Coverage Report

Created: 2024-01-20 12:36

/src/openssl/crypto/poly1305/poly1305.c
Line
Count
Source (jump to first uncovered line)
1
/*
2
 * Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
3
 *
4
 * Licensed under the Apache License 2.0 (the "License").  You may not use
5
 * this file except in compliance with the License.  You can obtain a copy
6
 * in the file LICENSE in the source distribution or at
7
 * https://www.openssl.org/source/license.html
8
 */
9
10
#include <stdlib.h>
11
#include <string.h>
12
#include <openssl/crypto.h>
13
14
#include "crypto/poly1305.h"
15
16
size_t Poly1305_ctx_size(void)
17
0
{
18
0
    return sizeof(struct poly1305_context);
19
0
}
20
21
/* pick 32-bit unsigned integer in little endian order */
22
static unsigned int U8TOU32(const unsigned char *p)
23
0
{
24
0
    return (((unsigned int)(p[0] & 0xff)) |
25
0
            ((unsigned int)(p[1] & 0xff) << 8) |
26
0
            ((unsigned int)(p[2] & 0xff) << 16) |
27
0
            ((unsigned int)(p[3] & 0xff) << 24));
28
0
}
29
30
/*
31
 * Implementations can be classified by amount of significant bits in
32
 * words making up the multi-precision value, or in other words radix
33
 * or base of numerical representation, e.g. base 2^64, base 2^32,
34
 * base 2^26. Complementary characteristic is how wide is the result of
35
 * multiplication of pair of digits, e.g. it would take 128 bits to
36
 * accommodate multiplication result in base 2^64 case. These are used
37
 * interchangeably. To describe implementation that is. But interface
38
 * is designed to isolate this so that low-level primitives implemented
39
 * in assembly can be self-contained/self-coherent.
40
 */
41
#ifndef POLY1305_ASM
42
/*
43
 * Even though there is __int128 reference implementation targeting
44
 * 64-bit platforms provided below, it's not obvious that it's optimal
45
 * choice for every one of them. Depending on instruction set overall
46
 * amount of instructions can be comparable to one in __int64
47
 * implementation. Amount of multiplication instructions would be lower,
48
 * but not necessarily overall. And in out-of-order execution context,
49
 * it is the latter that can be crucial...
50
 *
51
 * On related note. Poly1305 author, D. J. Bernstein, discusses and
52
 * provides floating-point implementations of the algorithm in question.
53
 * It made a lot of sense by the time of introduction, because most
54
 * then-modern processors didn't have pipelined integer multiplier.
55
 * [Not to mention that some had non-constant timing for integer
56
 * multiplications.] Floating-point instructions on the other hand could
57
 * be issued every cycle, which allowed to achieve better performance.
58
 * Nowadays, with SIMD and/or out-or-order execution, shared or
59
 * even emulated FPU, it's more complicated, and floating-point
60
 * implementation is not necessarily optimal choice in every situation,
61
 * rather contrary...
62
 *
63
 *                                              <appro@openssl.org>
64
 */
65
66
typedef unsigned int u32;
67
68
/*
69
 * poly1305_blocks processes a multiple of POLY1305_BLOCK_SIZE blocks
70
 * of |inp| no longer than |len|. Behaviour for |len| not divisible by
71
 * block size is unspecified in general case, even though in reference
72
 * implementation the trailing chunk is simply ignored. Per algorithm
73
 * specification, every input block, complete or last partial, is to be
74
 * padded with a bit past most significant byte. The latter kind is then
75
 * padded with zeros till block size. This last partial block padding
76
 * is caller(*)'s responsibility, and because of this the last partial
77
 * block is always processed with separate call with |len| set to
78
 * POLY1305_BLOCK_SIZE and |padbit| to 0. In all other cases |padbit|
79
 * should be set to 1 to perform implicit padding with 128th bit.
