lib/sha256.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * FIPS-180-2 compliant SHA-256 implementation
  *
  * Copyright (C) 2001-2003  Christophe Devine
  */

 #ifndef USE_HOSTCC
 #include <u-boot/schedule.h>
 #endif /* USE_HOSTCC */
 #include <string.h>
 #include <u-boot/sha256.h>

 #include <linux/compiler_attributes.h>

 const uint8_t sha256_der_prefix[SHA256_DER_LEN] = {
 	0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
 	0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
 	0x00, 0x04, 0x20
 };

 /*
  * 32-bit integer manipulation macros (big endian)
  */
 #ifndef GET_UINT32_BE
 #define GET_UINT32_BE(n,b,i) {				\
 	(n) = ( (unsigned long) (b)[(i)    ] << 24 )	\
 	    | ( (unsigned long) (b)[(i) + 1] << 16 )	\
 	    | ( (unsigned long) (b)[(i) + 2] <<  8 )	\
 	    | ( (unsigned long) (b)[(i) + 3]       );	\
 }
 #endif
 #ifndef PUT_UINT32_BE
 #define PUT_UINT32_BE(n,b,i) {				\
 	(b)[(i)    ] = (unsigned char) ( (n) >> 24 );	\
 	(b)[(i) + 1] = (unsigned char) ( (n) >> 16 );	\
 	(b)[(i) + 2] = (unsigned char) ( (n) >>  8 );	\
 	(b)[(i) + 3] = (unsigned char) ( (n)       );	\
 }
 #endif

 void sha256_starts(sha256_context * ctx)
 {
 	ctx->total[0] = 0;
 	ctx->total[1] = 0;

 	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;
 }

 static void sha256_process_one(sha256_context *ctx, const uint8_t data[64])
 {
 	uint32_t temp1, temp2;
 	uint32_t W[64];
 	uint32_t A, B, C, D, E, F, G, H;

 	GET_UINT32_BE(W[0], data, 0);
 	GET_UINT32_BE(W[1], data, 4);
 	GET_UINT32_BE(W[2], data, 8);
 	GET_UINT32_BE(W[3], data, 12);
 	GET_UINT32_BE(W[4], data, 16);
 	GET_UINT32_BE(W[5], data, 20);
 	GET_UINT32_BE(W[6], data, 24);
 	GET_UINT32_BE(W[7], data, 28);
 	GET_UINT32_BE(W[8], data, 32);
 	GET_UINT32_BE(W[9], data, 36);
 	GET_UINT32_BE(W[10], data, 40);
 	GET_UINT32_BE(W[11], data, 44);
 	GET_UINT32_BE(W[12], data, 48);
 	GET_UINT32_BE(W[13], data, 52);
 	GET_UINT32_BE(W[14], data, 56);
 	GET_UINT32_BE(W[15], data, 60);

 #define SHR(x,n) ((x & 0xFFFFFFFF) >> n)
 #define ROTR(x,n) (SHR(x,n) | (x << (32 - n)))

 #define S0(x) (ROTR(x, 7) ^ ROTR(x,18) ^ SHR(x, 3))
 #define S1(x) (ROTR(x,17) ^ ROTR(x,19) ^ SHR(x,10))

 #define S2(x) (ROTR(x, 2) ^ ROTR(x,13) ^ ROTR(x,22))
 #define S3(x) (ROTR(x, 6) ^ ROTR(x,11) ^ ROTR(x,25))

 #define F0(x,y,z) ((x & y) | (z & (x | y)))
 #define F1(x,y,z) (z ^ (x & (y ^ z)))

 #define R(t)					\
 (						\
 	W[t] = S1(W[t - 2]) + W[t - 7] +	\
 		S0(W[t - 15]) + W[t - 16]	\
 )

 #define P(a,b,c,d,e,f,g,h,x,K) {		\
 	temp1 = h + S3(e) + F1(e,f,g) + K + x;	\
 	temp2 = S2(a) + F0(a,b,c);		\
 	d += temp1; h = temp1 + temp2;		\
 }

 	A = ctx->state[0];
 	B = ctx->state[1];
 	C = ctx->state[2];
 	D = ctx->state[3];
 	E = ctx->state[4];
 	F = ctx->state[5];
 	G = ctx->state[6];
 	H = ctx->state[7];

