lib/sha1.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * SHA1 routine optimized to do word accesses rather than byte accesses,
   4  * and to avoid unnecessary copies into the context array.
   5  *
   6  * This was based on the git SHA1 implementation.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/export.h>
  11 #include <linux/bitops.h>
  12 #include <linux/string.h>
  13 #include <crypto/sha1.h>
  14 #include <asm/unaligned.h>
  15
  16 /*
  17  * If you have 32 registers or more, the compiler can (and should)
  18  * try to change the array[] accesses into registers. However, on
  19  * machines with less than ~25 registers, that won't really work,
  20  * and at least gcc will make an unholy mess of it.
  21  *
  22  * So to avoid that mess which just slows things down, we force
  23  * the stores to memory to actually happen (we might be better off
  24  * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as
  25  * suggested by Artur Skawina - that will also make gcc unable to
  26  * try to do the silly "optimize away loads" part because it won't
  27  * see what the value will be).
  28  *
  29  * Ben Herrenschmidt reports that on PPC, the C version comes close
  30  * to the optimized asm with this (ie on PPC you don't want that
  31  * 'volatile', since there are lots of registers).
  32  *
  33  * On ARM we get the best code generation by forcing a full memory barrier
  34  * between each SHA_ROUND, otherwise gcc happily get wild with spilling and
  35  * the stack frame size simply explode and performance goes down the drain.
  36  */
  37
  38 #ifdef CONFIG_X86
  39   #define setW(x, val) (*(volatile __u32 *)&W(x) = (val))
  40 #elif defined(CONFIG_ARM)
  41   #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)
  42 #else
  43   #define setW(x, val) (W(x) = (val))
  44 #endif
  45
  46 /* This "rolls" over the 512-bit array */
  47 #define W(x) (array[(x)&15])
  48
  49 /*
  50  * Where do we get the source from? The first 16 iterations get it from
  51  * the input data, the next mix it from the 512-bit array.
  52  */
  53 #define SHA_SRC(t) get_unaligned_be32((__u32 *)data + t)
  54 #define SHA_MIX(t) rol32(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1)
  55
  56 #define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \
  57         __u32 TEMP = input(t); setW(t, TEMP); \
  58         E += TEMP + rol32(A,5) + (fn) + (constant); \
  59         B = ror32(B, 2); \
  60         TEMP = E; E = D; D = C; C = B; B = A; A = TEMP; } while (0)
  61
  62 #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 )
  63 #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 )
  64 #define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0x6ed9eba1, A, B, C, D, E )
  65 #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 )
  66 #define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) ,  0xca62c1d6, A, B, C, D, E )
  67
  68 /**
  69  * sha1_transform - single block SHA1 transform (deprecated)
  70  *
  71  * @digest: 160 bit digest to update
  72  * @data:   512 bits of data to hash
  73  * @array:  16 words of workspace (see note)
  74  *
  75  * This function executes SHA-1's internal compression function.  It updates the
  76  * 160-bit internal state (@digest) with a single 512-bit data block (@data).
  77  *
  78  * Don't use this function.  SHA-1 is no longer considered secure.  And even if
  79  * you do have to use SHA-1, this isn't the correct way to hash something with
  80  * SHA-1 as this doesn't handle padding and finalization.
  81  *
  82  * Note: If the hash is security sensitive, the caller should be sure
  83  * to clear the workspace. This is left to the caller to avoid
  84  * unnecessary clears between chained hashing operations.
  85  */
  86 void sha1_transform(__u32 *digest, const char *data, __u32 *array)
  87 {
  88         __u32 A, B, C, D, E;
  89         unsigned int i = 0;
  90
  91         A = digest[0];
  92         B = digest[1];
  93         C = digest[2];
  94         D = digest[3];
  95         E = digest[4];
  96
  97         /* Round 1 - iterations 0-16 take their input from 'data' */
  98         for (; i < 16; ++i)
  99                 T_0_15(i, A, B, C, D, E);
 100
 101         /* Round 1 - tail. Input from 512-bit mixing array */
 102         for (; i < 20; ++i)
 103                 T_16_19(i, A, B, C, D, E);
 104
 105         /* Round 2 */
 106         for (; i < 40; ++i)
 107                 T_20_39(i, A, B, C, D, E);
 108
 109         /* Round 3 */
 110         for (; i < 60; ++i)
 111                 T_40_59(i, A, B, C, D, E);
 112
 113         /* Round 4 */
 114         for (; i < 80; ++i)
 115                 T_60_79(i, A, B, C, D, E);
 116
 117         digest[0] += A;
 118         digest[1] += B;
 119         digest[2] += C;
 120         digest[3] += D;
 121         digest[4] += E;
 122 }
 123 EXPORT_SYMBOL(sha1_transform);
 124
 125 /**
 126  * sha1_init - initialize the vectors for a SHA1 digest
 127  * @buf: vector to initialize
 128  */
 129 void sha1_init(__u32 *buf)
 130 {
 131         buf[0] = 0x67452301;
 132         buf[1] = 0xefcdab89;
 133         buf[2] = 0x98badcfe;
 134         buf[3] = 0x10325476;
 135         buf[4] = 0xc3d2e1f0;
 136 }
 137 EXPORT_SYMBOL(sha1_init);