[crypto] Add SHA-512/256 algorithm

SHA-512/256 is almost identical to SHA-512, with differing initial
hash values and a truncated output length.

This implementation has been verified using the NIST SHA-512/256 test
vectors.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/crypto/sha512_256.c

@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * 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 2 of the
+ * License, or 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * SHA-512/256 algorithm
+ *
+ */
+
+#include <stdint.h>
+#include <byteswap.h>
+#include <ipxe/crypto.h>
+#include <ipxe/asn1.h>
+#include <ipxe/sha512.h>
+
+/** SHA-512/256 initial digest values */
+static const struct sha512_digest sha512_256_init_digest = {
+	.h = {
+		cpu_to_be64 ( 0x22312194fc2bf72cULL ),
+		cpu_to_be64 ( 0x9f555fa3c84c64c2ULL ),
+		cpu_to_be64 ( 0x2393b86b6f53b151ULL ),
+		cpu_to_be64 ( 0x963877195940eabdULL ),
+		cpu_to_be64 ( 0x96283ee2a88effe3ULL ),
+		cpu_to_be64 ( 0xbe5e1e2553863992ULL ),
+		cpu_to_be64 ( 0x2b0199fc2c85b8aaULL ),
+		cpu_to_be64 ( 0x0eb72ddc81c52ca2ULL ),
+	},
+};
+
+/**
+ * Initialise SHA-512/256 algorithm
+ *
+ * @v ctx		SHA-512/256 context
+ */
+static void sha512_256_init ( void *ctx ) {
+	struct sha512_context *context = ctx;
+
+	sha512_family_init ( context, &sha512_256_init_digest,
+			     SHA512_256_DIGEST_SIZE );
+}
+
+/** SHA-512/256 algorithm */
+struct digest_algorithm sha512_256_algorithm = {
+	.name		= "sha512/256",
+	.ctxsize	= sizeof ( struct sha512_context ),
+	.blocksize	= sizeof ( union sha512_block ),
+	.digestsize	= SHA512_256_DIGEST_SIZE,
+	.init		= sha512_256_init,
+	.update		= sha512_update,
+	.final		= sha512_final,
+};
+
+/** "sha512_256" object identifier */
+static uint8_t oid_sha512_256[] = { ASN1_OID_SHA512_256 };
+
+/** "sha512_256" OID-identified algorithm */
+struct asn1_algorithm oid_sha512_256_algorithm __asn1_algorithm = {
+	.name = "sha512/256",
+	.digest = &sha512_256_algorithm,
+	.oid = ASN1_OID_CURSOR ( oid_sha512_256 ),
+};

src/include/ipxe/asn1.h

@@ -181,6 +181,13 @@ struct asn1_builder_header {
 	ASN1_OID_SINGLE ( 3 ), ASN1_OID_SINGLE ( 4 ),		\
 	ASN1_OID_SINGLE ( 2 ), ASN1_OID_SINGLE ( 4 )
 
+/** ASN.1 OID for id-sha512-256 (2.16.840.1.101.3.4.2.6) */
+#define ASN1_OID_SHA512_256						\
+	ASN1_OID_INITIAL ( 2, 16 ), ASN1_OID_DOUBLE ( 840 ),	\
+	ASN1_OID_SINGLE ( 1 ), ASN1_OID_SINGLE ( 101 ),		\
+	ASN1_OID_SINGLE ( 3 ), ASN1_OID_SINGLE ( 4 ),		\
+	ASN1_OID_SINGLE ( 2 ), ASN1_OID_SINGLE ( 6 )
+
 /** ASN.1 OID for commonName (2.5.4.3) */
 #define ASN1_OID_COMMON_NAME					\
 	ASN1_OID_INITIAL ( 2, 5 ), ASN1_OID_SINGLE ( 4 ),	\

src/include/ipxe/sha512.h

@@ -78,6 +78,9 @@ struct sha512_context {
 /** SHA-384 digest size */
 #define SHA384_DIGEST_SIZE ( SHA512_DIGEST_SIZE * 384 / 512 )
 
