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/*
* Copyright (C) 2013 Tobias Brunner
* Hochschule fuer Technik Rapperswil
*
* 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 "sshkey_encoder.h"
#include <asn1/asn1.h>
#include <asn1/oid.h>
#include <bio/bio_writer.h>
#define ECDSA_PREFIX "ecdsa-sha2-"
/**
* Write an EC domain parameter identifier as defined in RFC 5656
*/
static void write_ec_identifier(bio_writer_t *writer, char *prefix, int oid,
chunk_t enc)
{
char *curve, identifier[128];
switch (oid)
{
case OID_PRIME256V1:
curve = strdup("nistp256");
break;
case OID_SECT384R1:
curve = strdup("nistp384");
break;
case OID_SECT521R1:
curve = strdup("nistp521");
break;
default:
curve = asn1_oid_to_string(enc);
break;
}
if (curve && snprintf(identifier, sizeof(identifier), "%s%s", prefix,
curve) < sizeof(identifier))
{
writer->write_data32(writer, chunk_from_str(identifier));
}
free(curve);
}
/**
* Encode the public key as Base64 encoded SSH key blob
*/
static bool build_public_key(chunk_t *encoding, va_list args)
{
bio_writer_t *writer;
chunk_t n, e;
if (cred_encoding_args(args, CRED_PART_RSA_MODULUS, &n,
CRED_PART_RSA_PUB_EXP, &e, CRED_PART_END))
{
writer = bio_writer_create(0);
writer->write_data32(writer, chunk_from_str("ssh-rsa"));
writer->write_data32(writer, e);
writer->write_data32(writer, n);
*encoding = chunk_to_base64(writer->get_buf(writer), NULL);
writer->destroy(writer);
return TRUE;
}
else if (cred_encoding_args(args, CRED_PART_ECDSA_PUB_ASN1_DER, &n,
CRED_PART_END))
{
chunk_t params, alg, q;
int oid;
/* parse subjectPublicKeyInfo */
if (asn1_unwrap(&n, &n) != ASN1_SEQUENCE)
{
return FALSE;
}
oid = asn1_parse_algorithmIdentifier(n, 1, ¶ms);
if (oid != OID_EC_PUBLICKEY ||
asn1_unwrap(¶ms, ¶ms) != ASN1_OID)
{
return FALSE;
}
oid = asn1_known_oid(params);
if (oid == OID_UNKNOWN)
{
return FALSE;
}
if (asn1_unwrap(&n, &alg) != ASN1_SEQUENCE ||
asn1_unwrap(&n, &q) != ASN1_BIT_STRING)
{
return FALSE;
}
writer = bio_writer_create(0);
write_ec_identifier(writer, ECDSA_PREFIX, oid, params);
write_ec_identifier(writer, "", oid, params);
q = chunk_skip_zero(q);
writer->write_data32(writer, q);
*encoding = chunk_to_base64(writer->get_buf(writer), NULL);
writer->destroy(writer);
return TRUE;
}
return FALSE;
}
bool sshkey_encoder_encode(cred_encoding_type_t type, chunk_t *encoding,
va_list args)
{
switch (type)
{
case PUBKEY_SSHKEY:
return build_public_key(encoding, args);
default:
return FALSE;
}
}
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