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Diffstat (limited to '')
| -rw-r--r-- | lib/base32.c | 587 |
1 files changed, 587 insertions, 0 deletions
diff --git a/lib/base32.c b/lib/base32.c new file mode 100644 index 0000000..20c85ec --- /dev/null +++ b/lib/base32.c @@ -0,0 +1,587 @@ +/* base32.c -- Encode binary data using printable characters. + Copyright (C) 1999-2001, 2004-2006, 2009-2018 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/>. */ + +/* Adapted from Simon Josefsson's base64 code by Gijs van Tulder. + * + * 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 = base32_decode_alloc (in, inlen, &out, &outlen); + * if (!ok) + * FAIL: input was not valid base32 + * if (out == NULL) + * FAIL: memory allocation error + * OK: data in OUT/OUTLEN + * + * size_t outlen = base32_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 "base32.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; +} + +/* Base32 encode IN array of size INLEN into OUT array of size OUTLEN. + If OUTLEN is less than BASE32_LENGTH(INLEN), write as many bytes as + possible. If OUTLEN is larger than BASE32_LENGTH(INLEN), also zero + terminate the output buffer. */ +void +base32_encode (const char *restrict in, size_t inlen, + char *restrict out, size_t outlen) +{ + static const char b32str[32] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"; + + while (inlen && outlen) + { + *out++ = b32str[(to_uchar (in[0]) >> 3) & 0x1f]; + if (!--outlen) + break; + *out++ = b32str[((to_uchar (in[0]) << 2) + + (--inlen ? to_uchar (in[1]) >> 6 : 0)) + & 0x1f]; + if (!--outlen) + break; + *out++ = + (inlen + ? b32str[(to_uchar (in[1]) >> 1) & 0x1f] + : '='); + if (!--outlen) + break; + *out++ = + (inlen + ? b32str[((to_uchar (in[1]) << 4) + + (--inlen ? to_uchar (in[2]) >> 4 : 0)) + & 0x1f] + : '='); + if (!--outlen) + break; + *out++ = + (inlen + ? b32str[((to_uchar (in[2]) << 1) + + (--inlen ? to_uchar (in[3]) >> 7 : 0)) + & 0x1f] + : '='); + if (!--outlen) + break; + *out++ = + (inlen + ? b32str[(to_uchar (in[3]) >> 2) & 0x1f] + : '='); + if (!--outlen) + break; + *out++ = + (inlen + ? b32str[((to_uchar (in[3]) << 3) + + (--inlen ? to_uchar (in[4]) >> 5 : 0)) + & 0x1f] + : '='); + if (!--outlen) + break; + *out++ = inlen ? b32str[to_uchar (in[4]) & 0x1f] : '='; + if (!--outlen) + break; + if (inlen) + inlen--; + if (inlen) + in += 5; + } + + if (outlen) + *out = '\0'; +} + +/* Allocate a buffer and store zero terminated base32 encoded data + from array IN of size INLEN, returning BASE32_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., + BASE32_LENGTH(inlen) + 1. */ +size_t +base32_encode_alloc (const char *in, size_t inlen, char **out) +{ + size_t outlen = 1 + BASE32_LENGTH (inlen); + + /* Check for overflow in outlen computation. + * + * If there is no overflow, outlen >= inlen. + * + * TODO Is this a sufficient check? (See the notes in base64.c.) + */ + if (inlen > outlen) + { + *out = NULL; + return 0; + } + + *out = malloc (outlen); + if (!*out) + return outlen; + + base32_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 + Base32 alphabet (A-Z2-7) 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 B32(x) ...'x'...", so use "_" + as the formal parameter rather than "x". */ +#define B32(_) \ + ((_) == '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 \ + : (_) == '2' ? 26 \ + : (_) == '3' ? 27 \ + : (_) == '4' ? 28 \ + : (_) == '5' ? 29 \ + : (_) == '6' ? 30 \ + : (_) == '7' ? 