krb5_auth: update with correct UPN if needed

The Active Directory KDC handles request case in-sensitive and it might
not always to possible to guess the UPN with the correct case. We check
if the returned principal has a different case then the one used in the
request and updates the principal if needed. This will help using calls
from the Kerberos client libraries later on which would otherwise fail
because the principal is handled case sensitive by those libraries.

3 files changed, 133 insertions, 0 deletions

diff --git a/src/providers/krb5/krb5_auth.c b/src/providers/krb5/krb5_auth.c
index c1f9f14b..f2e00fac 100644
--- a/src/providers/krb5/krb5_auth.c
+++ b/src/providers/krb5/krb5_auth.c
@@ -782,6 +782,36 @@ static void krb5_child_done(struct tevent_req *subreq)
         }
     }
 
+    /* Check if the cases of our upn are correct and update it if needed.
+     * Fail if the upn differs by more than just the case. */
+    if (res->correct_upn != NULL &&
+        strcmp(kr->upn, res->correct_upn) != 0) {
+        if (strcasecmp(kr->upn, res->correct_upn) == 0) {
+            talloc_free(kr->upn);
+            kr->upn = talloc_strdup(kr, res->correct_upn);
+            if (kr->upn == NULL) {
+                DEBUG(SSSDBG_OP_FAILURE, ("talloc_strdup failed.\n"));
+                ret = ENOMEM;
+                goto done;
+            }
+
+            ret = check_if_cached_upn_needs_update(state->sysdb, pd->user,
+                                                   res->correct_upn);
+            if (ret != EOK) {
+                DEBUG(SSSDBG_OP_FAILURE,
+                      ("check_if_cached_upn_needs_update failed.\n"));
+                goto done;
+            }
+        } else {
+            DEBUG(SSSDBG_CRIT_FAILURE, ("UPN used in the request [%s] and " \
+                                        "returned UPN [%s] differ by more " \
+                                        "than just the case.\n",
+                                        kr->upn, res->correct_upn));
+            ret = EINVAL;
+            goto done;
+        }
+    }
+
     /* If the child request failed, but did not return an offline error code,
      * return with the status */
     if (res->msg_status != PAM_SUCCESS &&
diff --git a/src/providers/krb5/krb5_utils.c b/src/providers/krb5/krb5_utils.c
index 98376169..6cfd48cf 100644
--- a/src/providers/krb5/krb5_utils.c
+++ b/src/providers/krb5/krb5_utils.c
@@ -57,6 +57,105 @@ errno_t find_or_guess_upn(TALLOC_CTX *mem_ctx, struct ldb_message *msg,
     return EOK;
 }
 
+errno_t check_if_cached_upn_needs_update(struct sysdb_ctx *sysdb,
+                                         const char *user,
+                                         const char *upn)
+{
+    TALLOC_CTX *tmp_ctx;
+    int ret;
+    int sret;
+    const char *attrs[] = {SYSDB_UPN, NULL};
+    struct sysdb_attrs *new_attrs;
+    struct ldb_result *res;
+    bool in_transaction = false;
+    const char *cached_upn;
+
+    if (sysdb == NULL || user == NULL || upn == NULL) {
+        return EINVAL;
+    }
+
+    tmp_ctx = talloc_new(NULL);
+    if (tmp_ctx == NULL) {
+        DEBUG(SSSDBG_OP_FAILURE, ("talloc_new failed.\n"));
+        return ENOMEM;
+    }
+
+    ret = sysdb_get_user_attr(tmp_ctx, sysdb, user, attrs, &res);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_OP_FAILURE, ("sysdb_get_user_attr failed.\n"));
+        goto done;
+    }
+
+    if (res->count != 1) {
+        DEBUG(SSSDBG_OP_FAILURE, ("[%d] user objects for name [%s] found, " \
+                                  "expected 1.\n", res->count, user));
+        ret = EINVAL;
+        goto done;
+    }
+
+    cached_upn = ldb_msg_find_attr_as_string(res->msgs[0], SYSDB_UPN, NULL);
+
+    if (cached_upn != NULL && strcmp(cached_upn, upn) == 0) {
+        DEBUG(SSSDBG_TRACE_ALL, ("Cached UPN and new one match, "
+                                 "nothing to do.\n"));
+        ret = EOK;
+        goto done;
+    }
+
+    DEBUG(SSSDBG_TRACE_LIBS, ("Replacing UPN [%s] with [%s] for user [%s].\n",
+                              cached_upn, upn, user));
+
+    new_attrs = sysdb_new_attrs(tmp_ctx);
+    if (new_attrs == NULL) {
+        DEBUG(SSSDBG_OP_FAILURE, ("sysdb_new_attrs failed.\n"));
+        ret = ENOMEM;
+        goto done;
+    }
+
+    ret = sysdb_attrs_add_string(new_attrs, SYSDB_UPN, upn);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_OP_FAILURE, ("sysdb_attrs_add_string failed.\n"));
+        goto done;
+    }
+
+    ret = sysdb_transaction_start(sysdb);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_OP_FAILURE,
+              ("Error %d starting transaction (%s)\n", ret, strerror(ret)));
+        goto done;
+    }
+    in_transaction = true;
+
+    ret = sysdb_set_entry_attr(sysdb, res->msgs[0]->dn, new_attrs,
+                               SYSDB_MOD_REP);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_OP_FAILURE, ("sysdb_set_entry_attr failed [%d][%s].\n",
+                                  ret, strerror(ret)));
+        goto done;
+    }
+
+    ret = sysdb_transaction_commit(sysdb);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_OP_FAILURE, ("Failed to commit transaction!\n"));
+        goto done;
+    }
+    in_transaction = false;
+
+    ret = EOK;
+
+done:
+    if (in_transaction) {
+        sret = sysdb_transaction_cancel(sysdb);
+        if (sret != EOK) {
+            DEBUG(SSSDBG_CRIT_FAILURE, ("Failed to cancel transaction\n"));
+        }
+    }
+
+    talloc_free(tmp_ctx);
+
+    return ret;
+}
+
 char *expand_ccname_template(TALLOC_CTX *mem_ctx, struct krb5child_req *kr,
                              const char *template, bool file_mode,
                              bool case_sensitive, bool *private_path)
diff --git a/src/providers/krb5/krb5_utils.h b/src/providers/krb5/krb5_utils.h
index 28485458..25d8c6cf 100644
--- a/src/providers/krb5/krb5_utils.h
+++ b/src/providers/krb5/krb5_utils.h
@@ -37,6 +37,10 @@ errno_t find_or_guess_upn(TALLOC_CTX *mem_ctx, struct ldb_message *msg,
                           const char *domain_name, const char *user,
                           const char *user_dom, char **_upn);
 
+errno_t check_if_cached_upn_needs_update(struct sysdb_ctx *sysdb,
+                                         const char *user,
+                                         const char *upn);
+
 /* Operations on a credential cache */
 typedef errno_t (*cc_be_create_fn)(const char *location, pcre *illegal_re,
                                    uid_t uid, gid_t gid, bool private_path);