krb5 commit: Simplify and clarify lookup_etypes_for_keytab

[Greg Hudson]

https://github.com/krb5/krb5/commit/d77d40b0e2d3f60a49df0131d96cc05d80ca6107
commit d77d40b0e2d3f60a49df0131d96cc05d80ca6107
Author: Greg Hudson <ghudson at mit.edu>
Date:   Thu Feb 28 18:56:45 2013 -0500

    Simplify and clarify lookup_etypes_for_keytab

 src/lib/krb5/krb/gic_keytab.c |   48 ++++++++++++++++++-----------------------
 1 files changed, 21 insertions(+), 27 deletions(-)

diff --git a/src/lib/krb5/krb/gic_keytab.c b/src/lib/krb5/krb/gic_keytab.c
index ff26c18..9eef375 100644
--- a/src/lib/krb5/krb/gic_keytab.c
+++ b/src/lib/krb5/krb/gic_keytab.c
@@ -89,9 +89,10 @@ lookup_etypes_for_keytab(krb5_context context, krb5_keytab keytab,
 {
     krb5_kt_cursor cursor;
     krb5_keytab_entry entry;
-    krb5_enctype *p, *etypes = NULL;
-    krb5_kvno max_kvno = 0;
+    krb5_enctype *p, *etypes = NULL, etype;
+    krb5_kvno max_kvno = 0, vno;
     krb5_error_code ret;
+    krb5_boolean match;
     size_t count = 0;
 
     *etypes_out = NULL;
@@ -102,53 +103,46 @@ lookup_etypes_for_keytab(krb5_context context, krb5_keytab keytab,
     if (ret != 0)
         return ret;
 
-    for (;;) {
-        ret = krb5_kt_next_entry(context, keytab, &entry, &cursor);
-        if (ret == KRB5_KT_END)
-            break;
-        if (ret)
-            goto cleanup;
+    while (!(ret = krb5_kt_next_entry(context, keytab, &entry, &cursor))) {
+        /* Extract what we need from the entry and free it. */
+        etype = entry.key.enctype;
+        vno = entry.vno;
+        match = krb5_principal_compare(context, entry.principal, client);
+        krb5_free_keytab_entry_contents(context, &entry);
 
-        if (!krb5_c_valid_enctype(entry.key.enctype)) {
-            krb5_free_keytab_entry_contents(context, &entry);
-            continue;
-        }
-        if (!krb5_principal_compare(context, entry.principal, client)) {
-            krb5_free_keytab_entry_contents(context, &entry);
+        /* Filter out old or non-matching entries and invalid enctypes. */
+        if (vno < max_kvno || !match || !krb5_c_valid_enctype(etype))
             continue;
-        }
-        /* Make sure our list is for the highest kvno found for client. */
-        if (entry.vno > max_kvno) {
+
+        /* Update max_kvno and reset the list if we find a newer kvno. */
+        if (vno > max_kvno) {
+            max_kvno = vno;
             free(etypes);
             etypes = NULL;
             count = 0;
-            max_kvno = entry.vno;
-        } else if (entry.vno != max_kvno) {
-            krb5_free_keytab_entry_contents(context, &entry);
-            continue;
         }
 
         /* Leave room for the terminator and possibly a second entry. */
         p = realloc(etypes, (count + 3) * sizeof(*etypes));
         if (p == NULL) {
-            krb5_free_keytab_entry_contents(context, &entry);
             ret = ENOMEM;
             goto cleanup;
         }
         etypes = p;
-        etypes[count++] = entry.key.enctype;
+        etypes[count++] = etype;
         /* All DES key types work with des-cbc-crc, which is more likely to be
          * accepted by the KDC (since MIT KDCs refuse des-cbc-md5). */
-        if (entry.key.enctype == ENCTYPE_DES_CBC_MD5 ||
-            entry.key.enctype == ENCTYPE_DES_CBC_MD4)
+        if (etype == ENCTYPE_DES_CBC_MD5 || etype == ENCTYPE_DES_CBC_MD4)
             etypes[count++] = ENCTYPE_DES_CBC_CRC;
         etypes[count] = 0;
-        krb5_free_keytab_entry_contents(context, &entry);
     }
-
+    if (ret != KRB5_KT_END)
+        goto cleanup;
     ret = 0;
+
     *etypes_out = etypes;
     etypes = NULL;
+
 cleanup:
     krb5_kt_end_seq_get(context, keytab, &cursor);
     free(etypes);