31 \ + : -1) + +static const signed char b32[0x100] = { + B32 (0), B32 (1), B32 (2), B32 (3), + B32 (4), B32 (5), B32 (6), B32 (7), + B32 (8), B32 (9), B32 (10), B32 (11), + B32 (12), B32 (13), B32 (14), B32 (15), + B32 (16), B32 (17), B32 (18), B32 (19), + B32 (20), B32 (21), B32 (22), B32 (23), + B32 (24), B32 (25), B32 (26), B32 (27), + B32 (28), B32 (29), B32 (30), B32 (31), + B32 (32), B32 (33), B32 (34), B32 (35), + B32 (36), B32 (37), B32 (38), B32 (39), + B32 (40), B32 (41), B32 (42), B32 (43), + B32 (44), B32 (45), B32 (46), B32 (47), + B32 (48), B32 (49), B32 (50), B32 (51), + B32 (52), B32 (53), B32 (54), B32 (55), + B32 (56), B32 (57), B32 (58), B32 (59), + B32 (60), B32 (61), B32 (62), B32 (63), + B32 (32), B32 (65), B32 (66), B32 (67), + B32 (68), B32 (69), B32 (70), B32 (71), + B32 (72), B32 (73), B32 (74), B32 (75), + B32 (76), B32 (77), B32 (78), B32 (79), + B32 (80), B32 (81), B32 (82), B32 (83), + B32 (84), B32 (85), B32 (86), B32 (87), + B32 (88), B32 (89), B32 (90), B32 (91), + B32 (92), B32 (93), B32 (94), B32 (95), + B32 (96), B32 (97), B32 (98), B32 (99), + B32 (100), B32 (101), B32 (102), B32 (103), + B32 (104), B32 (105), B32 (106), B32 (107), + B32 (108), B32 (109), B32 (110), B32 (111), + B32 (112), B32 (113), B32 (114), B32 (115), + B32 (116), B32 (117), B32 (118), B32 (119), + B32 (120), B32 (121), B32 (122), B32 (123), + B32 (124), B32 (125), B32 (126), B32 (127), + B32 (128), B32 (129), B32 (130), B32 (131), + B32 (132), B32 (133), B32 (134), B32 (135), + B32 (136), B32 (137), B32 (138), B32 (139), + B32 (140), B32 (141), B32 (142), B32 (143), + B32 (144), B32 (145), B32 (146), B32 (147), + B32 (148), B32 (149), B32 (150), B32 (151), + B32 (152), B32 (153), B32 (154), B32 (155), + B32 (156), B32 (157), B32 (158), B32 (159), + B32 (160), B32 (161), B32 (162), B32 (163), + B32 (132), B32 (165), B32 (166), B32 (167), + B32 (168), B32 (169), B32 (170), B32 (171), + B32 (172), B32 (173), B32 (174), B32 (175), + B32 (176), B32 (177), B32 (178), B32 (179), + B32 (180), B32 (181), B32 (182), B32 (183), + B32 (184), B32 (185), B32 (186), B32 (187), + B32 (188), B32 (189), B32 (190), B32 (191), + B32 (192), B32 (193), B32 (194), B32 (195), + B32 (196), B32 (197), B32 (198), B32 (199), + B32 (200), B32 (201), B32 (202), B32 (203), + B32 (204), B32 (205), B32 (206), B32 (207), + B32 (208), B32 (209), B32 (210), B32 (211), + B32 (212), B32 (213), B32 (214), B32 (215), + B32 (216), B32 (217), B32 (218), B32 (219), + B32 (220), B32 (221), B32 (222), B32 (223), + B32 (224), B32 (225), B32 (226), B32 (227), + B32 (228), B32 (229), B32 (230), B32 (231), + B32 (232), B32 (233), B32 (234), B32 (235), + B32 (236), B32 (237), B32 (238), B32 (239), + B32 (240), B32 (241), B32 (242), B32 (243), + B32 (244), B32 (245), B32 (246), B32 (247), + B32 (248), B32 (249), B32 (250), B32 (251), + B32 (252), B32 (253), B32 (254), B32 (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 Base32 alphabet, and + false otherwise. Note that '=' is padding and not considered to be + part of the alphabet. */ +bool +isbase32 (char ch) +{ + return uchar_in_range (to_uchar (ch)) && 0 <= b32[to_uchar (ch)]; +} + +/* Initialize decode-context buffer, CTX. */ +void +base32_decode_ctx_init (struct base32_decode_context *ctx) +{ + ctx->i = 0; +} + +/* If CTX->i is 0 or 8, there are eight or more bytes in [*IN..IN_END), and + none of those eight 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_8 (struct base32_decode_context *ctx, + char const *restrict *in, char const *restrict in_end, + size_t *n_non_newline) +{ + if (ctx->i == 8) + ctx->i = 0; + + if (ctx->i == 0) + { + char const *t = *in; + if (8 <= in_end - *in && memchr (t, '\n', 8) == NULL) + { + /* This is