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/*
*****************************************************************************
*
* File: fko_decode.c
*
* Author: Damien S. Stuart
*
* Purpose: Decrypt and decode an FKO SPA message.
*
* Copyright 2009-2010 Damien Stuart (dstuart@dstuart.org)
*
* License (GNU Public License):
*
* 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.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*****************************************************************************
*/
#include "fko_common.h"
#include "fko.h"
#include "cipher_funcs.h"
#include "base64.h"
#include "digest.h"
/* Decrypt the encoded SPA data.
*/
int
fko_decode_spa_data(fko_ctx_t ctx)
{
char *tbuf, *ndx;
int t_size;
/* Check for required data.
*/
if(ctx->encoded_msg == NULL
|| strlen(ctx->encoded_msg) < MIN_SPA_ENCODED_MSG_SIZE)
return(FKO_ERROR_INVALID_DATA);
/* Move the Digest to its place in the context.
*/
ndx = strrchr(ctx->encoded_msg, ':'); /* Find the last : in the data */
if(ndx == NULL)
return(FKO_ERROR_INVALID_DATA);
ndx++;
t_size = strlen(ndx);
switch(t_size)
{
case MD5_B64_LENGTH:
ctx->digest_type = FKO_DIGEST_MD5;
break;
case SHA1_B64_LENGTH:
ctx->digest_type = FKO_DIGEST_SHA1;
break;
case SHA256_B64_LENGTH:
ctx->digest_type = FKO_DIGEST_SHA256;
break;
case SHA384_B64_LENGTH:
ctx->digest_type = FKO_DIGEST_SHA384;
break;
case SHA512_B64_LENGTH:
ctx->digest_type = FKO_DIGEST_SHA512;
break;
default: /* Invalid or unsupported digest */
return(FKO_ERROR_INVALID_DIGEST_TYPE);
}
/* Copy the digest into the context and terminate the encoded data
* at that point so the original digest is not part of the
* encoded string.
*/
ctx->digest = strdup(ndx);
if(ctx->digest == NULL)
return(FKO_ERROR_MEMORY_ALLOCATION);
/* Zero out the rest of the encoded_msg bucket...
*/
bzero((ndx-1), t_size);
/* Make a tmp bucket for processing base64 encoded data and
* other general use.
*/
tbuf = malloc(FKO_ENCODE_TMP_BUF_SIZE);
if(tbuf == NULL)
return(FKO_ERROR_MEMORY_ALLOCATION);
/* Can now verify the digest.
*/
switch(ctx->digest_type)
{
case FKO_DIGEST_MD5:
md5_base64(tbuf, (unsigned char*)ctx->encoded_msg, strlen(ctx->encoded_msg));
break;
case FKO_DIGEST_SHA1:
sha1_base64(tbuf, (unsigned char*)ctx->encoded_msg, strlen(ctx->encoded_msg));
break;
case FKO_DIGEST_SHA256:
sha256_base64(tbuf, (unsigned char*)ctx->encoded_msg, strlen(ctx->encoded_msg));
break;
case FKO_DIGEST_SHA384:
sha384_base64(tbuf, (unsigned char*)ctx->encoded_msg, strlen(ctx->encoded_msg));
break;
case FKO_DIGEST_SHA512:
sha512_base64(tbuf, (unsigned char*)ctx->encoded_msg, strlen(ctx->encoded_msg));
break;
}
/* We give up here if the computed digest does not match the
* digest in the message data.
*/
if(strcmp(ctx->digest, tbuf))
{
free(tbuf);
return(FKO_ERROR_DIGEST_VERIFICATION_FAILED);
}
/* Now we will work through the encoded data and extract (and base64-
* decode where necessary), the SPA data fields and populate the context.
*/
ndx = ctx->encoded_msg;
/* The rand val data */
if((t_size = strcspn(ndx, ":")) < FKO_RAND_VAL_SIZE)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
ctx->rand_val = calloc(1, FKO_RAND_VAL_SIZE+1);
if(ctx->rand_val == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
ctx->rand_val = strncpy(ctx->rand_val, ndx, FKO_RAND_VAL_SIZE);
/* Jump to the next field (username). We need to use the temp buffer
* for the base64 decode step.
*/
ndx += t_size + 1;
if((t_size = strcspn(ndx, ":")) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
strlcpy(tbuf, ndx, t_size+1);
ctx->username = malloc(t_size+1); /* Yes, more than we need */
if(ctx->username == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
b64_decode(tbuf, (unsigned char*)ctx->username);
/* Extract the timestamp value.
