xbps/lib/pubkey2fp.c

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/*
* An implementation of convertion from OpenSSL to OpenSSH public key format
*
* Copyright (c) 2008 Mounir IDRASSI <mounir.idrassi@idrix.fr>. All rights reserved.
*
* 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.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <openssl/bio.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include "xbps_api_impl.h"
static unsigned char pSshHeader[11] = {
0x00, 0x00, 0x00, 0x07, 0x73, 0x73, 0x68, 0x2D, 0x72, 0x73, 0x61
};
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static int
SshEncodeBuffer(unsigned char *pEncoding, int bufferLen, unsigned char *pBuffer)
{
int adjustedLen = bufferLen, index;
if (*pBuffer & 0x80) {
adjustedLen++;
pEncoding[4] = 0;
index = 5;
} else {
index = 4;
}
pEncoding[0] = (unsigned char) (adjustedLen >> 24);
pEncoding[1] = (unsigned char) (adjustedLen >> 16);
pEncoding[2] = (unsigned char) (adjustedLen >> 8);
pEncoding[3] = (unsigned char) (adjustedLen );
memcpy(&pEncoding[index], pBuffer, bufferLen);
return index + bufferLen;
}
unsigned char *
xbps_pubkey2fp(struct xbps_handle *xhp, xbps_data_t pubkey)
{
EVP_MD_CTX mdctx;
EVP_PKEY *pPubKey = NULL;
RSA *pRsa = NULL;
BIO *bio = NULL;
const void *pubkeydata;
unsigned char *md_value = NULL;
unsigned char *nBytes = NULL, *eBytes = NULL, *pEncoding = NULL;
unsigned int md_len = 0;
int index = 0, nLen = 0, eLen = 0, encodingLength = 0;
ERR_load_crypto_strings();
OpenSSL_add_all_algorithms();
pubkeydata = xbps_data_data_nocopy(pubkey);
bio = BIO_new_mem_buf(__UNCONST(pubkeydata), xbps_data_size(pubkey));
assert(bio);
pPubKey = PEM_read_bio_PUBKEY(bio, NULL, NULL, NULL);
if (!pPubKey) {
xbps_dbg_printf(xhp,
"unable to decode public key from the given file: %s\n",
ERR_error_string(ERR_get_error(), NULL));
goto error;
}
if (EVP_PKEY_type(pPubKey->type) != EVP_PKEY_RSA) {
xbps_dbg_printf(xhp, "only RSA public keys are currently supported\n");
goto error;
}
pRsa = EVP_PKEY_get1_RSA(pPubKey);
if (!pRsa) {
xbps_dbg_printf(xhp, "failed to get RSA public key : %s\n",
ERR_error_string(ERR_get_error(), NULL));
goto error;
}
// reading the modulus
nLen = BN_num_bytes(pRsa->n);
nBytes = (unsigned char*) malloc(nLen);
BN_bn2bin(pRsa->n, nBytes);
// reading the public exponent
eLen = BN_num_bytes(pRsa->e);
eBytes = (unsigned char*) malloc(eLen);
BN_bn2bin(pRsa->e, eBytes);
encodingLength = 11 + 4 + eLen + 4 + nLen;
// correct depending on the MSB of e and N
if (eBytes[0] & 0x80)
encodingLength++;
if (nBytes[0] & 0x80)
encodingLength++;
pEncoding = malloc(encodingLength);
memcpy(pEncoding, pSshHeader, 11);
index = SshEncodeBuffer(&pEncoding[11], eLen, eBytes);
index = SshEncodeBuffer(&pEncoding[11 + index], nLen, nBytes);
/*
* Compute the RSA fingerprint (MD5).
*/
EVP_MD_CTX_init(&mdctx);
EVP_DigestInit_ex(&mdctx, EVP_md5(), NULL);
EVP_DigestUpdate(&mdctx, pEncoding, encodingLength);
md_value = malloc(EVP_MAX_MD_SIZE);
if (EVP_DigestFinal_ex(&mdctx, md_value, &md_len) == 0) {
free(md_value);
md_value = NULL;
} else {
md_value[md_len] = '\0';
}
EVP_MD_CTX_cleanup(&mdctx);
error:
if (bio)
BIO_free_all(bio);
if (pRsa)
RSA_free(pRsa);
if (pPubKey)
EVP_PKEY_free(pPubKey);
if (nBytes)
free(nBytes);
if (eBytes)
free(eBytes);
if (pEncoding)
free(pEncoding);
EVP_cleanup();
ERR_free_strings();
return md_value;
}