subsurface/sha1.c

/*
 * SHA1 routine optimized to do word accesses rather than byte accesses,
 * and to avoid unnecessary copies into the context array.
 *
 * This was initially based on the Mozilla SHA1 implementation, although
 * none of the original Mozilla code remains.
 */

/* this is only to get definitions for memcpy(), ntohl() and htonl() */
#include <string.h>
#include <stdint.h>
#ifdef WIN32
#include <winsock2.h>
#else
#include <arpa/inet.h>
#endif
#include "sha1.h"

#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))

/*
 * Force usage of rol or ror by selecting the one with the smaller constant.
 * It _can_ generate slightly smaller code (a constant of 1 is special), but
 * perhaps more importantly it's possibly faster on any uarch that does a
 * rotate with a loop.
 */

#define SHA_ASM(op, x, n) ({ unsigned int __res; __asm__(op " %1,%0":"=r" (__res):"i" (n), "0" (x)); __res; })
#define SHA_ROL(x, n) SHA_ASM("rol", x, n)
#define SHA_ROR(x, n) SHA_ASM("ror", x, n)

#else

#define SHA_ROT(X, l, r) (((X) << (l)) | ((X) >> (r)))
#define SHA_ROL(X, n) SHA_ROT(X, n, 32 - (n))
#define SHA_ROR(X, n) SHA_ROT(X, 32 - (n), n)

#endif

/*
 * If you have 32 registers or more, the compiler can (and should)
 * try to change the array[] accesses into registers. However, on
 * machines with less than ~25 registers, that won't really work,
 * and at least gcc will make an unholy mess of it.
 *
 * So to avoid that mess which just slows things down, we force
 * the stores to memory to actually happen (we might be better off
 * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as
 * suggested by Artur Skawina - that will also make gcc unable to
 * try to do the silly "optimize away loads" part because it won't
 * see what the value will be).
 *
 * Ben Herrenschmidt reports that on PPC, the C version comes close
 * to the optimized asm with this (ie on PPC you don't want that
 * 'volatile', since there are lots of registers).
 *
 * On ARM we get the best code generation by forcing a full memory barrier
 * between each SHA_ROUND, otherwise gcc happily get wild with spilling and
 * the stack frame size simply explode and performance goes down the drain.
 */

#if defined(__i386__) || defined(__x86_64__)
#define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))
#elif defined(__GNUC__) && defined(__arm__)
#define setW(x, val)                       \
	do {                               \
		W(x) = (val);              \
		__asm__("" :: : "memory"); \
	} while (0)
#else
#define setW(x, val) (W(x) = (val))
#endif

/*
 * Performance might be improved if the CPU architecture is OK with
 * unaligned 32-bit loads and a fast ntohl() is available.
 * Otherwise fall back to byte loads and shifts which is portable,
 * and is faster on architectures with memory alignment issues.
 */

#if defined(__i386__) || defined(__x86_64__) ||       \
    defined(_M_IX86) || defined(_M_X64) ||            \
    defined(__ppc__) || defined(__ppc64__) ||         \
    defined(__powerpc__) || defined(__powerpc64__) || \
    defined(__s390__) || defined(__s390x__)

#define get_be32(p) ntohl(*(unsigned int *)(p))
#define put_be32(p, v)                           \
	do {                                     \
		*(unsigned int *)(p) = htonl(v); \
	} while (0)

#else

#define get_be32(p) (                     \
    (*((unsigned char *)(p) + 0) << 24) | \
    (*((unsigned char *)(p) + 1) << 16) | \
    (*((unsigned char *)(p) + 2) << 8) |  \
    (*((unsigned char *)(p) + 3) << 0))
#define put_be32(p, v)                                   \
	do {                                             \
		unsigned int __v = (v);                  \
		*((unsigned char *)(p) + 0) = __v >> 24; \
		*((unsigned char *)(p) + 1) = __v >> 16; \
		*((unsigned char *)(p) + 2) = __v >> 8;  \
		*((unsigned char *)(p) + 3) = __v >> 0;  \
	} while (0)

