[crypto] Add native RSA algorithm

Add an implementation of RSA that uses the iPXE big-integer support.

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

1 files changed, 600 insertions, 0 deletions

diff --git a/src/crypto/rsa.c b/src/crypto/rsa.c
new file mode 100644
index 00000000..4aba5cc3
--- /dev/null
+++ b/src/crypto/rsa.c
@@ -0,0 +1,600 @@
+/*
+ * 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 );
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#include <errno.h>
+#include <ipxe/asn1.h>
+#include <ipxe/crypto.h>
+#include <ipxe/bigint.h>
+#include <ipxe/random_nz.h>
+#include <ipxe/md5.h>
+#include <ipxe/sha1.h>
+#include <ipxe/sha256.h>
+#include <ipxe/rsa.h>
+
+/** @file
+ *
+ * RSA public-key cryptography
+ *
+ * RSA is documented in RFC 3447.
+ */
+
+/** An RSA digestInfo prefix */
+struct rsa_digestinfo_prefix {
+	/** Digest algorithm */
+	struct digest_algorithm *digest;
+	/** Prefix */
+	const void *data;
+	/** Length of prefix */
+	size_t len;
+};
+
+/** "id-md5" object identifier */
+static const uint8_t rsa_md5_prefix[] =
+	{ RSA_DIGESTINFO_PREFIX ( MD5_DIGEST_SIZE, ASN1_OID_MD5 ) };
+
+/** "id-sha1" object identifier */
+static const uint8_t rsa_sha1_prefix[] =
+	{ RSA_DIGESTINFO_PREFIX ( SHA1_DIGEST_SIZE, ASN1_OID_SHA1 ) };
+
+/** "id-sha256" object identifier */
+static const uint8_t rsa_sha256_prefix[] =
+	{ RSA_DIGESTINFO_PREFIX ( SHA256_DIGEST_SIZE, ASN1_OID_SHA256 ) };
+
+/** RSA digestInfo prefixes */
+static struct rsa_digestinfo_prefix rsa_digestinfo_prefixes[] = {
+	{
+		.digest = &md5_algorithm,
+		.data = rsa_md5_prefix,
+		.len = sizeof ( rsa_md5_prefix ),
+	},
+	{
+		.digest = &sha1_algorithm,
+		.data = rsa_sha1_prefix,
+		.len = sizeof ( rsa_sha1_prefix ),
+	},
+	{
+		.digest = &sha256_algorithm,
+		.data = rsa_sha256_prefix,
+		.len = sizeof ( rsa_sha256_prefix ),
+	},
+};
+
+/**
+ * Identify RSA prefix
+ *
+ * @v digest		Digest algorithm
+ * @ret prefix		RSA prefix, or NULL
+ */
+static struct rsa_digestinfo_prefix *
+rsa_find_prefix ( struct digest_algorithm *digest ) {
+	struct rsa_digestinfo_prefix *prefix;
+	unsigned int i;
+
+	for ( i = 0 ; i < ( sizeof ( rsa_digestinfo_prefixes ) /
+			    sizeof ( rsa_digestinfo_prefixes[0] ) ) ; i++ ) {
+		prefix = &rsa_digestinfo_prefixes[i];
+		if ( prefix->digest == digest )
+			return prefix;
+	}
+	return NULL;
+}
+
+/**
+ * Free RSA dynamic storage
+ *
+ * @v context		RSA context
+ */
+static void rsa_free ( struct rsa_context *context ) {
+
+	free ( context->dynamic );
+	context->dynamic = NULL;
+}
+
+/**
+ * Allocate RSA dynamic storage
+ *
+ * @v context		RSA context
+ * @v modulus_len	Modulus length
+ * @v exponent_len	Exponent length
+ * @ret rc		Return status code
+ */
+static int rsa_alloc ( struct rsa_context *context, size_t modulus_len,
+		       size_t exponent_len ) {
+	unsigned int size = bigint_required_size ( modulus_len );
+	unsigned int exponent_size = bigint_required_size ( exponent_len );
+	struct {
+		bigint_t ( size ) modulus;
+		bigint_t ( exponent_size ) exponent;
+		bigint_t ( size ) input;
+		bigint_t ( size ) output;
+	} __attribute__ (( packed )) *dynamic;
+
+	/* Free any existing dynamic storage */
+	rsa_free ( context );
