Exemplo n.º 1
0
static int
is_replay_file_cache(fko_srv_options_t *opts, char *digest)
{
    int         digest_len = 0;

    struct digest_cache_list *digest_list_ptr = NULL;

    digest_len = strlen(digest);

    /* Check the cache for the SPA packet digest
    */
    for (digest_list_ptr = opts->digest_cache;
            digest_list_ptr != NULL;
            digest_list_ptr = digest_list_ptr->next) {

        if (constant_runtime_cmp(digest_list_ptr->cache_info.digest,
                    digest, digest_len) == 0) {

            replay_warning(opts, &(digest_list_ptr->cache_info));

            return(SPA_MSG_REPLAY);
        }
    }
    return(SPA_MSG_SUCCESS);
}
Exemplo n.º 2
0
/* See if we need to add the "hQ" string to the front of the
 * encrypted data.
*/
int
add_gpg_prefix(fko_ctx_t ctx)
{
    char           *tbuf;

    if(constant_runtime_cmp(ctx->encrypted_msg,
            B64_GPG_PREFIX, B64_GPG_PREFIX_STR_LEN) != 0)
    {
        /* We need to realloc space for the prefix.
        */
        tbuf = realloc(ctx->encrypted_msg, ctx->encrypted_msg_len
                    + B64_GPG_PREFIX_STR_LEN+1);
        if(tbuf == NULL)
            return(FKO_ERROR_MEMORY_ALLOCATION);

        memmove(tbuf+B64_GPG_PREFIX_STR_LEN, tbuf, ctx->encrypted_msg_len);

        ctx->encrypted_msg = memcpy(tbuf,
                B64_GPG_PREFIX, B64_GPG_PREFIX_STR_LEN);

        /* Adjust the encoded msg len for added SALT value and Make sure we
         * are still a properly NULL-terminated string (Ubuntu was one system
         * for which this was an issue).
        */
        ctx->encrypted_msg_len += B64_GPG_PREFIX_STR_LEN;
        tbuf[ctx->encrypted_msg_len] = '\0';

        ctx->added_gpg_prefix = 1;
    }

    return(FKO_SUCCESS);
}
Exemplo n.º 3
0
/* See if we need to add the "Salted__" string to the front of the
 * encrypted data.
*/
int
add_salted_str(fko_ctx_t ctx)
{
    char           *tbuf;

#if AFL_FUZZING
    ctx->added_salted_str = 1;
    return(FKO_SUCCESS);
#endif

    /* We only add the base64 encoded salt to data that is already base64
     * encoded
    */
    if(is_base64((unsigned char *)ctx->encrypted_msg,
            ctx->encrypted_msg_len) == 0)
        return(FKO_ERROR_INVALID_DATA_ENCODE_NOTBASE64);

    if(constant_runtime_cmp(ctx->encrypted_msg,
            B64_RIJNDAEL_SALT, B64_RIJNDAEL_SALT_STR_LEN) != 0)
    {
        /* We need to realloc space for the salt.
        */
        tbuf = realloc(ctx->encrypted_msg, ctx->encrypted_msg_len
                    + B64_RIJNDAEL_SALT_STR_LEN+1);
        if(tbuf == NULL)
            return(FKO_ERROR_MEMORY_ALLOCATION);

        memmove(tbuf+B64_RIJNDAEL_SALT_STR_LEN, tbuf, ctx->encrypted_msg_len);
	//Ìí¼ÓÑΡ£
        ctx->encrypted_msg = memcpy(tbuf,
                B64_RIJNDAEL_SALT, B64_RIJNDAEL_SALT_STR_LEN);

        /* Adjust the encoded msg len for added SALT value and Make sure we
         * are still a properly NULL-terminated string (Ubuntu was one system
         * for which this was an issue).
        */
        ctx->encrypted_msg_len += B64_RIJNDAEL_SALT_STR_LEN;
        tbuf[ctx->encrypted_msg_len] = '\0';

        ctx->added_salted_str = 1;
    }

    return(FKO_SUCCESS);
}
Exemplo n.º 4
0
/* Validate and in some cases preprocess/reformat the SPA data.  Return an
 * error code value if there is any indication the data is not valid spa data.
*/
static int
preprocess_spa_data(const fko_srv_options_t *opts, spa_pkt_info_t *spa_pkt)
{

    char    *ndx = (char *)&(spa_pkt->packet_data);
    int      i, pkt_data_len = 0;

    pkt_data_len = spa_pkt->packet_data_len;

