1 /* base64.c -- Encode binary data using printable characters.
2 Copyright (C) 1999-2001, 2004-2006, 2009-2013 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, see <http://www.gnu.org/licenses/>. */
17 /* Written by Simon Josefsson. Partially adapted from GNU MailUtils
18 * (mailbox/filter_trans.c, as of 2004-11-28). Improved by review
19 * from Paul Eggert, Bruno Haible, and Stepan Kasal.
21 * See also RFC 4648 <http://www.ietf.org/rfc/rfc4648.txt>.
23 * Be careful with error checking. Here is how you would typically
24 * use these functions:
26 * bool ok = base64_decode_alloc (in, inlen, &out, &outlen);
28 * FAIL: input was not valid base64
30 * FAIL: memory allocation error
31 * OK: data in OUT/OUTLEN
33 * size_t outlen = base64_encode_alloc (in, inlen, &out);
34 * if (out == NULL && outlen == 0 && inlen != 0)
35 * FAIL: input too long
37 * FAIL: memory allocation error
38 * OK: data in OUT/OUTLEN.
55 /* C89 compliant way to cast 'char' to 'unsigned char'. */
62 static const char b64c[64] =
63 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
65 /* Base64 encode IN array of size INLEN into OUT array. OUT needs
66 to be of length >= BASE64_LENGTH(INLEN), and INLEN needs to be
69 base64_encode_fast (const char *restrict in, size_t inlen, char *restrict out)
73 *out++ = b64c[to_uchar (in[0]) >> 2];
74 *out++ = b64c[((to_uchar (in[0]) << 4) + (to_uchar (in[1]) >> 4)) & 0x3f];
75 *out++ = b64c[((to_uchar (in[1]) << 2) + (to_uchar (in[2]) >> 6)) & 0x3f];
76 *out++ = b64c[to_uchar (in[2]) & 0x3f];
83 /* Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
84 If OUTLEN is less than BASE64_LENGTH(INLEN), write as many bytes as
85 possible. If OUTLEN is larger than BASE64_LENGTH(INLEN), also zero
86 terminate the output buffer. */
88 base64_encode (const char *restrict in, size_t inlen,
89 char *restrict out, size_t outlen)
91 /* Note this outlen constraint can be enforced at compile time.
92 I.E. that the output buffer is exactly large enough to hold
93 the encoded inlen bytes. The inlen constraints (of corresponding
94 to outlen, and being a multiple of 3) can change at runtime
95 at the end of input. However the common case when reading
96 large inputs is to have both constraints satisfied, so we depend
97 on both in base_encode_fast(). */
98 if (outlen % 4 == 0 && inlen == outlen / 4 * 3)
99 return base64_encode_fast (in, inlen, out);
101 while (inlen && outlen)
103 *out++ = b64c[to_uchar (in[0]) >> 2];
106 *out++ = b64c[((to_uchar (in[0]) << 4)
107 + (--inlen ? to_uchar (in[1]) >> 4 : 0))
113 ? b64c[((to_uchar (in[1]) << 2)
114 + (--inlen ? to_uchar (in[2]) >> 6 : 0))
119 *out++ = inlen ? b64c[to_uchar (in[2]) & 0x3f] : '=';
132 /* Allocate a buffer and store zero terminated base64 encoded data
133 from array IN of size INLEN, returning BASE64_LENGTH(INLEN), i.e.,
134 the length of the encoded data, excluding the terminating zero. On
135 return, the OUT variable will hold a pointer to newly allocated
136 memory that must be deallocated by the caller. If output string
137 length would overflow, 0 is returned and OUT is set to NULL. If
138 memory allocation failed, OUT is set to NULL, and the return value
139 indicates length of the requested memory block, i.e.,
140 BASE64_LENGTH(inlen) + 1. */
142 base64_encode_alloc (const char *in, size_t inlen, char **out)
144 size_t outlen = 1 + BASE64_LENGTH (inlen);
146 /* Check for overflow in outlen computation.