+/** SHA-512/256 digest size */
+#define SHA512_256_DIGEST_SIZE ( SHA512_DIGEST_SIZE * 256 / 512 )
+
 extern void sha512_family_init ( struct sha512_context *context,
 				 const struct sha512_digest *init,
 				 size_t digestsize );
@@ -86,5 +89,6 @@ extern void sha512_final ( void *ctx, void *out );
 
 extern struct digest_algorithm sha512_algorithm;
 extern struct digest_algorithm sha384_algorithm;
+extern struct digest_algorithm sha512_256_algorithm;
 
 #endif /* IPXE_SHA512_H */

src/tests/sha512_test.c

@@ -31,6 +31,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  *
  *  http://csrc.nist.gov/groups/ST/toolkit/documents/Examples/SHA512.pdf
  *  http://csrc.nist.gov/groups/ST/toolkit/documents/Examples/SHA384.pdf
+ *  http://csrc.nist.gov/groups/ST/toolkit/documents/Examples/SHA512_256.pdf
  *
  */
 
@@ -101,6 +102,28 @@ DIGEST_TEST ( sha384_nist_abc_stu, &sha384_algorithm, DIGEST_NIST_ABC_STU,
 		       0x55, 0x7e, 0x2d, 0xb9, 0x66, 0xc3, 0xe9, 0xfa, 0x91,
 		       0x74, 0x60, 0x39 ) );
 
+/* Empty test vector (digest obtained from "shasum -a 512256 /dev/null") */
+DIGEST_TEST ( sha512_256_empty, &sha512_256_algorithm, DIGEST_EMPTY,
+	      DIGEST ( 0xc6, 0x72, 0xb8, 0xd1, 0xef, 0x56, 0xed, 0x28, 0xab,
+		       0x87, 0xc3, 0x62, 0x2c, 0x51, 0x14, 0x06, 0x9b, 0xdd,
+		       0x3a, 0xd7, 0xb8, 0xf9, 0x73, 0x74, 0x98, 0xd0, 0xc0,
+		       0x1e, 0xce, 0xf0, 0x96, 0x7a ) );
+
+/* NIST test vector "abc" */
+DIGEST_TEST ( sha512_256_nist_abc, &sha512_256_algorithm, DIGEST_NIST_ABC,
+	      DIGEST ( 0x53, 0x04, 0x8e, 0x26, 0x81, 0x94, 0x1e, 0xf9, 0x9b,
+		       0x2e, 0x29, 0xb7, 0x6b, 0x4c, 0x7d, 0xab, 0xe4, 0xc2,
+		       0xd0, 0xc6, 0x34, 0xfc, 0x6d, 0x46, 0xe0, 0xe2, 0xf1,
+		       0x31, 0x07, 0xe7, 0xaf, 0x23 ) );
+
+/* NIST test vector "abc...stu" */
+DIGEST_TEST ( sha512_256_nist_abc_stu, &sha512_256_algorithm,
+	      DIGEST_NIST_ABC_STU,
+	      DIGEST ( 0x39, 0x28, 0xe1, 0x84, 0xfb, 0x86, 0x90, 0xf8, 0x40,
+		       0xda, 0x39, 0x88, 0x12, 0x1d, 0x31, 0xbe, 0x65, 0xcb,
+		       0x9d, 0x3e, 0xf8, 0x3e, 0xe6, 0x14, 0x6f, 0xea, 0xc8,
+		       0x61, 0xe1, 0x9b, 0x56, 0x3a ) );
+
 /**
  * Perform SHA-512 family self-test
  *
@@ -114,12 +137,17 @@ static void sha512_test_exec ( void ) {
 	digest_ok ( &sha384_empty );
 	digest_ok ( &sha384_nist_abc );
 	digest_ok ( &sha384_nist_abc_stu );
+	digest_ok ( &sha512_256_empty );
+	digest_ok ( &sha512_256_nist_abc );
+	digest_ok ( &sha512_256_nist_abc_stu );
 
 	/* Speed tests */
 	DBG ( "SHA512 required %ld cycles per byte\n",
 	      digest_cost ( &sha512_algorithm ) );
 	DBG ( "SHA384 required %ld cycles per byte\n",
 	      digest_cost ( &sha384_algorithm ) );
+	DBG ( "SHA512/256 required %ld cycles per byte\n",
+	      digest_cost ( &sha512_256_algorithm ) );
 }
 
 /** SHA-512 family self-test */