X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/f2effd933f668bcb568c5c59f02e08b9e5df4b90..24ca682167d6d1f013d2733d96497cc545ce08f7:/auth-krb4.c diff --git a/auth-krb4.c b/auth-krb4.c index 556fef16..f7a144f9 100644 --- a/auth-krb4.c +++ b/auth-krb4.c @@ -1,210 +1,373 @@ /* - - auth-kerberos.c - - Dug Song - - Kerberos v4 authentication and ticket-passing routines. - - $Id$ -*/ + * Copyright (c) 1999 Dug Song. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ #include "includes.h" +RCSID("$OpenBSD: auth-krb4.c,v 1.25 2001/12/19 07:18:56 deraadt Exp $"); + +#include "ssh.h" +#include "ssh1.h" #include "packet.h" #include "xmalloc.h" -#include "ssh.h" +#include "log.h" +#include "servconf.h" +#include "uidswap.h" +#include "auth.h" + +#ifdef AFS +#include "radix.h" +#endif #ifdef KRB4 -int ssh_tf_init(uid_t uid) +extern ServerOptions options; + +static int +krb4_init(void *context) { - extern char *ticket; - char *tkt_root = TKT_ROOT; - struct stat st; - int fd; - - /* Set unique ticket string manually since we're still root. */ - ticket = xmalloc(MAXPATHLEN); + static int cleanup_registered = 0; + Authctxt *authctxt = (Authctxt *)context; + const char *tkt_root = TKT_ROOT; + struct stat st; + int fd; + + if (!authctxt->krb4_ticket_file) { + /* Set unique ticket string manually since we're still root. */ + authctxt->krb4_ticket_file = xmalloc(MAXPATHLEN); #ifdef AFS - if (lstat("/ticket", &st) != -1) - tkt_root = "/ticket/"; + 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); - - /* Make sure we own this ticket file, and we created it. */ - if (lstat(ticket, &st) == -1 && errno == ENOENT) { - /* good, no ticket file exists. create it. */ - if ((fd = open(ticket, O_RDWR|O_CREAT|O_EXCL, 0600)) != -1) { - close(fd); - return 1; - } - } - else { - /* file exists. make sure server_user owns it (e.g. just passed ticket), - and that it isn't a symlink, and that it is mode 600. */ - if (st.st_mode == (S_IFREG|S_IRUSR|S_IWUSR) && st.st_uid == uid) - return 1; - } - /* Failure. */ - log("WARNING: bad ticket file %s", ticket); - return 0; + snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%d", + tkt_root, authctxt->pw->pw_uid, getpid()); + krb_set_tkt_string(authctxt->krb4_ticket_file); + } + /* Register ticket cleanup in case of fatal error. */ + if (!cleanup_registered) { + fatal_add_cleanup(krb4_cleanup_proc, authctxt); + cleanup_registered = 1; + } + /* Try to create our ticket file. */ + if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) { + close(fd); + return (1); + } + /* Ticket file exists - make sure user owns it (just passed ticket). */ + if (lstat(authctxt->krb4_ticket_file, &st) != -1) { + if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) && + st.st_uid == authctxt->pw->pw_uid) + return (1); + } + /* Failure - cancel cleanup function, leaving ticket for inspection. */ + log("WARNING: bad ticket file %s", authctxt->krb4_ticket_file); + + fatal_remove_cleanup(krb4_cleanup_proc, authctxt); + cleanup_registered = 0; + + xfree(authctxt->krb4_ticket_file); + authctxt->krb4_ticket_file = NULL; + + return (0); } -int auth_krb4(const char *server_user, KTEXT auth, char **client) +/* + * try krb4 authentication, + * return 1 on success, 0 on failure, -1 if krb4 is not available + */ +int +auth_krb4_password(Authctxt *authctxt, const char *password) { - 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)); - - 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); - 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; + AUTH_DAT adata; + KTEXT_ST tkt; + struct hostent *hp; + struct passwd *pw; + char localhost[MAXHOSTNAMELEN], phost[INST_SZ], realm[REALM_SZ]; + u_int32_t faddr; + int r; + + if ((pw = authctxt->pw) == NULL) + return (0); + + /* + * 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(authctxt)) { + log("Couldn't initialize Kerberos ticket file for %s!", + pw->pw_name); + goto 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) { + debug("Kerberos v4 password authentication for %s " + "failed: %s", pw->pw_name, krb_err_txt[r]); + goto 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. + */ + gethostname(localhost, sizeof(localhost)); + strlcpy(phost, (char *)krb_get_phost(localhost), + sizeof(phost)); + r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33); + + if (r == KSUCCESS) { + if ((hp = gethostbyname(localhost)) == NULL) { + log("Couldn't get local host address!"); + goto 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. Disallow login. + */ + log("Kerberos v4 TGT for %s unverifiable, " + "no srvtab installed? krb_rd_req: %s", + pw->pw_name, krb_err_txt[r]); + goto failure; + } else if (r != KSUCCESS) { + log("Kerberos v4 %s ticket unverifiable: %s", + KRB4_SERVICE_NAME, krb_err_txt[r]); + goto failure; + } + } else if (r == KDC_PR_UNKNOWN) { + /* + * Disallow login if no rcmd service exists, and + * 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); + goto failure; + } else { + /* + * TGT is bad, forget it. Possibly