 	P(A, B, C, D, E, F, G, H, W[0], 0x428A2F98);
 	P(H, A, B, C, D, E, F, G, W[1], 0x71374491);
 	P(G, H, A, B, C, D, E, F, W[2], 0xB5C0FBCF);
 	P(F, G, H, A, B, C, D, E, W[3], 0xE9B5DBA5);
 	P(E, F, G, H, A, B, C, D, W[4], 0x3956C25B);
 	P(D, E, F, G, H, A, B, C, W[5], 0x59F111F1);
 	P(C, D, E, F, G, H, A, B, W[6], 0x923F82A4);
 	P(B, C, D, E, F, G, H, A, W[7], 0xAB1C5ED5);
 	P(A, B, C, D, E, F, G, H, W[8], 0xD807AA98);
 	P(H, A, B, C, D, E, F, G, W[9], 0x12835B01);
 	P(G, H, A, B, C, D, E, F, W[10], 0x243185BE);
 	P(F, G, H, A, B, C, D, E, W[11], 0x550C7DC3);
 	P(E, F, G, H, A, B, C, D, W[12], 0x72BE5D74);
 	P(D, E, F, G, H, A, B, C, W[13], 0x80DEB1FE);
 	P(C, D, E, F, G, H, A, B, W[14], 0x9BDC06A7);
 	P(B, C, D, E, F, G, H, A, W[15], 0xC19BF174);
 	P(A, B, C, D, E, F, G, H, R(16), 0xE49B69C1);
 	P(H, A, B, C, D, E, F, G, R(17), 0xEFBE4786);
 	P(G, H, A, B, C, D, E, F, R(18), 0x0FC19DC6);
 	P(F, G, H, A, B, C, D, E, R(19), 0x240CA1CC);
 	P(E, F, G, H, A, B, C, D, R(20), 0x2DE92C6F);
 	P(D, E, F, G, H, A, B, C, R(21), 0x4A7484AA);
 	P(C, D, E, F, G, H, A, B, R(22), 0x5CB0A9DC);
 	P(B, C, D, E, F, G, H, A, R(23), 0x76F988DA);
 	P(A, B, C, D, E, F, G, H, R(24), 0x983E5152);
 	P(H, A, B, C, D, E, F, G, R(25), 0xA831C66D);
 	P(G, H, A, B, C, D, E, F, R(26), 0xB00327C8);
 	P(F, G, H, A, B, C, D, E, R(27), 0xBF597FC7);
 	P(E, F, G, H, A, B, C, D, R(28), 0xC6E00BF3);
 	P(D, E, F, G, H, A, B, C, R(29), 0xD5A79147);
 	P(C, D, E, F, G, H, A, B, R(30), 0x06CA6351);
 	P(B, C, D, E, F, G, H, A, R(31), 0x14292967);
 	P(A, B, C, D, E, F, G, H, R(32), 0x27B70A85);
 	P(H, A, B, C, D, E, F, G, R(33), 0x2E1B2138);
 	P(G, H, A, B, C, D, E, F, R(34), 0x4D2C6DFC);
 	P(F, G, H, A, B, C, D, E, R(35), 0x53380D13);
 	P(E, F, G, H, A, B, C, D, R(36), 0x650A7354);
 	P(D, E, F, G, H, A, B, C, R(37), 0x766A0ABB);
 	P(C, D, E, F, G, H, A, B, R(38), 0x81C2C92E);
 	P(B, C, D, E, F, G, H, A, R(39), 0x92722C85);
 	P(A, B, C, D, E, F, G, H, R(40), 0xA2BFE8A1);
 	P(H, A, B, C, D, E, F, G, R(41), 0xA81A664B);
 	P(G, H, A, B, C, D, E, F, R(42), 0xC24B8B70);
 	P(F, G, H, A, B, C, D, E, R(43), 0xC76C51A3);
 	P(E, F, G, H, A, B, C, D, R(44), 0xD192E819);
 	P(D, E, F, G, H, A, B, C, R(45), 0xD6990624);
 	P(C, D, E, F, G, H, A, B, R(46), 0xF40E3585);
 	P(B, C, D, E, F, G, H, A, R(47), 0x106AA070);
 	P(A, B, C, D, E, F, G, H, R(48), 0x19A4C116);
 	P(H, A, B, C, D, E, F, G, R(49), 0x1E376C08);
 	P(G, H, A, B, C, D, E, F, R(50), 0x2748774C);
 	P(F, G, H, A, B, C, D, E, R(51), 0x34B0BCB5);
 	P(E, F, G, H, A, B, C, D, R(52), 0x391C0CB3);
 	P(D, E, F, G, H, A, B, C, R(53), 0x4ED8AA4A);
 	P(C, D, E, F, G, H, A, B, R(54), 0x5B9CCA4F);
 	P(B, C, D, E, F, G, H, A, R(55), 0x682E6FF3);
 	P(A, B, C, D, E, F, G, H, R(56), 0x748F82EE);
 	P(H, A, B, C, D, E, F, G, R(57), 0x78A5636F);
 	P(G, H, A, B, C, D, E, F, R(58), 0x84C87814);
 	P(F, G, H, A, B, C, D, E, R(59), 0x8CC70208);
 	P(E, F, G, H, A, B, C, D, R(60), 0x90BEFFFA);
 	P(D, E, F, G, H, A, B, C, R(61), 0xA4506CEB);
 	P(C, D, E, F, G, H, A, B, R(62), 0xBEF9A3F7);
 	P(B, C, D, E, F, G, H, A, R(63), 0xC67178F2);

