1 files changed, 320 insertions, 0 deletions
diff --git a/src/modules/rlm_totp/rlm_totp.c b/src/modules/rlm_totp/rlm_totp.c
new file mode 100644
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--- /dev/null
+++ b/src/modules/rlm_totp/rlm_totp.c
@@ -0,0 +1,320 @@
+/*
+ *   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 <freeradius-devel/radiusd.h>
+#include <freeradius-devel/modules.h>
+#include <freeradius-devel/rad_assert.h>
+
+#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 <time> <key> <8-character-expected-token>
+	 */
+	if (strcmp(argv[1], "totp") == 0) {
+		uint64_t now;
+
+		if (argc < 5) return 0;
+
+		(void) sscanf(argv[2], "%llu", &now);
+
+		if (totp_cmp((time_t) now, (uint8_t const *) argv[3], strlen(argv[3]), argv[4]) == 0) {
+			return 0;
+		}
+		printf("Fail\n");
+		return 1;
+	}
+
+	fprintf(stderr, "Unknown command argv[1]\n", argv[1]);
+	return 1;
+}
+#endif