/*
 * Copyright (C) 2023 Tobias Brunner
 * Copyright (C) 2012 Martin Willi
 *
 * Copyright (C) secunet Security Networks 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.
 */

#include "pkcs7_signed_data.h"
#include "pkcs7_attributes.h"

#include <time.h>

#include <utils/debug.h>
#include <asn1/oid.h>
#include <asn1/asn1.h>
#include <asn1/asn1_parser.h>
#include <credentials/sets/mem_cred.h>
#include <credentials/certificates/x509.h>
#include <credentials/keys/private_key.h>

typedef struct private_pkcs7_signed_data_t private_pkcs7_signed_data_t;

/**
 * Private data of a PKCS#7 signed-data container.
 */
struct private_pkcs7_signed_data_t {

	/**
	 * Implements pkcs7_t.
	 */
	pkcs7_t public;

	/**
	 * Signed content data
	 */
	container_t *content;

	/**
	 * Signature scheme
	 */
	signature_params_t *scheme;

	/**
	 * Encoded PKCS#7 signed-data
	 */
	chunk_t encoding;

	/**
	 * list of signerInfos, signerinfo_t
	 */
	linked_list_t *signerinfos;

	/**
	 * Contained certificates
	 */
	mem_cred_t *creds;
};

/**
 * A single signerInfo
 */
typedef struct {

	/**
	 * Signed attributes of signerInfo
	 */
	pkcs7_attributes_t *attributes;

	/**
	 * Serial of signing certificate
	 */
	identification_t *serial;

	/**
	 * Issuer of signing certificate
	 */
	identification_t *issuer;

	/**
	 * Signature
	 */
	chunk_t signature;

	/**
	 * Digesting algorithm OID
	 */
	int digest_alg;

	/**
	 * Signature algorithm
	 */
	signature_params_t sig_alg;

} signerinfo_t;

/**
 * Destroy a signerinfo_t entry
 */
static void signerinfo_destroy(signerinfo_t *this)
{
	DESTROY_IF(this->attributes);
	DESTROY_IF(this->serial);
	DESTROY_IF(this->issuer);
	signature_params_clear(&this->sig_alg);
	free(this->signature.ptr);
	free(this);
}

/**
 * ASN.1 definition of the PKCS#7 signedData type
 */
static const asn1Object_t signedDataObjects[] = {
	{ 0, "signedData",						ASN1_SEQUENCE,		ASN1_NONE }, /*  0 */
	{ 1,   "version",						ASN1_INTEGER,		ASN1_BODY }, /*  1 */
	{ 1,   "digestAlgorithms",				ASN1_SET,			ASN1_LOOP }, /*  2 */
	{ 2,     "algorithm",					ASN1_EOC,			ASN1_RAW  }, /*  3 */
	{ 1,   "end loop",						ASN1_EOC,			ASN1_END  }, /*  4 */
	{ 1,   "contentInfo",					ASN1_EOC,			ASN1_RAW  }, /*  5 */
	{ 1,   "certificates",					ASN1_CONTEXT_C_0,	ASN1_OPT |
																ASN1_LOOP }, /*  6 */
	{ 2,      "certificate",				ASN1_SEQUENCE,		ASN1_OBJ  }, /*  7 */
	{ 1,   "end opt or loop",				ASN1_EOC,			ASN1_END  }, /*  8 */
	{ 1,   "crls",							ASN1_CONTEXT_C_1,	ASN1_OPT |
																ASN1_LOOP }, /*  9 */
	{ 2,	    "crl",						ASN1_SEQUENCE,		ASN1_OBJ  }, /* 10 */
	{ 1,   "end opt or loop",				ASN1_EOC,			ASN1_END  }, /* 11 */
	{ 1,   "signerInfos",					ASN1_SET,			ASN1_LOOP }, /* 12 */
	{ 2,     "signerInfo",					ASN1_SEQUENCE,		ASN1_NONE }, /* 13 */
	{ 3,       "version",					ASN1_INTEGER,		ASN1_BODY }, /* 14 */
	{ 3,       "issuerAndSerialNumber",		ASN1_SEQUENCE,		ASN1_BODY }, /* 15 */
	{ 4,         "issuer",					ASN1_SEQUENCE,		ASN1_OBJ  }, /* 16 */
	{ 4,         "serial",					ASN1_INTEGER,		ASN1_BODY }, /* 17 */
	{ 3,       "digestAlgorithm",			ASN1_EOC,			ASN1_RAW  }, /* 18 */
	{ 3,       "authenticatedAttributes",	ASN1_CONTEXT_C_0,	ASN1_OPT |
																ASN1_OBJ  }, /* 19 */
	{ 3,       "end opt",					ASN1_EOC,			ASN1_END  }, /* 20 */
	{ 3,       "signatureAlgorithm",		ASN1_EOC,			ASN1_RAW  }, /* 21 */
	{ 3,       "signature",					ASN1_OCTET_STRING,	ASN1_BODY }, /* 22 */
	{ 3,       "unauthenticatedAttributes", ASN1_CONTEXT_C_1,	ASN1_OPT  }, /* 23 */
	{ 3,       "end opt",					ASN1_EOC,			ASN1_END  }, /* 24 */
	{ 1,   "end loop",						ASN1_EOC,			ASN1_END  }, /* 25 */
	{ 0, "exit",							ASN1_EOC,			ASN1_EXIT }
};
#define PKCS7_VERSION				 1
#define PKCS7_DIGEST_ALG			 3
#define PKCS7_CONTENT_INFO			 5
#define PKCS7_CERT					 7
#define PKCS7_SIGNER_INFO			13
#define PKCS7_SIGNER_INFO_VERSION	14
#define PKCS7_ISSUER				16
#define PKCS7_SERIAL_NUMBER			17
#define PKCS7_DIGEST_ALGORITHM		18
#define PKCS7_AUTH_ATTRIBUTES		19
#define PKCS7_SIGNATURE_ALGORITHM	21
#define PKCS7_SIGNATURE				22