    /* At this point, we can reset the packet data length to 0.  This is our
     * indicator to the rest of the program that we do not have a current
     * spa packet to process (after this one that is).
    */
    spa_pkt->packet_data_len = 0;

    /* These two checks are already done in process_packet(), but this is a
     * defensive measure to run them again here
    */
    if(pkt_data_len < MIN_SPA_DATA_SIZE)
        return(SPA_MSG_BAD_DATA);

    if(pkt_data_len > MAX_SPA_PACKET_LEN)
        return(SPA_MSG_BAD_DATA);

    /* Ignore any SPA packets that contain the Rijndael or GnuPG prefixes
     * since an attacker might have tacked them on to a previously seen
     * SPA packet in an attempt to get past the replay check.  And, we're
     * no worse off since a legitimate SPA packet that happens to include
     * a prefix after the outer one is stripped off won't decrypt properly
     * anyway because libfko would not add a new one.
    */
    if(constant_runtime_cmp(ndx, B64_RIJNDAEL_SALT, B64_RIJNDAEL_SALT_STR_LEN) == 0)
        return(SPA_MSG_BAD_DATA);

    if(pkt_data_len > MIN_GNUPG_MSG_SIZE
            && constant_runtime_cmp(ndx, B64_GPG_PREFIX, B64_GPG_PREFIX_STR_LEN) == 0)
        return(SPA_MSG_BAD_DATA);

    /* Detect and parse out SPA data from an HTTP request. If the SPA data
     * starts with "GET /" and the user agent starts with "Fwknop", then
     * assume it is a SPA over HTTP request.
    */
    if(strncasecmp(opts->config[CONF_ENABLE_SPA_OVER_HTTP], "Y", 1) == 0
      && strncasecmp(ndx, "GET /", 5) == 0
      && strstr(ndx, "User-Agent: Fwknop") != NULL)
    {
        /* This looks like an HTTP request, so let's see if we are
         * configured to accept such request and if so, find the SPA
         * data.
        */

        /* Now extract, adjust (convert characters translated by the fwknop
         * client), and reset the SPA message itself.
        */
        strlcpy((char *)spa_pkt->packet_data, ndx+5, pkt_data_len);
        pkt_data_len -= 5;

        for(i=0; i<pkt_data_len; i++)
        {
            if(isspace(*ndx)) /* The first space marks the end of the req */
            {
                *ndx = '\0';
                break;
            }
            else if(*ndx == '-') /* Convert '-' to '+' */
                *ndx = '+';
            else if(*ndx == '_') /* Convert '_' to '/' */
                *ndx = '/';

            ndx++;
        }

        if(i < MIN_SPA_DATA_SIZE)
            return(SPA_MSG_BAD_DATA);

        spa_pkt->packet_data_len = pkt_data_len = i;
    }

    /* Require base64-encoded data
    */
    if(! is_base64(spa_pkt->packet_data, pkt_data_len))
        return(SPA_MSG_NOT_SPA_DATA);


    /* If we made it here, we have no reason to assume this is not SPA data.
     * The ultimate test will be whether the SPA data authenticates via an
     * HMAC anyway.
    */
    return(FKO_SUCCESS);
}
Exemplo n.º 5
0
int
fko_verify_hmac(fko_ctx_t ctx,
    const char * const hmac_key, const int hmac_key_len)
{
    char    *hmac_digest_from_data = NULL;
    char    *tbuf = NULL;
    int      res = FKO_SUCCESS;
    int      hmac_b64_digest_len = 0, zero_free_rv = FKO_SUCCESS;

    /* Must be initialized
    */
    if(!CTX_INITIALIZED(ctx))
        return(FKO_ERROR_CTX_NOT_INITIALIZED);

    if (! is_valid_encoded_msg_len(ctx->encrypted_msg_len))
        return(FKO_ERROR_INVALID_DATA_HMAC_MSGLEN_VALIDFAIL);

    if(hmac_key_len > MAX_DIGEST_BLOCK_LEN)
        return(FKO_ERROR_INVALID_HMAC_KEY_LEN);