 	ctx->state[0] += A;
 	ctx->state[1] += B;
 	ctx->state[2] += C;
 	ctx->state[3] += D;
 	ctx->state[4] += E;
 	ctx->state[5] += F;
 	ctx->state[6] += G;
 	ctx->state[7] += H;
 }

 __weak void sha256_process(sha256_context *ctx, const unsigned char *data,
 			   unsigned int blocks)
 {
 	if (!blocks)
 		return;

 	while (blocks--) {
 		sha256_process_one(ctx, data);
 		data += 64;
 	}
 }

 void sha256_update(sha256_context *ctx, const uint8_t *input, uint32_t length)
 {
 	uint32_t left, fill;

 	if (!length)
 		return;

 	left = ctx->total[0] & 0x3F;
 	fill = 64 - left;

 	ctx->total[0] += length;
 	ctx->total[0] &= 0xFFFFFFFF;

 	if (ctx->total[0] < length)
 		ctx->total[1]++;

 	if (left && length >= fill) {
 		memcpy((void *) (ctx->buffer + left), (void *) input, fill);
 		sha256_process(ctx, ctx->buffer, 1);
 		length -= fill;
 		input += fill;
 		left = 0;
 	}

 	sha256_process(ctx, input, length / 64);
 	input += length / 64 * 64;
 	length = length % 64;

 	if (length)
 		memcpy((void *) (ctx->buffer + left), (void *) input, length);
 }

 static uint8_t sha256_padding[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
 };

 void sha256_finish(sha256_context * ctx, uint8_t digest[32])
 {
 	uint32_t last, padn;
 	uint32_t high, low;
 	uint8_t msglen[8];

 	high = ((ctx->total[0] >> 29)
 		| (ctx->total[1] << 3));
 	low = (ctx->total[0] << 3);

 	PUT_UINT32_BE(high, msglen, 0);
 	PUT_UINT32_BE(low, msglen, 4);

 	last = ctx->total[0] & 0x3F;
 	padn = (last < 56) ? (56 - last) : (120 - last);

 	sha256_update(ctx, sha256_padding, padn);
 	sha256_update(ctx, msglen, 8);

 	PUT_UINT32_BE(ctx->state[0], digest, 0);
 	PUT_UINT32_BE(ctx->state[1], digest, 4);
 	PUT_UINT32_BE(ctx->state[2], digest, 8);
 	PUT_UINT32_BE(ctx->state[3], digest, 12);
 	PUT_UINT32_BE(ctx->state[4], digest, 16);
 	PUT_UINT32_BE(ctx->state[5], digest, 20);
 	PUT_UINT32_BE(ctx->state[6], digest, 24);
 	PUT_UINT32_BE(ctx->state[7], digest, 28);
 }

 /*
  * Output = SHA-256( input buffer ). Trigger the watchdog every 'chunk_sz'
  * bytes of input processed.
  */
 void sha256_csum_wd(const unsigned char *input, unsigned int ilen,
 		unsigned char *output, unsigned int chunk_sz)
 {
 	sha256_context ctx;
 #if defined(CONFIG_HW_WATCHDOG) || defined(CONFIG_WATCHDOG)
 	const unsigned char *end;
 	unsigned char *curr;
 	int chunk;
 #endif

 	sha256_starts(&ctx);

