PKCS#7: Implement a parser [RFC 2315]

Implement a parser for a PKCS#7 signed-data message as described in part of
RFC 2315.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>

crypto/asymmetric_keys/Kconfig

@@ -37,4 +37,13 @@ config X509_CERTIFICATE_PARSER
 	  data and provides the ability to instantiate a crypto key from a
 	  public key packet found inside the certificate.
 
+config PKCS7_MESSAGE_PARSER
+	tristate "PKCS#7 message parser"
+	depends on X509_CERTIFICATE_PARSER
+	select ASN1
+	select OID_REGISTRY
+	help
+	  This option provides support for parsing PKCS#7 format messages for
+	  signature data and provides the ability to verify the signature.
+
 endif # ASYMMETRIC_KEY_TYPE

crypto/asymmetric_keys/Makefile

@@ -25,3 +25,16 @@ $(obj)/x509_rsakey-asn1.o: $(obj)/x509_rsakey-asn1.c $(obj)/x509_rsakey-asn1.h
 
 clean-files	+= x509-asn1.c x509-asn1.h
 clean-files	+= x509_rsakey-asn1.c x509_rsakey-asn1.h
+
+#
+# PKCS#7 message handling
+#
+obj-$(CONFIG_PKCS7_MESSAGE_PARSER) += pkcs7_message.o
+pkcs7_message-y := \
+	pkcs7-asn1.o \
+	pkcs7_parser.o
+
+$(obj)/pkcs7_parser.o: $(obj)/pkcs7-asn1.h
+$(obj)/pkcs7-asn1.o: $(obj)/pkcs7-asn1.c $(obj)/pkcs7-asn1.h
+
+clean-files	+= pkcs7-asn1.c pkcs7-asn1.h

crypto/asymmetric_keys/pkcs7.asn1

+PKCS7ContentInfo ::= SEQUENCE {
+	contentType	ContentType,
+	content		[0] EXPLICIT SignedData OPTIONAL
+}
+
+ContentType ::= OBJECT IDENTIFIER ({ pkcs7_note_OID })
+
+SignedData ::= SEQUENCE {
+	version			INTEGER,
+	digestAlgorithms	DigestAlgorithmIdentifiers,
+	contentInfo		ContentInfo,
+	certificates		CHOICE {
+		certSet		[0] IMPLICIT ExtendedCertificatesAndCertificates,
+		certSequence	[2] IMPLICIT Certificates
+	} OPTIONAL ({ pkcs7_note_certificate_list }),
+	crls CHOICE {
+		crlSet		[1] IMPLICIT CertificateRevocationLists,
+		crlSequence	[3] IMPLICIT CRLSequence
+	} OPTIONAL,
+	signerInfos		SignerInfos
+}
+
+ContentInfo ::= SEQUENCE {
+	contentType	ContentType,
+	content		[0] EXPLICIT Data OPTIONAL
+}
+
+Data ::= ANY ({ pkcs7_note_data })
+
+DigestAlgorithmIdentifiers ::= CHOICE {
+	daSet			SET OF DigestAlgorithmIdentifier,
+	daSequence		SEQUENCE OF DigestAlgorithmIdentifier
+}
+
+DigestAlgorithmIdentifier ::= SEQUENCE {
+	algorithm   OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+	parameters  ANY OPTIONAL
+}
+
+--
+-- Certificates and certificate lists
+--
+ExtendedCertificatesAndCertificates ::= SET OF ExtendedCertificateOrCertificate
+
+ExtendedCertificateOrCertificate ::= CHOICE {
+  certificate		Certificate,				-- X.509
+  extendedCertificate	[0] IMPLICIT ExtendedCertificate	-- PKCS#6
+}
+
+ExtendedCertificate ::= Certificate -- cheating
+
+Certificates ::= SEQUENCE OF Certificate
+
+CertificateRevocationLists ::= SET OF CertificateList
+
+CertificateList ::= SEQUENCE OF Certificate -- This may be defined incorrectly
+
+CRLSequence ::= SEQUENCE OF CertificateList
+
+Certificate ::= ANY ({ pkcs7_extract_cert }) -- X.509
+
+--
+-- Signer information
+--
+SignerInfos ::= CHOICE {
+	siSet		SET OF SignerInfo,
+	siSequence	SEQUENCE OF SignerInfo
+}
+
+SignerInfo ::= SEQUENCE {
+	version			INTEGER,
+	issuerAndSerialNumber	IssuerAndSerialNumber,
+	digestAlgorithm		DigestAlgorithmIdentifier ({ pkcs7_sig_note_digest_algo }),
+	authenticatedAttributes	CHOICE {
+		aaSet		[0] IMPLICIT SetOfAuthenticatedAttribute
+					({ pkcs7_sig_note_set_of_authattrs }),
+		aaSequence	[2] EXPLICIT SEQUENCE OF AuthenticatedAttribute
+			-- Explicit because easier to compute digest on
+			-- sequence of attributes and then reuse encoded
+			-- sequence in aaSequence.
+	} OPTIONAL,
+	digestEncryptionAlgorithm
+				DigestEncryptionAlgorithmIdentifier ({ pkcs7_sig_note_pkey_algo }),
+	encryptedDigest		EncryptedDigest,
+	unauthenticatedAttributes CHOICE {
+		uaSet		[1] IMPLICIT SET OF UnauthenticatedAttribute,
+		uaSequence	[3] IMPLICIT SEQUENCE OF UnauthenticatedAttribute
+	} OPTIONAL
+} ({ pkcs7_note_signed_info })
+
+IssuerAndSerialNumber ::= SEQUENCE {
+	issuer			Name ({ pkcs7_sig_note_issuer }),
+	serialNumber		CertificateSerialNumber ({ pkcs7_sig_note_serial })
+}
+
+CertificateSerialNumber ::= INTEGER
+
+SetOfAuthenticatedAttribute ::= SET OF AuthenticatedAttribute
+
+AuthenticatedAttribute ::= SEQUENCE {
+	type			OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+	values			SET OF ANY ({ pkcs7_sig_note_authenticated_attr })
+}
+
+UnauthenticatedAttribute ::= SEQUENCE {
+	type			OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+	values			SET OF ANY
+}
+
+DigestEncryptionAlgorithmIdentifier ::= SEQUENCE {
+	algorithm		OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+	parameters		ANY OPTIONAL
+}
+
+EncryptedDigest ::= OCTET STRING ({ pkcs7_sig_note_signature })
+
+---
+--- X.500 Name
+---
+Name ::= SEQUENCE OF RelativeDistinguishedName
+
+RelativeDistinguishedName ::= SET OF AttributeValueAssertion
+
+AttributeValueAssertion ::= SEQUENCE {
+	attributeType		OBJECT IDENTIFIER ({ pkcs7_note_OID }),
+	attributeValue		ANY
+}

