/* base64.c -- Encode binary data using printable characters.
Copyright (C) 1999-2001, 2004-2006, 2009-2012 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program 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 a copy of the GNU General Public License
along with this program; if not, see <http://www.gnu.org/licenses/>. */
/* Written by Simon Josefsson. Partially adapted from GNU MailUtils
* (mailbox/filter_trans.c, as of 2004-11-28). Improved by review
* from Paul Eggert, Bruno Haible, and Stepan Kasal.
*
* See also RFC 4648 <http://www.ietf.org/rfc/rfc4648.txt>.
*
* Be careful with error checking. Here is how you would typically
* use these functions:
*
* bool ok = base64_decode_alloc (in, inlen, &out, &outlen);
* if (!ok)
* FAIL: input was not valid base64
* if (out == NULL)
* FAIL: memory allocation error
* OK: data in OUT/OUTLEN
*
* size_t outlen = base64_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.
*
*/
/* Get prototype. */
#include "base64.h"
/* Get malloc. */
#include <stdlib.h>
/* Get UCHAR_MAX. */
#include <limits.h>
#include <string.h>
/* C89 compliant way to cast 'char' to 'unsigned char'. */
static inline unsigned char
to_uchar (char ch)
{
return ch;
}
/* Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
If OUTLEN is less than BASE64_LENGTH(INLEN), write as many bytes as
possible. If OUTLEN is larger than BASE64_LENGTH(INLEN), also zero
terminate the output buffer. */
void
base64_encode (const char *restrict in, size_t inlen,
char *restrict out, size_t outlen)
{
static const char b64str[64] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
while (inlen && outlen)
{
*out++ = b64str[(to_uchar (in[0]) >> 2) & 0x3f];
if (!--outlen)
break;
*out++ = b64str[((to_uchar (in[0]) << 4)
+ (--inlen ? to_uchar (in[1]) >> 4 : 0))
& 0x3f];
if (!--outlen)
break;
*out++ =
(inlen
? b64str[((to_uchar (in[1]) << 2)
+ (--inlen ? to_uchar (in[2]) >> 6 : 0))
& 0x3f]
: '=');
if (!--outlen)
break;
*out++ = inlen ? b64str[to_uchar (in[2]) & 0x3f] : '=';
if (!--outlen)
break;
if (inlen)
inlen--;
if (inlen)
in += 3;
}
if (outlen)
*out = '\0';
}
/* Allocate a buffer and store zero terminated base64 encoded data
from array IN of size INLEN, returning BASE64_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.,
BASE64_LENGTH(inlen) + 1. */
size_t
base64_encode_alloc (const char *in, size_t inlen, char **out)
{
size_t outlen = 1 + BASE64_LENGTH (inlen);
/* Check for overflow in outlen computation.
*
* If there is no overflow, outlen >= inlen.
*
* If the operation (inlen + 2) overflows then it yields at most +1, so
* outlen is 0.
*
* If the multiplication overflows, we lose at least half of the
* correct value, so the result is < ((inlen + 2) / 3) * 2, which is
* less than (inlen + 2) * 0.66667, which is less than inlen as soon as
* (inlen > 4).