METHOD(container_t, get_type, container_type_t,
	private_pkcs7_signed_data_t *this)
{
	return CONTAINER_PKCS7_SIGNED_DATA;
}

/**
 * Signature enumerator implementation
 */
typedef struct {
	/** implements enumerator */
	enumerator_t public;
	/** inner signerinfos enumerator */
	enumerator_t *inner;
	/** currently enumerated auth_cfg */
	auth_cfg_t *auth;
	/** currently enumerating signerinfo */
	signerinfo_t *info;
	/** reference to container */
	private_pkcs7_signed_data_t *this;
} signature_enumerator_t;

METHOD(enumerator_t, enumerate, bool,
	signature_enumerator_t *this, va_list args)
{
	signerinfo_t *info;
	hash_algorithm_t algorithm;
	enumerator_t *enumerator;
	certificate_t *cert;
	public_key_t *key;
	auth_cfg_t *auth, **out;
	chunk_t chunk, hash, content;
	hasher_t *hasher;
	bool valid;

	VA_ARGS_VGET(args, out);

	while (this->inner->enumerate(this->inner, &info))
	{
		/* clean up previous round */
		DESTROY_IF(this->auth);
		this->auth = NULL;

		if (!info->attributes)
		{
			DBG1(DBG_LIB, "no authenticatedAttributes object found");
			continue;
		}
		if (info->sig_alg.scheme == SIGN_UNKNOWN)
		{
			DBG1(DBG_LIB, "unsupported signature scheme");
			continue;
		}

		enumerator = lib->credmgr->create_trusted_enumerator(lib->credmgr,
							key_type_from_signature_scheme(info->sig_alg.scheme),
							info->serial, FALSE);
		while (enumerator->enumerate(enumerator, &cert, &auth))
		{
			if (info->issuer->equals(info->issuer, cert->get_issuer(cert)))
			{
				key = cert->get_public_key(cert);
				if (key)
				{
					chunk = info->attributes->get_encoding(info->attributes);
					if (key->verify(key, info->sig_alg.scheme,
									info->sig_alg.params, chunk, info->signature))
					{
						this->auth = auth->clone(auth);
						key->destroy(key);
						break;
					}
					key->destroy(key);
				}
			}
		}
		enumerator->destroy(enumerator);

		if (!this->auth)
		{
			DBG1(DBG_LIB, "unable to verify pkcs7 attributes signature");
			continue;
		}

		chunk = info->attributes->get_attribute(info->attributes,
												OID_PKCS9_MESSAGE_DIGEST);
		if (!chunk.len)
		{
			DBG1(DBG_LIB, "messageDigest attribute not found");
			continue;
		}
		if (!this->this->content->get_data(this->this->content, &content))
		{
			continue;
		}

		algorithm = hasher_algorithm_from_oid(info->digest_alg);
		hasher = lib->crypto->create_hasher(lib->crypto, algorithm);
		if (!hasher || !hasher->allocate_hash(hasher, content, &hash))
		{
			free(content.ptr);
			DESTROY_IF(hasher);
			DBG1(DBG_LIB, "hash algorithm %N not supported",
				 hash_algorithm_names, algorithm);
			continue;
		}
		free(content.ptr);
		hasher->destroy(hasher);
		DBG3(DBG_LIB, "hash: %B", &hash);

		valid = chunk_equals_const(chunk, hash);
		free(hash.ptr);
		if (!valid)
		{
			DBG1(DBG_LIB, "invalid messageDigest");
			continue;
		}
		*out = this->auth;
		this->info = info;
		return TRUE;
	}
	this->info = NULL;
	return FALSE;
}

