s4:kerberos Add 'net export keytab' command for wireshark decryption

It is much easier to do decryption with wireshark when the keytab is
available for every host in the domain.  Running 'net export keytab
<keytab name>' will export the current (as pointed to by the supplied
smb.conf) local Samba4 doamin.

(This uses Heimdal's 'hdb' keytab and then the existing hdb-samba4,
and so has a good chance of keeping working in the long term).

Andrew Bartlett

2 files changed, 148 insertions, 1 deletions

diff --git a/source4/auth/kerberos/config.mk b/source4/auth/kerberos/config.mk
index 822bf398a76..609b036b64d 100644
--- a/source4/auth/kerberos/config.mk
+++ b/source4/auth/kerberos/config.mk
@@ -12,7 +12,8 @@ KERBEROS_OBJ_FILES = $(addprefix $(authsrcdir)/kerberos/, \
 	kerberos_heimdal.o \
 	kerberos_pac.o \
 	gssapi_parse.o \
-	krb5_init_context.o)
+	krb5_init_context.o \
+	keytab_copy.o)
 
 $(eval $(call proto_header_template,$(authsrcdir)/kerberos/proto.h,$(KERBEROS_OBJ_FILES:.o=.c)))
 
diff --git a/source4/auth/kerberos/keytab_copy.c b/source4/auth/kerberos/keytab_copy.c
new file mode 100644
index 00000000000..ba4ea2bf39e
--- /dev/null
+++ b/source4/auth/kerberos/keytab_copy.c
@@ -0,0 +1,146 @@
+/*
+ * Copyright (c) 1997-2004 Kungliga Tekniska Högskolan
+ * (Royal Institute of Technology, Stockholm, Sweden).
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "includes.h"
+#include "system/kerberos.h"
+#include "auth/kerberos/kerberos.h"
+
+static const krb5_boolean verbose_flag = FALSE;
+
+static krb5_boolean
+compare_keyblock(const krb5_keyblock *a, const krb5_keyblock *b)
+{
+    if(a->keytype != b->keytype ||
+       a->keyvalue.length != b->keyvalue.length ||
+       memcmp(a->keyvalue.data, b->keyvalue.data, a->keyvalue.length) != 0)
+	return FALSE;
+    return TRUE;
+}
+
+krb5_error_code kt_copy (krb5_context context, const char *from, const char *to)
+{
+    krb5_error_code ret;
+    krb5_keytab src_keytab, dst_keytab;
+    krb5_kt_cursor cursor;
+    krb5_keytab_entry entry, dummy;
+
+    ret = krb5_kt_resolve (context, from, &src_keytab);
+    if (ret) {
+	krb5_warn (context, ret, "resolving src keytab `%s'", from);
+	return 1;
+    }
+
+    ret = krb5_kt_resolve (context, to, &dst_keytab);
+    if (ret) {
+	krb5_kt_close (context, src_keytab);
+	krb5_warn (context, ret, "resolving dst keytab `%s'", to);
+	return 1;
+    }
+
+    ret = krb5_kt_start_seq_get (context, src_keytab, &cursor);
+    if (ret) {
+	krb5_warn (context, ret, "krb5_kt_start_seq_get %s", from);
+	goto out;
+    }
+
+    if (verbose_flag)
+	fprintf(stderr, "copying %s to %s\n", from, to);
+
+    while((ret = krb5_kt_next_entry(context, src_keytab,
+				    &entry, &cursor)) == 0) {
+	char *name_str;
+	char *etype_str;
+	ret = krb5_unparse_name (context, entry.principal, &name_str);
+	if(ret) {
+	    krb5_warn(context, ret, "krb5_unparse_name");
+	    name_str = NULL; /* XXX */
+	}
+	ret = krb5_enctype_to_string(context, entry.keyblock.keytype, &etype_str);
+	if(ret) {
+	    krb5_warn(context, ret, "krb5_enctype_to_string");
+	    etype_str = NULL; /* XXX */
+	}
+	ret = krb5_kt_get_entry(context, dst_keytab,
+				entry.principal,
+				entry.vno,
+				entry.keyblock.keytype,
+				&dummy);
+	if(ret == 0) {
+	    /* this entry is already in the new keytab, so no need to
+               copy it; if the keyblocks are not the same, something
+               is weird, so complain about that */
+	    if(!compare_keyblock(&entry.keyblock, &dummy.keyblock)) {
+		krb5_warnx(context, "entry with different keyvalue "
+			   "already exists for %s, keytype %s, kvno %d",
+			   name_str, etype_str, entry.vno);
+	    }
+	    krb5_kt_free_entry(context, &dummy);
+	    krb5_kt_free_entry (context, &entry);
+	    free(name_str);
+	    free(etype_str);
+	    continue;
+	} else if(ret != KRB5_KT_NOTFOUND) {
+	    krb5_warn (context, ret, "%s: fetching %s/%s/%u",
+		       to, name_str, etype_str, entry.vno);
+	    krb5_kt_free_entry (context, &entry);
+	    free(name_str);
+	    free(etype_str);
+	    break;
+	} 
+	if (verbose_flag)
+	    fprintf (stderr, "copying %s, keytype %s, kvno %d\n", name_str,
+		     etype_str, entry.vno);
+	ret = krb5_kt_add_entry (context, dst_keytab, &entry);
+	krb5_kt_free_entry (context, &entry);
+	if (ret) {
+	    krb5_warn (context, ret, "%s: adding %s/%s/%u",
+		       to, name_str, etype_str, entry.vno);
+	    free(name_str);
+	    free(etype_str);
+	    break;
+	}
+	free(name_str);
+	free(etype_str);
+    }
+    krb5_kt_end_seq_get (context, src_keytab, &cursor);
+
+  out:
+    krb5_kt_close (context, src_keytab);
+    krb5_kt_close (context, dst_keytab);
+    if (ret == KRB5_KT_END) {
+	return 0;
+    } else if (ret == 0) {
+	return EINVAL;
+    }
+    return ret;
+}