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strongswan/src/pluto/pkcs7.c

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/* Support of PKCS#7 data structures
* Copyright (C) 2005 Jan Hutter, Martin Willi
* Copyright (C) 2002-2009 Andreas Steffen
*
* HSR 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 <stdlib.h>
#include <string.h>
#include <freeswan.h>
#include <library.h>
#include <debug.h>
#include <asn1/asn1.h>
#include <asn1/asn1_parser.h>
#include <asn1/oid.h>
#include <crypto/rngs/rng.h>
#include <crypto/crypters/crypter.h>
#include "constants.h"
#include "defs.h"
#include "x509.h"
#include "certs.h"
#include "pkcs7.h"
const contentInfo_t empty_contentInfo = {
OID_UNKNOWN , /* type */
{ NULL, 0 } /* content */
};
/**
* ASN.1 definition of the PKCS#7 ContentInfo type
*/
static const asn1Object_t contentInfoObjects[] = {
{ 0, "contentInfo", ASN1_SEQUENCE, ASN1_NONE }, /* 0 */
{ 1, "contentType", ASN1_OID, ASN1_BODY }, /* 1 */
{ 1, "content", ASN1_CONTEXT_C_0, ASN1_OPT|ASN1_BODY }, /* 2 */
{ 1, "end opt", ASN1_EOC, ASN1_END }, /* 3 */
{ 0, "exit", ASN1_EOC, ASN1_EXIT }
};
#define PKCS7_INFO_TYPE 1
#define PKCS7_INFO_CONTENT 2
/**
* 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, "digestEncryptionAlgorithm", ASN1_EOC, ASN1_RAW }, /* 21 */
{ 3, "encryptedDigest", 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_DIGEST_ALG 3
#define PKCS7_SIGNED_CONTENT_INFO 5
#define PKCS7_SIGNED_CERT 7
#define PKCS7_SIGNER_INFO 13
#define PKCS7_SIGNED_ISSUER 16
#define PKCS7_SIGNED_SERIAL_NUMBER 17
#define PKCS7_DIGEST_ALGORITHM 18
#define PKCS7_AUTH_ATTRIBUTES 19
#define PKCS7_DIGEST_ENC_ALGORITHM 21
#define PKCS7_ENCRYPTED_DIGEST 22
/**
* 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_ENVELOPED_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
#define PKCS7_ENVELOPED_ROOF 15
/**
* PKCS7 contentInfo OIDs
*/
static u_char ASN1_pkcs7_data_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x01
};
static u_char ASN1_pkcs7_signed_data_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x02
};
static u_char ASN1_pkcs7_enveloped_data_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x03
};
static u_char ASN1_pkcs7_signed_enveloped_data_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x04
};
static u_char ASN1_pkcs7_digested_data_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x05
};
static char ASN1_pkcs7_encrypted_data_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x06
};
static const chunk_t ASN1_pkcs7_data_oid =
chunk_from_buf(ASN1_pkcs7_data_oid_str);
static const chunk_t ASN1_pkcs7_signed_data_oid =
chunk_from_buf(ASN1_pkcs7_signed_data_oid_str);
static const chunk_t ASN1_pkcs7_enveloped_data_oid =
chunk_from_buf(ASN1_pkcs7_enveloped_data_oid_str);
static const chunk_t ASN1_pkcs7_signed_enveloped_data_oid =
chunk_from_buf(ASN1_pkcs7_signed_enveloped_data_oid_str);
static const chunk_t ASN1_pkcs7_digested_data_oid =
chunk_from_buf(ASN1_pkcs7_digested_data_oid_str);
static const chunk_t ASN1_pkcs7_encrypted_data_oid =
chunk_from_buf(ASN1_pkcs7_encrypted_data_oid_str);
/**
* 3DES and DES encryption OIDs
*/
static u_char ASN1_3des_ede_cbc_oid_str[] = {
0x06, 0x08, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x03, 0x07
};
static u_char ASN1_des_cbc_oid_str[] = {
0x06, 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x07
};
static const chunk_t ASN1_3des_ede_cbc_oid =
chunk_from_buf(ASN1_3des_ede_cbc_oid_str);
