Problem - Kevin Tafuro

* If it's the client's turn to speak, abort. */
if (ctx->nonce[0] != SPC_CLIENT_DISTINGUISHER) abort();
ctx->nonce[0] = SPC_SERVER_DISTINGUISHER;
spc_get_status_and_nonce(ctx->fd, &status, nonce);
*end = status;
return spc_finish_decryption(ctx, status, nonce, len);
}
static void spc_get_status_and_nonce(int fd, unsigned char *status,
unsigned char *nonce) {
/* Read the status byte. If it's 0x00 or 0xff, we're going to look at
* the rest of the message, otherwise we'll just give up right away. */
spc_ssock_read(fd, status, 1);
if (*status != spc_msg_ok && *status != spc_msg_end) abort( );
spc_ssock_read(fd, nonce, SPC_CWC_NONCE_LEN);
}
static unsigned char *spc_finish_decryption(spc_ssock_t *ctx, unsigned char status,
unsigned char *nonce, size_t *len) {
size_t ctlen = 0, i;
unsigned char *ct, encoded_len[SPC_MLEN_FIELD_LEN];
/* Check the nonce. */
for (i = 0; i < SPC_CWC_NONCE_LEN; i++)
if (nonce[i] != ctx->nonce[i]) abort();
/* Read the length field. */
spc_ssock_read(ctx->fd, encoded_len, SPC_MLEN_FIELD_LEN);
for (i = 0; i < SPC_MLEN_FIELD_LEN; i++) {
ctlen cwc), &status, 1, ct, ctlen, nonce, ct)) {
free(ct);
abort();
}
*len = ctlen - SPC_CWC_TAG_LEN;
/* We'll go ahead and avoid the realloc(), leaving SPC_CWC_TAG_LEN extra
* bytes at the end of the buffer than we need to leave.
*/
return ct;
}
static void spc_ssock_read(int fd, unsigned char *msg, size_t mlen) {
ssize_t r;
498 | Chapter 9: Networking
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