krb5_child: send back the client principal

In general Kerberos is case sensitive but the KDC of Active Directory
typically handles request case in-sensitive. In the case where we guess
a user principal by combining the user name and the realm and are not
sure about the cases of the letters used in the user name we might get a
valid ticket from the AD KDC but are not able to access it with the
Kerberos client library because we assume a wrong case.

The client principal in the returned credentials will always have the
right cases. To be able to update the cache user principal name the
krb5_child will return the principal for further processing.

4 files changed, 42 insertions, 5 deletions

diff --git a/src/providers/data_provider.h b/src/providers/data_provider.h
index b783081b..d49fcd52 100644
--- a/src/providers/data_provider.h
+++ b/src/providers/data_provider.h
@@ -195,6 +195,7 @@ struct pam_data {
 #define SSS_PROXY_INFO 0x10000000
 
 #define SSS_KRB5_INFO_TGT_LIFETIME (SSS_SERVER_INFO|SSS_KRB5_INFO|0x01)
+#define SSS_KRB5_INFO_UPN (SSS_SERVER_INFO|SSS_KRB5_INFO|0x02)
 
 errno_t copy_pam_data(TALLOC_CTX *mem_ctx, struct pam_data *old_pd,
                       struct pam_data **new_pd);
diff --git a/src/providers/krb5/krb5_auth.h b/src/providers/krb5/krb5_auth.h
index a23b8b47..bf49f7cf 100644
--- a/src/providers/krb5/krb5_auth.h
+++ b/src/providers/krb5/krb5_auth.h
@@ -80,6 +80,7 @@ struct krb5_child_response {
     int32_t msg_status;
     struct tgt_times tgtt;
     char *ccname;
+    char *correct_upn;
 };
 
 errno_t
diff --git a/src/providers/krb5/krb5_child.c b/src/providers/krb5/krb5_child.c
index 4bfbf4bf..3e64a865 100644
--- a/src/providers/krb5/krb5_child.c
+++ b/src/providers/krb5/krb5_child.c
@@ -785,10 +785,13 @@ static errno_t sendresponse(int fd, krb5_error_code kerr, int pam_status,
     return EOK;
 }
 
-static errno_t add_ticket_times_to_response(struct krb5_req *kr)
+static errno_t add_ticket_times_and_upn_to_response(struct krb5_req *kr)
 {
     int ret;
     int64_t t[4];
+    krb5_error_code kerr;
+    char *upn = NULL;
+    unsigned int upn_len = 0;
 
     t[0] = (int64_t) kr->creds->times.authtime;
     t[1] = (int64_t) kr->creds->times.starttime;
@@ -799,8 +802,24 @@ static errno_t add_ticket_times_to_response(struct krb5_req *kr)
                            4*sizeof(int64_t), (uint8_t *) t);
     if (ret != EOK) {
         DEBUG(1, ("pack_response_packet failed.\n"));
+        goto done;
+    }
+
+    kerr = krb5_unparse_name_ext(kr->ctx, kr->creds->client, &upn, &upn_len);
+    if (kerr != 0) {
+        DEBUG(SSSDBG_OP_FAILURE, ("krb5_unparse_name failed.\n"));
+        goto done;
+    }
+
+    ret = pam_add_response(kr->pd, SSS_KRB5_INFO_UPN, upn_len,
+                           (uint8_t *) upn);
+    krb5_free_unparsed_name(kr->ctx, upn);
+    if (ret != EOK) {
+        DEBUG(1, ("pack_response_packet failed.\n"));
+        goto done;
     }
 
+done:
     return ret;
 }
 
@@ -1054,9 +1073,9 @@ static krb5_error_code get_and_save_tgt(struct krb5_req *kr,
         goto done;
     }
 
-    ret = add_ticket_times_to_response(kr);
+    ret = add_ticket_times_and_upn_to_response(kr);
     if (ret != EOK) {
-        DEBUG(1, ("add_ticket_times_to_response failed.\n"));
+        DEBUG(1, ("add_ticket_times_and_upn_to_response failed.\n"));
     }
 
     kerr = 0;
@@ -1447,9 +1466,9 @@ static errno_t renew_tgt_child(int fd, struct krb5_req *kr)
         goto done;
     }
 
-    ret = add_ticket_times_to_response(kr);
+    ret = add_ticket_times_and_upn_to_response(kr);
     if (ret != EOK) {
-        DEBUG(1, ("add_ticket_times_to_response failed.\n"));
+        DEBUG(1, ("add_ticket_times_and_upn_to_response failed.\n"));
     }
 
     status = PAM_SUCCESS;
diff --git a/src/providers/krb5/krb5_child_handler.c b/src/providers/krb5/krb5_child_handler.c
index f0fe81b6..e792db3f 100644
--- a/src/providers/krb5/krb5_child_handler.c
+++ b/src/providers/krb5/krb5_child_handler.c
@@ -441,6 +441,8 @@ parse_krb5_child_response(TALLOC_CTX *mem_ctx, uint8_t *buf, ssize_t len,
     uint32_t *expiration;
     uint32_t *msg_subtype;
     struct krb5_child_response *res;
+    const char *upn = NULL;
+    size_t upn_len;
 
     if ((size_t) len < sizeof(int32_t)) {
         DEBUG(SSSDBG_CRIT_FAILURE, ("message too short.\n"));
@@ -505,6 +507,11 @@ parse_krb5_child_response(TALLOC_CTX *mem_ctx, uint8_t *buf, ssize_t len,
                   tgtt.authtime, tgtt.starttime, tgtt.endtime, tgtt.renew_till));
         }
 
+        if (msg_type == SSS_KRB5_INFO_UPN) {
+            upn = (char *) buf + p;
+            upn_len = msg_len;
+        }
+
         if (msg_type == SSS_PAM_USER_INFO) {
             msg_subtype = (uint32_t *)&buf[p];
             if (*msg_subtype == SSS_PAM_USER_INFO_EXPIRE_WARN)
@@ -549,6 +556,15 @@ parse_krb5_child_response(TALLOC_CTX *mem_ctx, uint8_t *buf, ssize_t len,
         }
     }
 
+    if (upn != NULL) {
+        res->correct_upn = talloc_strndup(res, upn, upn_len);
+        if (res->correct_upn == NULL) {
+            DEBUG(SSSDBG_CRIT_FAILURE, ("talloc_strndup failed.\n"));
+            talloc_free(res);
+            return ENOMEM;
+        }
+    }
+
     *_res = res;
     return EOK;
 }