src/lib/libcrypto/cms/cms_kari.c

/* $OpenBSD: cms_kari.c,v 1.16 2024/02/02 14:11:45 tb Exp $ */
/*
 * Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project.
 */
/* ====================================================================
 * Copyright (c) 2013 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 */

#include <string.h>

#include "cryptlib.h"
#include <openssl/asn1t.h>
#include <openssl/pem.h>
#include <openssl/x509v3.h>
#include <openssl/err.h>
#include <openssl/cms.h>
#include <openssl/aes.h>
#include "cms_local.h"
#include "asn1/asn1_local.h"

/* Key Agreement Recipient Info (KARI) routines */

int
CMS_RecipientInfo_kari_get0_alg(CMS_RecipientInfo *ri, X509_ALGOR **palg,
    ASN1_OCTET_STRING **pukm)
{
	if (ri->type != CMS_RECIPINFO_AGREE) {
		CMSerror(CMS_R_NOT_KEY_AGREEMENT);
		return 0;
	}
	if (palg)
		*palg = ri->d.kari->keyEncryptionAlgorithm;
	if (pukm)
		*pukm = ri->d.kari->ukm;

	return 1;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_get0_alg);

/* Retrieve recipient encrypted keys from a kari */

STACK_OF(CMS_RecipientEncryptedKey) *
CMS_RecipientInfo_kari_get0_reks(CMS_RecipientInfo *ri)
{
	if (ri->type != CMS_RECIPINFO_AGREE) {
		CMSerror(CMS_R_NOT_KEY_AGREEMENT);
		return NULL;
	}
	return ri->d.kari->recipientEncryptedKeys;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_get0_reks);

int
CMS_RecipientInfo_kari_get0_orig_id(CMS_RecipientInfo *ri, X509_ALGOR **pubalg,
    ASN1_BIT_STRING **pubkey, ASN1_OCTET_STRING **keyid, X509_NAME **issuer,
    ASN1_INTEGER **sno)
{
	CMS_OriginatorIdentifierOrKey *oik;

	if (ri->type != CMS_RECIPINFO_AGREE) {
		CMSerror(CMS_R_NOT_KEY_AGREEMENT);
		return 0;
	}
	oik = ri->d.kari->originator;
	if (issuer)
		*issuer = NULL;
	if (sno)
		*sno = NULL;
	if (keyid)
		*keyid = NULL;
	if (pubalg)
		*pubalg = NULL;
	if (pubkey)
		*pubkey = NULL;
	if (oik->type == CMS_OIK_ISSUER_SERIAL) {
		if (issuer)
			*issuer = oik->d.issuerAndSerialNumber->issuer;
		if (sno)
			*sno = oik->d.issuerAndSerialNumber->serialNumber;
	} else if (oik->type == CMS_OIK_KEYIDENTIFIER) {
		if (keyid)
			*keyid = oik->d.subjectKeyIdentifier;
	} else if (oik->type == CMS_OIK_PUBKEY) {
		if (pubalg)
			*pubalg = oik->d.originatorKey->algorithm;
		if (pubkey)
			*pubkey = oik->d.originatorKey->publicKey;
	} else
		return 0;

	return 1;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_get0_orig_id);

int
CMS_RecipientInfo_kari_orig_id_cmp(CMS_RecipientInfo *ri, X509 *cert)
{
	CMS_OriginatorIdentifierOrKey *oik;

	if (ri->type != CMS_RECIPINFO_AGREE) {
		CMSerror(CMS_R_NOT_KEY_AGREEMENT);
		return -2;
	}
	oik = ri->d.kari->originator;
	if (oik->type == CMS_OIK_ISSUER_SERIAL)
		return cms_ias_cert_cmp(oik->d.issuerAndSerialNumber, cert);
	else if (oik->type == CMS_OIK_KEYIDENTIFIER)
		return cms_keyid_cert_cmp(oik->d.subjectKeyIdentifier, cert);

	return -1;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_orig_id_cmp);