 #if defined(CONFIG_HW_WATCHDOG) || defined(CONFIG_WATCHDOG)
 	curr = (unsigned char *)input;
 	end = input + ilen;
 	while (curr < end) {
 		chunk = end - curr;
 		if (chunk > chunk_sz)
 			chunk = chunk_sz;
 		sha256_update(&ctx, curr, chunk);
 		curr += chunk;
 		schedule();
 	}
 #else
 	sha256_update(&ctx, input, ilen);
 #endif

 	sha256_finish(&ctx, output);
 }
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* FIPS-180-2 compliant SHA-256 implementation
	*
	* Copyright (C) 2001-2003 Christophe Devine
	*/

	#ifndef USE_HOSTCC
	#include <u-boot/schedule.h>
	#endif /* USE_HOSTCC */
	#include <string.h>
	#include <u-boot/sha256.h>

	#include <linux/compiler_attributes.h>

	const uint8_t sha256_der_prefix[SHA256_DER_LEN] = {
	0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
	0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
	0x00, 0x04, 0x20
	};

	/*
	* 32-bit integer manipulation macros (big endian)
	*/
	#ifndef GET_UINT32_BE
	#define GET_UINT32_BE(n,b,i) { \
	(n) = ( (unsigned long) (b)[(i) ] << 24 ) \
	\| ( (unsigned long) (b)[(i) + 1] << 16 ) \
	\| ( (unsigned long) (b)[(i) + 2] << 8 ) \
	\| ( (unsigned long) (b)[(i) + 3] ); \
	}
	#endif
	#ifndef PUT_UINT32_BE
	#define PUT_UINT32_BE(n,b,i) { \
	(b)[(i) ] = (unsigned char) ( (n) >> 24 ); \
	(b)[(i) + 1] = (unsigned char) ( (n) >> 16 ); \
	(b)[(i) + 2] = (unsigned char) ( (n) >> 8 ); \
	(b)[(i) + 3] = (unsigned char) ( (n) ); \
	}
	#endif

	void sha256_starts(sha256_context * ctx)
	{
	ctx->total[0] = 0;
	ctx->total[1] = 0;

	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;
	}

	static void sha256_process_one(sha256_context *ctx, const uint8_t data[64])
	{
	uint32_t temp1, temp2;
	uint32_t W[64];
	uint32_t A, B, C, D, E, F, G, H;

	GET_UINT32_BE(W[0], data, 0);
	GET_UINT32_BE(W[1], data, 4);
	GET_UINT32_BE(W[2], data, 8);
	GET_UINT32_BE(W[3], data, 12);
	GET_UINT32_BE(W[4], data, 16);
	GET_UINT32_BE(W[5], data, 20);
	GET_UINT32_BE(W[6], data, 24);
	GET_UINT32_BE(W[7], data, 28);
	GET_UINT32_BE(W[8], data, 32);
	GET_UINT32_BE(W[9], data, 36);
	GET_UINT32_BE(W[10], data, 40);
	GET_UINT32_BE(W[11], data, 44);
	GET_UINT32_BE(W[12], data, 48);
	GET_UINT32_BE(W[13], data, 52);
	GET_UINT32_BE(W[14], data, 56);
	GET_UINT32_BE(W[15], data, 60);

	#define SHR(x,n) ((x & 0xFFFFFFFF) >> n)
	#define ROTR(x,n) (SHR(x,n) \| (x << (32 - n)))

	#define S0(x) (ROTR(x, 7) ^ ROTR(x,18) ^ SHR(x, 3))
	#define S1(x) (ROTR(x,17) ^ ROTR(x,19) ^ SHR(x,10))

	#define S2(x) (ROTR(x, 2) ^ ROTR(x,13) ^ ROTR(x,22))
	#define S3(x) (ROTR(x, 6) ^ ROTR(x,11) ^ ROTR(x,25))

	#define F0(x,y,z) ((x & y) \| (z & (x \| y)))
	#define F1(x,y,z) (z ^ (x & (y ^ z)))

	#define R(t) \
	( \
	W[t] = S1(W[t - 2]) + W[t - 7] + \
	S0(W[t - 15]) + W[t - 16] \
	)

	#define P(a,b,c,d,e,f,g,h,x,K) { \
	temp1 = h + S3(e) + F1(e,f,g) + K + x; \
	temp2 = S2(a) + F0(a,b,c); \
	d += temp1; h = temp1 + temp2; \
	}

	A = ctx->state[0];
	B = ctx->state[1];
	C = ctx->state[2];
	D = ctx->state[3];
	E = ctx->state[4];
	F = ctx->state[5];
	G = ctx->state[6];
	H = ctx->state[7];

