cryptutils

otp: Add otp utility

Diffstat

3 files changed, 159 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index adbfbca..a6ba700 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,6 +8,8 @@ SET(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/lib)
 SET(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/bin)
 SET(CMAKE_STATIC_LIBRARY_PREFIX "")
 
+FIND_PACKAGE(OpenSSL REQUIRED)
+
 FILE(GLOB LIBSRC ${PROJECT_SOURCE_DIR}/src/lib/*)
 
 ADD_LIBRARY(lib STATIC ${LIBSRC})
@@ -16,3 +18,6 @@ LINK_LIBRARIES(lib)
 
 ADD_EXECUTABLE(alder32 ${PROJECT_SOURCE_DIR}/src/alder32.c)
 ADD_EXECUTABLE(crc32   ${PROJECT_SOURCE_DIR}/src/crc32.c)
+ADD_EXECUTABLE(otp     ${PROJECT_SOURCE_DIR}/src/otp.c)
+
+TARGET_LINK_LIBRARIES(otp OpenSSL::Crypto)
diff --git a/README.md b/README.md
index 433b85c..00ba130 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@ OMKOV cryptutils implements many cryptographic utilities.
 | ---------------- | ---------------------------------------- | -------- |
 | alder32          | Compute the Alder-32 for a file          |          |
 | crc32            | Compute the CRC-32 for a file            |          |
+| otp              | Compute HOTP or TOTP tokens              |          |
 
 ## Build Instructions
 
diff --git a/src/otp.c b/src/otp.c
new file mode 100644
index 0000000..d9841e2
--- /dev/null
+++ b/src/otp.c
@@ -0,0 +1,152 @@
+// otp.c, version 0.1.0
+// OMKOV cryptutils otp
+// Copyright (C) 2020, Jakob Wakeling
+// All rights reserved.
+
+/*
+OMKOV Permissive Licence, version 1.0
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal with
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimers.
+* Redistributions in binary form must reproduce the above copyright notice, this
+  list of conditions and the following disclaimers in the documentation and/or
+  other materials provided with the distribution.
+* Neither the names of the copyright holders, nor the names of its contributors
+  may be used to endorse or promote products derived from this Software without
+  specific prior written permission.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE COPYRIGHT
+HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE SOFTWARE.
+*/
+
+/*
+	TODO Switch to base32 for secret input, as this is more commonly used.
+*/
+
+#include "lib/error.c"
+#include "lib/optget.h"
+
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+
+#include <math.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#define VERSION "0.1.0"
+
+static struct lop lops[] = {
+	{ "help",    ARG_NUL, 256 },
+	{ "version", ARG_NUL, 257 },
+	{ NULL, 0, 0 }
+};
+
+static const uint8_t B16D[];
+
+static inline uint32_t hotp(uint8_t *K, size_t Klen, uint64_t C);
+static uint8_t *b16d(char *s, size_t l);
+
+static void hlp(void);
+static void ver(void);
+
+int main(int ac, char *av[]) { A0 = av[0];
+	struct opt opt = OPTGET_INIT; opt.str = ""; opt.lops = lops;
+	for (int o; (o = optget(&opt, av, 1)) != -1;) switch (o) {
+	case 256: { hlp(); return 0; }
+	case 257: { ver(); return 0; }
+	default: { return 1; }
+	}
+	
+	if (opt.ind == ac) { error(1, "missing operand"); }
+	
+	uint8_t *k; size_t l = strlen(av[opt.ind]); uint64_t c;
+	
+	if (opt.ind == ac - 1) { c = time(NULL) / 30; }
+	else {
+		register uint64_t d; register char *p = av[opt.ind + 1];
+		for (c = 0; *p >= '0' && *p <= '9'; ++p) {
+			d = (uint64_t)*p - '0';
+			if (c > (UINT64_MAX - d) / 10) { break; }
+			c = c * 10 + d;
+		}
+		
+		if (*p) { error(1, "invalid counter"); }
+	}
+	
+	if (!(k = b16d(av[opt.ind], l))) { error(1, "invalid secret"); }
+	printf("%06u\n", hotp(k, l / 2, c)); free(k); return 0;
+}
+
+/* Compute HOTP token with a key and counter */
+static inline uint32_t hotp(uint8_t *K, size_t Klen, uint64_t C) {
+	// Convert the counter to big endian if it isn't already
+	uint32_t e = 0x000000FF; if ((*(uint8_t *)&e) == 0xFF) {
+		C = ((C & 0x00000000FFFFFFFF) << 32) | ((C & 0xFFFFFFFF00000000) >> 32);
+		C = ((C & 0x0000FFFF0000FFFF) << 16) | ((C & 0xFFFF0000FFFF0000) >> 16);
+		C = ((C & 0x00FF00FF00FF00FF) <<  8) | ((C & 0xFF00FF00FF00FF00) >>  8);
+	}
+	
+	// Step 1: Generate HMAC-SHA-1 digest
+	uint8_t *d = HMAC(EVP_sha1(), K, Klen, (uint8_t *)&C, sizeof (C), NULL, 0);
+	
+	// Step 2: Truncate digest to 4 bytes
+	uint32_t dt =
+		(d[(d[19] & 0x0F)]     & 0x7F) << 24 |
+		(d[(d[19] & 0x0F) + 1] & 0xFF) << 16 |
+		(d[(d[19] & 0x0F) + 2] & 0xFF) << 8  |
+		(d[(d[19] & 0x0F) + 3] & 0xFF);
+	
+	// Step 3: Calculate modulus of dt to get HOTP token
+	return dt % (uint32_t)pow(10, 6/*Token length*/);
+}
+
+/* Decode base16 to an array */
+static uint8_t *b16d(char *s, size_t l) {
+	if (l % 2) { return NULL; }
+	
+	uint8_t *a = (uint8_t *)malloc((l / 2) * sizeof (*a));
+	
+	for (uint8_t *i = a; *s; ++i, s += 2) {
+		*i = (B16D[s[0]] << 4) | B16D[s[1]];
+	} return a;
+}
+
+/* Print help information */
+static void hlp(void) {
+	puts("otp - compute hotp or totp tokens\n");
+	puts("usage: otp secret [counter]\n");
+	puts("options:");
+	puts("  --help     Display help information");
+	puts("  --version  Display version information");
+	return;
+}
+
+/* Print version information */
+static void ver(void) {
+	puts("OMKOV cryptutils otp, version " VERSION);
+	puts("Copyright (C) 2020, Jakob Wakeling");
+	puts("All rights reserved.");
+	puts("OMKOV Permissive Licence (https://www.omkov.net/OLPE)");
+	return;
+}
+
+static const uint8_t B16D[] = {
+	0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0,  1,  2,  3,  4,  5,  6, 7, 8, 9, 0, 0, 0, 0, 0, 0,
+	0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0,  0,  0,  0,  0,  0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	0, 10, 11, 12, 13, 14, 15, 0
+};