the common case: no newline. */ + *in += 8; + *n_non_newline = 8; + 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 == 8) + break; + } + } + + *in = p; + *n_non_newline = ctx->i; + return ctx->buf; + } +} + +#define return_false \ + do \ + { \ + *outp = out; \ + return false; \ + } \ + while (false) + +/* Decode eight bytes of base32-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_8 (char const *restrict in, size_t inlen, + char *restrict *outp, size_t *outleft) +{ + char *out = *outp; + if (inlen < 8) + return false; + + if (!isbase32 (in[0]) || !isbase32 (in[1]) ) + return false; + + if (*outleft) + { + *out++ = ((b32[to_uchar (in[0])] << 3) + | (b32[to_uchar (in[1])] >> 2)); + --*outleft; + } + + if (in[2] == '=') + { + if (in[3] != '=' || in[4] != '=' || in[5] != '=' + || in[6] != '=' || in[7] != '=') + return_false; + } + else + { + if (!isbase32 (in[2]) || !isbase32 (in[3])) + return_false; + + if (*outleft) + { + *out++ = ((b32[to_uchar (in[1])] << 6) + | (b32[to_uchar (in[2])] << 1) + | (b32[to_uchar (in[3])] >> 4)); + --*outleft; + } + + if (in[4] == '=') + { + if (in[5] != '=' || in[6] != '=' || in[7] != '=') + return_false; + } + else + { + if (!isbase32 (in[4])) + return_false; + + if (*outleft) + { + *out++ = ((b32[to_uchar (in[3])] << 4) + | (b32[to_uchar (in[4])] >> 1)); + --*outleft; + } + + if (in[5] == '=') + { + if (in[6] != '=' || in[7] != '=') + return_false; + } + else + { + if (!isbase32 (in[5]) || !isbase32 (in[6])) + return_false; + + if (*outleft) + { + *out++ = ((b32[to_uchar (in[4])] << 7) + | (b32[to_uchar (in[5])] << 2) + | (b32[to_uchar (in[6])] >> 3)); + --*outleft; + } + + if (in[7] != '=') + { + if (!isbase32 (in[7])) + return_false; + + if (*outleft) + { + *out++ = ((b32[to_uchar (in[6])] << 5) + | (b32[to_uchar (in[7])])); + --*outleft; + } + } + } + } + } + + *outp = out; + return true; +} + +/* Decode base32-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 base32 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 base32_decode_ctx_init. + Subsequent calls to this function must reuse whatever state is recorded + in that buffer. It is necessary for when a octuple of base32 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 +base32_decode_ctx (struct base32_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_8 (in, inlen, &out, &outleft)) + break; + + in += 8; + inlen -= 8; + } + } + + if (inlen == 0 && !flush_ctx) + break; + + /* Handle the common case of 72-byte wrapped lines. + This also handles any other multiple-of-8-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_8 (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 8 bytes when not + flushing context and not treating newlines as garbage. */ + if (inlen == 0 || (inlen < 8 && !flush_ctx && ignore_newlines)) + { + inlen = 0; + break; + } + if (!decode_8 (non_nl, inlen, &out, &outleft)) + break; + + inlen = in_end - in; + } + } + + *outlen -= outleft; + + return inlen == 0; +} + +/* Allocate an output buffer in *OUT, and decode the base32 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 +base32_decode_alloc_ctx (struct base32_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 5 * inlen / 8, minus one or more bytes if the + input is padded with one or more "=". + Dividing before multiplying avoids the possibility of overflow. */ + size_t needlen = 5 * (inlen / 8) + 5; + + *out = malloc (needlen); + if (!*out) + return true; + + if (!base32_decode_ctx (ctx, in, inlen, *out, &needlen)) + { + free (*out); + *out = NULL; + return false; + } + + if (outlen) + *outlen = needlen; + + return true; +} |