/* * CIFS user-space helper. * Copyright (C) Igor Mammedov (niallain@gmail.com) 2007 * Copyright (C) Jeff Layton (jlayton@redhat.com) 2009 * * Used by /sbin/request-key for handling * cifs upcall for kerberos authorization of access to share and * cifs upcall for DFS srver name resolving (IPv4/IPv6 aware). * You should have keyutils installed and add something like the * following lines to /etc/request-key.conf file: create cifs.spnego * * /usr/local/sbin/cifs.upcall %k create dns_resolver * * /usr/local/sbin/cifs.upcall %k * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #include "includes.h" #include "../libcli/auth/spnego.h" #include "smb_krb5.h" #include <keyutils.h> #include <getopt.h> #include "cifs_spnego.h" #define CIFS_DEFAULT_KRB5_DIR "/tmp" #define CIFS_DEFAULT_KRB5_PREFIX "krb5cc_" #define MAX_CCNAME_LEN PATH_MAX + 5 const char *CIFSSPNEGO_VERSION = "1.3"; static const char *prog = "cifs.upcall"; typedef enum _sectype { NONE = 0, KRB5, MS_KRB5 } sectype_t; /* does the ccache have a valid TGT? */ static time_t get_tgt_time(const char *ccname) { krb5_context context; krb5_ccache ccache; krb5_cc_cursor cur; krb5_creds creds; krb5_principal principal; time_t credtime = 0; char *realm = NULL; if (krb5_init_context(&context)) { syslog(LOG_DEBUG, "%s: unable to init krb5 context", __func__); return 0; } if (krb5_cc_resolve(context, ccname, &ccache)) { syslog(LOG_DEBUG, "%s: unable to resolve krb5 cache", __func__); goto err_cache; } if (krb5_cc_set_flags(context, ccache, 0)) { syslog(LOG_DEBUG, "%s: unable to set flags", __func__); goto err_cache; } if (krb5_cc_get_principal(context, ccache, &principal)) { syslog(LOG_DEBUG, "%s: unable to get principal", __func__); goto err_princ; } if (krb5_cc_start_seq_get(context, ccache, &cur)) { syslog(LOG_DEBUG, "%s: unable to seq start", __func__); goto err_ccstart; } if ((realm = smb_krb5_principal_get_realm(context, principal)) == NULL) { syslog(LOG_DEBUG, "%s: unable to get realm", __func__); goto err_ccstart; } while (!credtime && !krb5_cc_next_cred(context, ccache, &cur, &creds)) { char *name; if (smb_krb5_unparse_name(NULL, context, creds.server, &name)) { syslog(LOG_DEBUG, "%s: unable to unparse name", __func__); goto err_endseq; } if (krb5_realm_compare(context, creds.server, principal) && strnequal(name, KRB5_TGS_NAME, KRB5_TGS_NAME_SIZE) && strnequal(name+KRB5_TGS_NAME_SIZE+1, realm, strlen(realm)) && creds.times.endtime > time(NULL)) credtime = creds.times.endtime; krb5_free_cred_contents(context, &creds); TALLOC_FREE(name); } err_endseq: krb5_cc_end_seq_get(context, ccache, &cur); err_ccstart: krb5_free_principal(context, principal); err_princ: #if defined(KRB5_TC_OPENCLOSE) krb5_cc_set_flags(context, ccache, KRB5_TC_OPENCLOSE); #endif krb5_cc_close(context, ccache); err_cache: krb5_free_context(context); return credtime; } static int krb5cc_filter(const struct dirent *dirent) { if (strstr(dirent->d_name, CIFS_DEFAULT_KRB5_PREFIX)) return 1; else return 0; } /* search for a credcache that looks like a likely candidate */ static char * find_krb5_cc(const char *dirname, uid_t uid) { struct dirent **namelist; struct stat sbuf; char ccname[MAX_CCNAME_LEN], *credpath, *best_cache = NULL; int i, n; time_t cred_time, best_time = 0; n = scandir(dirname, &namelist, krb5cc_filter, NULL); if (n < 0) { syslog(LOG_DEBUG, "%s: scandir error on directory '%s': %s", __func__, dirname, strerror(errno)); return NULL; } for (i = 0; i < n; i++) { snprintf(ccname, sizeof(ccname), "FILE:%s/%s", dirname, namelist[i]->d_name); credpath = ccname + 5; syslog(LOG_DEBUG, "%s: considering %s", __func__, credpath); if (lstat(credpath, &sbuf)) { syslog(LOG_DEBUG, "%s: stat error on '%s': %s", __func__, credpath, strerror(errno)); free(namelist[i]); continue; } if (sbuf.st_uid != uid) { syslog(LOG_DEBUG, "%s: %s is owned by %u, not %u", __func__, credpath, sbuf.st_uid, uid); free(namelist[i]); continue; } if (!S_ISREG(sbuf.st_mode)) { syslog(LOG_DEBUG, "%s: %s is not a regular file", __func__, credpath); free(namelist[i]); continue; } if (!