summaryrefslogtreecommitdiffstats
path: root/lib/base32.c
blob: ea873386f0a35c792ee8479eb126012f62ddb1fa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
/* base32.c -- Encode binary data using printable characters.
   Copyright (C) 1999-2001, 2004-2006, 2009-2022 Free Software Foundation, Inc.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Adapted from Simon Josefsson's base64 code by Gijs van Tulder.
 *
 * See also RFC 4648 <https://www.ietf.org/rfc/rfc4648.txt>.
 *
 * Be careful with error checking.  Here is how you would typically
 * use these functions:
 *
 * bool ok = base32_decode_alloc (in, inlen, &out, &outlen);
 * if (!ok)
 *   FAIL: input was not valid base32
 * if (out == NULL)
 *   FAIL: memory allocation error
 * OK: data in OUT/OUTLEN
 *
 * idx_t outlen = base32_encode_alloc (in, inlen, &out);
 * if (out == NULL && outlen == 0 && inlen != 0)
 *   FAIL: input too long
 * if (out == NULL)
 *   FAIL: memory allocation error
 * OK: data in OUT/OUTLEN.
 *
 */

#include <config.h>

/* Get prototype. */
#include "base32.h"

/* Get imalloc. */
#include <ialloc.h>

#include <intprops.h>

/* Get UCHAR_MAX. */
#include <limits.h>

#include <string.h>

/* Convert 'char' to 'unsigned char' without casting.  */
static unsigned char
to_uchar (char ch)
{
  return ch;
}

/* Base32 encode IN array of size INLEN into OUT array of size OUTLEN.
   If OUTLEN is less than BASE32_LENGTH(INLEN), write as many bytes as
   possible.  If OUTLEN is larger than BASE32_LENGTH(INLEN), also zero
   terminate the output buffer. */
void
base32_encode (const char *restrict in, idx_t inlen,
               char *restrict out, idx_t outlen)
{
  static const char b32str[32] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";

  while (inlen && outlen)
    {
      *out++ = b32str[(to_uchar (in[0]) >> 3) & 0x1f];
      if (!--outlen)
        break;
      *out++ = b32str[((to_uchar (in[0]) << 2)
                       + (--inlen ? to_uchar (in[1]) >> 6 : 0))
                      & 0x1f];
      if (!--outlen)
        break;
      *out++ =
        (inlen
         ? b32str[(to_uchar (in[1]) >> 1) & 0x1f]
         : '=');
      if (!--outlen)
        break;
      *out++ =
        (inlen
         ? b32str[((to_uchar (in[1]) << 4)
                   + (--inlen ? to_uchar (in[2]) >> 4 : 0))
                  & 0x1f]
         : '=');
      if (!--outlen)
        break;
      *out++ =
        (inlen
         ? b32str[((to_uchar (in[2]) << 1)
                   + (--inlen ? to_uchar (in[3]) >> 7 : 0))
                  & 0x1f]
         : '=');
      if (!--outlen)
        break;
      *out++ =
        (inlen
         ? b32str[(to_uchar (in[3]) >> 2) & 0x1f]
         : '=');
      if (!--outlen)
        break;
      *out++ =
        (inlen
         ? b32str[((to_uchar (in[3]) << 3)
                   + (--inlen ? to_uchar (in[4]) >> 5 : 0))
                  & 0x1f]
         : '=');
      if (!--outlen)
        break;
      *out++ = inlen ? b32str[to_uchar (in[4]) & 0x1f] : '=';
      if (!--outlen)
        break;
      if (inlen)
        inlen--;
      if (inlen)
        in += 5;
    }