+
+	/* Allocate dynamic storage */
+	dynamic = malloc ( sizeof ( *dynamic ) );
+	if ( ! dynamic )
+		return -ENOMEM;
+
+	/* Assign dynamic storage */
+	context->dynamic = dynamic;
+	context->modulus0 = &dynamic->modulus.element[0];
+	context->size = size;
+	context->max_len = modulus_len;
+	context->exponent0 = &dynamic->exponent.element[0];
+	context->exponent_size = exponent_size;
+	context->input0 = &dynamic->input.element[0];
+	context->output0 = &dynamic->output.element[0];
+
+	return 0;
+}
+
+/**
+ * Parse RSA integer
+ *
+ * @v context		RSA context
+ * @v integer		Integer to fill in
+ * @v raw		ASN.1 cursor
+ * @ret rc		Return status code
+ */
+static int rsa_parse_integer ( struct rsa_context *context,
+			       struct asn1_cursor *integer,
+			       const struct asn1_cursor *raw ) {
+
+	/* Enter integer */
+	memcpy ( integer, raw, sizeof ( *integer ) );
+	asn1_enter ( integer, ASN1_INTEGER );
+
+	/* Skip initial sign byte if applicable */
+	if ( ( integer->len > 1 ) &&
+	     ( *( ( uint8_t * ) integer->data ) == 0x00 ) ) {
+		integer->data++;
+		integer->len--;
+	}
+
+	/* Fail if cursor or integer are invalid */
+	if ( ! integer->len ) {
+		DBGC ( context, "RSA %p invalid integer:\n", context );
+		DBGC_HDA ( context, 0, raw->data, raw->len );
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * Initialise RSA cipher
+ *
+ * @v ctx		RSA context
+ * @v key		Key
+ * @v key_len		Length of key
+ * @ret rc		Return status code
+ */
+static int rsa_init ( void *ctx, const void *key, size_t key_len ) {
+	struct rsa_context *context = ctx;
+	const struct asn1_bit_string *bit_string;
+	struct asn1_cursor modulus;
+	struct asn1_cursor exponent;
+	struct asn1_cursor cursor;
+	int is_private;
+	int rc;
+
+	/* Initialise context */
+	memset ( context, 0, sizeof ( *context ) );
+
+	/* Initialise cursor */
+	cursor.data = key;
+	cursor.len = key_len;
+
+	/* Enter subjectPublicKeyInfo/RSAPrivateKey */
+	asn1_enter ( &cursor, ASN1_SEQUENCE );
+
+	/* Determine key format */
+	if ( asn1_type ( &cursor ) == ASN1_INTEGER ) {
+		/* Private key */
+		is_private = 1;
+
+		/* Skip version */
+		asn1_skip_any ( &cursor );
+
+	} else {
+		/* Public key */
+		is_private = 0;
+
+		/* Skip algorithm */
+		asn1_skip ( &cursor, ASN1_SEQUENCE );
+
+		/* Enter subjectPublicKey */
+		asn1_enter ( &cursor, ASN1_BIT_STRING );
+
+		/* Check and skip unused-bits byte of bit string */
+		bit_string = cursor.data;
+		if ( cursor.len < 1 ) {
+			rc = -EINVAL;
+			goto err_parse;
+		}
+		cursor.data++;
+		cursor.len--;
+
+		/* Enter RSAPublicKey */
+		asn1_enter ( &cursor, ASN1_SEQUENCE );
+	}
+
+	/* Extract modulus */
+	if ( ( rc = rsa_parse_integer ( context, &modulus, &cursor ) ) != 0 )
+		goto err_parse;
+	asn1_skip_any ( &cursor );
+
+	/* Skip public exponent, if applicable */
+	if ( is_private )
+		asn1_skip ( &cursor, ASN1_INTEGER );
+
+	/* Extract publicExponent/privateExponent */
+	if ( ( rc = rsa_parse_integer ( context, &exponent, &cursor ) ) != 0 )
+		goto err_parse;
+
+	DBGC ( context, "RSA %p modulus:\n", context );
+	DBGC_HDA ( context, 0, modulus.data, modulus.len );
+	DBGC ( context, "RSA %p exponent:\n", context );
