Problem - Kevin Tafuro

eturn result;
}
int spc_accept_key(char *filename, char *ipnum, EVP_PKEY *key) {
int result;
char answer[80];
result = spc_lookup_key(filename, ipnum, key);
if (result = = 1) return 1;
if (result = = -1) {
for (;;) {
printf("FATAL ERROR! A different key has been received from the server "
"%s\nthan we have on record. Do you wish to continue? ", ipnum);
if (!fgets(answer, sizeof(answer), stdin)) continue;
if (answer[0] = = 'Y' || answer[0] = = 'y') return 1;
if (answer[0] = = 'N' || answer[0] = = 'n') return 0;
}
}
for (;;) {
printf("WARNING! The server %s has presented has presented a key for which "
"we have no\nprior knowledge. Do you want to [r]eject the key, "
"[a]ccept and remember it,\nor allow its use for only this [o]ne "
"time? ", ipnum);
if (!fgets(answer, sizeof(answer), stdin)) continue;
if (answer[0] = = 'r' || answer[0] = = 'R') return 0;
if (answer[0] = = 'o' || answer[0] = = 'O') return 1;
if (answer[0] = = 'a' || answer[0] = = 'A') break;
}
if (!spc_remember_key(filename, ipnum, key))
printf("Error remembering the key! It will be accepted this one time only "
"instead.\n");
return 1;
}
See Also
Recipes 7.17, 10.5
8.20 Providing Forward Secrecy in a Symmetric
System
Problem
When using a series of (session) keys generated from a master secret, as described in
the previous recipe, we want to limit the scope of a key compromise. That is, if a
derived key is stolen, or even if the master key is stolen, we would like to ensure that
no data encrypted by previous session keys can be read by attackers as a result of the
444 | Chapter 8: Authentication and Key Exchange
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.