base64-decode.c 3.92 KB
Newer Older
1
/* base64-encode.c
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

   Copyright (C) 2002 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.

   GNU Nettle 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
   General Public License for more details.

   You should have received copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see http://www.gnu.org/licenses/.
*/
31

32
33
34
#if HAVE_CONFIG_H
# include "config.h"
#endif
35
36
37
38

#include <assert.h>
#include <stdlib.h>

39
40
#include "base64.h"

41
42
43
44
45
46
47
#define TABLE_INVALID -1
#define TABLE_SPACE -2
#define TABLE_END -3

void
base64_decode_init(struct base64_decode_ctx *ctx)
{
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
  static const signed char base64_decode_table[0x100] =
    {
      /* White space is HT, VT, FF, CR, LF and SPC */
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -1, -1, 
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -3, -1, -1,
      -1,  0,  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, -1, -1, -1, -1, -1,
      -1, 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, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    };

69
  ctx->word = ctx->bits = ctx->padding = 0;
70
  ctx->table = base64_decode_table;
71
72
}

73
int
74
75
base64_decode_single(struct base64_decode_ctx *ctx,
		     uint8_t *dst,
76
		     char src)
77
{
78
  int data = ctx->table[(uint8_t) src];
79
80
81
82

  switch(data)
    {
    default:
83
      assert(data >= 0 && data < 0x40);
84
85
86
87

      if (ctx->padding)
	return -1;
      
88
89
90
91
92
93
94
95
96
97
98
      ctx->word = ctx->word << 6 | data;
      ctx->bits += 6;

      if (ctx->bits >= 8)
	{
	  ctx->bits -= 8;
	  dst[0] = ctx->word >> ctx->bits;
	  return 1;
	}
      else return 0;

99
    case TABLE_INVALID:
100
101
      return -1;

102
    case TABLE_SPACE:
103
      return 0;
104
      
105
    case TABLE_END:
106
107
108
109
      /* There can be at most two padding characters. */
      if (!ctx->bits || ctx->padding > 2)
	return -1;
      
110
111
      if (ctx->word & ( (1<<ctx->bits) - 1))
	/* We shouldn't have any leftover bits */
112
113
114
	return -1;

      ctx->padding++;
115
116
117
118
119
      ctx->bits -= 2;
      return 0;
    }
}

120
int
121
base64_decode_update(struct base64_decode_ctx *ctx,
122
		     size_t *dst_length,
123
		     uint8_t *dst,
124
		     size_t src_length,
125
		     const char *src)
126
{
127
128
  size_t done;
  size_t i;
129

130
131
132
133
134
135
136
137
138
139
140
141
142
  for (i = 0, done = 0; i<src_length; i++)
    switch(base64_decode_single(ctx, dst + done, src[i]))
      {
      case -1:
	return 0;
      case 1:
	done++;
	/* Fall through */
      case 0:
	break;
      default:
	abort();
      }
143
  
144
145
146
147
  assert(done <= BASE64_DECODE_LENGTH(src_length));

  *dst_length = done;
  return 1;
148
149
150
}

int
151
base64_decode_final(struct base64_decode_ctx *ctx)
152
{
153
  return ctx->bits == 0;
154
}