spoofed! + */ + debug("WARNING: Kerberos v4 TGT possibly spoofed " + "for %s: %s", pw->pw_name, krb_err_txt[r]); + goto failure; + } + /* Authentication succeeded. */ + return (1); + } else + /* Logging in as root or no local Kerberos realm. */ + debug("Unable to authenticate to Kerberos."); + + failure: + krb4_cleanup_proc(authctxt); + + if (!options.kerberos_or_local_passwd) + return (0); + + /* Fall back to ordinary passwd authentication. */ + return (-1); +} + +void +krb4_cleanup_proc(void *context) +{ + Authctxt *authctxt = (Authctxt *)context; + debug("krb4_cleanup_proc called"); + if (authctxt->krb4_ticket_file) { + (void) dest_tkt(); + xfree(authctxt->krb4_ticket_file); + authctxt->krb4_ticket_file = NULL; + } +} + +int +auth_krb4(Authctxt *authctxt, KTEXT auth, char **client) +{ + AUTH_DAT adat = {0}; + KTEXT_ST reply; + Key_schedule schedule; + struct sockaddr_in local, foreign; + char instance[INST_SZ]; + socklen_t slen; + u_int cksum; + int r, s; + + s = packet_get_connection_in(); + + slen = sizeof(local); + memset(&local, 0, sizeof(local)); + if (getsockname(s, (struct sockaddr *) & local, &slen) < 0) + debug("getsockname failed: %.100s", strerror(errno)); + slen = sizeof(foreign); + memset(&foreign, 0, sizeof(foreign)); + if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 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, ""))) { + 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, authctxt->user) != KSUCCESS) { + log("Kerberos v4 .klogin authorization failed for %s to " + "account %s", *client, authctxt->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) { + 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) +int +auth_krb4_tgt(Authctxt *authctxt, const char *string) { - CREDENTIALS creds; - extern char *ticket; - int r; - - 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 uid %d", - creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm, - pw->pw_uid); - packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for uid %d", - creds.pname, creds.pinst[0] ? "." : "", creds.pinst, - creds.realm, pw->pw_uid); - goto auth_kerberos_tgt_failure; - } - if (!ssh_tf_init(pw->pw_uid) || - (r = in_tkt(creds.pname, creds.pinst)) || - (r = save_credentials(creds.service, creds.instance, creds.realm, - creds.session, creds.lifetime, creds.kvno, - &creds.ticket_st, creds.issue_date))) { - xfree(ticket); - ticket = NULL; - packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials"); - goto auth_kerberos_tgt_failure; - } - /* Successful authentication, passed all checks. */ - chown(ticket, 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); - - packet_start(SSH_SMSG_SUCCESS); - packet_send(); - packet_write_wait(); - return 1; - -auth_kerberos_tgt_failure: - memset(&creds, 0, sizeof(creds)); - packet_start(SSH_SMSG_FAILURE); - packet_send(); - packet_write_wait(); - return 0; + CREDENTIALS creds; + struct passwd *pw; + + if ((pw = authctxt->pw) == NULL) + goto failure; + + temporarily_use_uid(pw); + + if (!radix_to_creds(string, &creds)) { + log("Protocol error decoding Kerberos v4 TGT"); + goto 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); + goto failure; + } + if (!krb4_init(authctxt)) + goto failure; + + if (in_tkt(creds.pname, creds.pinst) != KSUCCESS) + goto failure; + + if (save_credentials(creds.service, creds.instance, creds.realm, + creds.session, creds.lifetime, creds.kvno, &creds.ticket_st, + creds.issue_date) != KSUCCESS) { + debug("Kerberos v4 TGT refused: couldn't save credentials"); + goto failure; + } + /* Successful authentication, passed all checks. */ + chown(tkt_string(), pw->pw_uid, pw->pw_gid); + + debug("Kerberos v4 TGT accepted (%s%s%s@%s)", + creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm); + memset(&creds, 0, sizeof(creds)); + + restore_uid(); + + return (1); + + failure: + krb4_cleanup_proc(authctxt); + memset(&creds, 0, sizeof(creds)); + restore_uid(); + + return (0); } -int auth_afs_token(struct passwd *pw, const char *token_string) +int +auth_afs_token(Authctxt *authctxt, 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 uid %d", creds.pname, - creds.realm, uid); - packet_send_debug("AFS token (%s@%s) rejected for uid %d", creds.pname, - creds.realm, uid); - 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); - packet_start(SSH_SMSG_SUCCESS); - packet_send(); - packet_write_wait(); - return 1; + CREDENTIALS creds; + struct passwd *pw; + uid_t uid; + + if ((pw = authctxt->pw) == NULL) + return (0); + + if (!radix_to_creds(token_string, &creds)) { + log("Protocol error decoding AFS token"); + 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); + else + uid = pw->pw_uid; + + if (kafs_settoken(creds.realm, uid, &creds)) { + log("AFS token (%s@%s) rejected for %s", + creds.pname, creds.realm, pw->pw_name); + memset(&creds, 0, sizeof(creds)); + return (0); + } + debug("AFS token accepted (%s@%s)", creds.pname, creds.realm); + memset(&creds, 0, sizeof(creds)); + + return (1); } #endif /* AFS */