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

@@ -0,0 +1,127 @@
+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.c

@@ -0,0 +1,396 @@
+/* PKCS#7 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.
+ */
+
+#define pr_fmt(fmt) "PKCS7: "fmt
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/oid_registry.h>
+#include "public_key.h"
+#include "pkcs7_parser.h"
+#include "pkcs7-asn1.h"
+
+struct pkcs7_parse_context {
+	struct pkcs7_message	*msg;		/* Message being constructed */
+	struct pkcs7_signed_info *sinfo;	/* SignedInfo being constructed */
+	struct pkcs7_signed_info **ppsinfo;
+	struct x509_certificate *certs;		/* Certificate cache */
+	struct x509_certificate **ppcerts;
+	unsigned long	data;			/* Start of data */
+	enum OID	last_oid;		/* Last OID encountered */
+	unsigned	x509_index;
+	unsigned	sinfo_index;
+};
+
+/**
+ * pkcs7_free_message - Free a PKCS#7 message
+ * @pkcs7: The PKCS#7 message to free
+ */
+void pkcs7_free_message(struct pkcs7_message *pkcs7)
+{
+	struct x509_certificate *cert;
+	struct pkcs7_signed_info *sinfo;
+
+	if (pkcs7) {
+		while (pkcs7->certs) {
+			cert = pkcs7->certs;
+			pkcs7->certs = cert->next;
+			x509_free_certificate(cert);
+		}
+		while (pkcs7->crl) {
+			cert = pkcs7->crl;
+			pkcs7->crl = cert->next;
+			x509_free_certificate(cert);
+		}
+		while (pkcs7->signed_infos) {
+			sinfo = pkcs7->signed_infos;
+			pkcs7->signed_infos = sinfo->next;
+			mpi_free(sinfo->sig.mpi[0]);
+			kfree(sinfo->sig.digest);
+			kfree(sinfo);
+		}
+		kfree(pkcs7);
+	}
+}
+EXPORT_SYMBOL_GPL(pkcs7_free_message);
+
+/**
+ * pkcs7_parse_message - Parse a PKCS#7 message
+ * @data: The raw binary ASN.1 encoded message to be parsed
+ * @datalen: The size of the encoded message
+ */
+struct pkcs7_message *pkcs7_parse_message(const void *data, size_t datalen)
+{
+	struct pkcs7_parse_context *ctx;
+	struct pkcs7_message *msg;
+	long ret;
+
+	ret = -ENOMEM;
+	msg = kzalloc(sizeof(struct pkcs7_message), GFP_KERNEL);
+	if (!msg)
+		goto error_no_sig;
+	ctx = kzalloc(sizeof(struct pkcs7_parse_context), GFP_KERNEL);
+	if (!ctx)
+		goto error_no_ctx;
+	ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
+	if (!ctx->sinfo)
+		goto error_no_sinfo;
+
+	ctx->msg = msg;
+	ctx->data = (unsigned long)data;
+	ctx->ppcerts = &ctx->certs;
+	ctx->ppsinfo = &ctx->msg->signed_infos;
+
+	/* Attempt to decode the signature */
+	ret = asn1_ber_decoder(&pkcs7_decoder, ctx, data, datalen);
+	if (ret < 0)
+		goto error_decode;
+
+	while (ctx->certs) {
+		struct x509_certificate *cert = ctx->certs;
+		ctx->certs = cert->next;
+		x509_free_certificate(cert);
+	}
+	mpi_free(ctx->sinfo->sig.mpi[0]);
+	kfree(ctx->sinfo->sig.digest);
+	kfree(ctx->sinfo);
+	kfree(ctx);
+	return msg;
+
+error_decode:
+	mpi_free(ctx->sinfo->sig.mpi[0]);
+	kfree(ctx->sinfo->sig.digest);
+	kfree(ctx->sinfo);
+error_no_sinfo:
+	kfree(ctx);
+error_no_ctx:
+	pkcs7_free_message(msg);
+error_no_sig:
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(pkcs7_parse_message);
+
+/**
+ * pkcs7_get_content_data - Get access to the PKCS#7 content
+ * @pkcs7: The preparsed PKCS#7 message to access
+ * @_data: Place to return a pointer to the data
+ * @_data_len: Place to return the data length
+ * @want_wrapper: True if the ASN.1 object header should be included in the data
+ *