148 * If there is no overflow, outlen >= inlen.
150 * If the operation (inlen + 2) overflows then it yields at most +1, so
153 * If the multiplication overflows, we lose at least half of the
154 * correct value, so the result is < ((inlen + 2) / 3) * 2, which is
155 * less than (inlen + 2) * 0.66667, which is less than inlen as soon as
164 *out = malloc (outlen);
168 base64_encode (in, inlen, *out, outlen);
173 /* With this approach this file works independent of the charset used
174 (think EBCDIC). However, it does assume that the characters in the
175 Base64 alphabet (A-Za-z0-9+/) are encoded in 0..255. POSIX
176 1003.1-2001 require that char and unsigned char are 8-bit
177 quantities, though, taking care of that problem. But this may be a
178 potential problem on non-POSIX C99 platforms.
180 IBM C V6 for AIX mishandles "#define B64(x) ...'x'...", so use "_"
181 as the formal parameter rather than "x". */
249 static const signed char b64[0x100] = {
250 B64 (0), B64 (1), B64 (2), B64 (3),
251 B64 (4), B64 (5), B64 (6), B64 (7),
252 B64 (8), B64 (9), B64 (10), B64 (11),
253 B64 (12), B64 (13), B64 (14), B64 (15),
254 B64 (16), B64 (17), B64 (18), B64 (19),
255 B64 (20), B64 (21), B64 (22), B64 (23),
256 B64 (24), B64 (25), B64 (26), B64 (27),
257 B64 (28), B64 (29), B64 (30), B64 (31),
258 B64 (32), B64 (33), B64 (34), B64 (35),
259 B64 (36), B64 (37), B64 (38), B64 (39),
260 B64 (40), B64 (41), B64 (42), B64 (43),
261 B64 (44), B64 (45), B64 (46), B64 (47),
262 B64 (48), B64 (49), B64 (50), B64 (51),
263 B64 (52), B64 (53), B64 (54), B64 (55),
264 B64 (56), B64 (57), B64 (58), B64 (59),
265 B64 (60), B64 (61), B64 (62), B64 (63),
266 B64 (64), B64 (65), B64 (66), B64 (67),
267 B64 (68), B64 (69), B64 (70), B64 (71),
268 B64 (72), B64 (73), B64 (74), B64 (75),
269 B64 (76), B64 (77), B64 (78), B64 (79),
270 B64 (80), B64 (81), B64 (82), B64 (83),
271 B64 (84), B64 (85), B64 (86), B64 (87),
272 B64 (88), B64 (89), B64 (90), B64 (91),
273 B64 (92), B64 (93), B64 (94), B64 (95),
274 B64 (96), B64 (97), B64 (98), B64 (99),
275 B64 (100), B64 (101), B64 (102), B64 (103),
276 B64 (104), B64 (105), B64 (106), B64 (107),
277 B64 (108), B64 (109), B64 (110), B64 (111),
278 B64 (112), B64 (113), B64 (114), B64 (115),
279 B64 (116), B64 (117), B64 (118), B64 (119),
280 B64 (120), B64 (121), B64 (122), B64 (123),
281 B64 (124), B64 (125), B64 (126), B64 (127),
282 B64 (128), B64 (129), B64 (130), B64 (131),
283 B64 (132), B64 (133), B64 (134), B64 (135),
284 B64 (136), B64 (137), B64 (138), B64 (139),
285 B64 (140), B64 (141), B64 (142), B64 (143),
286 B64 (144), B64 (145), B64 (146), B64 (147),
287 B64 (148), B64 (149), B64 (150), B64 (151),
288 B64 (152), B64 (153), B64 (154), B64 (155),
289 B64 (156), B64 (157), B64 (158), B64 (159),
290 B64 (160), B64 (161), B64 (162), B64 (163),
291 B64 (164), B64 (165), B64 (166), B64 (167),
292 B64 (168), B64 (169), B64 (170), B64 (171),
293 B64 (172), B64 (173), B64 (174), B64 (175),
294 B64 (176), B64 (177), B64 (178), B64 (179),
295 B64 (180), B64 (181), B64 (182), B64 (183),
296 B64 (184), B64 (185), B64 (186), B64 (187),
297 B64 (188), B64 (189), B64 (190), B64 (191),
298 B64 (192), B64 (193), B64 (194), B64 (195),
299 B64 (196), B64 (197), B64 (198), B64 (199),
300 B64 (200), B64 (201), B64 (202), B64 (203),
301 B64 (204), B64 (205), B64 (206), B64 (207),