  if (outlen)
    *out = '\0';
}

/* Allocate a buffer and store zero terminated base32 encoded data
   from array IN of size INLEN, returning BASE32_LENGTH(INLEN), i.e.,
   the length of the encoded data, excluding the terminating zero.  On
   return, the OUT variable will hold a pointer to newly allocated
   memory that must be deallocated by the caller.  If output string
   length would overflow, 0 is returned and OUT is set to NULL.  If
   memory allocation failed, OUT is set to NULL, and the return value
   indicates length of the requested memory block, i.e.,
   BASE32_LENGTH(inlen) + 1. */
idx_t
base32_encode_alloc (const char *in, idx_t inlen, char **out)
{
  /* Check for overflow in outlen computation.
     Treat negative INLEN as overflow, for better compatibility with
     pre-2021-08-27 API, which used size_t.  */
  idx_t in_over_5 = inlen / 5 + (inlen % 5 != 0), outlen;
  if (! INT_MULTIPLY_OK (in_over_5, 8, &outlen) || inlen < 0)
    {
      *out = NULL;
      return 0;
    }
  outlen++;

  *out = imalloc (outlen);
  if (!*out)
    return outlen;

  base32_encode (in, inlen, *out, outlen);

  return outlen - 1;
}

/* With this approach this file works independent of the charset used
   (think EBCDIC).  However, it does assume that the characters in the
   Base32 alphabet (A-Z2-7) are encoded in 0..255.  POSIX
   1003.1-2001 require that char and unsigned char are 8-bit
   quantities, though, taking care of that problem.  But this may be a
   potential problem on non-POSIX C99 platforms.

   IBM C V6 for AIX mishandles "#define B32(x) ...'x'...", so use "_"
   as the formal parameter rather than "x".  */
#define B32(_)                                  \
  ((_) == 'A' ? 0                               \
   : (_) == 'B' ? 1                             \
   : (_) == 'C' ? 2                             \
   : (_) == 'D' ? 3                             \
   : (_) == 'E' ? 4                             \
   : (_) == 'F' ? 5                             \
   : (_) == 'G' ? 6                             \
   : (_) == 'H' ? 7                             \
   : (_) == 'I' ? 8                             \
   : (_) == 'J' ? 9                             \
   : (_) == 'K' ? 10                            \
   : (_) == 'L' ? 11                            \
   : (_) == 'M' ? 12                            \
   : (_) == 'N' ? 13                            \
   : (_) == 'O' ? 14                            \
   : (_) == 'P' ? 15                            \
   : (_) == 'Q' ? 16                            \
   : (_) == 'R' ? 17                            \
   : (_) == 'S' ? 18                            \
   : (_) == 'T' ? 19                            \
   : (_) == 'U' ? 20                            \
   : (_) == 'V' ? 21                            \
   : (_) == 'W' ? 22                            \
   : (_) == 'X' ? 23                            \
   : (_) == 'Y' ? 24                            \
   : (_) == 'Z' ? 25                            \
   : (_) == '2' ? 26                            \
   : (_) == '3' ? 27                            \
   : (_) == '4' ? 28                            \
   : (_) == '5' ? 29                            \
   : (_) == '6' ? 30                            \
   : (_) == '7' ? 31                            \
   : -1)