	P(A, B, C, D, E, F, G, H, W[0], 0x428A2F98);
	P(H, A, B, C, D, E, F, G, W[1], 0x71374491);
	P(G, H, A, B, C, D, E, F, W[2], 0xB5C0FBCF);
	P(F, G, H, A, B, C, D, E, W[3], 0xE9B5DBA5);
	P(E, F, G, H, A, B, C, D, W[4], 0x3956C25B);
	P(D, E, F, G, H, A, B, C, W[5], 0x59F111F1);
	P(C, D, E, F, G, H, A, B, W[6], 0x923F82A4);
	P(B, C, D, E, F, G, H, A, W[7], 0xAB1C5ED5);
	P(A, B, C, D, E, F, G, H, W[8], 0xD807AA98);
	P(H, A, B, C, D, E, F, G, W[9], 0x12835B01);
	P(G, H, A, B, C, D, E, F, W[10], 0x243185BE);
	P(F, G, H, A, B, C, D, E, W[11], 0x550C7DC3);
	P(E, F, G, H, A, B, C, D, W[12], 0x72BE5D74);
	P(D, E, F, G, H, A, B, C, W[13], 0x80DEB1FE);
	P(C, D, E, F, G, H, A, B, W[14], 0x9BDC06A7);
	P(B, C, D, E, F, G, H, A, W[15], 0xC19BF174);
	P(A, B, C, D, E, F, G, H, R(16), 0xE49B69C1);
	P(H, A, B, C, D, E, F, G, R(17), 0xEFBE4786);
	P(G, H, A, B, C, D, E, F, R(18), 0x0FC19DC6);
	P(F, G, H, A, B, C, D, E, R(19), 0x240CA1CC);
	P(E, F, G, H, A, B, C, D, R(20), 0x2DE92C6F);
	P(D, E, F, G, H, A, B, C, R(21), 0x4A7484AA);
	P(C, D, E, F, G, H, A, B, R(22), 0x5CB0A9DC);
	P(B, C, D, E, F, G, H, A, R(23), 0x76F988DA);
	P(A, B, C, D, E, F, G, H, R(24), 0x983E5152);
	P(H, A, B, C, D, E, F, G, R(25), 0xA831C66D);
	P(G, H, A, B, C, D, E, F, R(26), 0xB00327C8);
	P(F, G, H, A, B, C, D, E, R(27), 0xBF597FC7);
	P(E, F, G, H, A, B, C, D, R(28), 0xC6E00BF3);
	P(D, E, F, G, H, A, B, C, R(29), 0xD5A79147);
	P(C, D, E, F, G, H, A, B, R(30), 0x06CA6351);
	P(B, C, D, E, F, G, H, A, R(31), 0x14292967);
	P(A, B, C, D, E, F, G, H, R(32), 0x27B70A85);
	P(H, A, B, C, D, E, F, G, R(33), 0x2E1B2138);
	P(G, H, A, B, C, D, E, F, R(34), 0x4D2C6DFC);
	P(F, G, H, A, B, C, D, E, R(35), 0x53380D13);
	P(E, F, G, H, A, B, C, D, R(36), 0x650A7354);
	P(D, E, F, G, H, A, B, C, R(37), 0x766A0ABB);
	P(C, D, E, F, G, H, A, B, R(38), 0x81C2C92E);
	P(B, C, D, E, F, G, H, A, R(39), 0x92722C85);
	P(A, B, C, D, E, F, G, H, R(40), 0xA2BFE8A1);
	P(H, A, B, C, D, E, F, G, R(41), 0xA81A664B);
	P(G, H, A, B, C, D, E, F, R(42), 0xC24B8B70);
	P(F, G, H, A, B, C, D, E, R(43), 0xC76C51A3);
	P(E, F, G, H, A, B, C, D, R(44), 0xD192E819);
	P(D, E, F, G, H, A, B, C, R(45), 0xD6990624);
	P(C, D, E, F, G, H, A, B, R(46), 0xF40E3585);
	P(B, C, D, E, F, G, H, A, R(47), 0x106AA070);
	P(A, B, C, D, E, F, G, H, R(48), 0x19A4C116);
	P(H, A, B, C, D, E, F, G, R(49), 0x1E376C08);
	P(G, H, A, B, C, D, E, F, R(50), 0x2748774C);
	P(F, G, H, A, B, C, D, E, R(51), 0x34B0BCB5);
	P(E, F, G, H, A, B, C, D, R(52), 0x391C0CB3);
	P(D, E, F, G, H, A, B, C, R(53), 0x4ED8AA4A);
	P(C, D, E, F, G, H, A, B, R(54), 0x5B9CCA4F);
	P(B, C, D, E, F, G, H, A, R(55), 0x682E6FF3);
	P(A, B, C, D, E, F, G, H, R(56), 0x748F82EE);
	P(H, A, B, C, D, E, F, G, R(57), 0x78A5636F);
	P(G, H, A, B, C, D, E, F, R(58), 0x84C87814);
	P(F, G, H, A, B, C, D, E, R(59), 0x8CC70208);
	P(E, F, G, H, A, B, C, D, R(60), 0x90BEFFFA);
	P(D, E, F, G, H, A, B, C, R(61), 0xA4506CEB);
	P(C, D, E, F, G, H, A, B, R(62), 0xBEF9A3F7);
	P(B, C, D, E, F, G, H, A, R(63), 0xC67178F2);

