cifs.upcall: use krb5 routines to get default ccname

Currently we end up groveling around in /tmp, trying to guess what the
credcache will be. Instead, just get the default ccname for the user,
and then see if it has a valid tgt. If it doesn't then we try to use
the keytab to init the credcache before proceeding.

Signed-off-by: Jeff Layton <jlayton@samba.org>

diff --git a/cifs.upcall.c b/cifs.upcall.c
index e8544c2b68ad549e6884c70eaf2a109c64012497..d0f6d089d8e1c7ba687c58435170538cecc47d79 100644 (file)
--- a/cifs.upcall.c
+++ b/cifs.upcall.c
@@ -52,12 +52,6 @@
 #include "spnego.h"
 #include "cifs_spnego.h"
 
-#define        CIFS_DEFAULT_KRB5_DIR           "/tmp"
-#define        CIFS_DEFAULT_KRB5_USER_DIR      "/run/user/%U"
-#define        CIFS_DEFAULT_KRB5_PREFIX        "krb5cc"
-
-#define        MAX_CCNAME_LEN                  PATH_MAX + 5
-
 static const char *prog = "cifs.upcall";
 typedef enum _sectype {
        NONE = 0,
@@ -178,13 +172,34 @@ err_cache:
        return credtime;
 }
 
-static int krb5cc_filter(const struct dirent *dirent)
+static char *
+get_default_cc(void)
 {
-       /* subtract 1 for the null terminator */
-       return !strncmp(dirent->d_name, CIFS_DEFAULT_KRB5_PREFIX,
-                       sizeof(CIFS_DEFAULT_KRB5_PREFIX) - 1);
+       krb5_error_code ret;
+       const char *ccname;
+       char *rcc = NULL;
+       krb5_context context = NULL;
+
+       ret = krb5_init_context(&context);
+       if (ret) {
+               syslog(LOG_DEBUG, "krb5_init_context: %d", (int)ret);
+               return NULL;
+       }
+
+       ccname = krb5_cc_default_name(context);
+       if (!ccname) {
+               syslog(LOG_DEBUG, "krb5_cc_default returned NULL.");
+               goto out_free_context;
+       }
+
+       if (get_tgt_time(ccname))
+               rcc = strdup(ccname);
+out_free_context:
+       krb5_free_context(context);
+       return rcc;
 }
 
+
 static char *
 init_cc_from_keytab(const char *keytab_name, const char *user)
 {
@@ -263,109 +278,6 @@ icfk_cleanup:
        return ccname;
 }
 
-/* resolve a pattern to an actual directory path */
-static char *resolve_krb5_dir(const char *pattern, uid_t uid)
-{
-       char name[MAX_CCNAME_LEN];
-       int i;
-       size_t j;
-       for (i = 0, j = 0; (pattern[i] != '\0') && (j < sizeof(name)); i++) {
-               switch (pattern[i]) {
-               case '%':
-                       switch (pattern[i + 1]) {
-                       case '%':
-                               name[j++] = pattern[i];
-                               i++;
-                               break;
-                       case 'U':
-                               j += snprintf(name + j, sizeof(name) - j,
-                                             "%lu", (unsigned long) uid);
-                               i++;
-                               break;
-                       }
-                       break;
-               default:
-                       name[j++] = pattern[i];
-                       break;
-               }
-       }
-       if ((j > 0) && (j < sizeof(name)))
-               return strndup(name, MAX_CCNAME_LEN);
-       else
-               return NULL;
-}
-
-/* search for a credcache that looks like a likely candidate */
-static char *find_krb5_cc(const char *dirname, uid_t uid,
-                         char **best_cache, time_t *best_time)
-{
-       struct dirent **namelist;
-       struct stat sbuf;
-       char ccname[MAX_CCNAME_LEN], *credpath;
-       int i, n;
-       time_t cred_time;
-
-       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_ISDIR(sbuf.st_mode)) {
-                       snprintf(ccname, sizeof(ccname), "DIR:%s/%s", dirname,
-                                namelist[i]->d_name);
-                       credpath = ccname + 4;
-               } else
-               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 = strndup(ccname, MAX_CCNAME_LEN);
-               *best_time = cred_time;
-               free(namelist[i]);
-       }
-       free(namelist);
-
-       return *best_cache;
-}
-
 static int
 cifs_krb5_get_req(const char *host, const char *ccname,
                  DATA_BLOB * mechtoken, DATA_BLOB * sess_key)
@@ -841,13 +753,12 @@ int main(const int argc, char *const argv[])
        unsigned int have;
        long rc = 1;
        int c, try_dns = 0, legacy_uid = 0;
-       char *buf, *ccdir = NULL, *ccname = NULL, *best_cache = NULL;
+       char *buf, *ccname = NULL;
        char hostbuf[NI_MAXHOST], *host;
        struct decoded_args arg;
        const char *oid;
        uid_t uid;
        char *keytab_name = NULL;
-       time_t best_time = 0;
 
        hostbuf[0] = '\0';
        memset(&arg, 0, sizeof(arg));
@@ -954,13 +865,8 @@ int main(const int argc, char *const argv[])
                syslog(LOG_ERR, "setuid: %s", strerror(errno));
                goto out;
        }
-       ccdir = resolve_krb5_dir(CIFS_DEFAULT_KRB5_USER_DIR, uid);
-       if (ccdir != NULL)
-               find_krb5_cc(ccdir, uid, &best_cache, &best_time);
-       ccname = find_krb5_cc(CIFS_DEFAULT_KRB5_DIR, uid, &best_cache,
-                             &best_time);
-       SAFE_FREE(ccdir);
 
+       ccname = get_default_cc();
        /* Couldn't find credcache? Try to use keytab */
        if (ccname == NULL && arg.username != NULL)
                ccname = init_cc_from_keytab(keytab_name, arg.username);