static const chunk_t ASN1_des_cbc_oid =
chunk_from_buf(ASN1_des_cbc_oid_str);
/**
* PKCS#7 attribute type OIDs
*/
static u_char ASN1_contentType_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x09, 0x03
};
static u_char ASN1_messageDigest_oid_str[] = {
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x09, 0x04
};
static const chunk_t ASN1_contentType_oid =
chunk_from_buf(ASN1_contentType_oid_str);
static const chunk_t ASN1_messageDigest_oid =
chunk_from_buf(ASN1_messageDigest_oid_str);
/**
* Parse PKCS#7 ContentInfo object
*/
bool pkcs7_parse_contentInfo(chunk_t blob, u_int level0, contentInfo_t *cInfo)
{
asn1_parser_t *parser;
chunk_t object;
int objectID;
bool success = FALSE;
parser = asn1_parser_create(contentInfoObjects, blob);
parser->set_top_level(parser, level0);
while (parser->iterate(parser, &objectID, &object))
{
if (objectID == PKCS7_INFO_TYPE)
{
cInfo->type = asn1_known_oid(object);
if (cInfo->type < OID_PKCS7_DATA
|| cInfo->type > OID_PKCS7_ENCRYPTED_DATA)
{
DBG1("unknown pkcs7 content type");
goto end;
}
}
else if (objectID == PKCS7_INFO_CONTENT)
{
cInfo->content = object;
}
}
success = parser->success(parser);
end:
parser->destroy(parser);
return success;
}
/**
* Parse a PKCS#7 signedData object
*/
bool pkcs7_parse_signedData(chunk_t blob, contentInfo_t *data, x509cert_t **cert,
chunk_t *attributes, const x509cert_t *cacert)
{
u_char buf[BUF_LEN];
asn1_parser_t *parser;
chunk_t object;
int digest_alg = OID_UNKNOWN;
int enc_alg = OID_UNKNOWN;
int signerInfos = 0;
int objectID;
bool success = FALSE;
contentInfo_t cInfo = empty_contentInfo;
chunk_t encrypted_digest = chunk_empty;
if (!pkcs7_parse_contentInfo(blob, 0, &cInfo))
{
return FALSE;
}
if (cInfo.type != OID_PKCS7_SIGNED_DATA)
{
DBG1("pkcs7 content type is not signedData");
return FALSE;
}
parser = asn1_parser_create(signedDataObjects, blob);
parser->set_top_level(parser, 2);
while (parser->iterate(parser, &objectID, &object))
{
u_int level = parser->get_level(parser);
switch (objectID)
{
case PKCS7_DIGEST_ALG:
digest_alg = asn1_parse_algorithmIdentifier(object, level, NULL);
break;
case PKCS7_SIGNED_CONTENT_INFO:
if (data != NULL)
{
pkcs7_parse_contentInfo(object, level, data);
}
break;
case PKCS7_SIGNED_CERT:
if (cert != NULL)
{
chunk_t cert_blob = chunk_clone(object);
x509cert_t *newcert = malloc_thing(x509cert_t);
*newcert = empty_x509cert;
DBG2(" parsing pkcs7-wrapped certificate");
if (parse_x509cert(cert_blob, level+1, newcert))
{
newcert->next = *cert;
*cert = newcert;
}
else
{
free_x509cert(newcert);
}
}
break;
case PKCS7_SIGNER_INFO:
signerInfos++;
DBG2(" signer #%d", signerInfos);
break;
case PKCS7_SIGNED_ISSUER:
dntoa(buf, BUF_LEN, object);
DBG2(" '%s'",buf);
break;
case PKCS7_AUTH_ATTRIBUTES:
if (attributes != NULL)
{
*attributes = object;
*attributes->ptr = ASN1_SET;
}
break;
case PKCS7_DIGEST_ALGORITHM:
digest_alg = asn1_parse_algorithmIdentifier(object, level, NULL);
break;
case PKCS7_DIGEST_ENC_ALGORITHM:
enc_alg = asn1_parse_algorithmIdentifier(object, level, NULL);
break;
case PKCS7_ENCRYPTED_DIGEST:
encrypted_digest = object;
}
}
success = parser->success(parser);
parser->destroy(parser);
if (!success)
{
return FALSE;
}
/* check the signature only if a cacert is available */
if (cacert != NULL)
{
if (signerInfos == 0)
{
DBG1("no signerInfo object found");
return FALSE;
}
else if (signerInfos > 1)
{
DBG1("more than one signerInfo object found");
return FALSE;
}
