Implement PKCS#7 enveloped-data parsing and decryption

4 files changed, 434 insertions, 0 deletions

diff --git a/src/libstrongswan/plugins/pkcs7/Makefile.am b/src/libstrongswan/plugins/pkcs7/Makefile.am
index f023deddc..944f22cec 100644
--- a/src/libstrongswan/plugins/pkcs7/Makefile.am
+++ b/src/libstrongswan/plugins/pkcs7/Makefile.am
@@ -12,6 +12,7 @@ endif
 libstrongswan_pkcs7_la_SOURCES = \
 	pkcs7_generic.h pkcs7_generic.c \
 	pkcs7_signed_data.h pkcs7_signed_data.c \
+	pkcs7_enveloped_data.h pkcs7_enveloped_data.c \
 	pkcs7_data.h pkcs7_data.c \
 	pkcs7_plugin.h pkcs7_plugin.c
 
diff --git a/src/libstrongswan/plugins/pkcs7/pkcs7_enveloped_data.c b/src/libstrongswan/plugins/pkcs7/pkcs7_enveloped_data.c
new file mode 100644
index 000000000..2df37414f
--- /dev/null
+++ b/src/libstrongswan/plugins/pkcs7/pkcs7_enveloped_data.c
@@ -0,0 +1,394 @@
+/*
+ * Copyright (C) 2012 Martin Willi
+ * Copyright (C) 2012 revosec AG
+ * Copyright (C) 2012 Tobias Brunner
+ * Copyright (C) 2002-2008 Andreas Steffen
+ * Copyright (C) 2005 Jan Hutter, Martin Willi
+ * Hochschule fuer Technik Rapperswil, Switzerland
+ *
+ * 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 (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ */
+
+#include "pkcs7_enveloped_data.h"
+
+#include <asn1/asn1.h>
+#include <asn1/asn1_parser.h>
+#include <asn1/oid.h>
+#include <credentials/certificates/x509.h>
+#include <utils/debug.h>
+
+typedef struct private_pkcs7_enveloped_data_t private_pkcs7_enveloped_data_t;
+
+/**
+ * Private data of a PKCS#7 signed-data container.
+ */
+struct private_pkcs7_enveloped_data_t {
+
+	/**
+	 * Implements pkcs7_t.
+	 */
+	pkcs7_t public;
+
+	/**
+	 * Decrypted content
+	 */
+	chunk_t content;
+
+	/**
+	 * Encrypted and encoded PKCS#7 enveloped-data
+	 */
+	chunk_t encoding;
+};
+
+/**
+ * ASN.1 definition of the PKCS#7 envelopedData type
+ */
+static const asn1Object_t envelopedDataObjects[] = {
+	{ 0, "envelopedData",					ASN1_SEQUENCE,		ASN1_NONE }, /*  0 */
+	{ 1,   "version",						ASN1_INTEGER, 		ASN1_BODY }, /*  1 */
+	{ 1,   "recipientInfos",				ASN1_SET,    		ASN1_LOOP }, /*  2 */
+	{ 2,     "recipientInfo",				ASN1_SEQUENCE, 		ASN1_BODY }, /*  3 */
+	{ 3,       "version",					ASN1_INTEGER, 		ASN1_BODY }, /*  4 */
+	{ 3,       "issuerAndSerialNumber",		ASN1_SEQUENCE,		ASN1_BODY }, /*  5 */
+	{ 4,         "issuer",					ASN1_SEQUENCE,		ASN1_OBJ  }, /*  6 */
+	{ 4,         "serial",					ASN1_INTEGER,		ASN1_BODY }, /*  7 */
+	{ 3,       "encryptionAlgorithm",		ASN1_EOC,			ASN1_RAW  }, /*  8 */
+	{ 3,       "encryptedKey",				ASN1_OCTET_STRING,	ASN1_BODY }, /*  9 */
+	{ 1,   "end loop",						ASN1_EOC,			ASN1_END  }, /* 10 */
+	{ 1,   "encryptedContentInfo",			ASN1_SEQUENCE,		ASN1_OBJ  }, /* 11 */
+	{ 2,     "contentType",					ASN1_OID,			ASN1_BODY }, /* 12 */
+	{ 2,     "contentEncryptionAlgorithm",	ASN1_EOC,			ASN1_RAW  }, /* 13 */
+	{ 2,     "encryptedContent",			ASN1_CONTEXT_S_0, 	ASN1_BODY }, /* 14 */
+	{ 0, "exit",							ASN1_EOC,			ASN1_EXIT }
+};
+#define PKCS7_VERSION					 1
+#define PKCS7_RECIPIENT_INFO_VERSION	 4
+#define PKCS7_ISSUER					 6
+#define PKCS7_SERIAL_NUMBER				 7
+#define PKCS7_ENCRYPTION_ALG			 8
+#define PKCS7_ENCRYPTED_KEY				 9
+#define PKCS7_CONTENT_TYPE				12
+#define PKCS7_CONTENT_ENC_ALGORITHM		13
+#define PKCS7_ENCRYPTED_CONTENT			14
+
+/**
