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git-commit-vandalism/block-sha1/sha1.c
Jeff King 9bb4542b8c block-sha1: take a size_t length parameter 
The block-sha1 implementation takes an "unsigned long" for the length of
a buffer to hash, but our hash algorithm wrappers take a size_t, as do
other implementations we support like openssl or sha1dc. On many
systems, including Linux, these two are equivalent, but they are not on
Windows (where only a "long long" is 64 bits). As a result, passing
large chunks to a single the_hash_algo->update_fn() would produce wrong
answers there.

Note that we don't need to update any other sizes outside of the
function interface. We store the cumulative size in a "long long" (which
we must do since we hash things bigger than 4GB, like packfiles, even on
32-bit platforms). And internally, we break that size_t len down into
64-byte blocks to feed into the guts of the algorithm.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-16 13:41:35 -08:00

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/*
* 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 "../git-compat-util.h"
#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
/* 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, size_t 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]);
}
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