1 byte */
typedef u_int32_t sha2_word32; /* Exactly 4 bytes */
typedef u_int64_t sha2_word64; /* Exactly 8 bytes */
#endif /* SHA2_USE_INTTYPES_H */
/*** SHA-256/384/512 Various Length Definitions ***********************/
/* NOTE: Most of these are in sha2.h */
#define SHA256_SHORT_BLOCK_LENGTH (SHA256_BLOCK_LENGTH - 8)
#define SHA384_SHORT_BLOCK_LENGTH (SHA384_BLOCK_LENGTH - 16)
#define SHA512_SHORT_BLOCK_LENGTH (SHA512_BLOCK_LENGTH - 16)
/*** ENDIAN REVERSAL MACROS *******************************************/
#if BYTE_ORDER == LITTLE_ENDIAN
#define REVERSE32(w,x) { \
sha2_word32 tmp = (w); \
tmp = (tmp >> 16) | (tmp << 16); \
(x) = ((tmp & 0xff00ff00UL) >> 8) | ((tmp & 0x00ff00ffUL) << 8); \
}
#ifdef WIN32
#define REVERSE64(w,x) { \
sha2_word64 tmp = (w); \
tmp = (tmp >> 32) | (tmp << 32); \
tmp = ((tmp & 0xff00ff00ff00ff00Ui64) >> 8) | \
((tmp & 0x00ff00ff00ff00ffUi64) << 8); \
(x) = ((tmp & 0xffff0000ffff0000Ui64) >> 16) | \
((tmp & 0x0000ffff0000ffffUi64) << 16); \
}
#else
#define REVERSE64(w,x) { \
sha2_word64 tmp = (w); \
tmp = (tmp >> 32) | (tmp << 32); \
tmp = ((tmp & 0xff00ff00ff00ff00ULL) >> 8) | \
((tmp & 0x00ff00ff00ff00ffULL) << 8); \
(x) = ((tmp & 0xffff0000ffff0000ULL) >> 16) | \
((tmp & 0x0000ffff0000ffffULL) << 16); \
}
#endif /* WIN32 */
#endif /* BYTE_ORDER == LITTLE_ENDIAN */
/*
* Macro for incrementally adding the unsigned 64-bit integer n to the
* unsigned 128-bit integer (represented using a two-element array of
* 64-bit words):
*/
#define ADDINC128(w,n) { \
(w)[0] += (sha2_word64)(n); \
if ((w)[0] < (n)) { \
(w)[1]++; \
} \
}
/*
* Macros for copying blocks of memory and for zeroing out ranges
* of memory. Using these macros makes it easy to switch from
* using memset()/memcpy() and using bzero()/bcopy().
*
* Please define either SHA2_USE_MEMSET_MEMCPY or define
* SHA2_USE_BZERO_BCOPY depending on which function set you
* choose to use:
*/
#if !defined(SHA2_USE_MEMSET_MEMCPY) && !defined(SHA2_USE_BZERO_BCOPY)
/* Default to memset()/memcpy() if no option is specified */
#define SHA2_USE_MEMSET_MEMCPY 1
#endif
#if defined(SHA2_USE_MEMSET_MEMCPY) && defined(SHA2_USE_BZERO_BCOPY)
/* Abort with an error if BOTH options are defined */
#error Define either SHA2_USE_MEMSET_MEMCPY or SHA2_USE_BZERO_BCOPY, not both!
#endif
#ifdef SHA2_USE_MEMSET_MEMCPY
#define MEMSET_BZERO(p,l) memset((p), 0, (l))
#define MEMCPY_BCOPY(d,s,l) memcpy((d), (s), (l))
#endif
#ifdef SHA2_USE_BZERO_BCOPY
#define MEMSET_BZERO(p,l) bzero((p), (l))
#define MEMCPY_BCOPY(d,s,l) bcopy((s), (d), (l))
#endif
/*** THE SIX LOGICAL FUNCTIONS ****************************************/
/*
* Bit shifting and rotation (used by the six SHA-XYZ logical functions:
*
* NOTE: The naming of R and S appears backwards here (R is a SHIFT and
* S is a ROTATION) because the SHA-256/384/512 description document
* (see http://csrc.nist.gov/cryptval/shs/sha256-384-512.pdf) uses this
* same "backwards" definition.
