1 /* base64.c -- Encode binary data using printable characters.
2 Copyright (C) 1999, 2000, 2001, 2004 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18 /* Written by Simon Josefsson. Partially adapted from GNU MailUtils
19 * (mailbox/filter_trans.c, as of 2004-11-28). Improved by review
20 * from Paul Eggert, Bruno Haible, and Stepan Kasal.
22 * See also RFC 3548 <http://www.ietf.org/rfc/rfc3548.txt>.
24 * Be careful with error checking. Here is how you would typically
25 * use these functions:
27 * bool ok = base64_decode_alloc (in, inlen, &out, &outlen);
29 * FAIL: input was not valid base64
31 * FAIL: memory allocation error
32 * OK: data in OUT/OUTLEN
34 * size_t outlen = base64_encode_alloc (in, inlen, &out);
35 * if (out == NULL && outlen == 0 && inlen != 0)
36 * FAIL: input too long
38 * FAIL: memory allocation error
39 * OK: data in OUT/LEN.
53 /* C89 compliant way to cast 'char' to 'unsigned char'. */
54 static inline unsigned char
60 /* Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
61 If OUTLEN is less than BASE64_LENGTH(INLEN), write as many bytes as
62 possible. If OUTLEN is larger than BASE64_LENGTH(INLEN), also zero
63 terminate the output buffer. */
65 base64_encode (const char *restrict in, size_t inlen,
66 char *restrict out, size_t outlen)
69 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
71 while (inlen && outlen)
73 *out++ = b64[to_uchar (in[0]) >> 2];
76 *out++ = b64[((to_uchar (in[0]) << 4)
77 + (--inlen ? to_uchar (in[1]) >> 4 : 0)) & 0x3f];
82 ? b64[((to_uchar (in[1]) << 2)
83 + (--inlen ? to_uchar (in[2]) >> 6 : 0)) & 0x3f] : '=');
86 *out++ = inlen ? b64[to_uchar (in[2]) & 0x3f] : '=';
98 /* Allocate a buffer and store zero terminated base64 encoded data
99 from array IN of size INLEN, returning BASE64_LENGTH(INLEN), i.e.,
100 the length of the encoded data, excluding the terminating zero. On
101 return, the OUT variable will hold a pointer to newly allocated
102 memory that must be deallocated by the caller. If output string
103 length would overflow, 0 is returned and OUT is set to NULL. If
104 memory allocation fail, OUT is set to NULL, and the return value
105 indicate length of the requested memory block, i.e.,
106 BASE64_LENGTH(inlen) + 1. */
108 base64_encode_alloc (const char *in, size_t inlen, char **out)
110 size_t outlen = 1 + BASE64_LENGTH (inlen);
112 /* Check for overflow in outlen computation.
114 * If there is no overflow, outlen >= inlen.
116 * If the operation (inlen + 2) overflows then it yields at most +1, so
119 * If the multiplication overflows, we lose at least half of the
120 * correct value, so the result is < ((inlen + 2) / 3) * 2, which is
121 * less than (inlen + 2) * 0.66667, which is less than inlen as soon as
130 *out = malloc (outlen);
132 base64_encode (in, inlen, *out, outlen);
137 /* With this approach this file works independent of the charset used
138 (think EBCDIC). However, it does assume that the characters in the
139 Base64 alphabet (A-Za-z0-9+/) are encoded in 0..255. POSIX
140 1003.1-2001 require that char and unsigned char are 8-bit
141 quantities, though, taking care of that problem. But this may be a
142 potential problem on non-POSIX C99 platforms. */
210 static const signed char b64[0x100] = {
211 B64 (0), B64 (1), B64 (2), B64 (3),
212 B64 (4), B64 (5), B64 (6), B64 (7),
213 B64 (8), B64 (9), B64 (10), B64 (11),
214 B64 (12), B64 (13), B64 (14), B64 (15),
215 B64 (16), B64 (17), B64 (18), B64 (19),
216 B64 (20), B64 (21), B64 (22), B64 (23),
217 B64 (24), B64 (25), B64 (26), B64 (27),
218 B64 (28), B64 (29), B64 (30), B64 (31),
219 B64 (32), B64 (33), B64 (34), B64 (35),
220 B64 (36), B64 (37), B64 (38), B64 (39),
221 B64 (40), B64 (41), B64 (42), B64 (43),
222 B64 (44), B64 (45), B64 (46), B64 (47),
223 B64 (48), B64 (49), B64 (50), B64 (51),
224 B64 (52), B64 (53), B64 (54), B64 (55),
225 B64 (56), B64 (57), B64 (58), B64 (59),
226 B64 (60), B64 (61), B64 (62), B64 (63),
227 B64 (64), B64 (65), B64 (66), B64 (67),
228 B64 (68), B64 (69), B64 (70), B64 (71),
229 B64 (72), B64 (73), B64 (74), B64 (75),
230 B64 (76), B64 (77), B64 (78), B64 (79),
231 B64 (80), B64 (81), B64 (82), B64 (83),
232 B64 (84), B64 (85), B64 (86), B64 (87),