    if(ctx->hmac_type == FKO_HMAC_MD5)
        hmac_b64_digest_len = MD5_B64_LEN;
    else if(ctx->hmac_type == FKO_HMAC_SHA1)
        hmac_b64_digest_len = SHA1_B64_LEN;
    else if(ctx->hmac_type == FKO_HMAC_SHA256)
        hmac_b64_digest_len = SHA256_B64_LEN;
    else if(ctx->hmac_type == FKO_HMAC_SHA384)
        hmac_b64_digest_len = SHA384_B64_LEN;
    else if(ctx->hmac_type == FKO_HMAC_SHA512)
        hmac_b64_digest_len = SHA512_B64_LEN;
    else
        return(FKO_ERROR_UNSUPPORTED_HMAC_MODE);

    if((ctx->encrypted_msg_len - hmac_b64_digest_len)
            < MIN_SPA_ENCODED_MSG_SIZE)
        return(FKO_ERROR_INVALID_DATA_HMAC_ENCMSGLEN_VALIDFAIL);

    /* Get digest value
    */
    hmac_digest_from_data = strndup((ctx->encrypted_msg
            + ctx->encrypted_msg_len - hmac_b64_digest_len),
            hmac_b64_digest_len);

    if(hmac_digest_from_data == NULL)
        return(FKO_ERROR_MEMORY_ALLOCATION);

    /* Now we chop the HMAC digest off of the encrypted msg
    */
    tbuf = strndup(ctx->encrypted_msg,
            ctx->encrypted_msg_len - hmac_b64_digest_len);

    if(tbuf == NULL)
    {
        if(zero_free(hmac_digest_from_data, strnlen(hmac_digest_from_data,
                MAX_SPA_ENCODED_MSG_SIZE)) == FKO_SUCCESS)
            return(FKO_ERROR_MEMORY_ALLOCATION);
        else
            return(FKO_ERROR_ZERO_OUT_DATA);
    }

    if(zero_free(ctx->encrypted_msg, ctx->encrypted_msg_len) != FKO_SUCCESS)
        zero_free_rv = FKO_ERROR_ZERO_OUT_DATA;

    ctx->encrypted_msg      = tbuf;
    ctx->encrypted_msg_len -= hmac_b64_digest_len;

    if(ctx->encryption_mode == FKO_ENC_MODE_ASYMMETRIC)
    {
        /* See if we need to add the "hQ" string to the front of the
         * encrypted data.
         */
        if(! ctx->added_gpg_prefix)
        {
            res = add_gpg_prefix(ctx);
        }
    }
    else
    {
        /* See if we need to add the "Salted__" string to the front of the
         * encrypted data.
         */
        if(! ctx->added_salted_str)
        {
            res = add_salted_str(ctx);
        }
    }

    if (res != FKO_SUCCESS)
    {
        if(zero_free(hmac_digest_from_data, strnlen(hmac_digest_from_data,
                        MAX_SPA_ENCODED_MSG_SIZE)) != FKO_SUCCESS)
            zero_free_rv = FKO_ERROR_ZERO_OUT_DATA;

        if(zero_free_rv == FKO_SUCCESS)
            return(res);
        else
            return(zero_free_rv);
    }

    /* Calculate the HMAC from the encrypted data and then
     * compare
    */
    res = fko_set_spa_hmac_type(ctx, ctx->hmac_type);
    if(res == FKO_SUCCESS)
    {
        res = fko_set_spa_hmac(ctx, hmac_key, hmac_key_len);

        if(res == FKO_SUCCESS)
        {
            if(constant_runtime_cmp(hmac_digest_from_data,
                    ctx->msg_hmac, hmac_b64_digest_len) != 0)
            {
                res = FKO_ERROR_INVALID_DATA_HMAC_COMPAREFAIL;
            }
        }
    }

    if(zero_free(hmac_digest_from_data, strnlen(hmac_digest_from_data,
                    MAX_SPA_ENCODED_MSG_SIZE)) != FKO_SUCCESS)
        zero_free_rv = FKO_ERROR_ZERO_OUT_DATA;

    if(res == FKO_SUCCESS)
        return(zero_free_rv);
    else
        return(res);
}
Exemplo n.º 6
0
static int
verify_digest(char *tbuf, int t_size, fko_ctx_t ctx)
{
#if AFL_FUZZING
    return FKO_SUCCESS;
#endif

    switch(ctx->digest_type)
    {
        case FKO_DIGEST_MD5:
            md5_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA1:
            sha1_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA256:
            sha256_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA384:
            sha384_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA512:
            sha512_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        /* Note that we check SHA3_256 and SHA3_512 below because the
         * digest lengths for these are the same as SHA256 and SHA512
         * respectively, and setting the digest type for an incoming
         * decrypted SPA packet is done initially by looking at the
         * length.
         */

        default: /* Invalid or unsupported digest */
            return(FKO_ERROR_INVALID_DIGEST_TYPE);
    }