*/
/* Shift-right (used in SHA-256, SHA-384, and SHA-512): */
#define R(b,x) ((x) >> (b))
/* 32-bit Rotate-right (used in SHA-256): */
#define S32(b,x) (((x) >> (b)) | ((x) << (32 - (b))))
/* 64-bit Rotate-right (used in SHA-384 and SHA-512): */
#define S64(b,x) (((x) >> (b)) | ((x) << (64 - (b))))
/* Two of six logical functions used in SHA-256, SHA-384, and SHA-512: */
#define Ch(x,y,z) (((x) & (y)) ^ ((~(x)) & (z)))
#define Maj(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
/* Four of six logical functions used in SHA-256: */
#define Sigma0_256(x) (S32(2, (x)) ^ S32(13, (x)) ^ S32(22, (x)))
#define Sigma1_256(x) (S32(6, (x)) ^ S32(11, (x)) ^ S32(25, (x)))
#define sigma0_256(x) (S32(7, (x)) ^ S32(18, (x)) ^ R(3 , (x)))
#define sigma1_256(x) (S32(17, (x)) ^ S32(19, (x)) ^ R(10, (x)))
/* Four of six logical functions used in SHA-384 and SHA-512: */
#define Sigma0_512(x) (S64(28, (x)) ^ S64(34, (x)) ^ S64(39, (x)))
#define Sigma1_512(x) (S64(14, (x)) ^ S64(18, (x)) ^ S64(41, (x)))
#define sigma0_512(x) (S64( 1, (x)) ^ S64( 8, (x)) ^ R( 7, (x)))
#define sigma1_512(x) (S64(19, (x)) ^ S64(61, (x)) ^ R( 6, (x)))
/*** INTERNAL FUNCTION PROTOTYPES *************************************/
/* NOTE: These should not be accessed directly from outside this
* library -- they are intended for private internal visibility/use
* only.
*/
void SHA512_Last(SHA512_CTX*);
void SHA256_Transform(SHA256_CTX*, const sha2_word32*);
void SHA512_Transform(SHA512_CTX*, const sha2_word64*);
/*** SHA-XYZ INITIAL HASH VALUES AND CONSTANTS ************************/
/* Hash constant words K for SHA-256: */
const static sha2_word32 K256[64] = {
0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL,
0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL,
0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL,
0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL,
0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL,
0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL,
0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL,
0xc6e00bf3UL, 0xd5a79147UL, 0x06ca6351UL, 0x14292967UL,
0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL,
0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL,
0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL,
0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL,
0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL,
0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL
};
/* Initial hash value H for SHA-256: */
const static sha2_word32 sha256_initial_hash_value[8] = {
0x6a09e667UL,
0xbb67ae85UL,
0x3c6ef372UL,
0xa54ff53aUL,
0x510e527fUL,
0x9b05688cUL,
0x1f83d9abUL,
0x5be0cd19UL
};
/*
* Constant used by SHA256/384/512_End() functions for converting the
* digest to a readable hexadecimal character string:
*/
static const char *sha2_hex_digits = "0123456789abcdef";
/*** SHA-256: *********************************************************/
void SHA256_Init(SHA256_CTX* context) {
if (context == (SHA256_CTX*)0) {
return;
}
MEMCPY_BCOPY(context->state, sha256_initial_hash_value, SHA256_DIGEST_LENGTH);
MEMSET_BZERO(context->buffer, SHA256_BLOCK_LENGTH);
context->bitcount = 0;
}
#ifdef SHA2_UNROLL_TRANSFORM
/* Unrolled SHA-256 round macros: */
#if BYTE_ORDER == LITTLE_ENDIAN
#define ROUND256_0_TO_15(a,b,c,d,e,f,g,h) \
REVERSE32(*data++, W256[j]); \
T1 = (h) + Sigma1_256(e) + Ch((e), (f), (g)) + \
K256[j] + W256[j]; \
(d) += T1; \
(h) = T1 + Sigma0_256(a) + Maj((a), (b), (c)); \
j++
#else /* BYTE_ORDER == LITTLE_ENDIAN */
#define ROUND256_0_TO_15(a,b,c,d,e,f,g,h) \
T1 = (h) + Sigma1_256(e) + Ch((e), (f), (g)) + \
K256[j] + (W256[j] = *data++); \
(d) += T1; \
