352 lines
9.6 KiB
C
352 lines
9.6 KiB
C
/*
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* Dug Song <dugsong@UMICH.EDU>
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* Kerberos v4 authentication and ticket-passing routines.
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*
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* $FreeBSD$
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*/
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#include "includes.h"
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#include "packet.h"
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#include "xmalloc.h"
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#include "ssh.h"
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#include "servconf.h"
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#ifdef KRB4
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char *ticket = NULL;
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extern ServerOptions options;
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/*
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* try krb4 authentication,
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* return 1 on success, 0 on failure, -1 if krb4 is not available
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*/
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int
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auth_krb4_password(struct passwd * pw, const char *password)
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{
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AUTH_DAT adata;
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KTEXT_ST tkt;
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struct hostent *hp;
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unsigned long faddr;
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char localhost[MAXHOSTNAMELEN];
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char phost[INST_SZ];
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char realm[REALM_SZ];
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int r;
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/*
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* Try Kerberos password authentication only for non-root
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* users and only if Kerberos is installed.
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*/
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if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
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/* Set up our ticket file. */
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if (!krb4_init(pw->pw_uid)) {
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log("Couldn't initialize Kerberos ticket file for %s!",
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pw->pw_name);
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goto kerberos_auth_failure;
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}
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/* Try to get TGT using our password. */
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r = krb_get_pw_in_tkt((char *) pw->pw_name, "",
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realm, "krbtgt", realm,
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DEFAULT_TKT_LIFE, (char *) password);
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if (r != INTK_OK) {
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packet_send_debug("Kerberos V4 password "
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"authentication for %s failed: %s",
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pw->pw_name, krb_err_txt[r]);
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goto kerberos_auth_failure;
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}
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/* Successful authentication. */
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chown(tkt_string(), pw->pw_uid, pw->pw_gid);
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/*
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* Now that we have a TGT, try to get a local
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* "rcmd" ticket to ensure that we are not talking
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* to a bogus Kerberos server.
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*/
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(void) gethostname(localhost, sizeof(localhost));
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(void) strlcpy(phost, (char *) krb_get_phost(localhost),
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INST_SZ);
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r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
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if (r == KSUCCESS) {
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if (!(hp = gethostbyname(localhost))) {
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log("Couldn't get local host address!");
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goto kerberos_auth_failure;
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}
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memmove((void *) &faddr, (void *) hp->h_addr,
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sizeof(faddr));
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/* Verify our "rcmd" ticket. */
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r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
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faddr, &adata, "");
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if (r == RD_AP_UNDEC) {
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/*
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* Probably didn't have a srvtab on
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* localhost. Allow login.
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*/
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log("Kerberos V4 TGT for %s unverifiable, "
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"no srvtab installed? krb_rd_req: %s",
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pw->pw_name, krb_err_txt[r]);
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} else if (r != KSUCCESS) {
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log("Kerberos V4 %s ticket unverifiable: %s",
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KRB4_SERVICE_NAME, krb_err_txt[r]);
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goto kerberos_auth_failure;
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}
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} else if (r == KDC_PR_UNKNOWN) {
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/*
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* Allow login if no rcmd service exists, but
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* log the error.
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*/
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log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
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"not registered, or srvtab is wrong?", pw->pw_name,
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krb_err_txt[r], KRB4_SERVICE_NAME, phost);
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} else {
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/*
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* TGT is bad, forget it. Possibly spoofed!
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*/
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packet_send_debug("WARNING: Kerberos V4 TGT "
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"possibly spoofed for %s: %s",
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pw->pw_name, krb_err_txt[r]);
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goto kerberos_auth_failure;
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}
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/* Authentication succeeded. */
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return 1;
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kerberos_auth_failure:
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krb4_cleanup_proc(NULL);
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if (!options.krb4_or_local_passwd)
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return 0;
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} else {
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/* Logging in as root or no local Kerberos realm. */
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packet_send_debug("Unable to authenticate to Kerberos.");
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}
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/* Fall back to ordinary passwd authentication. */
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return -1;
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}
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void
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krb4_cleanup_proc(void *ignore)
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{
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debug("krb4_cleanup_proc called");
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if (ticket) {
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(void) dest_tkt();
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xfree(ticket);
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ticket = NULL;
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}
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}
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int
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krb4_init(uid_t uid)
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{
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static int cleanup_registered = 0;
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const char *tkt_root = TKT_ROOT;
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struct stat st;
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int fd;
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if (!ticket) {
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/* Set unique ticket string manually since we're still root. */
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ticket = xmalloc(MAXPATHLEN);
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#ifdef AFS
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if (lstat("/ticket", &st) != -1)
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tkt_root = "/ticket/";
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#endif /* AFS */
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snprintf(ticket, MAXPATHLEN, "%s%d_%d", tkt_root, uid, getpid());
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(void) krb_set_tkt_string(ticket);
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}
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/* Register ticket cleanup in case of fatal error. */
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if (!cleanup_registered) {
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fatal_add_cleanup(krb4_cleanup_proc, NULL);
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cleanup_registered = 1;
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}
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/* Try to create our ticket file. */
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if ((fd = mkstemp(ticket)) != -1) {
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close(fd);
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return 1;
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}
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/* Ticket file exists - make sure user owns it (just passed ticket). */
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if (lstat(ticket, &st) != -1) {
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if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
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st.st_uid == uid)
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return 1;
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}
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/* Failure - cancel cleanup function, leaving bad ticket for inspection. */
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log("WARNING: bad ticket file %s", ticket);
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fatal_remove_cleanup(krb4_cleanup_proc, NULL);
