[rng] Add ANS X9.82 Approved HMAC_DRBG algorithm

ANS X9.82 specifies several Approved algorithms for use in a
Deterministic Random Bit Generator (DRBG).  One such algorithm is
HMAC_DRBG, which can be implemented using the existing iPXE SHA-1 and
HMAC functionality.  This algorithm provides a maximum security
strength of 128 bits.

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

3 files changed, 496 insertions, 0 deletions

diff --git a/src/crypto/hmac_drbg.c b/src/crypto/hmac_drbg.c
new file mode 100644
index 00000000..64613d01
--- /dev/null
+++ b/src/crypto/hmac_drbg.c
@@ -0,0 +1,342 @@
+/*
+ * Copyright (C) 2012 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * HMAC_DRBG algorithm
+ *
+ * This algorithm is designed to comply with ANS X9.82 Part 3-2007
+ * Section 10.2.2.2.  This standard is not freely available, but most
+ * of the text appears to be shared with NIST SP 800-90, which can be
+ * downloaded from
+ *
+ *     http://csrc.nist.gov/publications/nistpubs/800-90/SP800-90revised_March2007.pdf
+ *
+ * Where possible, references are given to both documents.  In the
+ * case of any disagreement, ANS X9.82 takes priority over NIST SP
+ * 800-90.  (In particular, note that some algorithms that are
+ * Approved by NIST SP 800-90 are not Approved by ANS X9.82.)
+ */
+
+#include <stdint.h>
+#include <errno.h>
+#include <ipxe/crypto.h>
+#include <ipxe/hmac.h>
+#include <ipxe/hmac_drbg.h>
+
+/**
+ * Update the HMAC_DRBG key
+ *
+ * @v state		HMAC_DRBG internal state
+ * @v data		Provided data
+ * @v len		Length of provided data
+ * @v single		Single byte used in concatenation
+ *
+ * This function carries out the operation
+ *
+ *     K = HMAC ( K, V || single || provided_data )
+ *
+ * as used by hmac_drbg_update()
+ */
+static void hmac_drbg_update_key ( struct hmac_drbg_state *state,
+				   const void *data, size_t len,
+				   const uint8_t single ) {
+	uint8_t context[HMAC_DRBG_CTX_SIZE];
+	size_t key_len = sizeof ( state->key );
+
+	DBGC ( state, "HMAC_DRBG %p provided data :\n", state );
+	DBGC_HDA ( state, 0, data, len );
+
+	/* Sanity checks */
+	assert ( state != NULL );
+	assert ( ( data != NULL ) || ( len == 0 ) );
+	assert ( ( single == 0x00 ) || ( single == 0x01 ) );
+
+	/* K = HMAC ( K, V || single || provided_data ) */
+	hmac_init ( &hmac_drbg_algorithm, context, state->key, &key_len );
+	assert ( key_len == sizeof ( state->key ) );
+	hmac_update ( &hmac_drbg_algorithm, context,
+		      state->value, sizeof ( state->value ) );
+	hmac_update ( &hmac_drbg_algorithm, context,
+		      &single, sizeof ( single ) );
+	hmac_update ( &hmac_drbg_algorithm, context, data, len );
+	hmac_final ( &hmac_drbg_algorithm, context, state->key, &key_len,
+		     state->key );
+	assert ( key_len == sizeof ( state->key ) );
+
+	DBGC ( state, "HMAC_DRBG %p K = HMAC ( K, V || %#02x || "
+	       "provided_data ) :\n", state, single );
+	DBGC_HDA ( state, 0, state->key, sizeof ( state->key ) );
+}
+
+/**
+ * Update the HMAC_DRBG value
+ *
+ * @v state		HMAC_DRBG internal state
+ * @v data		Provided data
+ * @v len		Length of provided data
+ * @v single		Single byte used in concatenation
+ *
+ * This function carries out the operation
+ *
+ *     V = HMAC ( K, V )
+ *
+ * as used by hmac_drbg_update() and hmac_drbg_generate()
+ */
+static void hmac_drbg_update_value ( struct hmac_drbg_state *state ) {
+	uint8_t context[HMAC_DRBG_CTX_SIZE];
+	size_t key_len = sizeof ( state->key );
+
+	/* Sanity checks */
+	assert ( state != NULL );
+
+	/* V = HMAC ( K, V ) */
+	hmac_init ( &hmac_drbg_algorithm, context, state->key, &key_len );
+	assert ( key_len == sizeof ( state->key ) );
+	hmac_update ( &hmac_drbg_algorithm, context,
+		      state->value, sizeof ( state->value ) );
+	hmac_final ( &hmac_drbg_algorithm, context, state->key, &key_len,
+		     state->value );
+	assert ( key_len == sizeof ( state->key ) );
+
+	DBGC ( state, "HMAC_DRBG %p V = HMAC ( K, V ) :\n", state );
+	DBGC_HDA ( state, 0, state->value, sizeof ( state->value ) );
+}
+
+/**
+ * Update HMAC_DRBG internal state
+ *
+ * @v state		HMAC_DRBG internal state
+ * @v data		Provided data
+ * @v len		Length of provided data
+ *
+ * This is the HMAC_DRBG_Update function defined in ANS X9.82 Part
+ * 3-2007 Section 10.2.2.2.2 (NIST SP 800-90 Section 10.1.2.2).