(h) = T1 + Sigma0_256(a) + Maj((a), (b), (c)); \
j++
#endif /* BYTE_ORDER == LITTLE_ENDIAN */
#define ROUND256(a,b,c,d,e,f,g,h) \
s0 = W256[(j+1)&0x0f]; \
s0 = sigma0_256(s0); \
s1 = W256[(j+14)&0x0f]; \
s1 = sigma1_256(s1); \
T1 = (h) + Sigma1_256(e) + Ch((e), (f), (g)) + K256[j] + \
(W256[j&0x0f] += s1 + W256[(j+9)&0x0f] + s0); \
(d) += T1; \
(h) = T1 + Sigma0_256(a) + Maj((a), (b), (c)); \
j++
void SHA256_Transform(SHA256_CTX* context, const sha2_word32* data) {
sha2_word32 a, b, c, d, e, f, g, h, s0, s1;
sha2_word32 T1, *W256;
int j;
W256 = (sha2_word32*)context->buffer;
/* Initialize registers with the prev. intermediate value */
a = context->state[0];
b = context->state[1];
c = context->state[2];
d = context->state[3];
e = context->state[4];
f = context->state[5];
g = context->state[6];
h = context->state[7];
j = 0;
do {
/* Rounds 0 to 15 (unrolled): */
ROUND256_0_TO_15(a,b,c,d,e,f,g,h);
ROUND256_0_TO_15(h,a,b,c,d,e,f,g);
ROUND256_0_TO_15(g,h,a,b,c,d,e,f);
ROUND256_0_TO_15(f,g,h,a,b,c,d,e);
ROUND256_0_TO_15(e,f,g,h,a,b,c,d);
ROUND256_0_TO_15(d,e,f,g,h,a,b,c);
ROUND256_0_TO_15(c,d,e,f,g,h,a,b);
ROUND256_0_TO_15(b,c,d,e,f,g,h,a);
} while (j < 16);
/* Now for the remaining rounds to 64: */
do {
ROUND256(a,b,c,d,e,f,g,h);
ROUND256(h,a,b,c,d,e,f,g);
ROUND256(g,h,a,b,c,d,e,f);
ROUND256(f,g,h,a,b,c,d,e);
ROUND256(e,f,g,h,a,b,c,d);
ROUND256(d,e,f,g,h,a,b,c);
ROUND256(c,d,e,f,g,h,a,b);
ROUND256(b,c,d,e,f,g,h,a);
} while (j < 64);
/* Compute the current intermediate hash value */
context->state[0] += a;
context->state[1] += b;
context->state[2] += c;
context->state[3] += d;
context->state[4] += e;
context->state[5] += f;
context->state[6] += g;
context->state[7] += h;
/* Clean up */
a = b = c = d = e = f = g = h = T1 = 0;
}
#else /* SHA2_UNROLL_TRANSFORM */
void SHA256_Transform(SHA256_CTX* context, const sha2_word32* data) {
sha2_word32 a, b, c, d, e, f, g, h;
sha2_word32 T1, T2, *W256;
int j;
W256 = (sha2_word32*)context->buffer;
/* Initialize registers with the prev. intermediate value */
a = context->state[0];
b = context->state[1];
c = context->state[2];
d = context->state[3];
e = context->state[4];
f = context->state[5];
g = context->state[6];
h = context->state[7];
j = 0;
do {
#if BYTE_ORDER == LITTLE_ENDIAN
/* Copy data while converting to host byte order */
REVERSE32(*data++,W256[j]);
/* Apply the SHA-256 compression function to update a..h */
T1 = h + Sigma1_256(e) + Ch(e, f, g) + K256[j] + W256[j];
#else /* BYTE_ORDER == LITTLE_ENDIAN */
/* Apply the SHA-256 compression function to update a..h with copy */
T1 = h + Sigma1_256(e) + Ch(e, f, g) + K256[j] + (W256[j] = *data++);
#endif /* BYTE_ORDER == LITTLE_ENDIAN */
T2 = Sigma0_256(a) + Maj(a, b, c);
h = g;
g = f;
f = e;
e = d + T1;
d = c;
c = b;
b = a;
a = T1 + T2;
j++;
} while (j < 16);
do {
sha2_word32 s0, s1;
/* Part of the message block expansion: */
s0 = W256[(j+1)&0x0f];
s0 = sigma0_256(s0);
s1 = W256[(j+14)&0x0f];
s1 = sigma1_256(s1);
/* Apply the SHA-256 compression function to update a..h */
T1 = h + Sigma1_256(e) + Ch(e, f, g) + K256[j] +
(W256[j&0x0f] += s1 + W256[(j+9)&0x0f] + s0);
T2 = Sigma0_256(a) + Maj(a, b, c);
h = g;
g = f;
f = e;
e = d + T1;
d = c;
c = b;
b = a;
a = T1 + T2;
j++;
} while (j < 64);
/* Compute the current intermediate hash value */
context->state[0] += a;
context->state[1] += b;
context->state[2] += c;
context->state[3] += d;
context->state[4] += e;
context->state[5] += f;
context->state[6] += g;
context->state[7] += h;
/* Clean up */
a = b = c = d = e = f = g = h = T1 = T2 = 0;
}
#endif /* SHA2_UNROLL_TRANSFORM */
void SHA256_Update(SHA256_CTX* context, const sha2_byte *data, size_t len) {