    /* We give up here if the computed digest does not match the
     * digest in the message data.
    */
    if(constant_runtime_cmp(ctx->digest, tbuf, t_size) != 0)
    {
        /* Could potentially also have been SHA3_256 or SHA3_512 */
        if(ctx->digest_type == FKO_DIGEST_SHA256)
        {
            memset(tbuf, 0, FKO_ENCODE_TMP_BUF_SIZE);
            sha3_256_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            if(constant_runtime_cmp(ctx->digest, tbuf, t_size) != 0)
            {
                return(FKO_ERROR_DIGEST_VERIFICATION_FAILED);
            }
            else
            {
                ctx->digest_type = FKO_DIGEST_SHA3_256;
                ctx->digest_len  = SHA3_256_B64_LEN;
            }

        }
        else if(ctx->digest_type == FKO_DIGEST_SHA512)
        {
            memset(tbuf, 0, FKO_ENCODE_TMP_BUF_SIZE);
            sha3_512_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            if(constant_runtime_cmp(ctx->digest, tbuf, t_size) != 0)
            {
                return(FKO_ERROR_DIGEST_VERIFICATION_FAILED);
            }
            else
            {
                ctx->digest_type = FKO_DIGEST_SHA3_512;
                ctx->digest_len  = SHA3_512_B64_LEN;
            }

        }
        else
            return(FKO_ERROR_DIGEST_VERIFICATION_FAILED);
    }

    return FKO_SUCCESS;
}
Exemplo n.º 7
0
/* Decode the encoded SPA data.
*/
int
fko_decode_spa_data(fko_ctx_t ctx)
{
    char       *tbuf, *ndx, *tmp;
    int         t_size, i, is_err;

    if (! is_valid_encoded_msg_len(ctx->encoded_msg_len))
        return(FKO_ERROR_INVALID_DATA_DECODE_MSGLEN_VALIDFAIL);

    /* Make sure there are no non-ascii printable chars
    */
    for (i=0; i < (int)strnlen(ctx->encoded_msg, MAX_SPA_ENCODED_MSG_SIZE); i++)
        if(isprint(ctx->encoded_msg[i]) == 0)
            return(FKO_ERROR_INVALID_DATA_DECODE_NON_ASCII);

    /* Make sure there are enough fields in the SPA packet
     * delimited with ':' chars
    */
    ndx = ctx->encoded_msg;
    for (i=0; i < MAX_SPA_FIELDS; i++)
    {
        if ((tmp = strchr(ndx, ':')) == NULL)
            break;

        ndx = tmp;
        ndx++;
    }

    if (i < MIN_SPA_FIELDS)
        return(FKO_ERROR_INVALID_DATA_DECODE_LT_MIN_FIELDS);

    t_size = strnlen(ndx, SHA512_B64_LEN+1);

    switch(t_size)
    {
        case MD5_B64_LEN:
            ctx->digest_type = FKO_DIGEST_MD5;
            ctx->digest_len  = MD5_B64_LEN;
            break;

        case SHA1_B64_LEN:
            ctx->digest_type = FKO_DIGEST_SHA1;
            ctx->digest_len  = SHA1_B64_LEN;
            break;

        case SHA256_B64_LEN:
            ctx->digest_type = FKO_DIGEST_SHA256;
            ctx->digest_len  = SHA256_B64_LEN;
            break;

        case SHA384_B64_LEN:
            ctx->digest_type = FKO_DIGEST_SHA384;
            ctx->digest_len  = SHA384_B64_LEN;
            break;

        case SHA512_B64_LEN:
            ctx->digest_type = FKO_DIGEST_SHA512;
            ctx->digest_len  = SHA512_B64_LEN;
            break;

        default: /* Invalid or unsupported digest */
            return(FKO_ERROR_INVALID_DIGEST_TYPE);
    }

    if (ctx->encoded_msg_len - t_size < 0)
        return(FKO_ERROR_INVALID_DATA_DECODE_ENC_MSG_LEN_MT_T_SIZE);

    if(ctx->digest != NULL)
        free(ctx->digest);