+ *
+ * The key and value are updated in-place within the HMAC_DRBG
+ * internal state.
+ */
+static void hmac_drbg_update ( struct hmac_drbg_state *state,
+			       const void *data, size_t len ) {
+
+	DBGC ( state, "HMAC_DRBG %p update\n", state );
+
+	/* Sanity checks */
+	assert ( state != NULL );
+	assert ( ( data != NULL ) || ( len == 0 ) );
+
+	/* 1.  K = HMAC ( K, V || 0x00 || provided_data ) */
+	hmac_drbg_update_key ( state, data, len, 0x00 );
+
+	/* 2.  V = HMAC ( K, V ) */
+	hmac_drbg_update_value ( state );
+
+	/* 3.  If ( provided_data = Null ), then return K and V */
+	if ( ! len )
+		return;
+
+	/* 4.  K = HMAC ( K, V || 0x01 || provided_data ) */
+	hmac_drbg_update_key ( state, data, len, 0x01 );
+
+	/* 5.  V = HMAC ( K, V ) */
+	hmac_drbg_update_value ( state );
+
+	/* 6.  Return K and V */
+}
+
+/**
+ * Instantiate HMAC_DRBG
+ *
+ * @v state		HMAC_DRBG internal state to be initialised
+ * @v entropy		Entropy input
+ * @v entropy_len	Length of entropy input
+ * @v personal		Personalisation string
+ * @v personal_len	Length of personalisation string
+ *
+ * This is the HMAC_DRBG_Instantiate_algorithm function defined in ANS
+ * X9.82 Part 3-2007 Section 10.2.2.2.3 (NIST SP 800-90 Section
+ * 10.1.2.3).
+ *
+ * The nonce must be included within the entropy input (i.e. the
+ * entropy input must contain at least 3/2 * security_strength bits of
+ * entropy, as per ANS X9.82 Part 3-2007 Section 8.4.2 (NIST SP 800-90
+ * Section 8.6.7).
+ *
+ * The key, value and reseed counter are updated in-place within the
+ * HMAC_DRBG internal state.
+ */
+void hmac_drbg_instantiate ( struct hmac_drbg_state *state,
+			     const void *entropy, size_t entropy_len,
+			     const void *personal, size_t personal_len ){
+
+	DBGC ( state, "HMAC_DRBG %p instantiate\n", state );
+
+	/* Sanity checks */
+	assert ( state != NULL );
+	assert ( entropy != NULL );
+	assert ( ( 8 * entropy_len ) >=
+		 ( 3 * HMAC_DRBG_SECURITY_STRENGTH / 2 ) );
+	assert ( ( personal != NULL ) || ( personal_len == 0 ) );
+
+	/* 1.  seed_material = entropy_input || nonce ||
+	 *     personalisation_string
+	 */
+
+	/* 2.  Key = 0x00 00..00 */
+	memset ( state->key, 0x00, sizeof ( state->key ) );
+
+	/* 3.  V = 0x01 01...01 */
+	memset ( state->value, 0x01, sizeof ( state->value ) );
+
+	/* 4.  ( Key, V ) = HMAC_DBRG_Update ( seed_material, Key, V )
+	 * 5.  reseed_counter = 1
+	 * 6.  Return V, Key and reseed_counter as the
+	 *     initial_working_state
+	 */
+	hmac_drbg_reseed ( state, entropy, entropy_len,
+			   personal, personal_len );
+}
+
+/**
+ * Reseed HMAC_DRBG
+ *
+ * @v state		HMAC_DRBG internal state
+ * @v entropy		Entropy input
+ * @v entropy_len	Length of entropy input
+ * @v additional	Additional input
+ * @v additional_len	Length of additional input
+ *
+ * This is the HMAC_DRBG_Reseed_algorithm function defined in ANS X9.82
+ * Part 3-2007 Section 10.2.2.2.4 (NIST SP 800-90 Section 10.1.2.4).
