1 /* Functions to compute SHA256 message digest of files or memory blocks.
2 according to the definition of SHA256 in FIPS 180-2.
3 Copyright (C) 2007 Free Software Foundation, Inc.
4
5 Copied here from the GNU C Library version 2.7 on the 10 May 2009
6 by Steve McIntyre <93sam@debian.org>. This code was under LGPL v2.1
7 in glibc, and that license gives us the option to use and
8 distribute the code under the terms of the GPL v2 instead. I'm
9 taking that option.
10
11 This program is free software; you can redistribute it and/or modify it
12 under the terms of the GNU General Public License as published by the
13 Free Software Foundation; either version 2, or (at your option) any
14 later version.
15
16 This program is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU General Public License for more details.
20
21 You should have received a copy of the GNU General Public License
22 along with this program; if not, write to the Free Software Foundation,
23 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
24
25 /* Written by Ulrich Drepper <drepper@redhat.com>, 2007. */
26
27 #include <stdlib.h>
28 #include <string.h>
29 #include <sys/endian.h>
30 #include <sys/types.h>
31
32 #include "sha256.h"
33
34 #if __BYTE_ORDER == __LITTLE_ENDIAN
35 # ifdef _LIBC
36 # include <byteswap.h>
37 # define SWAP(n) bswap_32 (n)
38 # else
39 # define SWAP(n) \
40 (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
41 # endif
42 #else
43 # define SWAP(n) (n)
44 #endif
45
46
47 /* This array contains the bytes used to pad the buffer to the next
48 64-byte boundary. (FIPS 180-2:5.1.1) */
49 static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ... */ };
50
51
52 /* Constants for SHA256 from FIPS 180-2:4.2.2. */
53 static const uint32_t K[64] =
54 {
55 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
56 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
57 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
58 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
59 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
60 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
61 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
62 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
63 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
64 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
65 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
66 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
67 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
68 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
69 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
70 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
71 };
72
73
74 /* Process LEN bytes of BUFFER, accumulating context into CTX.
75 It is assumed that LEN % 64 == 0. */
76 static void
sha256_process_block(const void * buffer,size_t len,struct sha256_ctx * ctx)77 sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
78 {
79 const uint32_t *words = buffer;
80 size_t nwords = len / sizeof (uint32_t);
81 uint32_t a = ctx->H[0];
82 uint32_t b = ctx->H[1];
83 uint32_t c = ctx->H[2];
84 uint32_t d = ctx->H[3];
85 uint32_t e = ctx->H[4];
86 uint32_t f = ctx->H[5];
87 uint32_t g = ctx->H[6];
88 uint32_t h = ctx->H[7];
89
90 /* First increment the byte count. FIPS 180-2 specifies the possible
91 length of the file up to 2^64 bits. Here we only compute the
92 number of bytes. Do a double word increment. */
93 ctx->total[0] += len;
94 if (ctx->total[0] < len)
95 ++ctx->total[1];
96
97 /* Process all bytes in the buffer with 64 bytes in each round of
98 the loop. */
99 while (nwords > 0)
100 {
101 uint32_t W[64];
102 uint32_t a_save = a;
103 uint32_t b_save = b;
104 uint32_t c_save = c;
105 uint32_t d_save = d;
106 uint32_t e_save = e;
107 uint32_t f_save = f;
108 uint32_t g_save = g;
109 uint32_t h_save = h;
110
111 unsigned int t;
112
113 /* Operators defined in FIPS 180-2:4.1.2. */
114 #define Ch(x, y, z) ((x & y) ^ (~x & z))
115 #define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
116 #define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
117 #define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
118 #define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
119 #define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
120
121 /* It is unfortunate that C does not provide an operator for
122 cyclic rotation. Hope the C compiler is smart enough. */
123 #define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
124
125 /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2. */
126 for (t = 0; t < 16; ++t)
127 {
128 W[t] = SWAP (*words);
129 ++words;
130 }
131 for (t = 16; t < 64; ++t)
132 W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];
133
134 /* The actual computation according to FIPS 180-2:6.2.2 step 3. */
135 for (t = 0; t < 64; ++t)
136 {
137 uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
138 uint32_t T2 = S0 (a) + Maj (a, b, c);
139 h = g;
140 g = f;
141 f = e;
142 e = d + T1;
143 d = c;
144 c = b;
145 b = a;
146 a = T1 + T2;
147 }
148
149 /* Add the starting values of the context according to FIPS 180-2:6.2.2
150 step 4. */
151 a += a_save;
152 b += b_save;
153 c += c_save;
154 d += d_save;
155 e += e_save;
156 f += f_save;
157 g += g_save;
158 h += h_save;
159
160 /* Prepare for the next round. */
161 nwords -= 16;
162 }
163
164 /* Put checksum in context given as argument. */
165 ctx->H[0] = a;
166 ctx->H[1] = b;
167 ctx->H[2] = c;
168 ctx->H[3] = d;
169 ctx->H[4] = e;
170 ctx->H[5] = f;
171 ctx->H[6] = g;
172 ctx->H[7] = h;
173 }
174
175
176 /* Initialize structure containing state of computation.