80
 * poly1305_blocks does not actually check for this constraint though,
81
 * it's caller(*)'s responsibility to comply.
82
 *
83
 * (*)  In the context "caller" is not application code, but higher
84
 *      level Poly1305_* from this very module, so that quirks are
85
 *      handled locally.
86
 */
87
static void
88
poly1305_blocks(void *ctx, const unsigned char *inp, size_t len, u32 padbit);
89
90
/*
91
 * Type-agnostic "rip-off" from constant_time.h
92
 */
93
# define CONSTANT_TIME_CARRY(a,b) ( \
94
         (a ^ ((a ^ b) | ((a - b) ^ b))) >> (sizeof(a) * 8 - 1) \
95
         )
96
97
# if (defined(__SIZEOF_INT128__) && __SIZEOF_INT128__==16) && \
98
     (defined(__SIZEOF_LONG__) && __SIZEOF_LONG__==8)
99
100
typedef unsigned long u64;
101
typedef __uint128_t u128;
102
103
typedef struct {
104
    u64 h[3];
105
    u64 r[2];
106
} poly1305_internal;
107
108
/* pick 32-bit unsigned integer in little endian order */
109
static u64 U8TOU64(const unsigned char *p)
110
{
111
    return (((u64)(p[0] & 0xff)) |
112
            ((u64)(p[1] & 0xff) << 8) |
113
            ((u64)(p[2] & 0xff) << 16) |
114
            ((u64)(p[3] & 0xff) << 24) |
115
            ((u64)(p[4] & 0xff) << 32) |
116
            ((u64)(p[5] & 0xff) << 40) |
117
            ((u64)(p[6] & 0xff) << 48) |
118
            ((u64)(p[7] & 0xff) << 56));
119
}
120
121
/* store a 32-bit unsigned integer in little endian */
122
static void U64TO8(unsigned char *p, u64 v)
123
{
124
    p[0] = (unsigned char)((v) & 0xff);
125
    p[1] = (unsigned char)((v >> 8) & 0xff);
126
    p[2] = (unsigned char)((v >> 16) & 0xff);
127
    p[3] = (unsigned char)((v >> 24) & 0xff);
128
    p[4] = (unsigned char)((v >> 32) & 0xff);
129
    p[5] = (unsigned char)((v >> 40) & 0xff);
130
    p[6] = (unsigned char)((v >> 48) & 0xff);
131
    p[7] = (unsigned char)((v >> 56) & 0xff);
132
}
133
134
static void poly1305_init(void *ctx, const unsigned char key[16])
135
{
136
    poly1305_internal *st = (poly1305_internal *) ctx;
137
138
    /* h = 0 */
139
    st->h[0] = 0;
140
    st->h[1] = 0;
141
    st->h[2] = 0;
142
143
    /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
144
    st->r[0] = U8TOU64(&key[0]) & 0x0ffffffc0fffffff;
145
    st->r[1] = U8TOU64(&key[8]) & 0x0ffffffc0ffffffc;
146
}
147
148
static void
149
poly1305_blocks(void *ctx, const unsigned char *inp, size_t len, u32 padbit)
150
{
151
    poly1305_internal *st = (poly1305_internal *)ctx;
152
    u64 r0, r1;
153
    u64 s1;
154
    u64 h0, h1, h2, c;
155
    u128 d0, d1;
156
157
    r0 = st->r[0];
158
    r1 = st->r[1];
159
160
    s1 = r1 + (r1 >> 2);
161
162
    h0 = st->h[0];
163
    h1 = st->h[1];
164
    h2 = st->h[2];
165
166
    while (len >= POLY1305_BLOCK_SIZE) {
167
        /* h += m[i] */
168
        h0 = (u64)(d0 = (u128)h0 + U8TOU64(inp + 0));
169
        h1 = (u64)(d1 = (u128)h1 + (d0 >> 64) + U8TOU64(inp + 8));
170
        /*
171
         * padbit can be zero only when original len was
172
         * POLY1306_BLOCK_SIZE, but we don't check
173
         */
174
        h2 += (u64)(d1 >> 64) + padbit;
175
176
        /* h *= r "%" p, where "%" stands for "partial remainder" */