*/
ndx += t_size + 1;
if((t_size = strcspn(ndx, ":")) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
strlcpy(tbuf, ndx, t_size+1);
ctx->timestamp = (unsigned int)atoi(tbuf);
/* Extract the version string.
*/
ndx += t_size + 1;
if((t_size = strcspn(ndx, ":")) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
ctx->version = malloc(t_size+1);
if(ctx->version == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
strlcpy(ctx->version, ndx, t_size+1);
/* Extract the message type value.
*/
ndx += t_size + 1;
if((t_size = strcspn(ndx, ":")) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
strlcpy(tbuf, ndx, t_size+1);
ctx->message_type = (unsigned int)atoi(tbuf);
/* Extract the SPA message string.
*/
ndx += t_size + 1;
if((t_size = strcspn(ndx, ":")) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
strlcpy(tbuf, ndx, t_size+1);
ctx->message = malloc(t_size+1); /* Yes, more than we need */
if(ctx->message == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
b64_decode(tbuf, (unsigned char*)ctx->message);
/* Extract nat_access string if the message_type indicates so.
*/
if( ctx->message_type == FKO_NAT_ACCESS_MSG
|| ctx->message_type == FKO_LOCAL_NAT_ACCESS_MSG
|| ctx->message_type == FKO_CLIENT_TIMEOUT_NAT_ACCESS_MSG
|| ctx->message_type == FKO_CLIENT_TIMEOUT_LOCAL_NAT_ACCESS_MSG)
{
ndx += t_size + 1;
if((t_size = strcspn(ndx, ":")) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
strlcpy(tbuf, ndx, t_size+1);
ctx->nat_access = malloc(t_size+1); /* Yes, more than we need */
if(ctx->nat_access == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
b64_decode(tbuf, (unsigned char*)ctx->nat_access);
}
/* Now look for a server_auth string.
*/
ndx += t_size + 1;
if((t_size = strlen(ndx)) > 0)
{
/* There is data, but what is it?
* If the message_type does not have a timeout, assume it is a
* server_auth field.
*/
if( ctx->message_type != FKO_CLIENT_TIMEOUT_ACCESS_MSG
&& ctx->message_type != FKO_CLIENT_TIMEOUT_NAT_ACCESS_MSG
&& ctx->message_type != FKO_CLIENT_TIMEOUT_LOCAL_NAT_ACCESS_MSG)
{
strlcpy(tbuf, ndx, t_size+1);
ctx->server_auth = malloc(t_size+1); /* Yes, more than we need */
if(ctx->server_auth == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
b64_decode(tbuf, (unsigned char*)ctx->server_auth);
/* At this point we should be done.
*/
free(tbuf);
/* Call the context initialized.
*/
ctx->initval = FKO_CTX_INITIALIZED;
FKO_SET_CTX_INITIALIZED(ctx);
return(FKO_SUCCESS);
}
/* If we are here then we may still have a server_auth string,
* or a timeout, or both. So we look for a ':' delimiter. If
* it is there we have both, if not we check the message_type
* again.
*/
if(strchr(ndx, ':'))
{
t_size = strcspn(ndx, ":");
/* Looks like we have both, so assume this is the
*/
strlcpy(tbuf, ndx, t_size+1);
ctx->server_auth = malloc(t_size+1); /* Yes, more than we need */
if(ctx->server_auth == NULL)
{
free(tbuf);
return(FKO_ERROR_MEMORY_ALLOCATION);
}
b64_decode(tbuf, (unsigned char*)ctx->server_auth);
ndx += t_size + 1;
}
/* Now we look for a timeout value if one is supposed to be there.
*/
if( ctx->message_type == FKO_CLIENT_TIMEOUT_ACCESS_MSG
|| ctx->message_type == FKO_CLIENT_TIMEOUT_NAT_ACCESS_MSG
|| ctx->message_type == FKO_CLIENT_TIMEOUT_LOCAL_NAT_ACCESS_MSG)
{
if((t_size = strlen(ndx)) < 1)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
/* Should be a number only.
*/
if(strspn(ndx, "0123456789") != t_size)
{
free(tbuf);
return(FKO_ERROR_INVALID_DATA);
}
ctx->client_timeout = (unsigned int)atoi(ndx);
}
}
/* Done with the tmp buffer.
*/
free(tbuf);
/* Call the context initialized.
*/
ctx->initval = FKO_CTX_INITIALIZED;
FKO_SET_CTX_INITIALIZED(ctx);
return(FKO_SUCCESS);
}
/***EOF***/
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