+ * Get access to the data content of the PKCS#7 message, including, optionally,
+ * the header of the ASN.1 object that contains it.  Returns -ENODATA if the
+ * data object was missing from the message.
+ */
+int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
+			   const void **_data, size_t *_data_len,
+			   bool want_wrapper)
+{
+	size_t wrapper;
+
+	if (!pkcs7->data)
+		return -ENODATA;
+
+	wrapper = want_wrapper ? pkcs7->data_hdrlen : 0;
+	*_data = pkcs7->data - wrapper;
+	*_data_len = pkcs7->data_len + wrapper;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pkcs7_get_content_data);
+
+/*
+ * Note an OID when we find one for later processing when we know how
+ * to interpret it.
+ */
+int pkcs7_note_OID(void *context, size_t hdrlen,
+		   unsigned char tag,
+		   const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	ctx->last_oid = look_up_OID(value, vlen);
+	if (ctx->last_oid == OID__NR) {
+		char buffer[50];
+		sprint_oid(value, vlen, buffer, sizeof(buffer));
+		printk("PKCS7: Unknown OID: [%lu] %s\n",
+		       (unsigned long)value - ctx->data, buffer);
+	}
+	return 0;
+}
+
+/*
+ * Note the digest algorithm for the signature.
+ */
+int pkcs7_sig_note_digest_algo(void *context, size_t hdrlen,
+			       unsigned char tag,
+			       const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	switch (ctx->last_oid) {
+	case OID_md4:
+		ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_MD4;
+		break;
+	case OID_md5:
+		ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_MD5;
+		break;
+	case OID_sha1:
+		ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_SHA1;
+		break;
+	case OID_sha256:
+		ctx->sinfo->sig.pkey_hash_algo = HASH_ALGO_SHA256;
+		break;
+	default:
+		printk("Unsupported digest algo: %u\n", ctx->last_oid);
+		return -ENOPKG;
+	}
+	return 0;
+}
+
+/*
+ * Note the public key algorithm for the signature.
+ */
+int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
+			     unsigned char tag,
+			     const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	switch (ctx->last_oid) {
+	case OID_rsaEncryption:
+		ctx->sinfo->sig.pkey_algo = PKEY_ALGO_RSA;
+		break;
+	default:
+		printk("Unsupported pkey algo: %u\n", ctx->last_oid);
+		return -ENOPKG;
+	}
+	return 0;
+}
+
+/*
+ * Extract a certificate and store it in the context.
+ */
+int pkcs7_extract_cert(void *context, size_t hdrlen,
+		       unsigned char tag,
+		       const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+	struct x509_certificate *x509;
+
+	if (tag != ((ASN1_UNIV << 6) | ASN1_CONS_BIT | ASN1_SEQ)) {
+		pr_debug("Cert began with tag %02x at %lu\n",
+			 tag, (unsigned long)ctx - ctx->data);
+		return -EBADMSG;
+	}
+
+	/* We have to correct for the header so that the X.509 parser can start
+	 * from the beginning.  Note that since X.509 stipulates DER, there
+	 * probably shouldn't be an EOC trailer - but it is in PKCS#7 (which
+	 * stipulates BER).
+	 */
+	value -= hdrlen;
+	vlen += hdrlen;
+
+	if (((u8*)value)[1] == 0x80)
+		vlen += 2; /* Indefinite length - there should be an EOC */
+
+	x509 = x509_cert_parse(value, vlen);
+	if (IS_ERR(x509))
+		return PTR_ERR(x509);
+
+	pr_debug("Got cert for %s\n", x509->subject);
+	pr_debug("- fingerprint %s\n", x509->fingerprint);
+
+	x509->index = ++ctx->x509_index;
+	*ctx->ppcerts = x509;
+	ctx->ppcerts = &x509->next;
+	return 0;
+}
+
+/*