int
CMS_RecipientEncryptedKey_get0_id(CMS_RecipientEncryptedKey *rek,
    ASN1_OCTET_STRING **keyid, ASN1_GENERALIZEDTIME **tm,
    CMS_OtherKeyAttribute **other, X509_NAME **issuer, ASN1_INTEGER **sno)
{
	CMS_KeyAgreeRecipientIdentifier *rid = rek->rid;

	if (rid->type == CMS_REK_ISSUER_SERIAL) {
		if (issuer)
			*issuer = rid->d.issuerAndSerialNumber->issuer;
		if (sno)
			*sno = rid->d.issuerAndSerialNumber->serialNumber;
		if (keyid)
			*keyid = NULL;
		if (tm)
			*tm = NULL;
		if (other)
			*other = NULL;
	} else if (rid->type == CMS_REK_KEYIDENTIFIER) {
		if (keyid)
			*keyid = rid->d.rKeyId->subjectKeyIdentifier;
		if (tm)
			*tm = rid->d.rKeyId->date;
		if (other)
			*other = rid->d.rKeyId->other;
		if (issuer)
			*issuer = NULL;
		if (sno)
			*sno = NULL;
	} else
		return 0;

	return 1;
}
LCRYPTO_ALIAS(CMS_RecipientEncryptedKey_get0_id);

int
CMS_RecipientEncryptedKey_cert_cmp(CMS_RecipientEncryptedKey *rek, X509 *cert)
{
	CMS_KeyAgreeRecipientIdentifier *rid = rek->rid;

	if (rid->type == CMS_REK_ISSUER_SERIAL)
		return cms_ias_cert_cmp(rid->d.issuerAndSerialNumber, cert);
	else if (rid->type == CMS_REK_KEYIDENTIFIER)
		return cms_keyid_cert_cmp(rid->d.rKeyId->subjectKeyIdentifier, cert);
	else
		return -1;
}
LCRYPTO_ALIAS(CMS_RecipientEncryptedKey_cert_cmp);

int
CMS_RecipientInfo_kari_set0_pkey(CMS_RecipientInfo *ri, EVP_PKEY *pk)
{
	EVP_PKEY_CTX *pctx;
	CMS_KeyAgreeRecipientInfo *kari = ri->d.kari;

	EVP_PKEY_CTX_free(kari->pctx);
	kari->pctx = NULL;
	if (!pk)
		return 1;
	pctx = EVP_PKEY_CTX_new(pk, NULL);
	if (!pctx || !EVP_PKEY_derive_init(pctx))
		goto err;
	kari->pctx = pctx;
	return 1;

 err:
	EVP_PKEY_CTX_free(pctx);
	return 0;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_set0_pkey);

EVP_CIPHER_CTX *
CMS_RecipientInfo_kari_get0_ctx(CMS_RecipientInfo *ri)
{
	if (ri->type == CMS_RECIPINFO_AGREE)
		return ri->d.kari->ctx;
	return NULL;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_get0_ctx);

/*
 * Derive KEK and decrypt/encrypt with it to produce either the original CEK
 * or the encrypted CEK.
 */

static int
cms_kek_cipher(unsigned char **pout, size_t *poutlen, const unsigned char *in,
    size_t inlen, CMS_KeyAgreeRecipientInfo *kari, int enc)
{
	/* Key encryption key */
	unsigned char kek[EVP_MAX_KEY_LENGTH];
	size_t keklen;
	int rv = 0;
	unsigned char *out = NULL;
	int outlen;

	keklen = EVP_CIPHER_CTX_key_length(kari->ctx);
	if (keklen > EVP_MAX_KEY_LENGTH)
		return 0;
	/* Derive KEK */
	if (EVP_PKEY_derive(kari->pctx, kek, &keklen) <= 0)
		goto err;
	/* Set KEK in context */
	if (!EVP_CipherInit_ex(kari->ctx, NULL, NULL, kek, NULL, enc))
		goto err;
	/* obtain output length of ciphered key */
	if (!EVP_CipherUpdate(kari->ctx, NULL, &outlen, in, inlen))
		goto err;
	out = malloc(outlen);
	if (out == NULL)
		goto err;
	if (!EVP_CipherUpdate(kari->ctx, out, &outlen, in, inlen))
		goto err;
	*pout = out;
	*poutlen = (size_t)outlen;
	rv = 1;