302 B64 (208), B64 (209), B64 (210), B64 (211),
303 B64 (212), B64 (213), B64 (214), B64 (215),
304 B64 (216), B64 (217), B64 (218), B64 (219),
305 B64 (220), B64 (221), B64 (222), B64 (223),
306 B64 (224), B64 (225), B64 (226), B64 (227),
307 B64 (228), B64 (229), B64 (230), B64 (231),
308 B64 (232), B64 (233), B64 (234), B64 (235),
309 B64 (236), B64 (237), B64 (238), B64 (239),
310 B64 (240), B64 (241), B64 (242), B64 (243),
311 B64 (244), B64 (245), B64 (246), B64 (247),
312 B64 (248), B64 (249), B64 (250), B64 (251),
313 B64 (252), B64 (253), B64 (254), B64 (255)
317 # define uchar_in_range(c) true
319 # define uchar_in_range(c) ((c) <= 255)
322 /* Return true if CH is a character from the Base64 alphabet, and
323 false otherwise. Note that '=' is padding and not considered to be
324 part of the alphabet. */
328 return uchar_in_range (to_uchar (ch)) && 0 <= b64[to_uchar (ch)];
331 /* Initialize decode-context buffer, CTX. */
333 base64_decode_ctx_init (struct base64_decode_context *ctx)
338 /* If CTX->i is 0 or 4, there are four or more bytes in [*IN..IN_END), and
339 none of those four is a newline, then return *IN. Otherwise, copy up to
340 4 - CTX->i non-newline bytes from that range into CTX->buf, starting at
341 index CTX->i and setting CTX->i to reflect the number of bytes copied,
342 and return CTX->buf. In either case, advance *IN to point to the byte
343 after the last one processed, and set *N_NON_NEWLINE to the number of
344 verified non-newline bytes accessible through the returned pointer. */
346 get_4 (struct base64_decode_context *ctx,
347 char const *restrict *in, char const *restrict in_end,
348 size_t *n_non_newline)
356 if (4 <= in_end - *in && memchr (t, '\n', 4) == NULL)
358 /* This is the common case: no newline. */
366 /* Copy non-newline bytes into BUF. */
373 ctx->buf[ctx->i++] = c;
380 *n_non_newline = ctx->i;
385 #define return_false \
393 /* Decode up to four bytes of base64-encoded data, IN, of length INLEN
394 into the output buffer, *OUT, of size *OUTLEN bytes. Return true if
395 decoding is successful, false otherwise. If *OUTLEN is too small,
396 as many bytes as possible are written to *OUT. On return, advance
397 *OUT to point to the byte after the last one written, and decrement
398 *OUTLEN to reflect the number of bytes remaining in *OUT. */
400 decode_4 (char const *restrict in, size_t inlen,
401 char *restrict *outp, size_t *outleft)
407 if (!isbase64 (in[0]) || !isbase64 (in[1]))
412 *out++ = ((b64[to_uchar (in[0])] << 2)
413 | (b64[to_uchar (in[1])] >> 4));
430 if (!isbase64 (in[2]))
435 *out++ = (((b64[to_uchar (in[1])] << 4) & 0xf0)
436 | (b64[to_uchar (in[2])] >> 2));
450 if (!isbase64 (in[3]))
455 *out++ = (((b64[to_uchar (in[2])] << 6) & 0xc0)
456 | b64[to_uchar (in[3])]);
466 /* Decode base64-encoded input array IN of length INLEN to output array
467 OUT that can hold *OUTLEN bytes. The input data may be interspersed
468 with newlines. Return true if decoding was successful, i.e. if the
469 input was valid base64 data, false otherwise. If *OUTLEN is too
470 small, as many bytes as possible will be written to OUT. On return,
471 *OUTLEN holds the length of decoded bytes in OUT. Note that as soon
472 as any non-alphabet, non-newline character is encountered, decoding
473 is stopped and false is returned. If INLEN is zero, then process
474 only whatever data is stored in CTX.