177
        d0 = ((u128)h0 * r0) +
178
             ((u128)h1 * s1);
179
        d1 = ((u128)h0 * r1) +
180
             ((u128)h1 * r0) +
181
             (h2 * s1);
182
        h2 = (h2 * r0);
183
184
        /* last reduction step: */
185
        /* a) h2:h0 = h2<<128 + d1<<64 + d0 */
186
        h0 = (u64)d0;
187
        h1 = (u64)(d1 += d0 >> 64);
188
        h2 += (u64)(d1 >> 64);
189
        /* b) (h2:h0 += (h2:h0>>130) * 5) %= 2^130 */
190
        c = (h2 >> 2) + (h2 & ~3UL);
191
        h2 &= 3;
192
        h0 += c;
193
        h1 += (c = CONSTANT_TIME_CARRY(h0,c));
194
        h2 += CONSTANT_TIME_CARRY(h1,c);
195
        /*
196
         * Occasional overflows to 3rd bit of h2 are taken care of
197
         * "naturally". If after this point we end up at the top of
198
         * this loop, then the overflow bit will be accounted for
199
         * in next iteration. If we end up in poly1305_emit, then
200
         * comparison to modulus below will still count as "carry
201
         * into 131st bit", so that properly reduced value will be
202
         * picked in conditional move.
203
         */
204
205
        inp += POLY1305_BLOCK_SIZE;
206
        len -= POLY1305_BLOCK_SIZE;
207
    }
208
209
    st->h[0] = h0;
210
    st->h[1] = h1;
211
    st->h[2] = h2;
212
}
213
214
static void poly1305_emit(void *ctx, unsigned char mac[16],
215
                          const u32 nonce[4])
216
{
217
    poly1305_internal *st = (poly1305_internal *) ctx;
218
    u64 h0, h1, h2;
219
    u64 g0, g1, g2;
220
    u128 t;
221
    u64 mask;
222
223
    h0 = st->h[0];
224
    h1 = st->h[1];
225
    h2 = st->h[2];
226
227
    /* compare to modulus by computing h + -p */
228
    g0 = (u64)(t = (u128)h0 + 5);
229
    g1 = (u64)(t = (u128)h1 + (t >> 64));
230
    g2 = h2 + (u64)(t >> 64);
231
232
    /* if there was carry into 131st bit, h1:h0 = g1:g0 */
233
    mask = 0 - (g2 >> 2);
234
    g0 &= mask;
235
    g1 &= mask;
236
    mask = ~mask;
237
    h0 = (h0 & mask) | g0;
238
    h1 = (h1 & mask) | g1;
239
240
    /* mac = (h + nonce) % (2^128) */
241
    h0 = (u64)(t = (u128)h0 + nonce[0] + ((u64)nonce[1]<<32));
242
    h1 = (u64)(t = (u128)h1 + nonce[2] + ((u64)nonce[3]<<32) + (t >> 64));
243
244
    U64TO8(mac + 0, h0);
245
    U64TO8(mac + 8, h1);
246
}
247
248
# else
249
250
#  if defined(_WIN32) && !defined(__MINGW32__)
251
typedef unsigned __int64 u64;
252
#  elif defined(__arch64__)
253
typedef unsigned long u64;
254
#  else
255
typedef unsigned long long u64;
256
#  endif
257
258
typedef struct {
259
    u32 h[5];
260
    u32 r[4];
261
} poly1305_internal;
262
263
/* store a 32-bit unsigned integer in little endian */
264
static void U32TO8(unsigned char *p, unsigned int v)
265
{
266
    p[0] = (unsigned char)((v) & 0xff);
267
    p[1] = (unsigned char)((v >> 8) & 0xff);
268
    p[2] = (unsigned char)((v >> 16) & 0xff);
269
    p[3] = (unsigned char)((v >> 24) & 0xff);
270
}
271
272
static void poly1305_init(void *ctx, const unsigned char key[16])
273
{
274
    poly1305_internal *st = (poly1305_internal *) ctx;
275
276
    /* h = 0 */
277
    st->h[0] = 0;
278
    st->h[1] = 0;
279