+	DBGC_HDA ( context, 0, exponent.data, exponent.len );
+
+	/* Allocate dynamic storage */
+	if ( ( rc = rsa_alloc ( context, modulus.len, exponent.len ) ) != 0 )
+		goto err_alloc;
+
+	/* Construct big integers */
+	bigint_init ( ( ( bigint_t ( context->size ) * ) context->modulus0 ),
+		      modulus.data, modulus.len );
+	bigint_init ( ( ( bigint_t ( context->exponent_size ) * )
+			context->exponent0 ), exponent.data, exponent.len );
+
+	return 0;
+
+	rsa_free ( context );
+ err_alloc:
+ err_parse:
+	return rc;
+}
+
+/**
+ * Calculate RSA maximum output length
+ *
+ * @v ctx		RSA context
+ * @ret max_len		Maximum output length
+ */
+static size_t rsa_max_len ( void *ctx ) {
+	struct rsa_context *context = ctx;
+
+	return context->max_len;
+}
+
+/**
+ * Perform RSA cipher operation
+ *
+ * @v context		RSA context
+ * @v in		Input buffer
+ * @v out		Output buffer
+ */
+static void rsa_cipher ( struct rsa_context *context,
+			 const void *in, void *out ) {
+	bigint_t ( context->size ) *input = ( ( void * ) context->input0 );
+	bigint_t ( context->size ) *output = ( ( void * ) context->output0 );
+	bigint_t ( context->size ) *modulus = ( ( void * ) context->modulus0 );
+	bigint_t ( context->exponent_size ) *exponent =
+		( ( void * ) context->exponent0 );
+
+	/* Initialise big integer */
+	bigint_init ( input, in, context->max_len );
+
+	/* Perform modular exponentiation */
+	bigint_mod_exp ( input, modulus, exponent, output );
+
+	/* Copy out result */
+	bigint_done ( output, out, context->max_len );
+}
+
+/**
+ * Encrypt using RSA
+ *
+ * @v ctx		RSA context
+ * @v plaintext		Plaintext
+ * @v plaintext_len	Length of plaintext
+ * @v ciphertext	Ciphertext
+ * @ret ciphertext_len	Length of ciphertext, or negative error
+ */
+static int rsa_encrypt ( void *ctx, const void *plaintext,
+			 size_t plaintext_len, void *ciphertext ) {
+	struct rsa_context *context = ctx;
+	void *temp;
+	uint8_t *encoded;
+	size_t max_len = ( context->max_len - 11 );
+	size_t random_nz_len = ( max_len - plaintext_len + 8 );
+	int rc;
+
+	/* Sanity check */
+	if ( plaintext_len > max_len ) {
+		DBGC ( context, "RSA %p plaintext too long (%zd bytes, max "
+		       "%zd)\n", context, plaintext_len, max_len );
+		return -ERANGE;
+	}
+	DBGC ( context, "RSA %p encrypting:\n", context );
+	DBGC_HDA ( context, 0, plaintext, plaintext_len );
+
+	/* Construct encoded message (using the big integer output
+	 * buffer as temporary storage)
+	 */
+	temp = context->output0;
+	encoded = temp;
+	encoded[0] = 0x00;
+	encoded[1] = 0x02;
+	if ( ( rc = get_random_nz ( &encoded[2], random_nz_len ) ) != 0 ) {
+		DBGC ( context, "RSA %p could not generate random data: %s\n",
+		       context, strerror ( rc ) );
+		return rc;
+	}
+	encoded[ 2 + random_nz_len ] = 0x00;
+	memcpy ( &encoded[ context->max_len - plaintext_len ],
+		 plaintext, plaintext_len );
+
+	/* Encipher the encoded message */
+	rsa_cipher ( context, encoded, ciphertext );
+	DBGC ( context, "RSA %p encrypted:\n", context );
+	DBGC_HDA ( context, 0, ciphertext, context->max_len );
+
+	return context->max_len;
+}
+
+/**
+ * Decrypt using RSA
+ *
+ * @v ctx		RSA context
+ * @v ciphertext	Ciphertext
+ * @v ciphertext_len	Ciphertext length