+ * Find a private key for issuerAndSerialNumber
+ */
+static private_key_t *find_private(identification_t *issuer,
+								   identification_t *serial)
+{
+	enumerator_t *enumerator;
+	certificate_t *cert;
+	public_key_t *public;
+	private_key_t *private = NULL;
+	identification_t *id;
+	chunk_t fp;
+
+	enumerator = lib->credmgr->create_cert_enumerator(lib->credmgr,
+											CERT_X509, KEY_RSA, serial, FALSE);
+	while (enumerator->enumerate(enumerator, &cert))
+	{
+		if (issuer->equals(issuer, cert->get_issuer(cert)))
+		{
+			public = cert->get_public_key(cert);
+			if (public)
+			{
+				if (public->get_fingerprint(public, KEYID_PUBKEY_SHA1, &fp))
+				{
+					id = identification_create_from_encoding(ID_KEY_ID, fp);
+					private = lib->credmgr->get_private(lib->credmgr,
+														KEY_ANY, id, NULL);
+					id->destroy(id);
+				}
+				public->destroy(public);
+			}
+		}
+		if (private)
+		{
+			break;
+		}
+	}
+	enumerator->destroy(enumerator);
+	return private;
+}
+
+/**
+ * Decrypt content using a private key from "issuer"
+ */
+static bool decrypt(private_key_t *private, chunk_t key, chunk_t iv, int oid,
+					chunk_t encrypted, chunk_t *plain)
+{
+	encryption_algorithm_t alg;
+	chunk_t plain_key;
+	crypter_t *crypter;
+	size_t key_size;
+
+	alg = encryption_algorithm_from_oid(oid, &key_size);
+	if (alg == ENCR_UNDEFINED)
+	{
+		DBG1(DBG_LIB, "unsupported content encryption algorithm");
+		return FALSE;
+	}
+	if (!private->decrypt(private, ENCRYPT_RSA_PKCS1, key, &plain_key))
+	{
+		DBG1(DBG_LIB, "symmetric key could not be decrypted with rsa");
+		return FALSE;
+	}
+	crypter = lib->crypto->create_crypter(lib->crypto, alg, key_size / 8);
+	if (!crypter)
+	{
+		DBG1(DBG_LIB, "crypter %N-%d not available",
+			 encryption_algorithm_names, alg, key_size);
+		free(plain_key.ptr);
+		return FALSE;
+	}
+	if (plain_key.len != crypter->get_key_size(crypter))
+	{
+		DBG1(DBG_LIB, "symmetric key length %d is wrong", plain_key.len);
+		free(plain_key.ptr);
+		crypter->destroy(crypter);
+		return FALSE;
+	}
+	if (iv.len != crypter->get_iv_size(crypter))
+	{
+		DBG1(DBG_LIB, "IV length %d is wrong", iv.len);
+		free(plain_key.ptr);
+		crypter->destroy(crypter);
+		return FALSE;
+	}
+	if (!crypter->set_key(crypter, plain_key) ||
+		!crypter->decrypt(crypter, encrypted, iv, plain))
+	{
+		free(plain_key.ptr);
+		crypter->destroy(crypter);
+		return FALSE;
+	}
+	DBG4(DBG_LIB, "decrypted content with padding: %B", plain);
+	free(plain_key.ptr);
+	crypter->destroy(crypter);
+	return TRUE;
+}
+
+/**
+ * Remove the padding from plain data
+ */
+static bool remove_padding(private_pkcs7_enveloped_data_t *this)
+{
+	u_char *pos = this->content.ptr + this->content.len - 1;
+	u_char pattern = *pos;
+	size_t padding = pattern;
+
+	if (padding > this->content.len)
+	{
+		DBG1(DBG_LIB, "padding greater than data length");
+		return FALSE;
+	}
+	this->content.len -= padding;
+
+	while (padding-- > 0)
+	{
+		if (*pos-- != pattern)
+		{
+			DBG1(DBG_LIB, "wrong padding pattern");
+			return FALSE;
+		}
+	}
+	return TRUE;
+}
+
+/**
+ * Parse and decrypt enveloped-data
+ */
+static bool parse(private_pkcs7_enveloped_data_t *this, chunk_t content)
+{
+	asn1_parser_t *parser;
+	chunk_t object;
+	int objectID, version, alg = OID_UNKNOWN;
+	bool success = FALSE;
+	identification_t *issuer = NULL, *serial = NULL;
+	private_key_t *private = NULL;
