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-rw-r--r--src/hkdf_sha256.c53
1 files changed, 53 insertions, 0 deletions
diff --git a/src/hkdf_sha256.c b/src/hkdf_sha256.c
new file mode 100644
index 0000000..a85f5e3
--- /dev/null
+++ b/src/hkdf_sha256.c
@@ -0,0 +1,53 @@
+/*
+ Copyright (c) 2012-2013, Matthias Schiffer <mschiffer@universe-factory.net>
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ 1. Redistributions of source code must retain the above copyright notice,
+ this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright notice,
+ this list of conditions and the following disclaimer in the documentation
+ and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#include "hkdf_sha256.h"
+
+#include <string.h>
+
+
+void fastd_hkdf_sha256_expand(fastd_sha256_t *out, size_t blocks, fastd_sha256_t *prk, const uint8_t *info, size_t infolen) {
+ if (!blocks)
+ return;
+
+ size_t len = sizeof(fastd_sha256_t) + infolen + 1;
+
+ uint8_t buf[len] __attribute__((align(4)));
+
+ memset(buf, 0, sizeof(fastd_sha256_t));
+ memcpy(buf+sizeof(fastd_sha256_t), info, infolen);
+ buf[len-1] = 0x01;
+
+ fastd_hmacsha256(out, prk->w, (uint32_t*)(buf+sizeof(fastd_sha256_t)), infolen + 1);
+
+ while (--blocks) {
+ memcpy(buf, out, sizeof(fastd_sha256_t));
+ out++;
+ buf[len-1]++;
+
+ fastd_hmacsha256(out, prk->w, (uint32_t*)buf, len);
+ }
+}