all the forgotten files

[labortage2013badge.git] / firmware / hotp.c

diff --git a/firmware/hotp.c b/firmware/hotp.c
new file mode 100644 (file)
index 0000000..f0e7c3c
--- /dev/null
+++ b/firmware/hotp.c
@@ -0,0 +1,75 @@
+/* htop.c */
+/*
+    This file is part of the AVR-Crypto-Lib.
+    Copyright (C) 2006-2013 Daniel Otte (daniel.otte@rub.de)
+
+    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 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, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <hmac-sha1.h>
+
+static
+uint32_t dtrunc(uint8_t* buffer) {
+    uint8_t idx;
+    union {
+        uint8_t w8[4];
+        uint32_t w32;
+    } r;
+
+    idx = buffer[19] & 0x0f;
+    r.w8[3] = buffer[idx++] & 0x7f;
+    r.w8[2] = buffer[idx++];
+    r.w8[1] = buffer[idx++];
+    r.w8[0] = buffer[idx];
+    return r.w32;
+}
+
+static
+void to_digits(char *buffer, uint32_t value, uint8_t digits) {
+    ldiv_t t;
+    if (value == 0) {
+        *buffer++ = '0';
+    }
+    while (value && digits--) {
+        t = ldiv(value, 10);
+        value = t.quot;
+        *buffer++ = t.rem + '0';
+    }
+    *buffer = '\0';
+}
+
+void hotp(char *buffer, void* secret, uint16_t secret_length_b, uint32_t counter, uint8_t digits) {
+    union {
+        uint8_t mac[20];
+        uint8_t ctr_buffer[8];
+    } d;
+    uint32_t s;
+    d.ctr_buffer[7] = 0;
+    d.ctr_buffer[6] = 0;
+    d.ctr_buffer[5] = 0;
+    d.ctr_buffer[4] = 0;
+    d.ctr_buffer[3] = counter & 0xff;
+    counter >>= 8;
+    d.ctr_buffer[2] = counter & 0xff;
+    counter >>= 8;
+    d.ctr_buffer[1] = counter & 0xff;
+    counter >>= 8;
+    d.ctr_buffer[0] = counter & 0xff;
+    hmac_sha1(d.mac, secret, secret_length_b, d.ctr_buffer, 64);
+    s = dtrunc(d.mac);
+    to_digits(buffer, s, digits);
+}