if (attributes->ptr == NULL)
{
DBG1("no authenticatedAttributes object found");
return FALSE;
}
if (!check_signature(*attributes, encrypted_digest, digest_alg,
enc_alg, cacert))
{
DBG1("invalid signature");
return FALSE;
}
else
{
DBG2("signature is valid");
}
}
return TRUE;
}
/**
* Parse a PKCS#7 envelopedData object
*/
bool pkcs7_parse_envelopedData(chunk_t blob, chunk_t *data,
chunk_t serialNumber,
const RSA_private_key_t *key)
{
asn1_parser_t *parser;
chunk_t object;
chunk_t iv = chunk_empty;
chunk_t symmetric_key = chunk_empty;
chunk_t encrypted_content = chunk_empty;
crypter_t *crypter = NULL;
u_char buf[BUF_LEN];
int enc_alg = OID_UNKNOWN;
int content_enc_alg = OID_UNKNOWN;
int objectID;
bool success = FALSE;
contentInfo_t cInfo = empty_contentInfo;
*data = chunk_empty;
if (!pkcs7_parse_contentInfo(blob, 0, &cInfo))
{
goto failed;
}
if (cInfo.type != OID_PKCS7_ENVELOPED_DATA)
{
DBG1("pkcs7 content type is not envelopedData");
goto failed;
}
parser = asn1_parser_create(envelopedDataObjects, cInfo.content);
parser->set_top_level(parser, 2);
while (parser->iterate(parser, &objectID, &object))
{
u_int level = parser->get_level(parser);
switch (objectID)
{
case PKCS7_ENVELOPED_VERSION:
if (*object.ptr != 0)
{
DBG1("envelopedData version is not 0");
goto end;
}
break;
case PKCS7_RECIPIENT_INFO_VERSION:
if (*object.ptr != 0)
{
DBG1("recipient info version is not 0");
goto end;
}
break;
case PKCS7_ISSUER:
dntoa(buf, BUF_LEN, object);
DBG2(" '%s'", buf);
break;
case PKCS7_SERIAL_NUMBER:
if (!chunk_equals(serialNumber, object))
{
DBG1("serial numbers do not match");
goto end;
}
break;
case PKCS7_ENCRYPTION_ALG:
enc_alg = asn1_parse_algorithmIdentifier(object, level, NULL);
if (enc_alg != OID_RSA_ENCRYPTION)
{
DBG1("only rsa encryption supported");
goto end;
}
break;
case PKCS7_ENCRYPTED_KEY:
if (!RSA_decrypt(key, object, &symmetric_key))
{
DBG1("symmetric key could not be decrypted with rsa");
goto end;
}
DBG4("symmetric key %B", &symmetric_key);
break;
case PKCS7_CONTENT_TYPE:
if (asn1_known_oid(object) != OID_PKCS7_DATA)
{
DBG1("encrypted content not of type pkcs7 data");
goto end;
}
break;
case PKCS7_CONTENT_ENC_ALGORITHM:
content_enc_alg = asn1_parse_algorithmIdentifier(object, level, &iv);
if (content_enc_alg == OID_UNKNOWN)
{
DBG1("unknown content encryption algorithm");
goto end;
}
if (!asn1_parse_simple_object(&iv, ASN1_OCTET_STRING, level+1, "IV"))
{
DBG1("IV could not be parsed");
goto end;
}
break;
case PKCS7_ENCRYPTED_CONTENT:
encrypted_content = object;
break;
}
}
success = parser->success(parser);
end:
parser->destroy(parser);
if (!success)
{
goto failed;
}
success = FALSE;
/* decrypt the content */
{
encryption_algorithm_t alg;
size_t key_size;
crypter_t *crypter;
alg = encryption_algorithm_from_oid(content_enc_alg, &key_size);
if (alg == ENCR_UNDEFINED)
{
DBG1("unsupported content encryption algorithm");
goto failed;
}
crypter = lib->crypto->create_crypter(lib->crypto, alg, key_size);
if (crypter == NULL)
{
DBG1("crypter %N not available", encryption_algorithm_names, alg);
goto failed;
}
if (symmetric_key.len != crypter->get_key_size(crypter))
{
DBG1("symmetric key length %d is wrong", symmetric_key.len);
goto failed;
}
if (iv.len != crypter->get_block_size(crypter))
{
DBG1("IV length %d is wrong", iv.len);
goto failed;
}
crypter->set_key(crypter, symmetric_key);
crypter->decrypt(crypter, encrypted_content, iv, data);
DBG4("decrypted content with padding: %B", data);
