From d6e26457b71c41531a500965cd6eb67c00bda1c3 Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Fri, 8 Apr 2011 16:50:13 +0000
Subject: [PATCH] Add k5_kt_get_principal, an internal krb5 interface to try to
 get a principal name from a keytab.  Used currently by vfy_increds.c (in
 place of its static helper); will also be used when querying the name of the
 default gss-krb5 acceptor cred.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24859 dc483132-0cff-0310-8789-dd5450dbe970
---
 src/include/k5-int.h           |  3 +++
 src/lib/krb5/keytab/ktfns.c    | 32 ++++++++++++++++++++++++++++++++
 src/lib/krb5/krb/vfy_increds.c | 25 ++-----------------------
 src/lib/krb5/libkrb5.exports   |  1 +
 src/lib/krb5_32.def            |  1 +
 5 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/src/include/k5-int.h b/src/include/k5-int.h
index 5e1324b2e..29f6ae5af 100644
--- a/src/include/k5-int.h
+++ b/src/include/k5-int.h
@@ -2618,6 +2618,9 @@ krb5_error_code krb5_generate_seq_number(krb5_context, const krb5_keyblock *,
 krb5_error_code KRB5_CALLCONV krb5_kt_register(krb5_context,
                                                const struct _krb5_kt_ops *);
 
+krb5_error_code k5_kt_get_principal(krb5_context context, krb5_keytab keytab,
+                                    krb5_principal *princ_out);
+
 krb5_error_code krb5_principal2salt_norealm(krb5_context, krb5_const_principal,
                                             krb5_data *);
 
diff --git a/src/lib/krb5/keytab/ktfns.c b/src/lib/krb5/keytab/ktfns.c
index a06689c4d..53d0b8364 100644
--- a/src/lib/krb5/keytab/ktfns.c
+++ b/src/lib/krb5/keytab/ktfns.c
@@ -97,4 +97,36 @@ krb5_kt_end_seq_get(krb5_context context, krb5_keytab keytab,
 {
     return krb5_x((keytab)->ops->end_get,(context, keytab, cursor));
 }
+
+/*
+ * In a couple of places we need to get a principal name from a keytab: when
+ * verifying credentials against a keytab, and when querying the name of a
+ * default GSS acceptor cred.  Keytabs do not have the concept of a default
+ * principal like ccaches do, so for now we just return the first principal
+ * listed in the keytab, or an error if it's not iterable.  In the future we
+ * could consider elevating this to a public API and giving keytab types an
+ * operation to return a default principal, and maybe extending the file format
+ * and tools to support it.  Returns KRB5_KT_NOTFOUND if the keytab is empty
+ * or non-iterable.
+ */
+krb5_error_code
+k5_kt_get_principal(krb5_context context, krb5_keytab keytab,
+                    krb5_principal *princ_out)
+{
+    krb5_error_code ret;
+    krb5_kt_cursor cursor;
+    krb5_keytab_entry kte;
+
+    *princ_out = NULL;
+    ret = krb5_kt_start_seq_get(context, keytab, &cursor);
+    if (ret)
+        return KRB5_KT_NOTFOUND;
+    ret = krb5_kt_next_entry(context, keytab, &kte, &cursor);
+    (void)krb5_kt_end_seq_get(context, keytab, &cursor);
+    if (ret)
+        return (ret == KRB5_KT_END) ? KRB5_KT_NOTFOUND : ret;
+    ret = krb5_copy_principal(context, kte.principal, princ_out);
+    krb5_kt_free_entry(context, &kte);
+    return ret;
+}
 #endif /* LEAN_CLIENT */
diff --git a/src/lib/krb5/krb/vfy_increds.c b/src/lib/krb5/krb/vfy_increds.c
index 1f4313fc3..207b3094d 100644
--- a/src/lib/krb5/krb/vfy_increds.c
+++ b/src/lib/krb5/krb/vfy_increds.c
@@ -20,27 +20,6 @@ nofail(krb5_context context, krb5_verify_init_creds_opt *options,
     return FALSE;
 }
 
-/* Set *server_out to the first principal name in keytab. */
-static krb5_error_code
-get_first_keytab_princ(krb5_context context, krb5_keytab keytab,
-                       krb5_principal *server_out)
-{
-    krb5_error_code ret;
-    krb5_kt_cursor cursor;
-    krb5_keytab_entry kte;
-
-    ret = krb5_kt_start_seq_get(context, keytab, &cursor);
-    if (ret)
-        return ret;
-    ret = krb5_kt_next_entry(context, keytab, &kte, &cursor);
-    (void)krb5_kt_end_seq_get(context, keytab, &cursor);
-    if (ret)
-        return ret;
-    ret = krb5_copy_principal(context, kte.principal, server_out);
-    krb5_kt_free_entry(context, &kte);
-    return ret;
-}
-
 static krb5_error_code
 copy_creds_except(krb5_context context, krb5_ccache incc,
                   krb5_ccache outcc, krb5_principal princ)
@@ -128,8 +107,8 @@ krb5_verify_init_creds(krb5_context context,
         if (ret)
             goto cleanup;
     } else {
-        /* Use the first principal name in the keytab. */
-        ret = get_first_keytab_princ(context, keytab, &server);
+        /* Use a principal name from the keytab. */
+        ret = k5_kt_get_principal(context, keytab, &server);
         if (ret) {
             /* There's no keytab, or it's empty, or we can't read it.
              * Allow this unless configuration demands verification. */
diff --git a/src/lib/krb5/libkrb5.exports b/src/lib/krb5/libkrb5.exports
index 98f914d9d..b531b70b5 100644
--- a/src/lib/krb5/libkrb5.exports
+++ b/src/lib/krb5/libkrb5.exports
@@ -108,6 +108,7 @@ initialize_k5e1_error_table
 initialize_kv5m_error_table
 initialize_prof_error_table
 k5_free_serverlist
+k5_kt_get_principal
 k5_locate_kdc
 k5_plugin_free_modules
 k5_plugin_load
diff --git a/src/lib/krb5_32.def b/src/lib/krb5_32.def
index 8c8a8f503..032faf759 100644
--- a/src/lib/krb5_32.def
+++ b/src/lib/krb5_32.def
@@ -408,3 +408,4 @@ EXPORTS
 
 ; new in 1.10
 	krb5_sname_match				@384
+	k5_kt_get_principal				@385 ; PRIVATE GSSAPI
-- 
2.26.2