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Diffstat (limited to 'lib/base64.c')
| -rw-r--r-- | lib/base64.c | 605 |
1 files changed, 605 insertions, 0 deletions
diff --git a/lib/base64.c b/lib/base64.c new file mode 100644 index 0000000..c7ef82c --- /dev/null +++ b/lib/base64.c @@ -0,0 +1,605 @@ +/* base64.c -- Encode binary data using printable characters. + Copyright (C) 1999-2001, 2004-2006, 2009-2020 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 3, 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 <https://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 <https://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. + * + */ + +#include <config.h> + +/* 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 unsigned char +to_uchar (char ch) +{ + return ch; +} + +static const char b64c[64] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; + +/* Base64 encode IN array of size INLEN into OUT array. OUT needs + to be of length >= BASE64_LENGTH(INLEN), and INLEN needs to be + a multiple of 3. */ +static void +base64_encode_fast (const char *restrict in, size_t inlen, char *restrict out) +{ + while (inlen) + { + *out++ = b64c[(to_uchar (in[0]) >> 2) & 0x3f]; + *out++ = b64c[((to_uchar (in[0]) << 4) + (to_uchar (in[1]) >> 4)) & 0x3f]; + *out++ = b64c[((to_uchar (in[1]) << 2) + (to_uchar (in[2]) >> 6)) & 0x3f]; + *out++ = b64c[to_uchar (in[2]) & 0x3f]; + + inlen -= 3; + in += 3; + } +} + +/* 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) +{ + /* Note this outlen constraint can be enforced at compile time. + I.E. that the output buffer is exactly large enough to hold + the encoded inlen bytes. The inlen constraints (of corresponding + to outlen, and being a multiple of 3) can change at runtime + at the end of input. However the common case when reading + large inputs is to have both constraints satisfied, so we depend + on both in base_encode_fast(). */ + if (outlen % 4 == 0 && inlen == outlen / 4 * 3) + { + base64_encode_fast (in, inlen, out); + return; + } + + while (inlen && outlen) + { + *out++ = b64c[(to_uchar (in[0]) >> 2) & 0x3f]; + if (!--outlen) + break; + *out++ = b64c[((to_uchar (in[0]) << 4) + + (--inlen ? to_uchar (in[1]) >> 4 : 0)) + & 0x3f]; + if (!--outlen) + break; + *out++ = + (inlen + ? b64c[((to_uchar (in[1]) << 2) + + (--inlen ? to_uchar (in[2]) >> 6 : 0)) + & 0x3f] + : '='); + if (!--outlen) + break; + *out++ = inlen ? b64c[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 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 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; +} |