(cred_time = get_tgt_time(ccname))) { syslog(LOG_DEBUG, "%s: %s is not a valid credcache.", __func__, ccname); free(namelist[i]); continue; } if (cred_time <= best_time) { syslog(LOG_DEBUG, "%s: %s expires sooner than current " "best.", __func__, ccname); free(namelist[i]); continue; } syslog(LOG_DEBUG, "%s: %s is valid ccache", __func__, ccname); free(best_cache); best_cache = SMB_STRNDUP(ccname, MAX_CCNAME_LEN); best_time = cred_time; free(namelist[i]); } free(namelist); return best_cache; } /* * Prepares AP-REQ data for mechToken and gets session key * Uses credentials from cache. It will not ask for password * you should receive credentials for yuor name manually using * kinit or whatever you wish. * * in: * oid - string with OID/ Could be OID_KERBEROS5 * or OID_KERBEROS5_OLD * principal - Service name. * Could be "cifs/FQDN" for KRB5 OID * or for MS_KRB5 OID style server principal * like "pdc$@YOUR.REALM.NAME" * * out: * secblob - pointer for spnego wrapped AP-REQ data to be stored * sess_key- pointer for SessionKey data to be stored * * ret: 0 - success, others - failure */ static int handle_krb5_mech(const char *oid, const char *principal, DATA_BLOB *secblob, DATA_BLOB *sess_key, const char *ccname) { int retval; DATA_BLOB tkt, tkt_wrapped; syslog(LOG_DEBUG, "%s: getting service ticket for %s", __func__, principal); /* get a kerberos ticket for the service and extract the session key */ retval = cli_krb5_get_ticket(principal, 0, &tkt, sess_key, 0, ccname, NULL, NULL); if (retval) { syslog(LOG_DEBUG, "%s: failed to obtain service ticket (%d)", __func__, retval); return retval; } syslog(LOG_DEBUG, "%s: obtained service ticket", __func__); /* wrap that up in a nice GSS-API wrapping */ tkt_wrapped = spnego_gen_krb5_wrap(tkt, TOK_ID_KRB_AP_REQ); /* and wrap that in a shiny SPNEGO wrapper */ *secblob = gen_negTokenInit(oid, tkt_wrapped); data_blob_free(&tkt_wrapped); data_blob_free(&tkt); return retval; } #define DKD_HAVE_HOSTNAME 0x1 #define DKD_HAVE_VERSION 0x2 #define DKD_HAVE_SEC 0x4 #define DKD_HAVE_IP 0x8 #define DKD_HAVE_UID 0x10 #define DKD_HAVE_PID 0x20 #define DKD_MUSTHAVE_SET (DKD_HAVE_HOSTNAME|DKD_HAVE_VERSION|DKD_HAVE_SEC) struct decoded_args { int ver; char *hostname; char *ip; uid_t uid; pid_t pid; sectype_t sec; }; static unsigned int decode_key_description(const char *desc, struct decoded_args *arg) { int len; int retval = 0; char *pos; const char *tkn = desc; do { pos = index(tkn, ';'); if (strncmp(tkn, "host=", 5) == 0) { if (pos == NULL) len = strlen(tkn); else len = pos - tkn; len -= 4; SAFE_FREE(arg->hostname); arg->hostname = SMB_XMALLOC_ARRAY(char, len); strlcpy(arg->hostname, tkn + 5, len); retval |= DKD_HAVE_HOSTNAME; } else if (!strncmp(tkn, "ip4=", 4) || !strncmp(tkn, "ip6=", 4)) { if (pos == NULL) len = strlen(tkn); else len = pos - tkn; len -= 3; SAFE_FREE(arg->ip); arg->ip = SMB_XMALLOC_ARRAY(char, len); strlcpy(arg->ip, tkn + 4, len); retval |= DKD_HAVE_IP; } else if (strncmp(tkn, "pid=", 4) == 0) { errno = 0; arg->pid = strtol(tkn + 4, NULL, 0); if (errno != 0) { syslog(LOG_ERR, "Invalid pid format: %s", strerror(errno)); return 1; } else { retval |= DKD_HAVE_PID; } } else if (strncmp(tkn, "sec=", 4) == 0) { if (strncmp(tkn + 4, "krb5", 4) == 0) { retval |= DKD_HAVE_SEC; arg->sec = KRB5; } else if (strncmp(tkn + 4, "mskrb5", 6) == 0) { retval |= DKD_HAVE_SEC; arg->sec = MS_KRB5; } } else if (strncmp(tkn, "uid=", 4) == 0) { errno = 0; arg->uid = strtol(tkn + 4, NULL, 16); if (errno != 0) { syslog(LOG_ERR, "Invalid uid format: %s", strerror(errno)); return 1; } else { retval |= DKD_HAVE_UID; } } else if (strncmp(tkn, "ver=", 4) == 0) { /* if version */ errno = 0; arg->ver = strtol(tkn + 4, NULL, 16); if (errno != 0) { syslog(LOG_ERR, "Invalid version format: %s", strerror(errno)); return 1; } else { retval |= DKD_HAVE_VERSION; } } if (pos == NULL) break; tkn = pos + 1; } while (tkn); return retval; } static int cifs_resolver(const key_serial_t key, const char *key_descr) { int c; struct addrinfo *addr; char ip[INET6_ADDRSTRLEN]; void *p; const char *keyend = key_descr; /* skip next 4 ';' delimiters to get to description */ for (c = 1; c <= 4; c++) { keyend = index(keyend+1, ';'); if (!keyend) { syslog(LOG_ERR, "invalid key description: %s", key_descr); return 1; } } keyend++; /* resolve name to ip */ c = getaddrinfo(keyend, NULL, NULL, &addr); if (c) { syslog(LOG_ERR, "unable to resolve hostname: %s [%s]", keyend, gai_strerror(c)); return 1; } /* conver ip to string form */ if (addr->ai_family == AF_INET) p = &(((struct sockaddr_in *)addr->ai_addr)->sin_addr); else p = &(((struct sockaddr_in6 *)addr->ai_addr)->sin6_addr); if (!inet_ntop(addr->ai_family, p, ip, sizeof(ip))) { syslog(LOG_ERR, "%s: inet_ntop: %s", __func__, strerror(errno)); freeaddrinfo(addr); return 1; } /* setup key */ c = keyctl_instantiate(key, ip, strlen(ip)+1, 0); if (c == -1) { syslog(LOG_ERR, "%s: keyctl_instantiate: %s", __func__, strerror(errno)); freeaddrinfo(addr); return 1; } freeaddrinfo(addr); return 0; } /* * Older kernels sent IPv6 addresses without colons. Well, at least * they're fixed-length strings. Convert these addresses to have colon * delimiters to make getaddrinfo happy. */ static void convert_inet6_addr(const char *from, char *to) { int i = 1; while (*from) { *to++ = *from++; if (!(i++ % 4) && *from) *to++ = ':'; } *to = 0; } static int ip_to_fqdn(const char *addrstr, char *host, size_t hostlen) { int rc; struct addrinfo hints = { .ai_flags = AI_NUMERICHOST }; struct addrinfo *res; const char *ipaddr = addrstr; char converted[INET6_ADDRSTRLEN + 1]; if ((strlen(ipaddr) > INET_ADDRSTRLEN) && !strchr(ipaddr, ':')) { convert_inet6_addr(ipaddr, converted); ipaddr = converted; } rc = getaddrinfo(ipaddr, NULL, &hints, &res); if (rc) { syslog(LOG_DEBUG, "%s: failed to resolve %s to " "ipaddr: %s", __func__, ipaddr, rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc)); return rc; } rc = getnameinfo(res->ai_addr, res->ai_addrlen, host, hostlen, NULL, 0, NI_NAMEREQD); freeaddrinfo(res); if (rc) { syslog(LOG_DEBUG, "%s: failed to resolve %s to fqdn: %s", __func__, ipaddr, rc == EAI_SYSTEM ? strerror(errno) : gai_strerror(rc)); return rc; } syslog(LOG_DEBUG, "%s: resolved %s to %s", __func__, ipaddr, host); return 0; } static void usage(void) { syslog(LOG_INFO, "Usage: %s [-t] [-v] key_serial", prog); fprintf(stderr, "Usage: %s [-t] [-v] key_serial\n", prog); } const struct option long_options[] = { { "trust-dns", 0, NULL, 't' }, { "version", 0, NULL, 'v' }, { NULL, 0, NULL, 0 } }; int main(const int argc, char *const argv[]) { struct cifs_spnego_msg *keydata = NULL; DATA_BLOB secblob = data_blob_null; DATA_BLOB sess_key = data_blob_null; key_serial_t key = 0; size_t datalen; unsigned int have; long rc = 1; int c, try_dns = 0; char *buf, *princ = NULL, *ccname = NULL; char hostbuf[NI_MAXHOST], *host; struct decoded_args arg = { }; const char *oid; hostbuf[0] = '\0'; openlog(prog, 0, LOG_DAEMON); while ((c = getopt_long(argc, argv, "ctv", long_options, NULL)) != -1) { switch (c) { case 'c': /* legacy option -- skip it */ break; case 't': try_dns++; break; case 'v': printf("version: %s\n", CIFSSPNEGO_VERSION); goto out; default: syslog(LOG_ERR, "unknown option: %c", c); goto out; } } /* is there a key? */ if (argc <= optind) { usage(); goto out; } /* get key and keyring values */ errno = 0; key = strtol(argv[optind], NULL, 10); if (errno != 0) { key = 0; syslog(LOG_ERR, "Invalid key format: %s", strerror(errno)); goto out; } rc = keyctl_describe_alloc(key, &buf); if (rc == -1) { syslog(LOG_ERR, "keyctl_describe_alloc failed: %s", strerror(errno)); rc = 1; goto out; } syslog(LOG_DEBUG, "key description: %s", buf); if ((strncmp(buf, "cifs.resolver", sizeof("cifs.resolver")-1) == 0) || (strncmp(buf, "dns_resolver", sizeof("dns_resolver")-1) == 0)) { rc = cifs_resolver(key, buf); goto out; } have = decode_key_description(buf, &arg); SAFE_FREE(buf); if ((have & DKD_MUSTHAVE_SET) != DKD_MUSTHAVE_SET) { syslog(LOG_ERR, "unable to get necessary params from key " "description (0x%x)", have); rc = 1; goto out; } if (arg.ver > CIFS_SPNEGO_UPCALL_VERSION) { syslog(LOG_ERR, "incompatible kernel upcall version: 0x%x", arg.ver); rc = 1; goto out; } if (have & DKD_HAVE_UID) { rc = setuid(arg.uid); if (rc == -1) { syslog(LOG_ERR, "setuid: %s", strerror(errno)); goto out; } ccname = find_krb5_cc(CIFS_DEFAULT_KRB5_DIR, arg.uid); } host = arg.hostname; // do mech specific authorization switch (arg.sec) { case MS_KRB5: case KRB5: retry_new_hostname: /* for "cifs/" service name + terminating 0 */ datalen = strlen(host) + 5 + 1; princ = SMB_XMALLOC_ARRAY(char, datalen); if (!princ) { rc = -ENOMEM; break; } if (arg.sec == MS_KRB5) oid = OID_KERBEROS5_OLD; else oid = OID_KERBEROS5; /* * try getting a cifs/ principal first and then fall back to * getting a host/ principal if that doesn't work. */ strlcpy(princ, "cifs/", datalen); strlcpy(princ + 5, host, datalen - 5); rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname); if (!rc) break; memcpy(princ, "host/", 5); rc = handle_krb5_mech(oid, princ, &secblob, &sess_key, ccname); if (!rc) break; if (!try_dns || !(have & DKD_HAVE_IP)) break; rc = ip_to_fqdn(arg.ip, hostbuf, sizeof(hostbuf)); if (rc) break; SAFE_FREE(princ); try_dns = 0; host = hostbuf; goto retry_new_hostname; default: syslog(LOG_ERR, "sectype: %d is not implemented", arg.sec); rc = 1; break; } SAFE_FREE(princ); if (rc) goto out; /* pack SecurityBLob and SessionKey into downcall packet */ datalen = sizeof(struct cifs_spnego_msg) + secblob.length + sess_key.length; keydata = (struct cifs_spnego_msg*)SMB_XMALLOC_ARRAY(char, datalen); if (!keydata) { rc = 1; goto out; } keydata->version = arg.ver; keydata->flags = 0; keydata->sesskey_len = sess_key.length; keydata->secblob_len = secblob.length; memcpy(&(keydata->data), sess_key.data, sess_key.length); memcpy(&(keydata->data) + keydata->sesskey_len, secblob.data, secblob.length); /* setup key */ rc = keyctl_instantiate(key, keydata, datalen, 0); if (rc == -1) { syslog(LOG_ERR, "keyctl_instantiate: %s", strerror(errno)); goto out; } /* BB: maybe we need use timeout for key: for example no more then * ticket lifietime? */ /* keyctl_set_timeout( key, 60); */ out: /* * on error, negatively instantiate the key ourselves so that we can * make sure the kernel doesn't hang it off of a searchable keyring * and interfere with the next attempt to instantiate the key. */ if (rc != 0 && key == 0) keyctl_negate(key, 1, KEY_REQKEY_DEFL_DEFAULT); data_blob_free(&secblob); data_blob_free(&sess_key); SAFE_FREE(ccname); SAFE_FREE(arg.hostname); SAFE_FREE(arg.ip); SAFE_FREE(keydata); return rc; }