#endif

/* This "rolls" over the 512-bit array */
#define W(x) (array[(x) & 15])

/*
 * Where do we get the source from? The first 16 iterations get it from
 * the input data, the next mix it from the 512-bit array.
 */
#define SHA_SRC(t) get_be32((unsigned char *)block + (t) * 4)
#define SHA_MIX(t) SHA_ROL(W((t) + 13) ^ W((t) + 8) ^ W((t) + 2) ^ W(t), 1);

#define SHA_ROUND(t, input, fn, constant, A, B, C, D, E)       \
	do {                                                   \
		unsigned int TEMP = input(t);                  \
		setW(t, TEMP);                                 \
		E += TEMP + SHA_ROL(A, 5) + (fn) + (constant); \
		B = SHA_ROR(B, 2);                             \
	} while (0)

#define T_0_15(t, A, B, C, D, E) SHA_ROUND(t, SHA_SRC, (((C ^ D) & B) ^ D), 0x5a827999, A, B, C, D, E)
#define T_16_19(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (((C ^ D) & B) ^ D), 0x5a827999, A, B, C, D, E)
#define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B ^ C ^ D), 0x6ed9eba1, A, B, C, D, E)
#define T_40_59(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, ((B &C) + (D &(B ^ C))), 0x8f1bbcdc, A, B, C, D, E)
#define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B ^ C ^ D), 0xca62c1d6, A, B, C, D, E)

static void blk_SHA1_Block(blk_SHA_CTX *ctx, const void *block)
{
	unsigned int A, B, C, D, E;
	unsigned int array[16];

	A = ctx->H[0];
	B = ctx->H[1];
	C = ctx->H[2];
	D = ctx->H[3];
	E = ctx->H[4];

	/* Round 1 - iterations 0-16 take their input from 'block' */
	T_0_15(0, A, B, C, D, E);
	T_0_15(1, E, A, B, C, D);
	T_0_15(2, D, E, A, B, C);
	T_0_15(3, C, D, E, A, B);
	T_0_15(4, B, C, D, E, A);
	T_0_15(5, A, B, C, D, E);
	T_0_15(6, E, A, B, C, D);
	T_0_15(7, D, E, A, B, C);
	T_0_15(8, C, D, E, A, B);
	T_0_15(9, B, C, D, E, A);
	T_0_15(10, A, B, C, D, E);
	T_0_15(11, E, A, B, C, D);
	T_0_15(12, D, E, A, B, C);
	T_0_15(13, C, D, E, A, B);
	T_0_15(14, B, C, D, E, A);
	T_0_15(15, A, B, C, D, E);

	/* Round 1 - tail. Input from 512-bit mixing array */
	T_16_19(16, E, A, B, C, D);
	T_16_19(17, D, E, A, B, C);
	T_16_19(18, C, D, E, A, B);
	T_16_19(19, B, C, D, E, A);

	/* Round 2 */
	T_20_39(20, A, B, C, D, E);
	T_20_39(21, E, A, B, C, D);
	T_20_39(22, D, E, A, B, C);
	T_20_39(23, C, D, E, A, B);
	T_20_39(24, B, C, D, E, A);
	T_20_39(25, A, B, C, D, E);
	T_20_39(26, E, A, B, C, D);
	T_20_39(27, D, E, A, B, C);
	T_20_39(28, C, D, E, A, B);
	T_20_39(29, B, C, D, E, A);
	T_20_39(30, A, B, C, D, E);
	T_20_39(31, E, A, B, C, D);
	T_20_39(32, D, E, A, B, C);
	T_20_39(33, C, D, E, A, B);
	T_20_39(34, B, C, D, E, A);
	T_20_39(35, A, B, C, D, E);
	T_20_39(36, E, A, B, C, D);
	T_20_39(37, D, E, A, B, C);
	T_20_39(38, C, D, E, A, B);
	T_20_39(39, B, C, D, E, A);

