/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│ │ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │ ╞══════════════════════════════════════════════════════════════════════════════╡ │ Copyright 2021 Justine Alexandra Roberts Tunney │ │ │ │ Permission to use, copy, modify, and/or distribute this software for │ │ any purpose with or without fee is hereby granted, provided that the │ │ above copyright notice and this permission notice appear in all copies. │ │ │ │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │ │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │ │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │ │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │ │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │ │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │ │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │ │ PERFORMANCE OF THIS SOFTWARE. │ ╚─────────────────────────────────────────────────────────────────────────────*/ #include "libc/assert.h" #include "libc/macros.h" #include "libc/mem/mem.h" #include "libc/str/str.h" const char base32def[] = "0123456789abcdefghjkmnpqrstvwxyz"; int tobits(int b) { int bits = 0; while (b && (b >>= 1)) bits++; return bits; } // these functions are based on // https://github.com/google/google-authenticator-libpam/blob/master/src/base32.c // Copyright 2010 Google Inc.; Author: Markus Gutschke // licensed under Apache License, Version 2.0 /** * Encodes binary to base32 ascii representation. * * @param s is input value * @param sl if -1 implies strlen * @param a is alphabet string (with power of 2 length) * @param al is alphabet length (if 0 then Crockford's encoding is used) * @param ol if non-NULL receives output length * @return allocated NUL-terminated buffer, or NULL w/ errno */ char *EncodeBase32(const char *s, size_t sl, const char *a, size_t al, size_t *ol) { size_t count = 0; char *r = NULL; if (sl == -1) sl = s ? strlen(s) : 0; if (al == 0) { a = base32def; al = sizeof(base32def) / sizeof(a[0]); } unassert(2 <= al && al <= 128); int bl = tobits(al); int mask = (1 << bl) - 1; size_t n = (sl * 8 + bl - 1) / bl; // calculate output length if ((r = malloc(n + 1))) { int buffer = s[0]; size_t next = 1; int bitsLeft = 8; while (count < n && (bitsLeft > 0 || next < sl)) { if (bitsLeft < bl) { if (next < sl) { buffer <<= 8; buffer |= s[next++] & 0xFF; bitsLeft += 8; } else { int pad = bl - bitsLeft; buffer <<= pad; bitsLeft += pad; } } bitsLeft -= bl; r[count++] = a[mask & (buffer >> bitsLeft)]; } r[count] = '\0'; } if (ol) *ol = r ? count : 0; return r; } static signed char kBase32cust[256]; static signed char kBase32[256] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1, // 0x00 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x10 -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -1, -1, // 0x20 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, // 0x30 -1, 10, 11, 12, 13, 14, 15, 16, 17, 1, 18, 19, 1, 20, 21, -1, // 0x40 22, 23, 24, 25, 26, 0, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, // 0x50 -1, 10, 11, 12, 13, 14, 15, 16, 17, 1, 18, 19, 1, 20, 21, -1, // 0x60 22, 23, 24, 25, 26, 0, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, // 0x70 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x80 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x90 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xa0 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xb0 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xc0 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xd0 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xe0 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xf0 }; /** * Decodes base32 ascii representation to binary. * * This uses Crockford's encoding and skips whitespaces. * The decoding stops at the first character not in the alphabet. * * @param s is input value * @param sl if -1 implies strlen * @param a is alphabet string (with power of 2 length) * @param al is alphabet length (if 0 then Crockford's encoding is used) * @param ol if non-NULL receives output length * @return allocated NUL-terminated buffer, or NULL w/ errno */ char *DecodeBase32(const char *s, size_t sl, const char *a, size_t al, size_t *ol) { size_t count = 0; char *r = NULL; if (sl == -1) sl = s ? strlen(s) : 0; if (al == 0) { a = base32def; al = sizeof(base32def) / sizeof(a[0]); } unassert(2 <= al && al <= 128); int bl = tobits(al); size_t n = (sl * bl + 1) / 8 + 1; // calculate output length // process input if ((r = malloc(n + 1))) { unsigned int buffer = 0; signed char *map = kBase32; int bitsLeft = 0; if (a != base32def) { // if the provided alphabet doesn't match the default map = kBase32cust; memset(map, -1, 256); // populate the map based on alphabet for (int i = 0; i < al; i++) map[a[i] & 0xff] = i; } while (count < n && *s) { signed char m = map[*s++ & 0xff]; if (m == -2) continue; if (m == -1) break; buffer <<= bl; buffer |= m; bitsLeft += bl; if (bitsLeft >= 8) { r[count++] = buffer >> (bitsLeft - 8); bitsLeft -= 8; } } r[count] = '\0'; } if (ol) *ol = r ? count : 0; return r; }