+ * Save the certificate list
+ */
+int pkcs7_note_certificate_list(void *context, size_t hdrlen,
+				unsigned char tag,
+				const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	pr_devel("Got cert list (%02x)\n", tag);
+
+	*ctx->ppcerts = ctx->msg->certs;
+	ctx->msg->certs = ctx->certs;
+	ctx->certs = NULL;
+	ctx->ppcerts = &ctx->certs;
+	return 0;
+}
+
+/*
+ * Extract the data from the message and store that and its content type OID in
+ * the context.
+ */
+int pkcs7_note_data(void *context, size_t hdrlen,
+		    unsigned char tag,
+		    const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	pr_debug("Got data\n");
+
+	ctx->msg->data = value;
+	ctx->msg->data_len = vlen;
+	ctx->msg->data_hdrlen = hdrlen;
+	ctx->msg->data_type = ctx->last_oid;
+	return 0;
+}
+
+/*
+ * Parse authenticated attributes
+ */
+int pkcs7_sig_note_authenticated_attr(void *context, size_t hdrlen,
+				      unsigned char tag,
+				      const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	pr_devel("AuthAttr: %02x %zu [%*ph]\n", tag, vlen, (unsigned)vlen, value);
+
+	switch (ctx->last_oid) {
+	case OID_messageDigest:
+		if (tag != ASN1_OTS)
+			return -EBADMSG;
+		ctx->sinfo->msgdigest = value;
+		ctx->sinfo->msgdigest_len = vlen;
+		return 0;
+	default:
+		return 0;
+	}
+}
+
+/*
+ * Note the set of auth attributes for digestion purposes [RFC2315 9.3]
+ */
+int pkcs7_sig_note_set_of_authattrs(void *context, size_t hdrlen,
+				    unsigned char tag,
+				    const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	/* We need to switch the 'CONT 0' to a 'SET OF' when we digest */
+	ctx->sinfo->authattrs = value - (hdrlen - 1);
+	ctx->sinfo->authattrs_len = vlen + (hdrlen - 1);
+	return 0;
+}
+
+/*
+ * Note the issuing certificate serial number
+ */
+int pkcs7_sig_note_serial(void *context, size_t hdrlen,
+			  unsigned char tag,
+			  const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+	ctx->sinfo->raw_serial = value;
+	ctx->sinfo->raw_serial_size = vlen;
+	return 0;
+}
+
+/*
+ * Note the issuer's name
+ */
+int pkcs7_sig_note_issuer(void *context, size_t hdrlen,
+			  unsigned char tag,
+			  const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+	ctx->sinfo->raw_issuer = value;
+	ctx->sinfo->raw_issuer_size = vlen;
+	return 0;
+}
+
+/*
+ * Note the signature data
+ */
+int pkcs7_sig_note_signature(void *context, size_t hdrlen,
+			     unsigned char tag,
+			     const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+	MPI mpi;
+
+	BUG_ON(ctx->sinfo->sig.pkey_algo != PKEY_ALGO_RSA);
+
+	mpi = mpi_read_raw_data(value, vlen);
+	if (!mpi)
+		return -ENOMEM;
+
+	ctx->sinfo->sig.mpi[0] = mpi;
+	ctx->sinfo->sig.nr_mpi = 1;
+	return 0;
+}
+
+/*
+ * Note a signature information block
+ */
+int pkcs7_note_signed_info(void *context, size_t hdrlen,
+			   unsigned char tag,
+			   const void *value, size_t vlen)
+{
+	struct pkcs7_parse_context *ctx = context;
+
+	ctx->sinfo->index = ++ctx->sinfo_index;
+	*ctx->ppsinfo = ctx->sinfo;
+	ctx->ppsinfo = &ctx->sinfo->next;
+	ctx->sinfo = kzalloc(sizeof(struct pkcs7_signed_info), GFP_KERNEL);
+	if (!ctx->sinfo)
+		return -ENOMEM;
+	return 0;
+}

crypto/asymmetric_keys/pkcs7_parser.h

@@ -0,0 +1,61 @@
+/* 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

@@ -0,0 +1,23 @@
+/* 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 */