+	chunk_t iv = chunk_empty, key = chunk_empty, encrypted = chunk_empty;
+
+	parser = asn1_parser_create(envelopedDataObjects, content);
+	parser->set_top_level(parser, 0);
+
+	while (parser->iterate(parser, &objectID, &object))
+	{
+		u_int level = parser->get_level(parser);
+
+		switch (objectID)
+		{
+			case PKCS7_VERSION:
+				version = object.len ? (int)*object.ptr : 0;
+				DBG2(DBG_LIB, "  v%d", version);
+				if (version != 0)
+				{
+					DBG1(DBG_LIB, "envelopedData version is not 0");
+					goto end;
+				}
+				break;
+			case PKCS7_RECIPIENT_INFO_VERSION:
+				version = object.len ? (int)*object.ptr : 0;
+				DBG2(DBG_LIB, "  v%d", version);
+				if (version != 0)
+				{
+					DBG1(DBG_LIB, "recipient info version is not 0");
+					goto end;
+				}
+				break;
+			case PKCS7_ISSUER:
+				if (!issuer)
+				{
+					issuer = identification_create_from_encoding(ID_DER_ASN1_DN,
+																 object);
+				}
+				break;
+			case PKCS7_SERIAL_NUMBER:
+				if (!serial)
+				{
+					serial = identification_create_from_encoding(ID_KEY_ID,
+																 object);
+				}
+				break;
+			case PKCS7_ENCRYPTION_ALG:
+				if (asn1_parse_algorithmIdentifier(object, level,
+												   NULL) != OID_RSA_ENCRYPTION)
+				{
+					DBG1(DBG_LIB, "only rsa encryption supported");
+					goto end;
+				}
+				break;
+			case PKCS7_ENCRYPTED_KEY:
+				key = object;
+				break;
+			case PKCS7_CONTENT_TYPE:
+				if (asn1_known_oid(object) != OID_PKCS7_DATA)
+				{
+					DBG1(DBG_LIB, "encrypted content not of type pkcs7 data");
+					goto end;
+				}
+				break;
+			case PKCS7_CONTENT_ENC_ALGORITHM:
+				alg = asn1_parse_algorithmIdentifier(object, level, &iv);
+				if (!asn1_parse_simple_object(&iv, ASN1_OCTET_STRING,
+											  level + 1, "IV"))
+				{
+					DBG1(DBG_LIB, "IV could not be parsed");
+					goto end;
+				}
+				break;
+			case PKCS7_ENCRYPTED_CONTENT:
+				encrypted = object;
+				break;
+		}
+	}
+	success = parser->success(parser);
+
+end:
+	parser->destroy(parser);
+	if (!success)
+	{
+		goto failed;
+	}
+	success = FALSE;
+	if (!issuer)
+	{
+		goto failed;
+	}
+	private = find_private(issuer, serial);
+	if (!private)
+	{
+		DBG1(DBG_LIB, "no private key found to decrypt pkcs7");
+		goto failed;
+	}
+	if (!decrypt(private, key, iv, alg, encrypted, &this->content))
+	{
+		goto failed;
+	}
+	if (!remove_padding(this))
+	{
+		goto failed;
+	}
+
+	success = TRUE;
+failed:
+	DESTROY_IF(issuer);
+	DESTROY_IF(serial);
+	DESTROY_IF(private);
+	return success;
+}
+
+METHOD(container_t, get_type, container_type_t,
+	private_pkcs7_enveloped_data_t *this)
+{
+	return CONTAINER_PKCS7_ENVELOPED_DATA;
+}
+
+METHOD(container_t, create_signature_enumerator, enumerator_t*,
+	private_pkcs7_enveloped_data_t *this)
+{
+	return enumerator_create_empty();
+}
+
+METHOD(container_t, get_data, bool,
+	private_pkcs7_enveloped_data_t *this, chunk_t *data)
+{
+	if (this->content.len)
+	{
+		*data = chunk_clone(this->content);
+		return TRUE;
+	}
+	return FALSE;
+}
+
+METHOD(container_t, get_encoding, bool,
+	private_pkcs7_enveloped_data_t *this, chunk_t *data)
+{
+	*data = chunk_clone(this->encoding);
+	return TRUE;
+}
+
+METHOD(container_t, destroy, void,
+	private_pkcs7_enveloped_data_t *this)
+{
+	free(this->content.ptr);
+	free(this->encoding.ptr);
+	free(this);
+}
+
+/**
+ * See header.