}
/* remove the padding */
{
u_char *pos = data->ptr + data->len - 1;
u_char pattern = *pos;
size_t padding = pattern;
if (padding > data->len)
{
DBG1("padding greater than data length");
goto failed;
}
data->len -= padding;
while (padding-- > 0)
{
if (*pos-- != pattern)
{
DBG1("wrong padding pattern");
goto failed;
}
}
}
success = TRUE;
failed:
DESTROY_IF(crypter);
chunk_clear(&symmetric_key);
if (!success)
{
free(data->ptr);
}
return success;
}
/**
* @brief Builds a contentType attribute
*
* @return ASN.1 encoded contentType attribute
*/
chunk_t pkcs7_contentType_attribute(void)
{
return asn1_wrap(ASN1_SEQUENCE, "cm"
, ASN1_contentType_oid
, asn1_simple_object(ASN1_SET, ASN1_pkcs7_data_oid));
}
/**
* @brief Builds a messageDigest attribute
*
*
* @param[in] blob content to create digest of
* @param[in] digest_alg digest algorithm to be used
* @return ASN.1 encoded messageDigest attribute
*
*/
chunk_t pkcs7_messageDigest_attribute(chunk_t content, int digest_alg)
{
u_char digest_buf[MAX_DIGEST_LEN];
chunk_t digest = { digest_buf, MAX_DIGEST_LEN };
compute_digest(content, digest_alg, &digest);
return asn1_wrap(ASN1_SEQUENCE, "cm"
, ASN1_messageDigest_oid
, asn1_wrap(ASN1_SET, "m"
, asn1_simple_object(ASN1_OCTET_STRING, digest)
)
);
}
/**
* build a DER-encoded contentInfo object
*/
static chunk_t pkcs7_build_contentInfo(contentInfo_t *cInfo)
{
chunk_t content_type;
/* select DER-encoded OID for pkcs7 contentInfo type */
switch(cInfo->type)
{
case OID_PKCS7_DATA:
content_type = ASN1_pkcs7_data_oid;
break;
case OID_PKCS7_SIGNED_DATA:
content_type = ASN1_pkcs7_signed_data_oid;
break;
case OID_PKCS7_ENVELOPED_DATA:
content_type = ASN1_pkcs7_enveloped_data_oid;
break;
case OID_PKCS7_SIGNED_ENVELOPED_DATA:
content_type = ASN1_pkcs7_signed_enveloped_data_oid;
break;
case OID_PKCS7_DIGESTED_DATA:
content_type = ASN1_pkcs7_digested_data_oid;
break;
case OID_PKCS7_ENCRYPTED_DATA:
content_type = ASN1_pkcs7_encrypted_data_oid;
break;
case OID_UNKNOWN:
default:
DBG1("invalid pkcs7 contentInfo type");
return chunk_empty;
}
return (cInfo->content.ptr == NULL)
? asn1_simple_object(ASN1_SEQUENCE, content_type)
: asn1_wrap(ASN1_SEQUENCE, "cm"
, content_type
, asn1_simple_object(ASN1_CONTEXT_C_0, cInfo->content)
);
}
/**
* build issuerAndSerialNumber object
*/
chunk_t pkcs7_build_issuerAndSerialNumber(const x509cert_t *cert)
{
return asn1_wrap(ASN1_SEQUENCE, "cm"
, cert->issuer
, asn1_simple_object(ASN1_INTEGER, cert->serialNumber));
}
/**
* create a signed pkcs7 contentInfo object
*/
chunk_t pkcs7_build_signedData(chunk_t data, chunk_t attributes,
const x509cert_t *cert, int digest_alg,
const RSA_private_key_t *key)
{
contentInfo_t pkcs7Data, signedData;
chunk_t authenticatedAttributes, encryptedDigest, signerInfo, cInfo;
chunk_t digestAlgorithm = asn1_algorithmIdentifier(digest_alg);
if (attributes.ptr != NULL)
{
encryptedDigest = pkcs1_build_signature(attributes, digest_alg
, key, FALSE);
authenticatedAttributes = chunk_clone(attributes);
*authenticatedAttributes.ptr = ASN1_CONTEXT_C_0;
}
else
{
encryptedDigest = (data.ptr == NULL)? chunk_empty
: pkcs1_build_signature(data, digest_alg, key, FALSE);
authenticatedAttributes = chunk_empty;
}
signerInfo = asn1_wrap(ASN1_SEQUENCE, "cmcmcm"
, ASN1_INTEGER_1
, pkcs7_build_issuerAndSerialNumber(cert)
, digestAlgorithm
, authenticatedAttributes
, asn1_algorithmIdentifier(OID_RSA_ENCRYPTION)
, encryptedDigest);
pkcs7Data.type = OID_PKCS7_DATA;
