3 files changed, 152 insertions, 15 deletions
diff --git a/src/crypto/drbg.c b/src/crypto/drbg.c
index 88cf3acde..afd75da3f 100644
--- a/src/crypto/drbg.c
+++ b/src/crypto/drbg.c
@@ -63,7 +63,7 @@ int drbg_instantiate ( struct drbg_state *state, const void *personal,
 	unsigned int entropy_bits = ( ( 3 * DRBG_SECURITY_STRENGTH + 1 ) / 2 );
 	size_t min_len = DRBG_MIN_ENTROPY_LEN_BYTES;
 	size_t max_len = DRBG_MAX_ENTROPY_LEN_BYTES;
-	uint8_t data[ entropy_bufsize ( entropy_bits, min_len, max_len ) ];
+	uint8_t data[max_len];
 	int len;
 	int rc;
 
@@ -175,7 +175,7 @@ int drbg_reseed ( struct drbg_state *state, const void *additional,
 	unsigned int entropy_bits = DRBG_SECURITY_STRENGTH;
 	size_t min_len = DRBG_MIN_ENTROPY_LEN_BYTES;
 	size_t max_len = DRBG_MAX_ENTROPY_LEN_BYTES;
-	uint8_t data[ entropy_bufsize ( entropy_bits, min_len, max_len ) ];
+	uint8_t data[max_len];
 	int len;
 	int rc;
 
diff --git a/src/crypto/entropy.c b/src/crypto/entropy.c
index 86fa89783..d5d06e579 100644
--- a/src/crypto/entropy.c
+++ b/src/crypto/entropy.c
@@ -22,27 +22,129 @@ FILE_LICENCE ( GPL2_OR_LATER );
  *
  * Entropy source
  *
+ * This algorithm is designed to comply with ANS X9.82 Part 4 (April
+ * 2011 Draft) Section 13.3.  This standard is unfortunately not
+ * freely available.
  */
 
+#include <stdint.h>
+#include <assert.h>
 #include <string.h>
+#include <ipxe/crypto.h>
+#include <ipxe/hash_df.h>
 #include <ipxe/entropy.h>
 
 /**
- * Obtain entropy input
+ * Get entropy sample
  *
- * @v entropy_bits	Minimum amount of entropy, in bits
- * @v data		Data buffer
- * @v min_len		Minimum length of entropy input, in bytes
- * @v max_len		Maximum length of entropy input, in bytes
- * @ret len		Length of entropy input, in bytes
+ * @ret entropy		Entropy sample
+ * @ret rc		Return status code
+ *
+ * This is the GetEntropy function defined in ANS X9.82 Part 2
+ * (October 2011 Draft) Section 6.5.1.
+ */
+static int get_entropy ( entropy_sample_t *entropy ) {
+	noise_sample_t noise;
+	int rc;
+
+	/* Get noise sample */
+	if ( ( rc = get_noise ( &noise ) ) != 0 )
+		return rc;
+
+	/* We do not use any optional conditioning component */
+	*entropy = noise;
+
+	return 0;
+}
+
+/**
+ * Create next nonce value
+ *
+ * @ret nonce		Nonce
+ *
+ * This is the MakeNextNonce function defined in ANS X9.82 Part 4
+ * (April 2011 Draft) Section 13.3.4.2.
  */
-int get_entropy_input ( unsigned int entropy_bits, void *data, size_t min_len,
-			size_t max_len ) {
+static uint32_t make_next_nonce ( void ) {
+	static uint32_t nonce;
+
+	/* The simplest implementation of a nonce uses a large counter */
+	nonce++;
+
+	return nonce;
+}
+
+/**
+ * Obtain entropy input temporary buffer
+ *
+ * @v num_samples	Number of entropy samples
+ * @v tmp		Temporary buffer
+ * @v tmp_len		Length of temporary buffer
+ * @ret rc		Return status code
+ *
+ * This is (part of) the implementation of the Get_entropy_input
+ * function (using an entropy source as the source of entropy input
+ * and condensing each entropy source output after each GetEntropy
+ * call) as defined in ANS X9.82 Part 4 (April 2011 Draft) Section
+ * 13.3.4.2.
+ *
+ * To minimise code size, the number of samples required is calculated
+ * at compilation time.
+ */
+int get_entropy_input_tmp ( unsigned int num_samples, uint8_t *tmp,
+			    size_t tmp_len ) {
+	struct {
+		uint32_t nonce;
+		entropy_sample_t sample;
+	} __attribute__ (( packed )) data;;
+	uint8_t df_buf[tmp_len];
+	unsigned int i;
+	int rc;
+
+	/* Enable entropy gathering */
+	entropy_enable();
+
+	/* 3.  entropy_total = 0
+	 *
+	 * (Nothing to do; the number of entropy samples required has
+	 * already been precalculated.)
+	 */
+
+	/* 4.  tmp = a fixed n-bit value, such as 0^n */
+	memset ( tmp, 0, tmp_len );
+
+	/* 5.  While ( entropy_total < min_entropy ) */
+	while ( num_samples-- ) {
+		/* 5.1.  ( status, entropy_bitstring, assessed_entropy )
+		 *       = GetEntropy()
+		 * 5.2.  If status indicates an error, return ( status, Null )
+		 */
+		if ( ( rc = get_entropy ( &data.sample ) ) != 0 )
+			goto err_get_entropy;
+
+		/* 5.3.  nonce = MakeNextNonce() */
+		data.nonce = make_next_nonce();
+
+		/* 5.4.  tmp = tmp XOR
+		 *             df ( ( nonce || entropy_bitstring ), n )
+		 */
+		hash_df ( &data, sizeof ( data ), df_buf, sizeof ( df_buf ) );
+		for ( i = 0 ; i < tmp_len ; i++ )
+			tmp[i] ^= df_buf[i];
+
+		/* 5.5.  entropy_total = entropy_total + assessed_entropy
+		 *
+		 * (Nothing to do; the number of entropy samples
+		 * required has already been precalculated.)
+		 */
+	}
+
+	/* Disable entropy gathering */
+	entropy_disable();
 
-	/* Placeholder to allow remainder of RBG code to be tested */
-	( void ) entropy_bits;
-	( void ) min_len;
-	memset ( data, 0x01, max_len );
+	return 0;
 
-	return max_len;
+ err_get_entropy:
+	entropy_disable();
+	return rc;
 }
diff --git a/src/crypto/null_entropy.c b/src/crypto/null_entropy.c
new file mode 100644
index 000000000..be2acae37
--- /dev/null
+++ b/src/crypto/null_entropy.c
@@ -0,0 +1,35 @@
+/*
+ * 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
+ *
+ * Nonexistent entropy source
+ *
+ *
+ * This source provides no entropy and must NOT be used in a
+ * security-sensitive environment.
+ */
+
+#include <ipxe/entropy.h>
+
+PROVIDE_ENTROPY_INLINE ( null, min_entropy_per_sample );
+PROVIDE_ENTROPY_INLINE ( null, entropy_enable );
+PROVIDE_ENTROPY_INLINE ( null, entropy_disable );
+PROVIDE_ENTROPY_INLINE ( null, get_noise );