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openssh/auth-krb4.c

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