    st->h[2] = 0;
280
    st->h[3] = 0;
281
    st->h[4] = 0;
282
283
    /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
284
    st->r[0] = U8TOU32(&key[0]) & 0x0fffffff;
285
    st->r[1] = U8TOU32(&key[4]) & 0x0ffffffc;
286
    st->r[2] = U8TOU32(&key[8]) & 0x0ffffffc;
287
    st->r[3] = U8TOU32(&key[12]) & 0x0ffffffc;
288
}
289
290
static void
291
poly1305_blocks(void *ctx, const unsigned char *inp, size_t len, u32 padbit)
292
{
293
    poly1305_internal *st = (poly1305_internal *)ctx;
294
    u32 r0, r1, r2, r3;
295
    u32 s1, s2, s3;
296
    u32 h0, h1, h2, h3, h4, c;
297
    u64 d0, d1, d2, d3;
298
299
    r0 = st->r[0];
300
    r1 = st->r[1];
301
    r2 = st->r[2];
302
    r3 = st->r[3];
303
304
    s1 = r1 + (r1 >> 2);
305
    s2 = r2 + (r2 >> 2);
306
    s3 = r3 + (r3 >> 2);
307
308
    h0 = st->h[0];
309
    h1 = st->h[1];
310
    h2 = st->h[2];
311
    h3 = st->h[3];
312
    h4 = st->h[4];
313
314
    while (len >= POLY1305_BLOCK_SIZE) {
315
        /* h += m[i] */
316
        h0 = (u32)(d0 = (u64)h0 + U8TOU32(inp + 0));
317
        h1 = (u32)(d1 = (u64)h1 + (d0 >> 32) + U8TOU32(inp + 4));
318
        h2 = (u32)(d2 = (u64)h2 + (d1 >> 32) + U8TOU32(inp + 8));
319
        h3 = (u32)(d3 = (u64)h3 + (d2 >> 32) + U8TOU32(inp + 12));
320
        h4 += (u32)(d3 >> 32) + padbit;
321
322
        /* h *= r "%" p, where "%" stands for "partial remainder" */
323
        d0 = ((u64)h0 * r0) +
324
             ((u64)h1 * s3) +
325
             ((u64)h2 * s2) +
326
             ((u64)h3 * s1);
327
        d1 = ((u64)h0 * r1) +
328
             ((u64)h1 * r0) +
329
             ((u64)h2 * s3) +
330
             ((u64)h3 * s2) +
331
             (h4 * s1);
332
        d2 = ((u64)h0 * r2) +
333
             ((u64)h1 * r1) +
334
             ((u64)h2 * r0) +
335
             ((u64)h3 * s3) +
336
             (h4 * s2);
337
        d3 = ((u64)h0 * r3) +
338
             ((u64)h1 * r2) +
339
             ((u64)h2 * r1) +
340
             ((u64)h3 * r0) +
341
             (h4 * s3);
342
        h4 = (h4 * r0);
343
344
        /* last reduction step: */
345
        /* a) h4:h0 = h4<<128 + d3<<96 + d2<<64 + d1<<32 + d0 */
346
        h0 = (u32)d0;
347
        h1 = (u32)(d1 += d0 >> 32);
348
        h2 = (u32)(d2 += d1 >> 32);
349
        h3 = (u32)(d3 += d2 >> 32);
350
        h4 += (u32)(d3 >> 32);
351
        /* b) (h4:h0 += (h4:h0>>130) * 5) %= 2^130 */
352
        c = (h4 >> 2) + (h4 & ~3U);
353
        h4 &= 3;
354
        h0 += c;
355
        h1 += (c = CONSTANT_TIME_CARRY(h0,c));
356
        h2 += (c = CONSTANT_TIME_CARRY(h1,c));
357
        h3 += (c = CONSTANT_TIME_CARRY(h2,c));
358
        h4 += CONSTANT_TIME_CARRY(h3,c);
359
        /*
360
         * Occasional overflows to 3rd bit of h4 are taken care of
361
         * "naturally". If after this point we end up at the top of
362
         * this loop, then the overflow bit will be accounted for
363
         * in next iteration. If we end up in poly1305_emit, then
364
         * comparison to modulus below will still count as "carry
365
         * into 131st bit", so that properly reduced value will be
366
         * picked in conditional move.