+ *
+ * The key, value and reseed counter are updated in-place within the
+ * HMAC_DRBG internal state.
+ */
+void hmac_drbg_reseed ( struct hmac_drbg_state *state,
+			const void *entropy, size_t entropy_len,
+			const void *additional, size_t additional_len ) {
+	uint8_t seed_material[ entropy_len + additional_len ];
+
+	DBGC ( state, "HMAC_DRBG %p (re)seed\n", state );
+
+	/* Sanity checks */
+	assert ( state != NULL );
+	assert ( entropy != NULL );
+	assert ( ( 8 * entropy_len ) >= HMAC_DRBG_SECURITY_STRENGTH );
+	assert ( ( additional != NULL ) || ( additional_len == 0 ) );
+
+	/* 1.  seed_material = entropy_input || additional_input */
+	memcpy ( seed_material, entropy, entropy_len );
+	memcpy ( ( seed_material + entropy_len ), additional, additional_len );
+	DBGC ( state, "HMAC_DRBG %p seed material :\n", state );
+	DBGC_HDA ( state, 0, seed_material, sizeof ( seed_material ) );
+
+	/* 2.  ( Key, V ) = HMAC_DBRG_Update ( seed_material, Key, V ) */
+	hmac_drbg_update ( state, seed_material, sizeof ( seed_material ) );
+
+	/* 3.  reseed_counter = 1 */
+	state->reseed_counter = 1;
+
+	/* 4.  Return V, Key and reseed_counter as the new_working_state */
+}
+
+/**
+ * Generate pseudorandom bits using HMAC_DRBG
+ *
+ * @v state		HMAC_DRBG internal state
+ * @v additional	Additional input
+ * @v additional_len	Length of additional input
+ * @v data		Output buffer
+ * @v len		Length of output buffer
+ * @ret rc		Return status code
+ *
+ * This is the HMAC_DRBG_Generate_algorithm function defined in ANS X9.82
+ * Part 3-2007 Section 10.2.2.2.5 (NIST SP 800-90 Section 10.1.2.5).
+ *
+ * Requests must be for an integral number of bytes.
+ *
+ * The key, value and reseed counter are updated in-place within the
+ * HMAC_DRBG internal state.
+ *
+ * Note that the only permitted error is "reseed required".
+ */
+int hmac_drbg_generate ( struct hmac_drbg_state *state,
+			 const void *additional, size_t additional_len,
+			 void *data, size_t len ) {
+	void *orig_data = data;
+	size_t orig_len = len;
+	size_t frag_len;
+
+	DBGC ( state, "HMAC_DRBG %p generate\n", state );
+
+	/* Sanity checks */
+	assert ( state != NULL );
+	assert ( data != NULL );
+	assert ( ( additional != NULL ) || ( additional_len == 0 ) );
+
+	/* 1.  If reseed_counter > reseed_interval, then return an
+	 *     indication that a reseed is required
+	 */
+	if ( state->reseed_counter > HMAC_DRBG_RESEED_INTERVAL ) {
+		DBGC ( state, "HMAC_DRBG %p reseed interval exceeded\n",
+		       state );
+		return -ESTALE;
+	}
+
+	/* 2.  If additional_input != Null, then
+	 *     ( Key, V ) = HMAC_DRBG_Update ( additional_input, Key, V )
+	 */
+	if ( additional_len )
+		hmac_drbg_update ( state, additional, additional_len );
+
+	/* 3.  temp = Null
+	 * 4.  While ( len ( temp ) < requested_number_of_bits ) do:
+	 */
+	while ( len ) {
+
+		/* 4.1  V = HMAC ( Key, V ) */
+		hmac_drbg_update_value ( state );
+
+		/* 4.2.  temp = temp || V
+		 * 5.    returned_bits = Leftmost requested_number_of_bits
+		 *       of temp
+		 */
+		frag_len = len;
+		if ( frag_len > sizeof ( state->value ) )