METHOD(enumerator_t, enumerator_destroy, void,
	signature_enumerator_t *this)
{
	lib->credmgr->remove_local_set(lib->credmgr, &this->this->creds->set);
	this->inner->destroy(this->inner);
	DESTROY_IF(this->auth);
	free(this);
}

METHOD(container_t, create_signature_enumerator, enumerator_t*,
	private_pkcs7_signed_data_t *this)
{
	signature_enumerator_t *enumerator;

	INIT(enumerator,
		.public = {
			.enumerate = enumerator_enumerate_default,
			.venumerate = _enumerate,
			.destroy = _enumerator_destroy,
		},
		.inner = this->signerinfos->create_enumerator(this->signerinfos),
		.this = this,
	);

	lib->credmgr->add_local_set(lib->credmgr, &this->creds->set, FALSE);
	return &enumerator->public;
}

METHOD(pkcs7_t, get_attribute, bool,
	private_pkcs7_signed_data_t *this, int oid, enumerator_t *enumerator, chunk_t *value)
{
	signature_enumerator_t *e;
	chunk_t chunk;

	e = (signature_enumerator_t*)enumerator;
	if (e->info)
	{
		chunk = e->info->attributes->get_attribute(e->info->attributes, oid);
		if (chunk.len)
		{
			*value = chunk_clone(chunk);
			return TRUE;
		}
	}
	return FALSE;
}

METHOD(pkcs7_t, create_cert_enumerator, enumerator_t*,
	private_pkcs7_signed_data_t *this)
{
	return this->creds->set.create_cert_enumerator(&this->creds->set,
											CERT_ANY, KEY_ANY, NULL, FALSE);
}

METHOD(container_t, get_data, bool,
	private_pkcs7_signed_data_t *this, chunk_t *data)
{
	if (this->content)
	{
		return this->content->get_data(this->content, data);
	}
	return FALSE;
}

METHOD(container_t, get_encoding, bool,
	private_pkcs7_signed_data_t *this, chunk_t *data)
{
	*data = chunk_clone(this->encoding);
	return TRUE;
}

METHOD(container_t, destroy, void,
	private_pkcs7_signed_data_t *this)
{
	this->creds->destroy(this->creds);
	this->signerinfos->destroy_function(this->signerinfos,
										(void*)signerinfo_destroy);
	signature_params_destroy(this->scheme);
	DESTROY_IF(this->content);
	free(this->encoding.ptr);
	free(this);
}

/**
 * Create an empty PKCS#7 signed-data container.
 */
static private_pkcs7_signed_data_t* create_empty()
{
	private_pkcs7_signed_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,
			},
			.get_attribute = _get_attribute,
			.create_cert_enumerator = _create_cert_enumerator,
		},
		.creds = mem_cred_create(),
		.signerinfos = linked_list_create(),
	);

	return this;
}

/**
 * Parse PKCS#7 signed data
 */
static bool parse(private_pkcs7_signed_data_t *this, chunk_t content)
{
	asn1_parser_t *parser;
	chunk_t object;
	int objectID;
	signerinfo_t *info = NULL;
	bool success = FALSE;

	parser = asn1_parser_create(signedDataObjects, 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:
				DBG2(DBG_LIB, "  v%d", object.len ? (int)*object.ptr : 0);
				break;
			case PKCS7_CONTENT_INFO:
				this->content = lib->creds->create(lib->creds,
										CRED_CONTAINER, CONTAINER_PKCS7,
										BUILD_BLOB_ASN1_DER, object, BUILD_END);
				break;
			case PKCS7_CERT:
			{
				certificate_t *cert;