static const signed char b32[0x100] = {
  B32 (0), B32 (1), B32 (2), B32 (3),
  B32 (4), B32 (5), B32 (6), B32 (7),
  B32 (8), B32 (9), B32 (10), B32 (11),
  B32 (12), B32 (13), B32 (14), B32 (15),
  B32 (16), B32 (17), B32 (18), B32 (19),
  B32 (20), B32 (21), B32 (22), B32 (23),
  B32 (24), B32 (25), B32 (26), B32 (27),
  B32 (28), B32 (29), B32 (30), B32 (31),
  B32 (32), B32 (33), B32 (34), B32 (35),
  B32 (36), B32 (37), B32 (38), B32 (39),
  B32 (40), B32 (41), B32 (42), B32 (43),
  B32 (44), B32 (45), B32 (46), B32 (47),
  B32 (48), B32 (49), B32 (50), B32 (51),
  B32 (52), B32 (53), B32 (54), B32 (55),
  B32 (56), B32 (57), B32 (58), B32 (59),
  B32 (60), B32 (61), B32 (62), B32 (63),
  B32 (32), B32 (65), B32 (66), B32 (67),
  B32 (68), B32 (69), B32 (70), B32 (71),
  B32 (72), B32 (73), B32 (74), B32 (75),
  B32 (76), B32 (77), B32 (78), B32 (79),
  B32 (80), B32 (81), B32 (82), B32 (83),
  B32 (84), B32 (85), B32 (86), B32 (87),
  B32 (88), B32 (89), B32 (90), B32 (91),
  B32 (92), B32 (93), B32 (94), B32 (95),
  B32 (96), B32 (97), B32 (98), B32 (99),
  B32 (100), B32 (101), B32 (102), B32 (103),
  B32 (104), B32 (105), B32 (106), B32 (107),
  B32 (108), B32 (109), B32 (110), B32 (111),
  B32 (112), B32 (113), B32 (114), B32 (115),
  B32 (116), B32 (117), B32 (118), B32 (119),
  B32 (120), B32 (121), B32 (122), B32 (123),
  B32 (124), B32 (125), B32 (126), B32 (127),
  B32 (128), B32 (129), B32 (130), B32 (131),
  B32 (132), B32 (133), B32 (134), B32 (135),
  B32 (136), B32 (137), B32 (138), B32 (139),
  B32 (140), B32 (141), B32 (142), B32 (143),
  B32 (144), B32 (145), B32 (146), B32 (147),
  B32 (148), B32 (149), B32 (150), B32 (151),
  B32 (152), B32 (153), B32 (154), B32 (155),
  B32 (156), B32 (157), B32 (158), B32 (159),
  B32 (160), B32 (161), B32 (162), B32 (163),
  B32 (132), B32 (165), B32 (166), B32 (167),
  B32 (168), B32 (169), B32 (170), B32 (171),
  B32 (172), B32 (173), B32 (174), B32 (175),
  B32 (176), B32 (177), B32 (178), B32 (179),
  B32 (180), B32 (181), B32 (182), B32 (183),
  B32 (184), B32 (185), B32 (186), B32 (187),
  B32 (188), B32 (189), B32 (190), B32 (191),
  B32 (192), B32 (193), B32 (194), B32 (195),
  B32 (196), B32 (197), B32 (198), B32 (199),
  B32 (200), B32 (201), B32 (202), B32 (203),
  B32 (204), B32 (205), B32 (206), B32 (207),
  B32 (208), B32 (209), B32 (210), B32 (211),
  B32 (212), B32 (213), B32 (214), B32 (215),
  B32 (216), B32 (217), B32 (218), B32 (219),
  B32 (220), B32 (221), B32 (222), B32 (223),
  B32 (224), B32 (225), B32 (226), B32 (227),
  B32 (228), B32 (229), B32 (230), B32 (231),
  B32 (232), B32 (233), B32 (234), B32 (235),
  B32 (236), B32 (237), B32 (238), B32 (239),
  B32 (240), B32 (241), B32 (242), B32 (243),
  B32 (244), B32 (245), B32 (246), B32 (247),
  B32 (248), B32 (249), B32 (250), B32 (251),
  B32 (252), B32 (253), B32 (254), B32 (255)
};

#if UCHAR_MAX == 255
# define uchar_in_range(c) true
#else
# define uchar_in_range(c) ((c) <= 255)
#endif

/* Return true if CH is a character from the Base32 alphabet, and
   false otherwise.  Note that '=' is padding and not considered to be
   part of the alphabet.  */
bool
isbase32 (char ch)
{
  return uchar_in_range (to_uchar (ch)) && 0 <= b32[to_uchar (ch)];
}

/* Initialize decode-context buffer, CTX.  */
void
base32_decode_ctx_init (struct base32_decode_context *ctx)
{
  ctx->i = 0;
}