+			frag_len = sizeof ( state->value );
+		memcpy ( data, state->value, frag_len );
+		data += frag_len;
+		len -= frag_len;
+	}
+
+	/* 6.  ( Key, V ) = HMAC_DRBG_Update ( additional_input, Key, V ) */
+	hmac_drbg_update ( state, additional, additional_len );
+
+	/* 7.  reseed_counter = reseed_counter + 1 */
+	state->reseed_counter++;
+
+	DBGC ( state, "HMAC_DRBG %p generated :\n", state );
+	DBGC_HDA ( state, 0, orig_data, orig_len );
+
+	/* 8.  Return SUCCESS, returned_bits, and the new values of
+	 *     Key, V and reseed_counter as the new_working_state
+	 */
+	return 0;
+}
diff --git a/src/include/ipxe/errfile.h b/src/include/ipxe/errfile.h
index aacc722d..2094b78c 100644
--- a/src/include/ipxe/errfile.h
+++ b/src/include/ipxe/errfile.h
@@ -242,6 +242,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define ERRFILE_bofm		      ( ERRFILE_OTHER | 0x00210000 )
 #define ERRFILE_prompt		      ( ERRFILE_OTHER | 0x00220000 )
 #define ERRFILE_nvo_cmd		      ( ERRFILE_OTHER | 0x00230000 )
+#define ERRFILE_hmac_drbg	      ( ERRFILE_OTHER | 0x00240000 )
 
 /** @} */
 
diff --git a/src/include/ipxe/hmac_drbg.h b/src/include/ipxe/hmac_drbg.h
new file mode 100644
index 00000000..c751cbcb
--- /dev/null
+++ b/src/include/ipxe/hmac_drbg.h
@@ -0,0 +1,153 @@
+#ifndef _IPXE_HMAC_DRBG_H
+#define _IPXE_HMAC_DRBG_H
+
+/** @file
+ *
+ * HMAC_DRBG algorithm
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <ipxe/sha1.h>
+
+/** Use SHA-1 as the underlying hash algorithm
+ *
+ * HMAC_DRBG using SHA-1 is an Approved algorithm in ANS X9.82.
+ */
+#define hmac_drbg_algorithm sha1_algorithm
+
+/** Maximum security strength
+ *
+ * The maximum security strength of HMAC_DRBG using SHA-1 is 128 bits
+ * (according to the list of maximum security strengths documented in
+ * NIST SP 800-57 Part 1 Section 5.6.1 Table 3).
+ */
+#define HMAC_DRBG_MAX_SECURITY_STRENGTH 128
+
+/** Security strength
+ *
+ * For the sake of implementation simplicity, only a single security
+ * strength is supported, which is the maximum security strength
+ * supported by the algorithm.
+ */
+#define HMAC_DRBG_SECURITY_STRENGTH HMAC_DRBG_MAX_SECURITY_STRENGTH
+
+/** Underlying hash algorithm output length (in bytes) */
+#define HMAC_DRBG_OUTLEN_BYTES SHA1_DIGEST_SIZE
+
+/** Required minimum entropy for instantiate and reseed
+ *
+ * The minimum required entropy for HMAC_DRBG is equal to the security
+ * strength according to ANS X9.82 Part 3-2007 Section 10.2.1 Table 2
+ * (NIST SP 800-90 Section 10.1 Table 2).
+ */
+#define HMAC_DRBG_MIN_ENTROPY_BYTES ( HMAC_DRBG_SECURITY_STRENGTH / 8 )
+
+/** Minimum entropy input length
+ *
+ * The minimum entropy input length for HMAC_DRBG is equal to the
+ * security strength according to ANS X9.82 Part 3-2007 Section 10.2.1
+ * Table 2 (NIST SP 800-90 Section 10.1 Table 2).
+ */
+#define HMAC_DRBG_MIN_ENTROPY_LEN_BYTES ( HMAC_DRBG_SECURITY_STRENGTH / 8 )
+
+/** Maximum entropy input length
+ *
+ * The maximum entropy input length for HMAC_DRBG is 2^35 bits
+ * according to ANS X9.82 Part 3-2007 Section 10.2.1 Table 2 (NIST SP
+ * 800-90 Section 10.1 Table 2).