*/
if (inlen > outlen)
{
*out = NULL;
return 0;
}
*out = malloc (outlen);
if (!*out)
return outlen;
base64_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
Base64 alphabet (A-Za-z0-9+/) 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 B64(x) ...'x'...", so use "_"
as the formal parameter rather than "x". */
#define B64(_) \
((_) == '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 \
: (_) == 'a' ? 26 \
: (_) == 'b' ? 27 \
: (_) == 'c' ? 28 \
: (_) == 'd' ? 29 \
: (_) == 'e' ? 30 \
: (_) == 'f' ? 31 \
: (_) == 'g' ? 32 \
: (_) == 'h' ? 33 \
: (_) == 'i' ? 34 \
: (_) == 'j' ? 35 \
: (_) == 'k' ? 36 \
: (_) == 'l' ? 37 \
: (_) == 'm' ? 38 \
: (_) == 'n' ? 39 \
: (_) == 'o' ? 40 \
: (_) == 'p' ? 41 \
: (_) == 'q' ? 42 \
: (_) == 'r' ? 43 \
: (_) == 's' ? 44 \
: (_) == 't' ? 45 \
: (_) == 'u' ? 46 \
: (_) == 'v' ? 47 \
: (_) == 'w' ? 48 \
: (_) == 'x' ? 49 \
: (_) == 'y' ? 50 \
: (_) == 'z' ? 51 \
: (_) == '0' ? 52 \
: (_) == '1' ? 53 \
: (_) == '2' ? 54 \
: (_) == '3' ? 55 \
: (_) == '4' ? 56 \
: (_) == '5' ? 57 \
: (_) == '6' ? 58 \
: (_) == '7' ? 59 \
: (_) == '8' ? 60 \
: (_) == '9' ? 61 \
: (_) == '+' ? 62 \
: (_) == '/' ? 63 \
: -1)
static const signed char b64[0x100] = {
B64 (0), B64 (1), B64 (2), B64 (3),
B64 (4), B64 (5), B64 (6), B64 (7),
B64 (8), B64 (9), B64 (10), B64 (11),
B64 (12), B64 (13), B64 (14), B64 (15),
B64 (16), B64 (17), B64 (18), B64 (19),
B64 (20), B64 (21), B64 (22), B64 (23),
B64 (24), B64 (25), B64 (26), B64 (27),
B64 (28), B64 (29), B64 (30), B64 (31),
B64 (32), B64 (33), B64 (34), B64 (35),
B64 (36), B64 (37), B64 (38), B64 (39),
B64 (40), B64 (41), B64 (42), B64 (43),
B64 (44), B64 (45), B64 (46), B64 (47),
B64 (48), B64 (49), B64 (50), B64 (51),
B64 (52), B64 (53), B64 (54), B64 (55),
B64 (56), B64 (57), B64 (58), B64 (59),
B64 (60), B64 (61), B64 (62), B64 (63),
B64 (64), B64 (65), B64 (66), B64 (67),
B64 (68), B64 (69), B64 (70), B64 (71),
B64 (72), B64 (73), B64 (74), B64 (75),
B64 (76), B64 (77), B64 (78), B64 (79),
B64 (80), B64 (81), B64 (82), B64 (83),
B64 (84), B64 (85), B64 (86), B64 (87),
B64 (88), B64 (89), B64 (90), B64 (91),
B64 (92), B64 (93), B64 (94), B64 (95),
B64 (96), B64 (97), B64 (98), B64 (99),
B64 (100), B64 (101), B64 (102), B64 (103),
B64 (104), B64 (105), B64 (106), B64 (107),
B64 (108), B64 (109), B64 (110), B64 (111),
B64 (112), B64 (113), B64 (114), B64 (115),
B64 (116), B64 (117), B64 (118), B64 (119),
B64 (120), B64 (121), B64 (122), B64 (123),
B64 (124), B64 (125), B64 (126), B64 (127),
B64 (128), B64 (129), B64 (130), B64 (131),
B64 (132), B64 (133), B64 (134), B64 (135),
B64 (136), B64 (137), B64 (138), B64 (139),
B64 (140), B64 (141), B64 (142), B64 (143),
B64 (144), B64 (145), B64 (146), B64 (147),
B64 (148), B64 (149), B64 (150), B64 (151),
B64 (152), B64 (153), B64 (154), B64 (155),
B64 (156), B64 (157), B64 (158), B64 (159),
B64 (160), B64 (161), B64 (162), B64 (163),
B64 (164), B64 (165), B64 (166), B64 (167),
B64 (168), B64 (169), B64 (170), B64 (171),
B64 (172), B64 (173), B64 (174), B64 (175),
B64 (176), B64 (177), B64 (178), B64 (179),
B64 (180), B64 (181), B64 (182), B64 (183),
B64 (184), B64 (185), B64 (186), B64 (187),
B64 (188), B64 (189), B64 (190), B64 (191),
B64 (192), B64 (193), B64 (194), B64 (195),
B64 (196), B64 (197), B64 (198), B64 (199),
B64 (200), B64 (201), B64 (202), B64 (203),
B64 (204), B64 (205), B64 (206), B64 (207),
B64 (208), B64 (209), B64 (210), B64 (211),
B64 (212), B64 (213), B64 (214), B64 (215),
B64 (216), B64 (217), B64 (218), B64 (219),
B64 (220), B64 (221), B64 (222), B64 (223),
B64 (224), B64 (225), B64 (226), B64 (227),
B64 (228), B64 (229), B64 (230), B64 (231),
B64 (232), B64 (233), B64 (234), B64 (235),
B64 (236), B64 (237), B64 (238), B64 (239),
B64 (240), B64 (241), B64 (242), B64 (243),
B64 (244), B64 (245), B64 (246), B64 (247),
B64 (248), B64 (249), B64 (250), B64 (251),