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cleanup_registered = 0;
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xfree(ticket);
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ticket = NULL;
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return 0;
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}
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int
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auth_krb4(const char *server_user, KTEXT auth, char **client)
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{
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AUTH_DAT adat = {0};
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KTEXT_ST reply;
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char instance[INST_SZ];
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int r, s;
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socklen_t slen;
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u_int cksum;
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Key_schedule schedule;
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struct sockaddr_in local, foreign;
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s = packet_get_connection_in();
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slen = sizeof(local);
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memset(&local, 0, sizeof(local));
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if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
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debug("getsockname failed: %.100s", strerror(errno));
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slen = sizeof(foreign);
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memset(&foreign, 0, sizeof(foreign));
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if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
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debug("getpeername failed: %.100s", strerror(errno));
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fatal_cleanup();
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}
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instance[0] = '*';
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instance[1] = 0;
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/* Get the encrypted request, challenge, and session key. */
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if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, ""))) {
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packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
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return 0;
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}
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des_key_sched((des_cblock *) adat.session, schedule);
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*client = xmalloc(MAX_K_NAME_SZ);
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(void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
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*adat.pinst ? "." : "", adat.pinst, adat.prealm);
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/* Check ~/.klogin authorization now. */
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if (kuserok(&adat, (char *) server_user) != KSUCCESS) {
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packet_send_debug("Kerberos V4 .klogin authorization failed!");
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log("Kerberos V4 .klogin authorization failed for %s to account %s",
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*client, server_user);
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xfree(*client);
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return 0;
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}
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/* Increment the checksum, and return it encrypted with the
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session key. */
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cksum = adat.checksum + 1;
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cksum = htonl(cksum);
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/* If we can't successfully encrypt the checksum, we send back an
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empty message, admitting our failure. */
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if ((r = krb_mk_priv((u_char *) & cksum, reply.dat, sizeof(cksum) + 1,
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schedule, &adat.session, &local, &foreign)) < 0) {
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packet_send_debug("Kerberos V4 mk_priv: (%d) %s", r, krb_err_txt[r]);
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reply.dat[0] = 0;
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reply.length = 0;
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} else
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reply.length = r;
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/* Clear session key. */
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memset(&adat.session, 0, sizeof(&adat.session));
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packet_start(SSH_SMSG_AUTH_KRB4_RESPONSE);
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packet_put_string((char *) reply.dat, reply.length);
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packet_send();
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packet_write_wait();
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return 1;
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}
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#endif /* KRB4 */
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#ifdef AFS
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int
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auth_krb4_tgt(struct passwd *pw, const char *string)
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{
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CREDENTIALS creds;
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if (!radix_to_creds(string, &creds)) {
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log("Protocol error decoding Kerberos V4 tgt");
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packet_send_debug("Protocol error decoding Kerberos V4 tgt");
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goto auth_kerberos_tgt_failure;
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}
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if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
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strlcpy(creds.service, "krbtgt", sizeof creds.service);
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if (strcmp(creds.service, "krbtgt")) {
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log("Kerberos V4 tgt (%s%s%s@%s) rejected for %s", creds.pname,
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creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
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pw->pw_name);
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packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
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creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
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creds.realm, pw->pw_name);
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goto auth_kerberos_tgt_failure;
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}
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if (!krb4_init(pw->pw_uid))
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goto auth_kerberos_tgt_failure;
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if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
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goto auth_kerberos_tgt_failure;
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if (save_credentials(creds.service, creds.instance, creds.realm,
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creds.session, creds.lifetime, creds.kvno,
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&creds.ticket_st, creds.issue_date) != KSUCCESS) {
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packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
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goto auth_kerberos_tgt_failure;
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}
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/* Successful authentication, passed all checks. */
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chown(tkt_string(), pw->pw_uid, pw->pw_gid);
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packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
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creds.service, creds.instance, creds.realm, creds.pname,
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creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
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memset(&creds, 0, sizeof(creds));
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packet_start(SSH_SMSG_SUCCESS);
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packet_send();
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packet_write_wait();
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return 1;
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auth_kerberos_tgt_failure:
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krb4_cleanup_proc(NULL);
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memset(&creds, 0, sizeof(creds));
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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return 0;
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}
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int
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auth_afs_token(struct passwd *pw, const char *token_string)
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{
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CREDENTIALS creds;
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uid_t uid = pw->pw_uid;
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if (!radix_to_creds(token_string, &creds)) {
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log("Protocol error decoding AFS token");
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packet_send_debug("Protocol error decoding AFS token");
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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return 0;
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}
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if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
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strlcpy(creds.service, "afs", sizeof creds.service);
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if (strncmp(creds.pname, "AFS ID ", 7) == 0)
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uid = atoi(creds.pname + 7);
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if (kafs_settoken(creds.realm, uid, &creds)) {
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log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
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pw->pw_name);
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packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
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creds.realm, pw->pw_name);
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memset(&creds, 0, sizeof(creds));
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packet_start(SSH_SMSG_FAILURE);
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packet_send();
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packet_write_wait();
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return 0;
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}
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packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
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creds.realm, creds.pname, creds.realm);
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memset(&creds, 0, sizeof(creds));
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packet_start(SSH_SMSG_SUCCESS);
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packet_send();
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packet_write_wait();
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return 1;
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}
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#endif /* AFS */
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