	ctx->state[0] += A;
	ctx->state[1] += B;
	ctx->state[2] += C;
	ctx->state[3] += D;
	ctx->state[4] += E;
	ctx->state[5] += F;
	ctx->state[6] += G;
	ctx->state[7] += H;
	}

	__weak void sha256_process(sha256_context ctx, const unsigned char data,
	unsigned int blocks)
	{
	if (!blocks)
	return;

	while (blocks--) {
	sha256_process_one(ctx, data);
	data += 64;
	}
	}

	void sha256_update(sha256_context ctx, const uint8_t input, uint32_t length)
	{
	uint32_t left, fill;

	if (!length)
	return;

	left = ctx->total[0] & 0x3F;
	fill = 64 - left;

	ctx->total[0] += length;
	ctx->total[0] &= 0xFFFFFFFF;

	if (ctx->total[0] < length)
	ctx->total[1]++;

	if (left && length >= fill) {
	memcpy((void ) (ctx->buffer + left), (void ) input, fill);
	sha256_process(ctx, ctx->buffer, 1);
	length -= fill;
	input += fill;
	left = 0;
	}

	sha256_process(ctx, input, length / 64);
	input += length / 64 * 64;
	length = length % 64;

	if (length)
	memcpy((void ) (ctx->buffer + left), (void ) input, length);
	}

	static uint8_t sha256_padding[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
	};

	void sha256_finish(sha256_context * ctx, uint8_t digest[32])
	{
	uint32_t last, padn;
	uint32_t high, low;
	uint8_t msglen[8];

	high = ((ctx->total[0] >> 29)
	\| (ctx->total[1] << 3));
	low = (ctx->total[0] << 3);

	PUT_UINT32_BE(high, msglen, 0);
	PUT_UINT32_BE(low, msglen, 4);

	last = ctx->total[0] & 0x3F;
	padn = (last < 56) ? (56 - last) : (120 - last);

	sha256_update(ctx, sha256_padding, padn);
	sha256_update(ctx, msglen, 8);

	PUT_UINT32_BE(ctx->state[0], digest, 0);
	PUT_UINT32_BE(ctx->state[1], digest, 4);
	PUT_UINT32_BE(ctx->state[2], digest, 8);
	PUT_UINT32_BE(ctx->state[3], digest, 12);
	PUT_UINT32_BE(ctx->state[4], digest, 16);
	PUT_UINT32_BE(ctx->state[5], digest, 20);
	PUT_UINT32_BE(ctx->state[6], digest, 24);
	PUT_UINT32_BE(ctx->state[7], digest, 28);
	}

	/*
	* Output = SHA-256( input buffer ). Trigger the watchdog every 'chunk_sz'
	* bytes of input processed.
	*/
	void sha256_csum_wd(const unsigned char *input, unsigned int ilen,
	unsigned char *output, unsigned int chunk_sz)
	{
	sha256_context ctx;
	#if defined(CONFIG_HW_WATCHDOG) \|\| defined(CONFIG_WATCHDOG)
	const unsigned char *end;
	unsigned char *curr;
	int chunk;
	#endif

	sha256_starts(&ctx);

	#if defined(CONFIG_HW_WATCHDOG) \|\| defined(CONFIG_WATCHDOG)
	curr = (unsigned char *)input;
	end = input + ilen;
	while (curr < end) {
	chunk = end - curr;
	if (chunk > chunk_sz)
	chunk = chunk_sz;
	sha256_update(&ctx, curr, chunk);
	curr += chunk;
	schedule();
	}
	#else
	sha256_update(&ctx, input, ilen);
	#endif

	sha256_finish(&ctx, output);
	}