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-rw-r--r--src/crypto/sha256-kdf.c76
-rw-r--r--src/crypto/sha256.h5
2 files changed, 80 insertions, 1 deletions
diff --git a/src/crypto/sha256-kdf.c b/src/crypto/sha256-kdf.c
new file mode 100644
index 0000000..d8a1beb
--- /dev/null
+++ b/src/crypto/sha256-kdf.c
@@ -0,0 +1,76 @@
+/*
+ * HMAC-SHA256 KDF (RFC 5295)
+ * Copyright (c) 2014, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "includes.h"
+
+#include "common.h"
+#include "sha256.h"
+
+
+/**
+ * hmac_sha256_kdf - HMAC-SHA256 based KDF (RFC 5295)
+ * @secret: Key for KDF
+ * @secret_len: Length of the key in bytes
+ * @label: A unique label for each purpose of the KDF
+ * @seed: Seed value to bind into the key
+ * @seed_len: Length of the seed
+ * @out: Buffer for the generated pseudo-random key
+ * @outlen: Number of bytes of key to generate
+ * Returns: 0 on success, -1 on failure.
+ *
+ * This function is used to derive new, cryptographically separate keys from a
+ * given key in ERP. This KDF is defined in RFC 5295, Chapter 3.1.2.
+ */
+int hmac_sha256_kdf(const u8 *secret, size_t secret_len,
+ const char *label, const u8 *seed, size_t seed_len,
+ u8 *out, size_t outlen)
+{
+ u8 T[SHA256_MAC_LEN];
+ u8 iter = 1;
+ const unsigned char *addr[4];
+ size_t len[4];
+ size_t pos, clen;
+
+ addr[0] = T;
+ len[0] = SHA256_MAC_LEN;
+ addr[1] = (const unsigned char *) label;
+ len[1] = os_strlen(label) + 1;
+ addr[2] = seed;
+ len[2] = seed_len;
+ addr[3] = &iter;
+ len[3] = 1;
+
+ if (hmac_sha256_vector(secret, secret_len, 3, &addr[1], &len[1], T) < 0)
+ return -1;
+
+ pos = 0;
+ for (;;) {
+ clen = outlen - pos;
+ if (clen > SHA256_MAC_LEN)
+ clen = SHA256_MAC_LEN;
+ os_memcpy(out + pos, T, clen);
+ pos += clen;
+
+ if (pos == outlen)
+ break;
+
+ if (iter == 255) {
+ os_memset(out, 0, outlen);
+ return -1;
+ }
+ iter++;
+
+ if (hmac_sha256_vector(secret, secret_len, 4, addr, len, T) < 0)
+ {
+ os_memset(out, 0, outlen);
+ return -1;
+ }
+ }
+
+ return 0;
+}
diff --git a/src/crypto/sha256.h b/src/crypto/sha256.h
index 7596a52..b15f511 100644
--- a/src/crypto/sha256.h
+++ b/src/crypto/sha256.h
@@ -1,6 +1,6 @@
/*
* SHA256 hash implementation and interface functions
- * Copyright (c) 2003-2013, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2003-2014, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
@@ -23,5 +23,8 @@ void sha256_prf_bits(const u8 *key, size_t key_len, const char *label,
void tls_prf_sha256(const u8 *secret, size_t secret_len,
const char *label, const u8 *seed, size_t seed_len,
u8 *out, size_t outlen);
+int hmac_sha256_kdf(const u8 *secret, size_t secret_len,
+ const char *label, const u8 *seed, size_t seed_len,
+ u8 *out, size_t outlen);
#endif /* SHA256_H */