+ *
+ * We choose to allow up to 2^32-1 bytes (i.e. 2^35-8 bits).
+ */
+#define HMAC_DRBG_MAX_ENTROPY_LEN_BYTES 0xffffffffUL
+
+/** Maximum personalisation string length
+ *
+ * The maximum permitted personalisation string length for HMAC_DRBG
+ * is 2^35 bits according to ANS X9.82 Part 3-2007 Section 10.2.1
+ * Table 1 (NIST SP 800-90 Section 10.1 Table 2).
+ *
+ * We choose to allow up to 2^32-1 bytes (i.e. 2^35-8 bits).
+ */
+#define HMAC_DRBG_MAX_PERSONAL_LEN_BYTES 0xffffffffUL
+
+/** Maximum additional input length
+ *
+ * The maximum permitted additional input length for HMAC_DRBG is 2^35
+ * bits according to ANS X9.82 Part 3-2007 Section 10.2.1 Table 1
+ * (NIST SP 800-90 Section 10.1 Table 2).
+ *
+ * We choose to allow up to 2^32-1 bytes (i.e. 2^35-8 bits).
+ */
+#define HMAC_DRBG_MAX_ADDITIONAL_LEN_BYTES 0xffffffffUL
+
+/** Maximum length of generated pseudorandom data per request
+ *
+ * The maximum number of bits per request for HMAC_DRBG is 2^19 bits
+ * according to ANS X9.82 Part 3-2007 Section 10.2.1 Table 1 (NIST SP
+ * 800-90 Section 10.1 Table 2).
+ *
+ * We choose to allow up to 2^16-1 bytes (i.e. 2^19-8 bits).
+ */
+#define HMAC_DRBG_MAX_GENERATED_LEN_BYTES 0x0000ffffUL
+
+/** Reseed interval
+ *
+ * The maximum permitted reseed interval for HMAC_DRBG using SHA-1 is
+ * 2^48 according to ANS X9.82 Part 3-2007 Section 10.2.1 Table 2
+ * (NIST SP 800-90 Section 10.1 Table 2).  However, the sample
+ * implementation given in ANS X9.82 Part 3-2007 Annex E.2.1 (NIST SP
+ * 800-90 Appendix F.2) shows a reseed interval of 10000.
+ *
+ * We choose a very conservative reseed interval.
+ */
+#define HMAC_DRBG_RESEED_INTERVAL 1024
+
+/** Underlying hash algorithm context size (in bytes) */
+#define HMAC_DRBG_CTX_SIZE SHA1_CTX_SIZE
+
+/**
+ * HMAC_DRBG internal state
+ *
+ * This structure is defined by ANS X9.82 Part 3-2007 Section
+ * 10.2.2.2.1 (NIST SP 800-90 Section 10.1.2.1).
+ *
+ * The "administrative information" portions (security_strength and
+ * prediction_resistance) are design-time constants and so are not
+ * present as fields in this structure.
+ */
+struct hmac_drbg_state {
+	/** Current value
+	 *
+	 * "The value V of outlen bits, which is updated each time
+	 * another outlen bits of output are produced"
+	 */
+	uint8_t value[HMAC_DRBG_OUTLEN_BYTES];
+	/** Current key
+	 *
+	 * "The outlen-bit Key, which is updated at least once each
+	 * time that the DRBG mechanism generates pseudorandom bits."
+	 */
+	uint8_t key[HMAC_DRBG_OUTLEN_BYTES];
+	/** Reseed counter
+	 *
+	 * "A counter (reseed_counter) that indicates the number of
+	 * requests for pseudorandom bits since instantiation or
+	 * reseeding"
+	 */
+	unsigned int reseed_counter;
+};
+
+extern void hmac_drbg_instantiate ( struct hmac_drbg_state *state,
+				    const void *entropy, size_t entropy_len,
+				    const void *personal, size_t personal_len );
+extern void hmac_drbg_reseed ( struct hmac_drbg_state *state,
+			       const void *entropy, size_t entropy_len,
+			       const void *additional, size_t additional_len );
+extern int hmac_drbg_generate ( struct hmac_drbg_state *state,
+				const void *additional, size_t additional_len,
+				void *data, size_t len );
+
+#endif /* _IPXE_HMAC_DRBG_H */