sha1.c

Go to the documentation of this file.

/*
 * SHA1 routine optimized to do word accesses rather than byte accesses,
 * and to avoid unnecessary copies into the context array.
 *
 * This was based on the git SHA1 implementation.
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/bitops.h>
#include <linux/cryptohash.h>
#include <asm/unaligned.h>

/*
 * 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.
 */

#ifdef CONFIG_X86
  #define setW(x, val) (*(volatile __u32 *)&W(x) = (val))
#elif defined(CONFIG_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_unaligned_be32((__u32 *)data + t)
#define SHA_MIX(t) rol32(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 { \
    __u32 TEMP = input(t); setW(t, TEMP); \
    E += TEMP + rol32(A,5) + (fn) + (constant); \
    B = ror32(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 )

void sha_transform(__u32 *digest, const char *data, __u32 *array)
{
    __u32 A, B, C, D, E;

    A = digest[0];
    B = digest[1];
    C = digest[2];
    D = digest[3];
    E = digest[4];

    /* Round 1 - iterations 0-16 take their input from 'data' */
    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);

    digest[0] += A;
    digest[1] += B;
    digest[2] += C;
    digest[3] += D;
    digest[4] += E;
}
EXPORT_SYMBOL(sha_transform);

void sha_init(__u32 *buf)
{
    buf[0] = 0x67452301;
    buf[1] = 0xefcdab89;
    buf[2] = 0x98badcfe;
    buf[3] = 0x10325476;
    buf[4] = 0xc3d2e1f0;
}