B64 (252), B64 (253), B64 (254), B64 (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 Base64 alphabet, and
false otherwise. Note that '=' is padding and not considered to be
part of the alphabet. */
bool
isbase64 (char ch)
{
return uchar_in_range (to_uchar (ch)) && 0 <= b64[to_uchar (ch)];
}
/* Initialize decode-context buffer, CTX. */
void
base64_decode_ctx_init (struct base64_decode_context *ctx)
{
ctx->i = 0;
}
/* If CTX->i is 0 or 4, there are four or more bytes in [*IN..IN_END), and
none of those four 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 inline char *
get_4 (struct base64_decode_context *ctx,
char const *restrict *in, char const *restrict in_end,
size_t *n_non_newline)
{
if (ctx->i == 4)
ctx->i = 0;
if (ctx->i == 0)
{
char const *t = *in;
if (4 <= in_end - *in && memchr (t, '\n', 4) == NULL)
{
/* This is the common case: no newline. */
*in += 4;
*n_non_newline = 4;
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 == 4)
break;
}
}
*in = p;
*n_non_newline = ctx->i;
return ctx->buf;
}
}
#define return_false \
do \
{ \
*outp = out; \
return false; \
} \
while (false)
/* Decode up to four bytes of base64-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 inline bool
decode_4 (char const *restrict in, size_t inlen,
char *restrict *outp, size_t *outleft)
{
char *out = *outp;
if (inlen < 2)
return false;
if (!isbase64 (in[0]) || !isbase64 (in[1]))
return false;
if (*outleft)
{
*out++ = ((b64[to_uchar (in[0])] << 2)
| (b64[to_uchar (in[1])] >> 4));
--*outleft;
}
if (inlen == 2)
return_false;
if (in[2] == '=')
{
if (inlen != 4)
return_false;
if (in[3] != '=')
return_false;
}
else
{
if (!isbase64 (in[2]))
return_false;
if (*outleft)
{
*out++ = (((b64[to_uchar (in[1])] << 4) & 0xf0)
| (b64[to_uchar (in[2])] >> 2));
--*outleft;
}
if (inlen == 3)
return_false;
if (in[3] == '=')
{
if (inlen != 4)
return_false;
}
else
{
if (!isbase64 (in[3]))
return_false;
if (*outleft)
{
*out++ = (((b64[to_uchar (in[2])] << 6) & 0xc0)
| b64[to_uchar (in[3])]);
--*outleft;
}
}
}
*outp = out;
return true;
}
/* Decode base64-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 base64 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 base64_decode_ctx_init.
Subsequent calls to this function must reuse whatever state is recorded
in that buffer. It is necessary for when a quadruple of base64 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
base64_decode_ctx (struct base64_decode_context *ctx,
const char *restrict in, size_t inlen,
char *restrict out, size_t *outlen)
{
size_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)
{
size_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_4 (in, inlen, &out, &outleft))
break;
in += 4;
inlen -= 4;
}
}
if (inlen == 0 && !flush_ctx)
break;
/* Handle the common case of 72-byte wrapped lines.
This also handles any other multiple-of-4-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_4 (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 4 bytes when not
flushing context and not treating newlines as garbage. */
if (inlen == 0 || (inlen < 4 && !flush_ctx && ignore_newlines))
{
inlen = 0;
break;
}
if (!decode_4 (non_nl, inlen, &out, &outleft))
break;
inlen = in_end - in;
}
}
*outlen -= outleft;
return inlen == 0;
}
/* Allocate an output buffer in *OUT, and decode the base64 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
base64_decode_alloc_ctx (struct base64_decode_context *ctx,
const char *in, size_t inlen, char **out,
size_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 3 * (inlen + (ctx ? ctx->i : 0)) / 4, minus 1 if the
input ends with "=" and minus another 1 if the input ends with "==".
Dividing before multiplying avoids the possibility of overflow. */
size_t needlen = 3 * (inlen / 4) + 3;
*out = malloc (needlen);
if (!*out)
return true;
if (!base64_decode_ctx (ctx, in, inlen, *out, &needlen))
{
free (*out);
*out = NULL;
return false;
}
if (outlen)
*outlen = needlen;
return true;
}