+ */
+pkcs7_t *pkcs7_enveloped_data_load(chunk_t encoding, chunk_t content)
+{
+	private_pkcs7_enveloped_data_t *this;
+
+	INIT(this,
+		.public = {
+			.container = {
+				.get_type = _get_type,
+				.create_signature_enumerator = _create_signature_enumerator,
+				.get_data = _get_data,
+				.get_encoding = _get_encoding,
+				.destroy = _destroy,
+			},
+		},
+		.encoding = chunk_clone(encoding),
+	);
+
+	if (!parse(this, content))
+	{
+		destroy(this);
+		return NULL;
+	}
+
+	return &this->public;
+}
diff --git a/src/libstrongswan/plugins/pkcs7/pkcs7_enveloped_data.h b/src/libstrongswan/plugins/pkcs7/pkcs7_enveloped_data.h
new file mode 100644
index 000000000..917560969
--- /dev/null
+++ b/src/libstrongswan/plugins/pkcs7/pkcs7_enveloped_data.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2012 Martin Willi
+ * Copyright (C) 2012 revosec AG
+ *
+ * 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 (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ */
+
+/**
+ * @defgroup pkcs7_enveloped_data pkcs7_enveloped_data
+ * @{ @ingroup pkcs7
+ */
+
+#ifndef PKCS7_ENVELOPED_DATA_H_
+#define PKCS7_ENVELOPED_DATA_H_
+
+#include <credentials/builder.h>
+#include <credentials/containers/pkcs7.h>
+
+/**
+ * Parse a PKCS#7 enveloped-data container.
+ *
+ * @param encoding	full contentInfo encoding
+ * @param content	DER encoded content from contentInfo
+ * @return			CONTAINER_PKCS7_ENVELOPED_DATA container, NULL on failure
+ */
+pkcs7_t *pkcs7_enveloped_data_load(chunk_t encoding, chunk_t content);
+
+#endif /** PKCS7_ENVELOPED_DATA_H_ @}*/
diff --git a/src/libstrongswan/plugins/pkcs7/pkcs7_generic.c b/src/libstrongswan/plugins/pkcs7/pkcs7_generic.c
index 3c9fb867c..0a8b1bbd0 100644
--- a/src/libstrongswan/plugins/pkcs7/pkcs7_generic.c
+++ b/src/libstrongswan/plugins/pkcs7/pkcs7_generic.c
@@ -20,6 +20,7 @@
 #include "pkcs7_generic.h"
 #include "pkcs7_data.h"
 #include "pkcs7_signed_data.h"
+#include "pkcs7_enveloped_data.h"
 
 #include <utils/debug.h>
 #include <asn1/oid.h>
@@ -82,6 +83,8 @@ end:
 				return pkcs7_data_load(blob, content);
 			case OID_PKCS7_SIGNED_DATA:
 				return pkcs7_signed_data_load(blob, content);
+			case OID_PKCS7_ENVELOPED_DATA:
+				return pkcs7_enveloped_data_load(blob, content);
 			default:
 				DBG1(DBG_ASN, "pkcs7 content type %d not supported", type);
 				return NULL;