+ * @v plaintext		Plaintext
+ * @ret plaintext_len	Plaintext length, or negative error
+ */
+static int rsa_decrypt ( void *ctx, const void *ciphertext,
+			 size_t ciphertext_len, void *plaintext ) {
+	struct rsa_context *context = ctx;
+	void *temp;
+	uint8_t *encoded;
+	uint8_t *end;
+	uint8_t *zero;
+	uint8_t *start;
+	size_t plaintext_len;
+
+	/* Sanity check */
+	if ( ciphertext_len != context->max_len ) {
+		DBGC ( context, "RSA %p ciphertext incorrect length (%zd "
+		       "bytes, should be %zd)\n",
+		       context, ciphertext_len, context->max_len );
+		return -ERANGE;
+	}
+	DBGC ( context, "RSA %p decrypting:\n", context );
+	DBGC_HDA ( context, 0, ciphertext, ciphertext_len );
+
+	/* Decipher the message (using the big integer input buffer as
+	 * temporary storage)
+	 */
+	temp = context->input0;
+	encoded = temp;
+	rsa_cipher ( context, ciphertext, encoded );
+
+	/* Parse the message */
+	end = ( encoded + context->max_len );
+	if ( ( encoded[0] != 0x00 ) || ( encoded[1] != 0x02 ) )
+		goto invalid;
+	zero = memchr ( &encoded[2], 0, ( end - &encoded[2] ) );
+	if ( ! zero )
+		goto invalid;
+	start = ( zero + 1 );
+	plaintext_len = ( end - start );
+
+	/* Copy out message */
+	memcpy ( plaintext, start, plaintext_len );
+	DBGC ( context, "RSA %p decrypted:\n", context );
+	DBGC_HDA ( context, 0, plaintext, plaintext_len );
+
+	return plaintext_len;
+
+ invalid:
+	DBGC ( context, "RSA %p invalid decrypted message:\n", context );
+	DBGC_HDA ( context, 0, encoded, context->max_len );
+	return -EINVAL;
+}
+
+/**
+ * Encode RSA digest
+ *
+ * @v context		RSA context
+ * @v digest		Digest algorithm
+ * @v value		Digest value
+ * @v encoded		Encoded digest
+ * @ret rc		Return status code
+ */
+static int rsa_encode_digest ( struct rsa_context *context,
+			       struct digest_algorithm *digest,
+			       const void *value, void *encoded ) {
+	struct rsa_digestinfo_prefix *prefix;
+	size_t digest_len = digest->digestsize;
+	uint8_t *temp = encoded;
+	size_t digestinfo_len;
+	size_t max_len;
+	size_t pad_len;
+
+	/* Identify prefix */
+	prefix = rsa_find_prefix ( digest );
+	if ( ! prefix ) {
+		DBGC ( context, "RSA %p has no prefix for %s\n",
+		       context, digest->name );
+		return -ENOTSUP;
+	}
+	digestinfo_len = ( prefix->len + digest_len );
+
+	/* Sanity check */
+	max_len = ( context->max_len - 11 );
+	if ( digestinfo_len > max_len ) {
+		DBGC ( context, "RSA %p %s digestInfo too long (%zd bytes, max"
+		       "%zd)\n",
+		       context, digest->name, digestinfo_len, max_len );
+		return -ERANGE;
+	}
+	DBGC ( context, "RSA %p encoding %s digest:\n",
+	       context, digest->name );
+	DBGC_HDA ( context, 0, value, digest_len );
+
+	/* Construct encoded message */
+	*(temp++) = 0x00;
+	*(temp++) = 0x01;
+	pad_len = ( max_len - digestinfo_len + 8 );
+	memset ( temp, 0xff, pad_len );
+	temp += pad_len;
+	*(temp++) = 0x00;
+	memcpy ( temp, prefix->data, prefix->len );
+	temp += prefix->len;
+	memcpy ( temp, value, digest_len );
+	temp += digest_len;
+	assert ( temp == ( encoded + context->max_len ) );
+	DBGC ( context, "RSA %p encoded %s digest:\n", context, digest->name );
+	DBGC_HDA ( context, 0, encoded, context->max_len );
+
