1 /* b64dec.c - Simple Base64 decoder.
2 * Copyright (C) 2008 Free Software Foundation, Inc.
3 *
4 * This file is part of GnuPG.
5 *
6 * GnuPG is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 3 of the License, or
9 * (at your option) any later version.
10 *
11 * GnuPG is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, see <http://www.gnu.org/licenses/>.
18 */
19
20 #include <config.h>
21 #include <stdio.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <errno.h>
25 #include <assert.h>
26
27 #include "i18n.h"
28 #include "util.h"
29
30
31 /* The reverse base-64 list used for base-64 decoding. */
32 static unsigned char const asctobin[128] =
33 {
34 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
35 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
36 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
37 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
38 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
39 0xff, 0xff, 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
40 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
41 0x3c, 0x3d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
42 0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
43 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
44 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
45 0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
46 0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
47 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
48 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
49 0x31, 0x32, 0x33, 0xff, 0xff, 0xff, 0xff, 0xff
50 };
51
52 enum decoder_states
53 {
54 s_init, s_idle, s_lfseen, s_begin,
55 s_b64_0, s_b64_1, s_b64_2, s_b64_3,
56 s_waitendtitle, s_waitend
57 };
58
59
60
61 /* Initialize the context for the base64 decoder. If TITLE is NULL a
62 plain base64 decoding is done. If it is the empty string the
63 decoder will skip everything until a "-----BEGIN " line has been
64 seen, decoding ends at a "----END " line.
65
66 Not yet implemented: If TITLE is either "PGP" or begins with "PGP "
67 the PGP armor lines are skipped as well. */
68 gpg_error_t
b64dec_start(struct b64state * state,const char * title)69 b64dec_start (struct b64state *state, const char *title)
70 {
71 memset (state, 0, sizeof *state);
72 if (title)
73 {
74 if (!strncmp (title, "PGP", 3) && (!title[3] || title[3] == ' '))
75 return gpg_error (GPG_ERR_NOT_IMPLEMENTED);
76
77 state->title = xtrystrdup (title);
78 if (!state->title)
79 return gpg_error_from_syserror ();
80 state->idx = s_init;
81 }
82 else
83 state->idx = s_b64_0;
84 return 0;
85 }
86
87
88 /* Do in-place decoding of base-64 data of LENGTH in BUFFER. Stores the
89 new length of the buffer at R_NBYTES. */
90 gpg_error_t
b64dec_proc(struct b64state * state,void * buffer,size_t length,size_t * r_nbytes)91 b64dec_proc (struct b64state *state, void *buffer, size_t length,
92 size_t *r_nbytes)
93 {
94 enum decoder_states ds = state->idx;
95 unsigned char val = state->radbuf[0];
96 int pos = state->quad_count;
97 char *d, *s;
98
99 if (state->stop_seen)
100 {
101 *r_nbytes = 0;
102 return gpg_error (GPG_ERR_EOF);
103 }
104
105 for (s=d=buffer; length && !state->stop_seen; length--, s++)
106 {
107 switch (ds)
108 {
109 case s_idle:
110 if (*s == '\n')
111 {
112 ds = s_lfseen;
113 pos = 0;
114 }
115 break;
116 case s_init:
117 ds = s_lfseen;
118 case s_lfseen:
119 if (*s != "-----BEGIN "[pos])
120 ds = s_idle;
121 else if (pos == 10)
122 ds = s_begin;
123 else
124 pos++;
125 break;
126 case s_begin:
127 if (*s == '\n')
128 ds = s_b64_0;
129 break;
130 case s_b64_0:
131 case s_b64_1:
132 case s_b64_2:
133 case s_b64_3:
134 {
135 int c;
136
137 if (*s == '-' && state->title)
138 {
139 /* Not a valid Base64 character: assume end
140 header. */
141 ds = s_waitend;
142 }
143 else if (*s == '=')
144 {
145 /* Pad character: stop */
146 if (ds == s_b64_1)
147 *d++ = val;
148 ds = state->title? s_waitendtitle : s_waitend;
149 }
150 else if (*s == '\n' || *s == ' ' || *s == '\r' || *s == '\t')
151 ; /* Skip white spaces. */
152 else if ( (*s & 0x80)
153 || (c = asctobin[*(unsigned char *)s]) == 255)
154 {
155 /* Skip invalid encodings. */
156 state->invalid_encoding = 1;
157 }
158 else if (ds == s_b64_0)
159 {
160 val = c << 2;
161 ds = s_b64_1;
162 }
163 else if (ds == s_b64_1)
164 {
165 val |= (c>>4)&3;
166 *d++ = val;
167 val = (c<<4)&0xf0;
168 ds = s_b64_2;
169 }
170 else if (ds == s_b64_2)
171 {
172 val |= (c>>2)&15;
173 *d++ = val;
174 val = (c<<6)&0xc0;
175 ds = s_b64_3;
176 }
177 else
178 {
179 val |= c&0x3f;
180 *d++ = val;
181 ds = s_b64_0;
182 }
183 }
184 break;
185 case s_waitendtitle:
186 if (*s == '-')
187 ds = s_waitend;
188 break;
189 case s_waitend:
190 if ( *s == '\n')
191 state->stop_seen = 1;
192 break;
193 default:
194 BUG();
195 }
196 }
197
198
199 state->idx = ds;
200 state->radbuf[0] = val;
201 state->quad_count = pos;
202 *r_nbytes = (d -(char*) buffer);
203 return 0;
204 }
205
206
207 /* This function needs to be called before releasing the decoder
208 state. It may return an error code in case an encoding error has
209 been found during decoding. */
210 gpg_error_t
b64dec_finish(struct b64state * state)211 b64dec_finish (struct b64state *state)
212 {
213 xfree (state->title);
214 state->title = NULL;
215 return state->invalid_encoding? gpg_error(GPG_ERR_BAD_DATA): 0;
216 }
217
218