/* If CTX->i is 0 or 8, there are eight or more bytes in [*IN..IN_END), and
   none of those eight is a newline, then return *IN.  Otherwise, copy up to
   4 - CTX->i non-newline bytes from that range into CTX->buf, starting at
   index CTX->i and setting CTX->i to reflect the number of bytes copied,
   and return CTX->buf.  In either case, advance *IN to point to the byte
   after the last one processed, and set *N_NON_NEWLINE to the number of
   verified non-newline bytes accessible through the returned pointer.  */
static char *
get_8 (struct base32_decode_context *ctx,
       char const *restrict *in, char const *restrict in_end,
       idx_t *n_non_newline)
{
  if (ctx->i == 8)
    ctx->i = 0;

  if (ctx->i == 0)
    {
      char const *t = *in;
      if (8 <= in_end - *in && memchr (t, '\n', 8) == NULL)
        {
          /* This is the common case: no newline.  */
          *in += 8;
          *n_non_newline = 8;
          return (char *) t;
        }
    }

  {
    /* Copy non-newline bytes into BUF.  */
    char const *p = *in;
    while (p < in_end)
      {
        char c = *p++;
        if (c != '\n')
          {
            ctx->buf[ctx->i++] = c;
            if (ctx->i == 8)
              break;
          }
      }

    *in = p;
    *n_non_newline = ctx->i;
    return ctx->buf;
  }
}

#define return_false                            \
  do                                            \
    {                                           \
      *outp = out;                              \
      return false;                             \
    }                                           \
  while (false)

/* Decode eight bytes of base32-encoded data, IN, of length INLEN
   into the output buffer, *OUT, of size *OUTLEN bytes.  Return true if
   decoding is successful, false otherwise.  If *OUTLEN is too small,
   as many bytes as possible are written to *OUT.  On return, advance
   *OUT to point to the byte after the last one written, and decrement
   *OUTLEN to reflect the number of bytes remaining in *OUT.  */
static bool
decode_8 (char const *restrict in, idx_t inlen,
          char *restrict *outp, idx_t *outleft)
{
  char *out = *outp;
  if (inlen < 8)
    return false;

  if (!isbase32 (in[0]) || !isbase32 (in[1]))
    return false;

  if (*outleft)
    {
      *out++ = ((b32[to_uchar (in[0])] << 3)
                | (b32[to_uchar (in[1])] >> 2));
      --*outleft;
    }

  if (in[2] == '=')
    {
      if (in[3] != '=' || in[4] != '=' || in[5] != '='
          || in[6] != '=' || in[7] != '=')
        return_false;
    }
  else
    {
      if (!isbase32 (in[2]) || !isbase32 (in[3]))
        return_false;

      if (*outleft)
        {
          *out++ = ((b32[to_uchar (in[1])] << 6)
                    | (b32[to_uchar (in[2])] << 1)
                    | (b32[to_uchar (in[3])] >> 4));
          --*outleft;
        }

      if (in[4] == '=')
        {
          if (in[5] != '=' || in[6] != '=' || in[7] != '=')
            return_false;
        }
      else
        {
          if (!isbase32 (in[4]))
            return_false;

          if (*outleft)
            {
              *out++ = ((b32[to_uchar (in[3])] << 4)
                        | (b32[to_uchar (in[4])] >> 1));
              --*outleft;
            }

          if (in[5] == '=')
            {
              if (in[6] != '=' || in[7] != '=')
                return_false;
            }
          else
            {
              if (!isbase32 (in[5]) || !isbase32 (in[6]))
                return_false;

              if (*outleft)
                {
                  *out++ = ((b32[to_uchar (in[4])] << 7)
                            | (b32[to_uchar (in[5])] << 2)
                            | (b32[to_uchar (in[6])] >> 3));
                  --*outleft;
                }

              if (in[7] != '=')
                {
                  if (!isbase32 (in[7]))
                    return_false;

                  if (*outleft)
                    {
                      *out++ = ((b32[to_uchar (in[6])] << 5)
                                | (b32[to_uchar (in[7])]));
                      --*outleft;
                    }
                }
            }
        }
    }

  *outp = out;
  return true;
}

/* Decode base32-encoded input array IN of length INLEN to output array
   OUT that can hold *OUTLEN bytes.  The input data may be interspersed
   with newlines.  Return true if decoding was successful, i.e. if the
   input was valid base32 data, false otherwise.  If *OUTLEN is too
   small, as many bytes as possible will be written to OUT.  On return,
   *OUTLEN holds the length of decoded bytes in OUT.  Note that as soon
   as any non-alphabet, non-newline character is encountered, decoding
   is stopped and false is returned.  If INLEN is zero, then process
   only whatever data is stored in CTX.