 err:
	explicit_bzero(kek, keklen);
	if (!rv)
		free(out);
	(void)EVP_CIPHER_CTX_reset(kari->ctx);
	/* FIXME: WHY IS kari->pctx freed here?  /RL */
	EVP_PKEY_CTX_free(kari->pctx);
	kari->pctx = NULL;

	return rv;
}

int
CMS_RecipientInfo_kari_decrypt(CMS_ContentInfo *cms, CMS_RecipientInfo *ri,
    CMS_RecipientEncryptedKey *rek)
{
	int rv = 0;
	unsigned char *enckey = NULL, *cek = NULL;
	size_t enckeylen;
	size_t ceklen;
	CMS_EncryptedContentInfo *ec;

	enckeylen = rek->encryptedKey->length;
	enckey = rek->encryptedKey->data;
	/* Setup all parameters to derive KEK */
	if (!cms_env_asn1_ctrl(ri, 1))
		goto err;
	/* Attempt to decrypt CEK */
	if (!cms_kek_cipher(&cek, &ceklen, enckey, enckeylen, ri->d.kari, 0))
		goto err;
	ec = cms->d.envelopedData->encryptedContentInfo;
	freezero(ec->key, ec->keylen);
	ec->key = cek;
	ec->keylen = ceklen;
	cek = NULL;
	rv = 1;

 err:
	free(cek);

	return rv;
}
LCRYPTO_ALIAS(CMS_RecipientInfo_kari_decrypt);

/* Create ephemeral key and initialise context based on it */
static int
cms_kari_create_ephemeral_key(CMS_KeyAgreeRecipientInfo *kari, EVP_PKEY *pk)
{
	EVP_PKEY_CTX *pctx = NULL;
	EVP_PKEY *ekey = NULL;
	int rv = 0;

	pctx = EVP_PKEY_CTX_new(pk, NULL);
	if (!pctx)
		goto err;
	if (EVP_PKEY_keygen_init(pctx) <= 0)
		goto err;
	if (EVP_PKEY_keygen(pctx, &ekey) <= 0)
		goto err;
	EVP_PKEY_CTX_free(pctx);
	pctx = EVP_PKEY_CTX_new(ekey, NULL);
	if (!pctx)
		goto err;
	if (EVP_PKEY_derive_init(pctx) <= 0)
		goto err;
	kari->pctx = pctx;
	rv = 1;

 err:
	if (!rv)
		EVP_PKEY_CTX_free(pctx);
	EVP_PKEY_free(ekey);

	return rv;
}

/* Initialise a kari based on passed certificate and key */

int
cms_RecipientInfo_kari_init(CMS_RecipientInfo *ri, X509 *recip, EVP_PKEY *pk,
    unsigned int flags)
{
	CMS_KeyAgreeRecipientInfo *kari;
	CMS_RecipientEncryptedKey *rek = NULL;

	ri->d.kari = (CMS_KeyAgreeRecipientInfo *)ASN1_item_new(&CMS_KeyAgreeRecipientInfo_it);
	if (!ri->d.kari)
		return 0;
	ri->type = CMS_RECIPINFO_AGREE;

	kari = ri->d.kari;
	kari->version = 3;

	rek = (CMS_RecipientEncryptedKey *)ASN1_item_new(&CMS_RecipientEncryptedKey_it);
	if (rek == NULL)
		return 0;

	if (!sk_CMS_RecipientEncryptedKey_push(kari->recipientEncryptedKeys, rek)) {
		ASN1_item_free((ASN1_VALUE *)rek, &CMS_RecipientEncryptedKey_it);
		return 0;
	}

	if (flags & CMS_USE_KEYID) {
		rek->rid->type = CMS_REK_KEYIDENTIFIER;
		rek->rid->d.rKeyId = (CMS_RecipientKeyIdentifier *)ASN1_item_new(&CMS_RecipientKeyIdentifier_it);
		if (rek->rid->d.rKeyId == NULL)
			return 0;
		if (!cms_set1_keyid(&rek->rid->d.rKeyId->subjectKeyIdentifier, recip))
			return 0;
	} else {
		rek->rid->type = CMS_REK_ISSUER_SERIAL;
		if (!cms_set1_ias(&rek->rid->d.issuerAndSerialNumber, recip))
			return 0;
	}