crypto/asymmetric_keys/pkcs7_parser.h

+/* PKCS#7 crypto data parser internal definitions
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/oid_registry.h>
+#include <crypto/pkcs7.h>
+#include "x509_parser.h"
+
+#define kenter(FMT, ...) \
+	pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+	pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
+
+struct pkcs7_signed_info {
+	struct pkcs7_signed_info *next;
+	struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
+	unsigned index;
+	bool trusted;
+
+	/* Message digest - the digest of the Content Data (or NULL) */
+	const void	*msgdigest;
+	unsigned	msgdigest_len;
+
+	/* Authenticated Attribute data (or NULL) */
+	unsigned	authattrs_len;
+	const void	*authattrs;
+
+	/* Issuing cert serial number and issuer's name */
+	const void	*raw_serial;
+	unsigned	raw_serial_size;
+	unsigned	raw_issuer_size;
+	const void	*raw_issuer;
+
+	/* Message signature.
+	 *
+	 * This contains the generated digest of _either_ the Content Data or
+	 * the Authenticated Attributes [RFC2315 9.3].  If the latter, one of
+	 * the attributes contains the digest of the the Content Data within
+	 * it.
+	 */
+	struct public_key_signature sig;
+};
+
+struct pkcs7_message {
+	struct x509_certificate *certs;	/* Certificate list */
+	struct x509_certificate *crl;	/* Revocation list */
+	struct pkcs7_signed_info *signed_infos;
+
+	/* Content Data (or NULL) */
+	enum OID	data_type;	/* Type of Data */
+	size_t		data_len;	/* Length of Data */
+	size_t		data_hdrlen;	/* Length of Data ASN.1 header */
+	const void	*data;		/* Content Data (or 0) */
+};

include/crypto/pkcs7.h

+/* PKCS#7 crypto data parser
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+struct pkcs7_message;
+
+/*
+ * pkcs7_parser.c
+ */
+extern struct pkcs7_message *pkcs7_parse_message(const void *data,
+						 size_t datalen);
+extern void pkcs7_free_message(struct pkcs7_message *pkcs7);
+
+extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
+				  const void **_data, size_t *_datalen,
+				  bool want_wrapper);

include/linux/oid_registry.h

@@ -55,6 +55,7 @@ enum OID {
 	OID_certAuthInfoAccess,		/* 1.3.6.1.5.5.7.1.1 */
 	OID_msOutlookExpress,		/* 1.3.6.1.4.1.311.16.4 */
 	OID_sha1,			/* 1.3.14.3.2.26 */
+	OID_sha256,			/* 2.16.840.1.101.3.4.2.1 */
 
 	/* Distinguished Name attribute IDs [RFC 2256] */
 	OID_commonName,			/* 2.5.4.3 */