177 (FIPS 180-2:5.3.2) */
178 void
sha256_init_ctx(ctx)179 sha256_init_ctx (ctx)
180 struct sha256_ctx *ctx;
181 {
182 ctx->H[0] = 0x6a09e667;
183 ctx->H[1] = 0xbb67ae85;
184 ctx->H[2] = 0x3c6ef372;
185 ctx->H[3] = 0xa54ff53a;
186 ctx->H[4] = 0x510e527f;
187 ctx->H[5] = 0x9b05688c;
188 ctx->H[6] = 0x1f83d9ab;
189 ctx->H[7] = 0x5be0cd19;
190
191 ctx->total[0] = ctx->total[1] = 0;
192 ctx->buflen = 0;
193 }
194
195
196 /* Process the remaining bytes in the internal buffer and the usual
197 prolog according to the standard and write the result to RESBUF.
198
199 IMPORTANT: On some systems it is required that RESBUF is correctly
200 aligned for a 32 bits value. */
201 void *
sha256_finish_ctx(ctx,resbuf)202 sha256_finish_ctx (ctx, resbuf)
203 struct sha256_ctx *ctx;
204 void *resbuf;
205 {
206 /* Take yet unprocessed bytes into account. */
207 uint32_t bytes = ctx->buflen;
208 size_t pad;
209 unsigned int i;
210
211 /* Now count remaining bytes. */
212 ctx->total[0] += bytes;
213 if (ctx->total[0] < bytes)
214 ++ctx->total[1];
215
216 pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
217 memcpy (&ctx->buffer[bytes], fillbuf, pad);
218
219 /* Put the 64-bit file length in *bits* at the end of the buffer. */
220 *(uint32_t *) &ctx->buffer[bytes + pad + 4] = SWAP (ctx->total[0] << 3);
221 *(uint32_t *) &ctx->buffer[bytes + pad] = SWAP ((ctx->total[1] << 3) |
222 (ctx->total[0] >> 29));
223
224 /* Process last bytes. */
225 sha256_process_block (ctx->buffer, bytes + pad + 8, ctx);
226
227 /* Put result from CTX in first 32 bytes following RESBUF. */
228 for (i = 0; i < 8; ++i)
229 ((uint32_t *) resbuf)[i] = SWAP (ctx->H[i]);
230
231 return resbuf;
232 }
233
234
235 void
sha256_process_bytes(buffer,len,ctx)236 sha256_process_bytes (buffer, len, ctx)
237 const void *buffer;
238 size_t len;
239 struct sha256_ctx *ctx;
240 {
241 /* When we already have some bits in our internal buffer concatenate
242 both inputs first. */
243 if (ctx->buflen != 0)
244 {
245 size_t left_over = ctx->buflen;
246 size_t add = 128 - left_over > len ? len : 128 - left_over;
247
248 memcpy (&ctx->buffer[left_over], buffer, add);
249 ctx->buflen += add;
250
251 if (ctx->buflen > 64)
252 {
253 sha256_process_block (ctx->buffer, ctx->buflen & ~63, ctx);
254
255 ctx->buflen &= 63;
256 /* The regions in the following copy operation cannot overlap. */
257 memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
258 ctx->buflen);
259 }
260
261 buffer = (const char *) buffer + add;
262 len -= add;
263 }
264
265 /* Process available complete blocks. */
266 if (len >= 64)
267 {
268 #if !_STRING_ARCH_unaligned
269 /* To check alignment gcc has an appropriate operator. Other
270 compilers don't. */
271 # if __GNUC__ >= 2
272 # define UNALIGNED_P(p) (((uintptr_t) p) % __alignof__ (uint32_t) != 0)
273 # else
274 # define UNALIGNED_P(p) (((uintptr_t) p) % sizeof (uint32_t) != 0)
275 # endif
276 if (UNALIGNED_P (buffer))
277 while (len > 64)
278 {
279 sha256_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
280 buffer = (const char *) buffer + 64;
281 len -= 64;
282 }
283 else
284 #endif
285 {
286 sha256_process_block (buffer, len & ~63, ctx);
287 buffer = (const char *) buffer + (len & ~63);
288 len &= 63;
289 }
290 }
291
292 /* Move remaining bytes into internal buffer. */
293 if (len > 0)
294 {
295 size_t left_over = ctx->buflen;
296
297 memcpy (&ctx->buffer[left_over], buffer, len);
298 left_over += len;
299 if (left_over >= 64)
300 {
301 sha256_process_block (ctx->buffer, 64, ctx);
302 left_over -= 64;
303 memcpy (ctx->buffer, &ctx->buffer[64], left_over);
304 }
305 ctx->buflen = left_over;
306 }
307 }
308