The SP800-108 compliant Key Derivation Function is implemented as a
random number generator considering that it behaves like a deterministic
RNG.
All three KDF types specified in SP800-108 are implemented.
The code comments provide details about how to invoke the different KDF
types.
Signed-off-by: Stephan Mueller
---
crypto/kdf.c | 514 +++
1 file changed, 514 insertions(+)
create mode 100644 crypto/kdf.c
diff --git a/crypto/kdf.c b/crypto/kdf.c
new file mode 100644
index 000..b39bddf
--- /dev/null
+++ b/crypto/kdf.c
@@ -0,0 +1,514 @@
+/*
+ * Copyright (C) 2015, Stephan Mueller
+ *
+ * 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, and the entire permission notice in its entirety,
+ *including the disclaimer of warranties.
+ * 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.
+ * 3. The name of the author may not be used to endorse or promote
+ *products derived from this software without specific prior
+ *written permission.
+ *
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU General Public License, in which case the provisions of the GPL2
+ * are required INSTEAD OF the above restrictions. (This clause is
+ * necessary due to a potential bad interaction between the GPL and
+ * the restrictions contained in a BSD-style copyright.)
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
+ * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR 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 NOT ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+/*
+ * For performing a KDF operation, the following input is required
+ * from the caller:
+ *
+ * * Keying material to be used to derive the new keys from
+ * (denoted as Ko in SP800-108)
+ * * Label -- a free form binary string
+ * * Context -- a free form binary string
+ *
+ * The KDF is implemented as a random number generator.
+ *
+ * The Ko keying material is to be provided with the initialization of the KDF
+ * "random number generator", i.e. with the crypto_rng_reset function.
+ *
+ * The Label and Context concatenated string is provided when obtaining random
+ * numbers, i.e. with the crypto_rng_generate function. The caller must format
+ * the free-form Label || Context input as deemed necessary for the given
+ * purpose. Note, SP800-108 mandates that the Label and Context are separated
+ * by a 0x00 byte, i.e. the caller shall provide the input as
+ * Label || 0x00 || Context when trying to be compliant to SP800-108. For
+ * the feedback KDF, an IV is required as documented below.
+ *
+ * Example without proper error handling:
+ * char *keying_material = "\x00\x11\x22\x33\x44\x55\x66\x77";
+ * char *label_context = "\xde\xad\xbe\xef\x00\xde\xad\xbe\xef";
+ * kdf = crypto_alloc_rng(name, 0, 0);
+ * crypto_rng_reset(kdf, keying_material, 8);
+ * crypto_rng_generate(kdf, label_context, 9, outbuf, outbuflen);
+ *
+ * NOTE: Technically you can use one buffer for holding the label_context and
+ * the outbuf in the example above. Howerver, multiple rounds of the
+ * KDF are to be expected with the input must always be the same.
+ * The first round would replace the input in case of one buffer, and the
+ * KDF would calculate a cryptographically strong result which, however,
+ * is not portable to other KDF implementations! Thus, always use
+ * different buffers for the label_context and the outbuf. A safe
+ * in-place operation can only be done when only one round of the KDF
+ * is executed (i.e. the size of the requested buffer is equal to the
+ * digestsize of the used MAC).
+ */
+
+#include
+#include
+#include
+#include
+
+struct crypto_kdf_ctx {
+ struct shash_desc shash;
+ char ctx[];
+};
+
+/* convert 32 bit integer into its string representation */
+static inline void crypto_kw_cpu_to_be32(u32 val, u8 *buf)
+{
+ __be32 *a = (__be32 *)buf;
+
+ *a = cpu_to_be32(val);
+}
+
+/*
+ * Implementation of the KDF in double pipeline iteration