pkcs7Data.content = (data.ptr == NULL)? chunk_empty
: asn1_simple_object(ASN1_OCTET_STRING, data);
signedData.type = OID_PKCS7_SIGNED_DATA;
signedData.content = asn1_wrap(ASN1_SEQUENCE, "cmmmm"
, ASN1_INTEGER_1
, asn1_simple_object(ASN1_SET, digestAlgorithm)
, pkcs7_build_contentInfo(&pkcs7Data)
, asn1_simple_object(ASN1_CONTEXT_C_0, cert->certificate)
, asn1_wrap(ASN1_SET, "m", signerInfo));
cInfo = pkcs7_build_contentInfo(&signedData);
DBG3("signedData %B", &cInfo);
free(pkcs7Data.content.ptr);
free(signedData.content.ptr);
return cInfo;
}
/**
* create a symmetrically encrypted pkcs7 contentInfo object
*/
chunk_t pkcs7_build_envelopedData(chunk_t data, const x509cert_t *cert, int enc_alg)
{
encryption_algorithm_t alg;
size_t alg_key_size;
RSA_public_key_t public_key;
chunk_t symmetricKey, iv, in, out;
crypter_t *crypter;
alg = encryption_algorithm_from_oid(enc_alg, &alg_key_size);
crypter = lib->crypto->create_crypter(lib->crypto, alg,
alg_key_size/BITS_PER_BYTE);
if (crypter == NULL)
{
DBG1("crypter for %N not available", encryption_algorithm_names, alg);
return chunk_empty;
}
/* generate a true random symmetric encryption key and a pseudo-random iv */
{
rng_t *rng;
rng = lib->crypto->create_rng(lib->crypto, RNG_TRUE);
rng->allocate_bytes(rng, crypter->get_key_size(crypter), &symmetricKey);
DBG4("symmetric encryption key %B", &symmetricKey);
rng->destroy(rng);
rng = lib->crypto->create_rng(lib->crypto, RNG_WEAK);
rng->allocate_bytes(rng, crypter->get_block_size(crypter), &iv);
DBG4("initialization vector: %B", &iv);
rng->destroy(rng);
}
/* pad the data to a multiple of the block size */
{
size_t block_size = crypter->get_block_size(crypter);
size_t padding = block_size - data.len % block_size;
in.len = data.len + padding;
in.ptr = malloc(in.len);
DBG2("padding %u bytes of data to multiple block size of %u bytes",
data.len, in.len);
/* copy data */
memcpy(in.ptr, data.ptr, data.len);
/* append padding */
memset(in.ptr + data.len, padding, padding);
}
DBG3("padded unencrypted data %B", &in);
/* symmetric encryption of data object */
crypter->set_key(crypter, symmetricKey);
crypter->encrypt(crypter, in, iv, &out);
crypter->destroy(crypter);
DBG3("encrypted data %B", &out);
free(in.ptr);
free(iv.ptr);
init_RSA_public_key(&public_key, cert->publicExponent, cert->modulus);
/* build pkcs7 enveloped data object */
{
chunk_t contentEncryptionAlgorithm = asn1_wrap(ASN1_SEQUENCE, "mm"
, asn1_build_known_oid(enc_alg)
, asn1_simple_object(ASN1_OCTET_STRING, iv));
chunk_t encryptedContentInfo = asn1_wrap(ASN1_SEQUENCE, "cmm"
, ASN1_pkcs7_data_oid
, contentEncryptionAlgorithm
, asn1_wrap(ASN1_CONTEXT_S_0, "m", out));
chunk_t encryptedKey = asn1_wrap(ASN1_OCTET_STRING, "m"
, RSA_encrypt(&public_key, symmetricKey));
chunk_t recipientInfo = asn1_wrap(ASN1_SEQUENCE, "cmcm"
, ASN1_INTEGER_0
, pkcs7_build_issuerAndSerialNumber(cert)
, asn1_algorithmIdentifier(OID_RSA_ENCRYPTION)
, encryptedKey);
chunk_t cInfo;
contentInfo_t envelopedData;
envelopedData.type = OID_PKCS7_ENVELOPED_DATA;
envelopedData.content = asn1_wrap(ASN1_SEQUENCE, "cmm"
, ASN1_INTEGER_0
, asn1_wrap(ASN1_SET, "m", recipientInfo)
, encryptedContentInfo);
cInfo = pkcs7_build_contentInfo(&envelopedData);
DBG3("envelopedData %B", &cInfo);
free_RSA_public_content(&public_key);
free(envelopedData.content.ptr);
free(symmetricKey.ptr);
return cInfo;
}
}
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