/* * This program is 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 of the License, 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, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA */ /** * $Id$ * @file rlm_totp.c * @brief Execute commands and parse the results. * * @copyright 2021 The FreeRADIUS server project * @copyright 2021 Network RADIUS SARL (legal@networkradius.com) */ RCSID("$Id$") #include #include #include #define TIME_STEP (30) /* * RFC 4648 base32 decoding. */ static const uint8_t alphabet[UINT8_MAX] = { ['A'] = 1, ['B'] = 2, ['C'] = 3, ['D'] = 4, ['E'] = 5, ['F'] = 6, ['G'] = 7, ['H'] = 8, ['I'] = 9, ['J'] = 10, ['K'] = 11, ['L'] = 12, ['M'] = 13, ['N'] = 14, ['O'] = 15, ['P'] = 16, ['Q'] = 17, ['R'] = 18, ['S'] = 19, ['T'] = 20, ['U'] = 21, ['V'] = 22, ['W'] = 23, ['X'] = 24, ['Y'] = 25, ['Z'] = 26, ['2'] = 27, ['3'] = 28, ['4'] = 29, ['5'] = 30, ['6'] = 31, ['7'] = 32, }; static ssize_t base32_decode(uint8_t *out, size_t outlen, char const *in) { uint8_t *p, *end, *b; char const *q; p = out; end = p + outlen; memset(out, 0, outlen); /* * Convert ASCII to binary. */ for (q = in; *q != '\0'; q++) { /* * Padding at the end, stop. */ if (*q == '=') { break; } if (!alphabet[*((uint8_t const *) q)]) return -1; *(p++) = alphabet[*((uint8_t const *) q)] - 1; if (p == end) return -1; /* too much data */ } /* * Reset to the end of the actual data we have */ end = p; /* * Convert input 5-bit groups into output 8-bit groups. * We do this in 8-byte blocks. * * 00011111 00022222 00033333 00044444 00055555 00066666 00077777 00088888 * * Will get converted to * * 11111222 22333334 44445555 56666677 77788888 */ for (p = b = out; p < end; p += 8) { b[0] = p[0] << 3; b[0] |= p[1] >> 2; b[1] = p[1] << 6; b[1] |= p[2] << 1; b[1] |= p[3] >> 4; b[2] = p[3] << 4; b[2] |= p[4] >> 1; b[3] = p[4] << 7; b[3] |= p[5] << 2; b[3] |= p[6] >> 3; b[4] = p[6] << 5; b[4] |= p[7]; b += 5; /* * Clear out the remaining 3 octets of this block. */ b[0] = 0; b[1] = 0; b[2] = 0; } return b - out; } #ifndef TESTING #define LEN 6 #define PRINT "%06u" #define DIV 1000000 #else #define LEN 8 #define PRINT "%08u" #define DIV 100000000 #endif /* * Implement RFC 6238 TOTP algorithm. * * Appendix B has test vectors. Note that the test vectors are * for 8-character challenges, and not for 6 character * challenges! */ static int totp_cmp(time_t now, uint8_t const *key, size_t keylen, char const *totp) { uint8_t offset; uint32_t challenge; uint64_t padded; char buffer[9]; uint8_t data[8]; uint8_t digest[SHA1_DIGEST_LENGTH]; padded = ((uint64_t) now) / TIME_STEP; data[0] = padded >> 56; data[1] = padded >> 48; data[2] = padded >> 40; data[3] = padded >> 32; data[4] = padded >> 24; data[5] = padded >> 16; data[6] = padded >> 8; data[7] = padded & 0xff; /* * Encrypt the network order time with the key. */ fr_hmac_sha1(digest, data, 8, key, keylen); /* * Take the least significant 4 bits. */ offset = digest[SHA1_DIGEST_LENGTH - 1] & 0x0f; /* * Grab the 32bits at "offset", and drop the high bit. */ challenge = (digest[offset] & 0x7f) << 24; challenge |= digest[offset + 1] << 16; challenge |= digest[offset + 2] << 8; challenge |= digest[offset + 3]; /* * The token is the last 6 digits in the number. */ snprintf(buffer, sizeof(buffer), PRINT, challenge % DIV); return rad_digest_cmp((uint8_t const *) buffer, (uint8_t const *) totp, LEN); } #ifndef TESTING /* * Do the authentication */ static rlm_rcode_t CC_HINT(nonnull) mod_authenticate(UNUSED void *instance, REQUEST *request) { VALUE_PAIR *vp, *password; uint8_t const *key; size_t keylen; uint8_t buffer[80]; /* multiple of 5*8 characters */ password = fr_pair_find_by_num(request->packet->vps, PW_TOTP_PASSWORD, 0, TAG_ANY); if (!password) return RLM_MODULE_NOOP; if (password->vp_length != 6) { RDEBUG("TOTP-Password has incorrect length %d", (int) password->vp_length); return RLM_MODULE_FAIL; } /* * Look for the raw key first. */ vp = fr_pair_find_by_num(request->config, PW_TOTP_KEY, 0, TAG_ANY); if (vp) { key = vp->vp_octets; keylen = vp->vp_length; } else { ssize_t len; vp = fr_pair_find_by_num(request->config, PW_TOTP_SECRET, 0, TAG_ANY); if (!vp) return RLM_MODULE_NOOP; len = base32_decode(buffer, sizeof(buffer), vp->vp_strvalue); if (len < 0) { RDEBUG("TOTP-Secret cannot be decoded"); return RLM_MODULE_FAIL; } key = buffer; keylen = len; } if (totp_cmp(time(NULL), key, keylen, password->vp_strvalue) != 0) return RLM_MODULE_FAIL; return RLM_MODULE_OK; } /* * The module name should be the only globally exported symbol. * That is, everything else should be 'static'. * * If the module needs to temporarily modify it's instantiation * data, the type should be changed to RLM_TYPE_THREAD_UNSAFE. * The server will then take care of ensuring that the module * is single-threaded. */ extern module_t rlm_totp; module_t rlm_totp = { .magic = RLM_MODULE_INIT, .name = "totp", .type = RLM_TYPE_THREAD_SAFE, .methods = { [MOD_AUTHENTICATE] = mod_authenticate, }, }; #else /* TESTING */ int main(int argc, char **argv) { size_t len; uint8_t *p; uint8_t key[80]; if (argc < 2) return 0; if (strcmp(argv[1], "decode") == 0) { if (argc < 3) return 0; len = base32_decode(key, sizeof(key), argv[2]); printf("Decoded %ld %s\n", len, key); for (p = key; p < (key + len); p++) { printf("%02x ", *p); }; printf("\n"); return 0; } /* * TOTP