+	return 0;
+}
+
+/**
+ * Sign digest value using RSA
+ *
+ * @v ctx		RSA context
+ * @v digest		Digest algorithm
+ * @v value		Digest value
+ * @v signature		Signature
+ * @ret signature_len	Signature length, or negative error
+ */
+static int rsa_sign ( void *ctx, struct digest_algorithm *digest,
+		      const void *value, void *signature ) {
+	struct rsa_context *context = ctx;
+	void *temp;
+	int rc;
+
+	DBGC ( context, "RSA %p signing %s digest:\n", context, digest->name );
+	DBGC_HDA ( context, 0, value, digest->digestsize );
+
+	/* Encode digest (using the big integer output buffer as
+	 * temporary storage)
+	 */
+	temp = context->output0;
+	if ( ( rc = rsa_encode_digest ( context, digest, value, temp ) ) != 0 )
+		return rc;
+
+	/* Encipher the encoded digest */
+	rsa_cipher ( context, temp, signature );
+	DBGC ( context, "RSA %p signed %s digest:\n", context, digest->name );
+	DBGC_HDA ( context, 0, signature, context->max_len );
+
+	return context->max_len;
+}
+
+/**
+ * Verify signed digest value using RSA
+ *
+ * @v ctx		RSA context
+ * @v digest		Digest algorithm
+ * @v value		Digest value
+ * @v signature		Signature
+ * @v signature_len	Signature length
+ * @ret rc		Return status code
+ */
+static int rsa_verify ( void *ctx, struct digest_algorithm *digest,
+			const void *value, const void *signature,
+			size_t signature_len ) {
+	struct rsa_context *context = ctx;
+	void *temp;
+	void *expected;
+	void *actual;
+	int rc;
+
+	/* Sanity check */
+	if ( signature_len != context->max_len ) {
+		DBGC ( context, "RSA %p signature incorrect length (%zd "
+		       "bytes, should be %zd)\n",
+		       context, signature_len, context->max_len );
+		return -ERANGE;
+	}
+	DBGC ( context, "RSA %p verifying %s digest:\n",
+	       context, digest->name );
+	DBGC_HDA ( context, 0, value, digest->digestsize );
+	DBGC_HDA ( context, 0, signature, signature_len );
+
+	/* Decipher the signature (using the big integer input buffer
+	 * as temporary storage)
+	 */
+	temp = context->input0;
+	expected = temp;
+	rsa_cipher ( context, signature, expected );
+	DBGC ( context, "RSA %p deciphered signature:\n", context );
+	DBGC_HDA ( context, 0, expected, context->max_len );
+
+	/* Encode digest (using the big integer output buffer as
+	 * temporary storage)
+	 */
+	temp = context->output0;
+	actual = temp;
+	if ( ( rc = rsa_encode_digest ( context, digest, value, actual ) ) !=0 )
+		return rc;
+
+	/* Verify the signature */
+	if ( memcmp ( actual, expected, context->max_len ) != 0 ) {
+		DBGC ( context, "RSA %p signature verification failed\n",
+		       context );
+		return -EACCES;
+	}
+
+	DBGC ( context, "RSA %p signature verified successfully\n", context );
+	return 0;
+}
+
+/**
+ * Finalise RSA cipher
+ *
+ * @v ctx		RSA context
+ */
+static void rsa_final ( void *ctx ) {
+	struct rsa_context *context = ctx;
+
+	rsa_free ( context );
+}
+
+/** RSA public-key algorithm */
+struct pubkey_algorithm rsa_algorithm = {
+	.name		= "rsa",
+	.ctxsize	= sizeof ( struct rsa_context ),
+	.init		= rsa_init,
+	.max_len	= rsa_max_len,
+	.encrypt	= rsa_encrypt,
+	.decrypt	= rsa_decrypt,
+	.sign		= rsa_sign,
+	.verify		= rsa_verify,
+	.final		= rsa_final,
+};