	/* Create ephemeral key */
	if (!cms_kari_create_ephemeral_key(kari, pk))
		return 0;

	EVP_PKEY_up_ref(pk);
	rek->pkey = pk;

	return 1;
}

static int
cms_wrap_init(CMS_KeyAgreeRecipientInfo *kari, const EVP_CIPHER *cipher)
{
	EVP_CIPHER_CTX *ctx = kari->ctx;
	const EVP_CIPHER *kekcipher;
	int keylen = EVP_CIPHER_key_length(cipher);

	/* If a suitable wrap algorithm is already set nothing to do */
	kekcipher = EVP_CIPHER_CTX_cipher(ctx);

	if (kekcipher) {
		if (EVP_CIPHER_CTX_mode(ctx) != EVP_CIPH_WRAP_MODE)
			return 0;
		return 1;
	}
	/*
	 * Pick a cipher based on content encryption cipher. If it is DES3 use
	 * DES3 wrap otherwise use AES wrap similar to key size.
	 */
#ifndef OPENSSL_NO_DES
#if 0
	/*
	 * XXX - we do not currently support DES3 wrap and probably should just
	 * drop this code.
	 */
	if (EVP_CIPHER_type(cipher) == NID_des_ede3_cbc)
		kekcipher = EVP_des_ede3_wrap();
	else
#endif
#endif
	if (keylen <= 16)
		kekcipher = EVP_aes_128_wrap();
	else if (keylen <= 24)
		kekcipher = EVP_aes_192_wrap();
	else
		kekcipher = EVP_aes_256_wrap();

	return EVP_EncryptInit_ex(ctx, kekcipher, NULL, NULL, NULL);
}

/* Encrypt content key in key agreement recipient info */

int
cms_RecipientInfo_kari_encrypt(CMS_ContentInfo *cms, CMS_RecipientInfo *ri)
{
	CMS_KeyAgreeRecipientInfo *kari;
	CMS_EncryptedContentInfo *ec;
	CMS_RecipientEncryptedKey *rek;
	STACK_OF(CMS_RecipientEncryptedKey) *reks;
	int i;

	if (ri->type != CMS_RECIPINFO_AGREE) {
		CMSerror(CMS_R_NOT_KEY_AGREEMENT);
		return 0;
	}
	kari = ri->d.kari;
	reks = kari->recipientEncryptedKeys;
	ec = cms->d.envelopedData->encryptedContentInfo;
	/* Initialise wrap algorithm parameters */
	if (!cms_wrap_init(kari, ec->cipher))
		return 0;
	/*
	 * If no originator key set up initialise for ephemeral key the public key
	 * ASN1 structure will set the actual public key value.
	 */
	if (kari->originator->type == -1) {
		CMS_OriginatorIdentifierOrKey *oik = kari->originator;
		oik->type = CMS_OIK_PUBKEY;
		oik->d.originatorKey = (CMS_OriginatorPublicKey *)ASN1_item_new(&CMS_OriginatorPublicKey_it);
		if (!oik->d.originatorKey)
			return 0;
	}
	/* Initialise KDF algorithm */
	if (!cms_env_asn1_ctrl(ri, 0))
		return 0;
	/* For each rek, derive KEK, encrypt CEK */
	for (i = 0; i < sk_CMS_RecipientEncryptedKey_num(reks); i++) {
		unsigned char *enckey;
		size_t enckeylen;
		rek = sk_CMS_RecipientEncryptedKey_value(reks, i);
		if (EVP_PKEY_derive_set_peer(kari->pctx, rek->pkey) <= 0)
			return 0;
		if (!cms_kek_cipher(&enckey, &enckeylen, ec->key, ec->keylen,
			                kari, 1))
			return 0;
		ASN1_STRING_set0(rek->encryptedKey, enckey, enckeylen);
	}

	return 1;
}