				DBG2(DBG_LIB, "  parsing pkcs7-wrapped certificate");
				cert = lib->creds->create(lib->creds,
										  CRED_CERTIFICATE, CERT_X509,
										  BUILD_BLOB_ASN1_DER, object,
										  BUILD_END);
				if (cert)
				{
					this->creds->add_cert(this->creds, FALSE, cert);
				}
				break;
			}
			case PKCS7_SIGNER_INFO:
				INIT(info,
					.digest_alg = OID_UNKNOWN,
				);
				this->signerinfos->insert_last(this->signerinfos, info);
				break;
			case PKCS7_SIGNER_INFO_VERSION:
				DBG2(DBG_LIB, "  v%d", object.len ? (int)*object.ptr : 0);
				break;
			case PKCS7_ISSUER:
				info->issuer = identification_create_from_encoding(
														ID_DER_ASN1_DN, object);
				break;
			case PKCS7_SERIAL_NUMBER:
				info->serial = identification_create_from_encoding(
														ID_KEY_ID, object);
				break;
			case PKCS7_AUTH_ATTRIBUTES:
				*object.ptr = ASN1_SET;
				info->attributes = pkcs7_attributes_create_from_chunk(
														object, level+1);
				*object.ptr = ASN1_CONTEXT_C_0;
				break;
			case PKCS7_DIGEST_ALGORITHM:
				info->digest_alg = asn1_parse_algorithmIdentifier(object,
														level, NULL);
				break;
			case PKCS7_SIGNATURE_ALGORITHM:
				if (!signature_params_parse(object, level, &info->sig_alg))
				{
					if (asn1_parse_algorithmIdentifier(object, -1,
												NULL) == OID_RSA_ENCRYPTION &&
						info->digest_alg != OID_UNKNOWN)
					{
						/* derive the signature scheme from the digest algorithm
						 * for the classic PKCS#7 RSA mechanism */
						info->sig_alg.scheme = signature_scheme_from_oid(
															info->digest_alg);
					}
				}
				break;
			case PKCS7_SIGNATURE:
				info->signature = chunk_clone(object);
				break;
		}
	}
	success = parser->success(parser);
	parser->destroy(parser);

	return success;
}

/**
 * See header.
 */
pkcs7_t *pkcs7_signed_data_load(chunk_t encoding, chunk_t content)
{
	private_pkcs7_signed_data_t *this = create_empty();

	this->encoding = chunk_clone(encoding);
	if (!parse(this, content))
	{
		destroy(this);
		return NULL;
	}
	return &this->public;
}

/**
 * build a DER-encoded issuerAndSerialNumber object
 */
static chunk_t build_issuerAndSerialNumber(certificate_t *cert)
{
	identification_t *issuer = cert->get_issuer(cert);
	chunk_t serial = chunk_empty;

	if (cert->get_type(cert) == CERT_X509)
	{
		x509_t *x509 = (x509_t*)cert;
		serial = x509->get_serial(x509);
	}

	return asn1_wrap(ASN1_SEQUENCE, "cm",
					 issuer->get_encoding(issuer),
					 asn1_integer("c", serial));
}

/**
 * Generate a new PKCS#7 signed-data container
 */
static bool generate(private_pkcs7_signed_data_t *this, private_key_t *key,
					 certificate_t *cert, hash_algorithm_t alg,
					 pkcs7_attributes_t *pkcs9)
{
	chunk_t authenticatedAttributes = chunk_empty;
	chunk_t encryptedDigest = chunk_empty;
	chunk_t data = chunk_empty, encoding = chunk_empty;
	chunk_t digest_alg = chunk_empty, sig_scheme = chunk_empty;
	chunk_t signerInfo = chunk_empty, messageDigest, signingTime, attributes;
	hasher_t *hasher;
	time_t now;

	/* select signature scheme, if not already specified */
	if (!this->scheme)
	{
		INIT(this->scheme,
			.scheme = signature_scheme_from_oid(
							hasher_signature_algorithm_to_oid(alg,
								key->get_type(key))),
		);
	}
	if (this->scheme->scheme == SIGN_UNKNOWN)
	{
		return FALSE;
	}
	if (!signature_params_build(this->scheme, &sig_scheme))
	{
		return FALSE;
	}
	if (!this->content->get_data(this->content, &data))
	{
		goto err;
	}

	hasher = lib->crypto->create_hasher(lib->crypto, alg);
	if (!hasher || !hasher->allocate_hash(hasher, data, &messageDigest))
	{
		DESTROY_IF(hasher);
		DBG1(DBG_LIB, "  hash algorithm %N not supported",
			 hash_algorithm_names, alg);
		goto err;
	}
	chunk_free(&data);
	hasher->destroy(hasher);

	pkcs9->add_attribute(pkcs9,
					OID_PKCS9_MESSAGE_DIGEST,
					asn1_wrap(ASN1_OCTET_STRING, "m", messageDigest));