233 B64 (88), B64 (89), B64 (90), B64 (91),
234 B64 (92), B64 (93), B64 (94), B64 (95),
235 B64 (96), B64 (97), B64 (98), B64 (99),
236 B64 (100), B64 (101), B64 (102), B64 (103),
237 B64 (104), B64 (105), B64 (106), B64 (107),
238 B64 (108), B64 (109), B64 (110), B64 (111),
239 B64 (112), B64 (113), B64 (114), B64 (115),
240 B64 (116), B64 (117), B64 (118), B64 (119),
241 B64 (120), B64 (121), B64 (122), B64 (123),
242 B64 (124), B64 (125), B64 (126), B64 (127),
243 B64 (128), B64 (129), B64 (130), B64 (131),
244 B64 (132), B64 (133), B64 (134), B64 (135),
245 B64 (136), B64 (137), B64 (138), B64 (139),
246 B64 (140), B64 (141), B64 (142), B64 (143),
247 B64 (144), B64 (145), B64 (146), B64 (147),
248 B64 (148), B64 (149), B64 (150), B64 (151),
249 B64 (152), B64 (153), B64 (154), B64 (155),
250 B64 (156), B64 (157), B64 (158), B64 (159),
251 B64 (160), B64 (161), B64 (162), B64 (163),
252 B64 (164), B64 (165), B64 (166), B64 (167),
253 B64 (168), B64 (169), B64 (170), B64 (171),
254 B64 (172), B64 (173), B64 (174), B64 (175),
255 B64 (176), B64 (177), B64 (178), B64 (179),
256 B64 (180), B64 (181), B64 (182), B64 (183),
257 B64 (184), B64 (185), B64 (186), B64 (187),
258 B64 (188), B64 (189), B64 (190), B64 (191),
259 B64 (192), B64 (193), B64 (194), B64 (195),
260 B64 (196), B64 (197), B64 (198), B64 (199),
261 B64 (200), B64 (201), B64 (202), B64 (203),
262 B64 (204), B64 (205), B64 (206), B64 (207),
263 B64 (208), B64 (209), B64 (210), B64 (211),
264 B64 (212), B64 (213), B64 (214), B64 (215),
265 B64 (216), B64 (217), B64 (218), B64 (219),
266 B64 (220), B64 (221), B64 (222), B64 (223),
267 B64 (224), B64 (225), B64 (226), B64 (227),
268 B64 (228), B64 (229), B64 (230), B64 (231),
269 B64 (232), B64 (233), B64 (234), B64 (235),
270 B64 (236), B64 (237), B64 (238), B64 (239),
271 B64 (240), B64 (241), B64 (242), B64 (243),
272 B64 (244), B64 (245), B64 (246), B64 (247),
273 B64 (248), B64 (249), B64 (250), B64 (251),
274 B64 (252), B64 (253), B64 (254), B64 (255)
280 return to_uchar (ch) <= 255 && 0 <= b64[to_uchar (ch)];
283 /* Decode base64 encoded input array IN of length INLEN to output
284 array OUT that can hold *OUTLEN bytes. Return true if decoding was
285 successful, i.e. if the input was valid base64 data, false
286 otherwise. If *OUTLEN is too small, as many bytes as possible will
287 be written to OUT. On return, *OUTLEN holds the length of decoded
288 bytes in OUT. Note that as soon as any non-alphabet characters are
289 encountered, decoding is stopped and false is returned. */
291 base64_decode (const char *restrict in, size_t inlen,
292 char *restrict out, size_t * outlen)
294 size_t outleft = *outlen;
298 if (!isbase64 (in[0]) || !isbase64 (in[1]))
303 *out++ = ((b64[to_uchar (in[0])] << 2)
304 | (b64[to_uchar (in[1])] >> 4));
322 if (!isbase64 (in[2]))
327 *out++ = (((b64[to_uchar (in[1])] << 4) & 0xf0)
328 | (b64[to_uchar (in[2])] >> 2));
342 if (!isbase64 (in[3]))
347 *out++ = (((b64[to_uchar (in[2])] << 6) & 0xc0)
348 | b64[to_uchar (in[3])]);
366 /* Allocate an output buffer in *OUT, and decode the base64 encoded
367 data stored in IN of size INLEN to the *OUT buffer. On return, the
368 size of the decoded data is stored in *OUTLEN. OUTLEN may be NULL,
369 if the caller is not interested in the decoded length. *OUT may be
370 NULL to indicate an out of memory error, in which case *OUTLEN
371 contain the size of the memory block needed. The function return
372 true on successful decoding and memory allocation errors. (Use the
373 *OUT and *OUTLEN parameters to differentiate between successful
374 decoding and memory error.) The function return false if the input
375 was invalid, in which case *OUT is NULL and *OUTLEN is
378 base64_decode_alloc (const char *in, size_t inlen, char **out,
381 /* This may allocate a few bytes too much, depending on input,
382 but it's not worth the extra CPU time to compute the exact amount.
383 The exact amount is 3 * inlen / 4, minus 1 if the input ends
384 with "=" and minus another 1 if the input ends with "==".
385 Dividing before multiplying avoids the possibility of overflow. */
386 size_t needlen = 3 * (inlen / 4) + 2;
388 *out = malloc (needlen);
392 if (!base64_decode (in, inlen, *out, &needlen))