   Initially, CTX must have been initialized via base32_decode_ctx_init.
   Subsequent calls to this function must reuse whatever state is recorded
   in that buffer.  It is necessary for when a octuple of base32 input
   bytes spans two input buffers.

   If CTX is NULL then newlines are treated as garbage and the input
   buffer is processed as a unit.  */

bool
base32_decode_ctx (struct base32_decode_context *ctx,
                   const char *restrict in, idx_t inlen,
                   char *restrict out, idx_t *outlen)
{
  idx_t outleft = *outlen;
  bool ignore_newlines = ctx != NULL;
  bool flush_ctx = false;
  unsigned int ctx_i = 0;

  if (ignore_newlines)
    {
      ctx_i = ctx->i;
      flush_ctx = inlen == 0;
    }


  while (true)
    {
      idx_t outleft_save = outleft;
      if (ctx_i == 0 && !flush_ctx)
        {
          while (true)
            {
              /* Save a copy of outleft, in case we need to re-parse this
                 block of four bytes.  */
              outleft_save = outleft;
              if (!decode_8 (in, inlen, &out, &outleft))
                break;

              in += 8;
              inlen -= 8;
            }
        }

      if (inlen == 0 && !flush_ctx)
        break;

      /* Handle the common case of 72-byte wrapped lines.
         This also handles any other multiple-of-8-byte wrapping.  */
      if (inlen && *in == '\n' && ignore_newlines)
        {
          ++in;
          --inlen;
          continue;
        }

      /* Restore OUT and OUTLEFT.  */
      out -= outleft_save - outleft;
      outleft = outleft_save;

      {
        char const *in_end = in + inlen;
        char const *non_nl;

        if (ignore_newlines)
          non_nl = get_8 (ctx, &in, in_end, &inlen);
        else
          non_nl = in;  /* Might have nl in this case. */

        /* If the input is empty or consists solely of newlines (0 non-newlines),
           then we're done.  Likewise if there are fewer than 8 bytes when not
           flushing context and not treating newlines as garbage.  */
        if (inlen == 0 || (inlen < 8 && !flush_ctx && ignore_newlines))
          {
            inlen = 0;
            break;
          }
        if (!decode_8 (non_nl, inlen, &out, &outleft))
          break;

        inlen = in_end - in;
      }
    }

  *outlen -= outleft;

  return inlen == 0;
}

/* Allocate an output buffer in *OUT, and decode the base32 encoded
   data stored in IN of size INLEN to the *OUT buffer.  On return, the
   size of the decoded data is stored in *OUTLEN.  OUTLEN may be NULL,
   if the caller is not interested in the decoded length.  *OUT may be
   NULL to indicate an out of memory error, in which case *OUTLEN
   contains the size of the memory block needed.  The function returns
   true on successful decoding and memory allocation errors.  (Use the
   *OUT and *OUTLEN parameters to differentiate between successful
   decoding and memory error.)  The function returns false if the
   input was invalid, in which case *OUT is NULL and *OUTLEN is
   undefined. */
bool
base32_decode_alloc_ctx (struct base32_decode_context *ctx,
                         const char *in, idx_t inlen, char **out,
                         idx_t *outlen)
{
  /* This may allocate a few bytes too many, depending on input,
     but it's not worth the extra CPU time to compute the exact size.
     The exact size is 5 * inlen / 8, minus one or more bytes if the
     input is padded with one or more "=".
     Shifting before multiplying avoids the possibility of overflow.  */
  idx_t needlen = 5 * ((inlen >> 3) + 1);

  *out = imalloc (needlen);
  if (!*out)
    return true;

  if (!base32_decode_ctx (ctx, in, inlen, *out, &needlen))
    {
      free (*out);
      *out = NULL;
      return false;
    }

  if (outlen)
    *outlen = needlen;

  return true;
}