	/* take the current time as signingTime */
	now = time(NULL);
	signingTime = asn1_from_time(&now, ASN1_UTCTIME);
	pkcs9->add_attribute(pkcs9, OID_PKCS9_SIGNING_TIME, signingTime);
	pkcs9->add_attribute(pkcs9, OID_PKCS9_CONTENT_TYPE,
						 asn1_build_known_oid(OID_PKCS7_DATA));
	attributes = pkcs9->get_encoding(pkcs9);

	if (!key->sign(key, this->scheme->scheme, this->scheme->params, attributes,
				   &encryptedDigest))
	{
		goto err;
	}
	authenticatedAttributes = chunk_clone(attributes);
	*authenticatedAttributes.ptr = ASN1_CONTEXT_C_0;

	if (encryptedDigest.ptr)
	{
		encryptedDigest = asn1_wrap(ASN1_OCTET_STRING, "m", encryptedDigest);
	}

	digest_alg = asn1_algorithmIdentifier(hasher_algorithm_to_oid(alg));
	signerInfo = asn1_wrap(ASN1_SEQUENCE, "cmcmmm",
					ASN1_INTEGER_1,
					build_issuerAndSerialNumber(cert),
					digest_alg,
					authenticatedAttributes,
					sig_scheme,
					encryptedDigest);
	sig_scheme = chunk_empty;

	if (!cert->get_encoding(cert, CERT_ASN1_DER, &encoding))
	{
		goto err;
	}
	if (!this->content->get_encoding(this->content, &data))
	{
		goto err;
	}

	this->encoding = asn1_wrap(ASN1_SEQUENCE, "mm",
		asn1_build_known_oid(OID_PKCS7_SIGNED_DATA),
		asn1_wrap(ASN1_CONTEXT_C_0, "m",
			asn1_wrap(ASN1_SEQUENCE, "cmmmm",
				ASN1_INTEGER_1,
				asn1_wrap(ASN1_SET, "m", digest_alg),
				data,
				asn1_wrap(ASN1_CONTEXT_C_0, "m", encoding),
				asn1_wrap(ASN1_SET, "m", signerInfo))));

	pkcs9->destroy(pkcs9);
	/* TODO: create signerInfos entry */
	return TRUE;

err:
	chunk_free(&data);
	chunk_free(&digest_alg);
	chunk_free(&sig_scheme);
	chunk_free(&signerInfo);
	chunk_free(&encoding);
	return FALSE;
}

/**
 * See header.
 */
pkcs7_t *pkcs7_signed_data_gen(container_type_t type, va_list args)
{
	private_pkcs7_signed_data_t *this;
	chunk_t blob = chunk_empty;
	hash_algorithm_t alg = HASH_SHA256;
	signature_params_t *scheme = NULL;
	private_key_t *key = NULL;
	certificate_t *cert = NULL;
	pkcs7_attributes_t *pkcs9;
	chunk_t value;
	int oid;

	pkcs9 = pkcs7_attributes_create();

	while (TRUE)
	{
		switch (va_arg(args, builder_part_t))
		{
			case BUILD_SIGNING_KEY:
				key = va_arg(args, private_key_t*);
				continue;
			case BUILD_SIGNING_CERT:
				cert = va_arg(args, certificate_t*);
				continue;
			case BUILD_DIGEST_ALG:
				alg = va_arg(args, int);
				continue;
			case BUILD_BLOB:
				blob = va_arg(args, chunk_t);
				continue;
			case BUILD_SIGNATURE_SCHEME:
				scheme = va_arg(args, signature_params_t*);
				continue;
			case BUILD_PKCS7_ATTRIBUTE:
				oid = va_arg(args, int);
				value = va_arg(args, chunk_t);
				pkcs9->add_attribute(pkcs9, oid, chunk_clone(value));
				continue;
			case BUILD_END:
				break;
			default:
				pkcs9->destroy(pkcs9);
				return NULL;
		}
		break;
	}
	if (blob.len && key && cert)
	{
		this = create_empty();

		this->scheme = signature_params_clone(scheme);
		this->creds->add_cert(this->creds, FALSE, cert->get_ref(cert));
		this->content = lib->creds->create(lib->creds,
										   CRED_CONTAINER, CONTAINER_PKCS7_DATA,
										   BUILD_BLOB, blob, BUILD_END);
		if (this->content && generate(this, key, cert, alg, pkcs9))
		{
			return &this->public;
		}
		pkcs9->destroy(pkcs9);
		destroy(this);
	}
	else
	{
		pkcs9->destroy(pkcs9);
	}
	return NULL;
}