    /* 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);

    ctx->encoded_msg_len -= t_size+1;

    /* 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, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA1:
            sha1_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA256:
            sha256_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA384:
            sha384_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;

        case FKO_DIGEST_SHA512:
            sha512_base64(tbuf, (unsigned char*)ctx->encoded_msg, ctx->encoded_msg_len);
            break;
    }

    /* We give up here if the computed digest does not match the
     * digest in the message data.
    */
    if(constant_runtime_cmp(ctx->digest, tbuf, t_size) != 0)
    {
        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_DECODE_RAND_MISSING);
    }

    if(ctx->rand_val != NULL)
        free(ctx->rand_val);

    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_DECODE_USERNAME_MISSING);
    }

    if (t_size > MAX_SPA_USERNAME_SIZE)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_USERNAME_TOOBIG);
    }

    strlcpy(tbuf, ndx, t_size+1);

    if(ctx->username != NULL)
        free(ctx->username);

    ctx->username = malloc(t_size+1); /* Yes, more than we need */
    if(ctx->username == NULL)
    {
        free(tbuf);
        return(FKO_ERROR_MEMORY_ALLOCATION);
    }

    if(b64_decode(tbuf, (unsigned char*)ctx->username) < 0)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_USERNAME_DECODEFAIL);
    }
    if(validate_username(ctx->username) != FKO_SUCCESS)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_USERNAME_VALIDFAIL);
    }

    /* Extract the timestamp value.
    */
    ndx += t_size + 1;
    if((t_size = strcspn(ndx, ":")) < 1)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_TIMESTAMP_MISSING);
    }

    if (t_size > MAX_SPA_TIMESTAMP_SIZE)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_TIMESTAMP_TOOBIG);
    }

    strlcpy(tbuf, ndx, t_size+1);

    ctx->timestamp = (unsigned int) strtol_wrapper(tbuf,
            0, -1, NO_EXIT_UPON_ERR, &is_err);
    if(is_err != FKO_SUCCESS)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_TIMESTAMP_DECODEFAIL);
    }

    /* Extract the version string.
    */
    ndx += t_size + 1;
    if((t_size = strcspn(ndx, ":")) < 1)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_VERSION_MISSING);
    }

    if (t_size > MAX_SPA_VERSION_SIZE)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_VERSION_TOOBIG);
    }

    if(ctx->version != NULL)
        free(ctx->version);

    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_DECODE_MSGTYPE_MISSING);
    }

    if (t_size > MAX_SPA_MESSAGE_TYPE_SIZE)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_MSGTYPE_TOOBIG);
    }

    strlcpy(tbuf, ndx, t_size+1);

    ctx->message_type = strtol_wrapper(tbuf, 0,
            FKO_LAST_MSG_TYPE, NO_EXIT_UPON_ERR, &is_err);
    if(is_err != FKO_SUCCESS)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_MSGTYPE_DECODEFAIL);
    }

    /* Extract the SPA message string.
    */
    ndx += t_size + 1;
    if((t_size = strcspn(ndx, ":")) < 1)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_MESSAGE_MISSING);
    }

    if (t_size > MAX_SPA_MESSAGE_SIZE)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_MESSAGE_TOOBIG);
    }

    strlcpy(tbuf, ndx, t_size+1);

    if(ctx->message != NULL)
        free(ctx->message);

    ctx->message = malloc(t_size+1); /* Yes, more than we need */
    if(ctx->message == NULL)
    {
        free(tbuf);
        return(FKO_ERROR_MEMORY_ALLOCATION);
    }

    if(b64_decode(tbuf, (unsigned char*)ctx->message) < 0)
    {
        free(tbuf);
        return(FKO_ERROR_INVALID_DATA_DECODE_MESSAGE_DECODEFAIL);
    }

    if(ctx->message_type == FKO_COMMAND_MSG)
    {
        /* Require a message similar to: 1.2.3.4,<command>
        */
        if(validate_cmd_msg(ctx->message) != FKO_SUCCESS)
        {
            free(tbuf);
            return(FKO_ERROR_INVALID_DATA_DECODE_MESSAGE_VALIDFAIL);
        }
    }
    else
    {
        /* Require a message similar to: 1.2.3.4,tcp/22
        */
        if(validate_access_msg(ctx->message) != FKO_SUCCESS)
        {
            free(tbuf);
            return(FKO_ERROR_INVALID_DATA_DECODE_ACCESS_VALIDFAIL);
        }
    }