	/* Round 3 */
	T_40_59(40, A, B, C, D, E);
	T_40_59(41, E, A, B, C, D);
	T_40_59(42, D, E, A, B, C);
	T_40_59(43, C, D, E, A, B);
	T_40_59(44, B, C, D, E, A);
	T_40_59(45, A, B, C, D, E);
	T_40_59(46, E, A, B, C, D);
	T_40_59(47, D, E, A, B, C);
	T_40_59(48, C, D, E, A, B);
	T_40_59(49, B, C, D, E, A);
	T_40_59(50, A, B, C, D, E);
	T_40_59(51, E, A, B, C, D);
	T_40_59(52, D, E, A, B, C);
	T_40_59(53, C, D, E, A, B);
	T_40_59(54, B, C, D, E, A);
	T_40_59(55, A, B, C, D, E);
	T_40_59(56, E, A, B, C, D);
	T_40_59(57, D, E, A, B, C);
	T_40_59(58, C, D, E, A, B);
	T_40_59(59, B, C, D, E, A);

	/* Round 4 */
	T_60_79(60, A, B, C, D, E);
	T_60_79(61, E, A, B, C, D);
	T_60_79(62, D, E, A, B, C);
	T_60_79(63, C, D, E, A, B);
	T_60_79(64, B, C, D, E, A);
	T_60_79(65, A, B, C, D, E);
	T_60_79(66, E, A, B, C, D);
	T_60_79(67, D, E, A, B, C);
	T_60_79(68, C, D, E, A, B);
	T_60_79(69, B, C, D, E, A);
	T_60_79(70, A, B, C, D, E);
	T_60_79(71, E, A, B, C, D);
	T_60_79(72, D, E, A, B, C);
	T_60_79(73, C, D, E, A, B);
	T_60_79(74, B, C, D, E, A);
	T_60_79(75, A, B, C, D, E);
	T_60_79(76, E, A, B, C, D);
	T_60_79(77, D, E, A, B, C);
	T_60_79(78, C, D, E, A, B);
	T_60_79(79, B, C, D, E, A);

	ctx->H[0] += A;
	ctx->H[1] += B;
	ctx->H[2] += C;
	ctx->H[3] += D;
	ctx->H[4] += E;
}

void blk_SHA1_Init(blk_SHA_CTX *ctx)
{
	ctx->size = 0;

	/* Initialize H with the magic constants (see FIPS180 for constants) */
	ctx->H[0] = 0x67452301;
	ctx->H[1] = 0xefcdab89;
	ctx->H[2] = 0x98badcfe;
	ctx->H[3] = 0x10325476;
	ctx->H[4] = 0xc3d2e1f0;
}

void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
{
	unsigned int lenW = ctx->size & 63;

	ctx->size += len;

	/* Read the data into W and process blocks as they get full */
	if (lenW) {
		unsigned int left = 64 - lenW;
		if (len < left)
			left = len;
		memcpy(lenW + (char *)ctx->W, data, left);
		lenW = (lenW + left) & 63;
		len -= left;
		data = ((const char *)data + left);
		if (lenW)
			return;
		blk_SHA1_Block(ctx, ctx->W);
	}
	while (len >= 64) {
		blk_SHA1_Block(ctx, data);
		data = ((const char *)data + 64);
		len -= 64;
	}
	if (len)
		memcpy(ctx->W, data, len);
}

void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
{
	static const unsigned char pad[64] = { 0x80 };
	unsigned int padlen[2];
	int i;

	/* Pad with a binary 1 (ie 0x80), then zeroes, then length */
	padlen[0] = htonl((uint32_t)(ctx->size >> 29));
	padlen[1] = htonl((uint32_t)(ctx->size << 3));

	i = ctx->size & 63;
	blk_SHA1_Update(ctx, pad, 1 + (63 & (55 - i)));
	blk_SHA1_Update(ctx, padlen, 8);

	/* Output hash */
	for (i = 0; i < 5; i++)
		put_be32(hashout + i * 4, ctx->H[i]);
}