unsigned int freespace, usedspace;
if (len == 0) {
/* Calling with no data is valid - we do nothing */
return;
}
/* Sanity check: */
assert(context != (SHA256_CTX*)0 && data != (sha2_byte*)0);
usedspace = (context->bitcount >> 3) % SHA256_BLOCK_LENGTH;
if (usedspace > 0) {
/* Calculate how much free space is available in the buffer */
freespace = SHA256_BLOCK_LENGTH - usedspace;
if (len >= freespace) {
/* Fill the buffer completely and process it */
MEMCPY_BCOPY(&context->buffer[usedspace], data, freespace);
context->bitcount += freespace << 3;
len -= freespace;
data += freespace;
SHA256_Transform(context, (sha2_word32*)context->buffer);
} else {
/* The buffer is not yet full */
MEMCPY_BCOPY(&context->buffer[usedspace], data, len);
context->bitcount += len << 3;
/* Clean up: */
usedspace = freespace = 0;
return;
}
}
while (len >= SHA256_BLOCK_LENGTH) {
/* Process as many complete blocks as we can */
SHA256_Transform(context, (sha2_word32*)data);
context->bitcount += SHA256_BLOCK_LENGTH << 3;
len -= SHA256_BLOCK_LENGTH;
data += SHA256_BLOCK_LENGTH;
}
if (len > 0) {
/* There's left-overs, so save 'em */
MEMCPY_BCOPY(context->buffer, data, len);
context->bitcount += len << 3;
}
/* Clean up: */
usedspace = freespace = 0;
}
void SHA256_Final(sha2_byte digest[], SHA256_CTX* context) {
sha2_word32 *d = (sha2_word32*)digest;
unsigned int usedspace;
/* Sanity check: */
assert(context != (SHA256_CTX*)0);
/* If no digest buffer is passed, we don't bother doing this: */
if (digest != (sha2_byte*)0) {
usedspace = (context->bitcount >> 3) % SHA256_BLOCK_LENGTH;
#if BYTE_ORDER == LITTLE_ENDIAN
/* Convert FROM host byte order */
REVERSE64(context->bitcount,context->bitcount);
#endif
if (usedspace > 0) {
/* Begin padding with a 1 bit: */
context->buffer[usedspace++] = 0x80;
if (usedspace <= SHA256_SHORT_BLOCK_LENGTH) {
/* Set-up for the last transform: */
MEMSET_BZERO(&context->buffer[usedspace], SHA256_SHORT_BLOCK_LENGTH - usedspace);
} else {
if (usedspace < SHA256_BLOCK_LENGTH) {
MEMSET_BZERO(&context->buffer[usedspace], SHA256_BLOCK_LENGTH - usedspace);
}
/* Do second-to-last transform: */
SHA256_Transform(context, (sha2_word32*)context->buffer);
/* And set-up for the last transform: */
MEMSET_BZERO(context->buffer, SHA256_SHORT_BLOCK_LENGTH);
}
} else {
/* Set-up for the last transform: */
MEMSET_BZERO(context->buffer, SHA256_SHORT_BLOCK_LENGTH);
/* Begin padding with a 1 bit: */
*context->buffer = 0x80;
}
/* Set the bit count: */
*(sha2_word64*)&context->buffer[SHA256_SHORT_BLOCK_LENGTH] = context->bitcount;
/* Final transform: */
SHA256_Transform(context, (sha2_word32*)context->buffer);
#if BYTE_ORDER == LITTLE_ENDIAN
{
/* Convert TO host byte order */
int j;
for (j = 0; j < 8; j++) {
REVERSE32(context->state[j],context->state[j]);
*d++ = context->state[j];
}
}
#else
MEMCPY_BCOPY(d, context->state, SHA256_DIGEST_LENGTH);
#endif
}
/* Clean up state data: */
MEMSET_BZERO(context, sizeof(context));
usedspace = 0;
}
char *SHA256_End(SHA256_CTX* context, char buffer[]) {
sha2_byte digest[SHA256_DIGEST_LENGTH], *d = digest;
/* Sanity check: */
assert(context != (SHA256_CTX*)0);
if (buffer != (char*)0) {
int i = 0;
SHA256_Final(digest, context);
for (; i < SHA256_DIGEST_LENGTH; i++) {
*buffer++ = sha2_hex_digits[(*d & 0xf0) >> 4];
*buffer++ = sha2_hex_digits[*d & 0x0f];
d++;
}
*buffer = (char)0;
} else {
MEMSET_BZERO(context, sizeof(context));
}
MEMSET_BZERO(digest, SHA256_DIGEST_LENGTH);
return buffer;
}
char* SHA256_Data(const sha2_byte* data, size_t len, char digest[SHA256_DIGEST_STRING_LENGTH]) {
SHA256_CTX context;
SHA256_Init(&context);
SHA256_Update(&context, data, len);
return SHA256_End(&context, digest);
}