367
         */
368
369
        inp += POLY1305_BLOCK_SIZE;
370
        len -= POLY1305_BLOCK_SIZE;
371
    }
372
373
    st->h[0] = h0;
374
    st->h[1] = h1;
375
    st->h[2] = h2;
376
    st->h[3] = h3;
377
    st->h[4] = h4;
378
}
379
380
static void poly1305_emit(void *ctx, unsigned char mac[16],
381
                          const u32 nonce[4])
382
{
383
    poly1305_internal *st = (poly1305_internal *) ctx;
384
    u32 h0, h1, h2, h3, h4;
385
    u32 g0, g1, g2, g3, g4;
386
    u64 t;
387
    u32 mask;
388
389
    h0 = st->h[0];
390
    h1 = st->h[1];
391
    h2 = st->h[2];
392
    h3 = st->h[3];
393
    h4 = st->h[4];
394
395
    /* compare to modulus by computing h + -p */
396
    g0 = (u32)(t = (u64)h0 + 5);
397
    g1 = (u32)(t = (u64)h1 + (t >> 32));
398
    g2 = (u32)(t = (u64)h2 + (t >> 32));
399
    g3 = (u32)(t = (u64)h3 + (t >> 32));
400
    g4 = h4 + (u32)(t >> 32);
401
402
    /* if there was carry into 131st bit, h3:h0 = g3:g0 */
403
    mask = 0 - (g4 >> 2);
404
    g0 &= mask;
405
    g1 &= mask;
406
    g2 &= mask;
407
    g3 &= mask;
408
    mask = ~mask;
409
    h0 = (h0 & mask) | g0;
410
    h1 = (h1 & mask) | g1;
411
    h2 = (h2 & mask) | g2;
412
    h3 = (h3 & mask) | g3;
413
414
    /* mac = (h + nonce) % (2^128) */
415
    h0 = (u32)(t = (u64)h0 + nonce[0]);
416
    h1 = (u32)(t = (u64)h1 + (t >> 32) + nonce[1]);
417
    h2 = (u32)(t = (u64)h2 + (t >> 32) + nonce[2]);
418
    h3 = (u32)(t = (u64)h3 + (t >> 32) + nonce[3]);
419
420
    U32TO8(mac + 0, h0);
421
    U32TO8(mac + 4, h1);
422
    U32TO8(mac + 8, h2);
423
    U32TO8(mac + 12, h3);
424
}
425
# endif
426
#else
427
int poly1305_init(void *ctx, const unsigned char key[16], void *func);
428
void poly1305_blocks(void *ctx, const unsigned char *inp, size_t len,
429
                     unsigned int padbit);
430
void poly1305_emit(void *ctx, unsigned char mac[16],
431
                   const unsigned int nonce[4]);
432
#endif
433
434
void Poly1305_Init(POLY1305 *ctx, const unsigned char key[32])
435
0
{
436
0
    ctx->nonce[0] = U8TOU32(&key[16]);
437
0
    ctx->nonce[1] = U8TOU32(&key[20]);
438
0
    ctx->nonce[2] = U8TOU32(&key[24]);
439
0
    ctx->nonce[3] = U8TOU32(&key[28]);
440
441
#ifndef POLY1305_ASM
442
    poly1305_init(ctx->opaque, key);
443
#else
444
    /*
445
     * Unlike reference poly1305_init assembly counterpart is expected
446
     * to return a value: non-zero if it initializes ctx->func, and zero
447
     * otherwise. Latter is to simplify assembly in cases when there no
448
     * multiple code paths to switch between.