    /* 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_DECODE_NATACCESS_MISSING);
        }

        if (t_size > MAX_SPA_MESSAGE_SIZE)
        {
            free(tbuf);
            return(FKO_ERROR_INVALID_DATA_DECODE_NATACCESS_TOOBIG);
        }

        strlcpy(tbuf, ndx, t_size+1);

        if(ctx->nat_access != NULL)
            free(ctx->nat_access);

        ctx->nat_access = malloc(t_size+1); /* Yes, more than we need */
        if(ctx->nat_access == NULL)
        {
            free(tbuf);
            return(FKO_ERROR_MEMORY_ALLOCATION);
        }

        if(b64_decode(tbuf, (unsigned char*)ctx->nat_access) < 0)
        {
            free(tbuf);
            return(FKO_ERROR_INVALID_DATA_DECODE_NATACCESS_DECODEFAIL);
        }

        if(validate_nat_access_msg(ctx->nat_access) != FKO_SUCCESS)
        {
            free(tbuf);
            return(FKO_ERROR_INVALID_DATA_DECODE_NATACCESS_VALIDFAIL);
        }
    }

    /* Now look for a server_auth string.
    */
    ndx += t_size + 1;
    if((t_size = strlen(ndx)) > 0)
    {
        if (t_size > MAX_SPA_MESSAGE_SIZE)
        {
            free(tbuf);
            return(FKO_ERROR_INVALID_DATA_DECODE_SRVAUTH_MISSING);
        }

        /* 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);

            if(ctx->server_auth != NULL)
                free(ctx->server_auth);

            ctx->server_auth = malloc(t_size+1); /* Yes, more than we need */
            if(ctx->server_auth == NULL)
            {
                free(tbuf);
                return(FKO_ERROR_MEMORY_ALLOCATION);
            }

            if(b64_decode(tbuf, (unsigned char*)ctx->server_auth) < 0)
            {
                free(tbuf);
                return(FKO_ERROR_INVALID_DATA_DECODE_SRVAUTH_DECODEFAIL);
            }

            /* 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, ":");

            if (t_size > MAX_SPA_MESSAGE_SIZE)
            {
                free(tbuf);
                return(FKO_ERROR_INVALID_DATA_DECODE_EXTRA_TOOBIG);
            }

            /* Looks like we have both, so assume this is the 
            */
            strlcpy(tbuf, ndx, t_size+1);

            if(ctx->server_auth != NULL)
                free(ctx->server_auth);

            ctx->server_auth = malloc(t_size+1); /* Yes, more than we need */
            if(ctx->server_auth == NULL)
            {
                free(tbuf);
                return(FKO_ERROR_MEMORY_ALLOCATION);
            }

            if(b64_decode(tbuf, (unsigned char*)ctx->server_auth) < 0)
            {
                free(tbuf);
                return(FKO_ERROR_INVALID_DATA_DECODE_EXTRA_DECODEFAIL);
            }

            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_DECODE_TIMEOUT_MISSING);
            }
            if (t_size > MAX_SPA_MESSAGE_SIZE)
            {
                free(tbuf);
                return(FKO_ERROR_INVALID_DATA_DECODE_TIMEOUT_TOOBIG);
            }

            /* Should be a number only.
            */
            if(strspn(ndx, "0123456789") != t_size)
            {
                free(tbuf);
                return(FKO_ERROR_INVALID_DATA_DECODE_TIMEOUT_VALIDFAIL);
            }

            ctx->client_timeout = (unsigned int) strtol_wrapper(ndx, 0,
                    (2 << 15), NO_EXIT_UPON_ERR, &is_err);
            if(is_err != FKO_SUCCESS)
            {
                free(tbuf);
                return(FKO_ERROR_INVALID_DATA_DECODE_TIMEOUT_DECODEFAIL);
            }
        }
    }

    /* Done with the tmp buffer.
    */
    free(tbuf);

    /* Call the context initialized.
    */
    ctx->initval = FKO_CTX_INITIALIZED;
    FKO_SET_CTX_INITIALIZED(ctx);

    return(FKO_SUCCESS);
}