476 Initially, CTX must have been initialized via base64_decode_ctx_init.
477 Subsequent calls to this function must reuse whatever state is recorded
478 in that buffer. It is necessary for when a quadruple of base64 input
479 bytes spans two input buffers.
481 If CTX is NULL then newlines are treated as garbage and the input
482 buffer is processed as a unit. */
485 base64_decode_ctx (struct base64_decode_context *ctx,
486 const char *restrict in, size_t inlen,
487 char *restrict out, size_t *outlen)
489 size_t outleft = *outlen;
490 bool ignore_newlines = ctx != NULL;
491 bool flush_ctx = false;
492 unsigned int ctx_i = 0;
497 flush_ctx = inlen == 0;
503 size_t outleft_save = outleft;
504 if (ctx_i == 0 && !flush_ctx)
508 /* Save a copy of outleft, in case we need to re-parse this
509 block of four bytes. */
510 outleft_save = outleft;
511 if (!decode_4 (in, inlen, &out, &outleft))
519 if (inlen == 0 && !flush_ctx)
522 /* Handle the common case of 72-byte wrapped lines.
523 This also handles any other multiple-of-4-byte wrapping. */
524 if (inlen && *in == '\n' && ignore_newlines)
531 /* Restore OUT and OUTLEFT. */
532 out -= outleft_save - outleft;
533 outleft = outleft_save;
536 char const *in_end = in + inlen;
540 non_nl = get_4 (ctx, &in, in_end, &inlen);
542 non_nl = in; /* Might have nl in this case. */
544 /* If the input is empty or consists solely of newlines (0 non-newlines),
545 then we're done. Likewise if there are fewer than 4 bytes when not
546 flushing context and not treating newlines as garbage. */
547 if (inlen == 0 || (inlen < 4 && !flush_ctx && ignore_newlines))
552 if (!decode_4 (non_nl, inlen, &out, &outleft))
564 /* Allocate an output buffer in *OUT, and decode the base64 encoded
565 data stored in IN of size INLEN to the *OUT buffer. On return, the
566 size of the decoded data is stored in *OUTLEN. OUTLEN may be NULL,
567 if the caller is not interested in the decoded length. *OUT may be
568 NULL to indicate an out of memory error, in which case *OUTLEN
569 contains the size of the memory block needed. The function returns
570 true on successful decoding and memory allocation errors. (Use the
571 *OUT and *OUTLEN parameters to differentiate between successful
572 decoding and memory error.) The function returns false if the
573 input was invalid, in which case *OUT is NULL and *OUTLEN is
576 base64_decode_alloc_ctx (struct base64_decode_context *ctx,
577 const char *in, size_t inlen, char **out,
580 /* This may allocate a few bytes too many, depending on input,
581 but it's not worth the extra CPU time to compute the exact size.
582 The exact size is 3 * (inlen + (ctx ? ctx->i : 0)) / 4, minus 1 if the
583 input ends with "=" and minus another 1 if the input ends with "==".
584 Dividing before multiplying avoids the possibility of overflow. */
585 size_t needlen = 3 * (inlen / 4) + 3;
587 *out = malloc (needlen);
591 if (!base64_decode_ctx (ctx, in, inlen, *out, &needlen))