449
     */
450
0
    if (!poly1305_init(ctx->opaque, key, &ctx->func)) {
451
0
        ctx->func.blocks = poly1305_blocks;
452
0
        ctx->func.emit = poly1305_emit;
453
0
    }
454
0
#endif
455
456
0
    ctx->num = 0;
457
458
0
}
459
460
#ifdef POLY1305_ASM
461
/*
462
 * This "eclipses" poly1305_blocks and poly1305_emit, but it's
463
 * conscious choice imposed by -Wshadow compiler warnings.
464
 */
465
0
# define poly1305_blocks (*poly1305_blocks_p)
466
0
# define poly1305_emit   (*poly1305_emit_p)
467
#endif
468
469
void Poly1305_Update(POLY1305 *ctx, const unsigned char *inp, size_t len)
470
0
{
471
0
#ifdef POLY1305_ASM
472
    /*
473
     * As documented, poly1305_blocks is never called with input
474
     * longer than single block and padbit argument set to 0. This
475
     * property is fluently used in assembly modules to optimize
476
     * padbit handling on loop boundary.
477
     */
478
0
    poly1305_blocks_f poly1305_blocks_p = ctx->func.blocks;
479
0
#endif
480
0
    size_t rem, num;
481
482
0
    if ((num = ctx->num)) {
483
0
        rem = POLY1305_BLOCK_SIZE - num;
484
0
        if (len >= rem) {
485
0
            memcpy(ctx->data + num, inp, rem);
486
0
            poly1305_blocks(ctx->opaque, ctx->data, POLY1305_BLOCK_SIZE, 1);
487
0
            inp += rem;
488
0
            len -= rem;
489
0
        } else {
490
            /* Still not enough data to process a block. */
491
0
            memcpy(ctx->data + num, inp, len);
492
0
            ctx->num = num + len;
493
0
            return;
494
0
        }
495
0
    }
496
497
0
    rem = len % POLY1305_BLOCK_SIZE;
498
0
    len -= rem;
499
500
0
    if (len >= POLY1305_BLOCK_SIZE) {
501
0
        poly1305_blocks(ctx->opaque, inp, len, 1);
502
0
        inp += len;
503
0
    }
504
505
0
    if (rem)
506
0
        memcpy(ctx->data, inp, rem);
507
508
0
    ctx->num = rem;
509
0
}
510
511
void Poly1305_Final(POLY1305 *ctx, unsigned char mac[16])
512
0
{
513
0
#ifdef POLY1305_ASM
514
0
    poly1305_blocks_f poly1305_blocks_p = ctx->func.blocks;
515
0
    poly1305_emit_f poly1305_emit_p = ctx->func.emit;
516
0
#endif
517
0
    size_t num;
518
519
0
    if ((num = ctx->num)) {
520
0
        ctx->data[num++] = 1;   /* pad bit */
521
0
        while (num < POLY1305_BLOCK_SIZE)
522
0
            ctx->data[num++] = 0;
523
0
        poly1305_blocks(ctx->opaque, ctx->data, POLY1305_BLOCK_SIZE, 0);
524
0
    }
525
526
0
    poly1305_emit(ctx->opaque, mac, ctx->nonce);
527
528
    /* zero out the state */
529
0
    OPENSSL_cleanse(ctx, sizeof(*ctx));
530
0
}