A utility for removing principals from a keytab.

When we un-enroll a client we'll do a bit of cleanup including removing
any principals for the IPA realm from /etc/krb5.keytab.

This removes principals in 2 ways:
- By principal, only entries matching the full principal are removed
- By realm. Any principal for that realm is removed

This does not change the KDC at all, just removes entries from a file
on the client machine.

4 files changed, 319 insertions, 0 deletions

diff --git a/ipa-client/Makefile.am b/ipa-client/Makefile.am
index 9a8b5f690..3f3c13b1a 100644
--- a/ipa-client/Makefile.am
+++ b/ipa-client/Makefile.am
@@ -22,6 +22,7 @@ INCLUDES =							\
 
 sbin_PROGRAMS =			\
 	ipa-getkeytab		\
+	ipa-rmkeytab		\
 	ipa-join		\
 	$(NULL)
 
@@ -37,6 +38,15 @@ ipa_getkeytab_LDADD = 		\
 	$(POPT_LIBS)		\
 	$(NULL)
 
+ipa_rmkeytab_SOURCES =		\
+	ipa-rmkeytab.c		\
+	$(NULL)
+
+ipa_rmkeytab_LDADD = 		\
+	$(KRB5_LIBS)		\
+	$(POPT_LIBS)		\
+	$(NULL)
+
 ipa_join_SOURCES =		\
 	config.c		\
 	ipa-join.c		\
diff --git a/ipa-client/ipa-rmkeytab.c b/ipa-client/ipa-rmkeytab.c
new file mode 100644
index 000000000..d3f1ded37
--- /dev/null
+++ b/ipa-client/ipa-rmkeytab.c
@@ -0,0 +1,218 @@
+/* Authors: Rob Crittenden <rcritten@redhat.com>
+ *
+ * Copyright (C) 2009  Red Hat
+ * see file 'COPYING' for use and warranty information
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; version 2 only
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <krb5.h>
+#include <popt.h>
+#include <errno.h>
+
+int
+remove_principal(krb5_context context, krb5_keytab ktid, const char *principal, int debug)
+{
+    krb5_error_code krberr;
+    krb5_keytab_entry entry, entry2;
+    int rval = 0;
+    int removed = 0;
+
+    memset(&entry, 0, sizeof(entry));
+    krberr = krb5_parse_name(context, principal, &entry.principal);
+    if (krberr) {
+        fprintf(stderr, "Unable to parse principal name\n");
+        if (debug)
+            fprintf(stderr, "krb5_parse_name %d: %s\n", krberr, error_message(krberr));
+        rval = 4;
+        goto done;
+    }
+
+    /* Loop through the keytab and remove all entries with this principal name
+     * irrespective of the encryption type. A failure to find one after the
+     * first means we're done.
+     */
+    fprintf(stderr, "Removing principal %s\n", principal);
+    while (1) {
+        memset(&entry2, 0, sizeof(entry2));
+        krberr = krb5_kt_get_entry(context, ktid,
+                                entry.principal,
+                                0,
+                                0,
+                                &entry2);
+        if (krberr) {
+            if (removed > 0)
+                /* not found but we've removed some, we're done */
+                break;
+            if (krberr == ENOENT) {
+                fprintf(stderr, "Failed to open keytab\n");
+                rval = 3;
+                goto done;
+            }
+            fprintf(stderr, "principal not found\n");
+            if (debug)
+                fprintf(stderr, "krb5_kt_get_entry %d: %s\n", krberr, error_message(krberr));
+            rval = 5;
+            break;
+        }
+
+        krberr = krb5_kt_remove_entry(context, ktid, &entry2);
+        if (krberr) {
+            fprintf(stderr, "Unable to remove entry\n");
+            if (debug) {
+                fprintf(stdout, "kvno %d\n", entry2.vno);
+                fprintf(stderr, "krb5_kt_remove_entry %d: %s\n", krberr, error_message(krberr));
+            }
+            rval = 6;
+            break;
+        }
+
+        krb5_free_keytab_entry_contents(context, &entry2);
+        removed++;
+    }
+
+    if (entry2.principal)
+        krb5_free_keytab_entry_contents(context, &entry2);
+
+done:
+
+    return rval;
+}
+
+int
+remove_realm(krb5_context context, krb5_keytab ktid, const char *realm, int debug)
+{
+    krb5_error_code krberr;
+    krb5_keytab_entry entry;
+    krb5_kt_cursor kt_cursor;
+    char * entry_princ_s = NULL;
+    int rval = 0;
+
+    krberr = krb5_kt_start_seq_get(context, ktid, &kt_cursor);
+    memset(&entry, 0, sizeof(entry));
+    while (krb5_kt_next_entry(context, ktid, &entry, &kt_cursor) == 0) {
+        krberr = krb5_unparse_name(context, entry.principal, &entry_princ_s);
+        if (krberr) {
+            fprintf(stderr, "Unable to parse principal\n");
+            if (debug) {
+                fprintf(stderr, "krb5_unparse_name %d: %s\n", krberr, error_message(krberr));
+            }
+            rval = 4;
+            goto done;
+        }
+
+        if (strstr(entry_princ_s, realm) != NULL) {
+            rval = remove_principal(context, ktid, entry_princ_s, debug);
+            if (rval != 0)
+                goto done;
+            /* Have to reset the cursor */
+            krberr = krb5_kt_start_seq_get(context, ktid, &kt_cursor);
+        }
+    }
+
+done:
+
+    return rval;
+}
+
+int
+main(int argc, char **argv)
+{
+    krb5_context context;
+    krb5_error_code krberr;
+    krb5_keytab ktid;
+    char * ktname;
+    char * atrealm;
+    poptContext pc;
+    static const char *keytab = NULL;
+    static const char *principal = NULL;
+    static const char *realm = NULL;
+    int debug = 0;
+    int ret, rval;
+    struct poptOption options[] = {
+        { "debug", 'd', POPT_ARG_NONE, &debug, 0, "Print debugging information", "Debugging output" },
+        { "principal", 'p', POPT_ARG_STRING, &principal, 0, "The principal to get a keytab for (ex: ftp/ftp.example.com@EXAMPLE.COM)", "Kerberos Service Principal Name" },
+        { "keytab", 'k', POPT_ARG_STRING, &keytab, 0, "File were to store the keytab information", "Keytab File Name" },
+        { "realm", 'r', POPT_ARG_STRING, &realm, 0, "Remove all principals in this realm", "Realm name" },
+{ NULL, 0, POPT_ARG_NONE, NULL, 0, NULL, NULL }
+    };
+
+    memset(&ktid, 0, sizeof(ktid));
+
+    krberr = krb5_init_context(&context);
+    if (krberr) {
+        fprintf(stderr, "Kerberos context initialization failed\n");
+        exit(1);
+    }
+
+    pc = poptGetContext("ipa-rmkeytab", argc, (const char **)argv, options, 0);
+    ret = poptGetNextOpt(pc);
+    if (ret != -1 || (!principal && !realm) || !keytab) {
+        poptPrintUsage(pc, stderr, 0);
+        rval = 1;
+        goto cleanup;
+    }
+
+    ret = asprintf(&ktname, "WRFILE:%s", keytab);
+    if (ret == -1) {
+        rval = 2;
+        goto cleanup;
+    }
+
+    /* The remove_realm function just does a substring match. Ensure that
+     * the string we pass in looks like a realm.
+     */
+    if (realm) {
+        if (realm[0] != '@')
+            ret = asprintf(&atrealm, "@%s", realm);
+            if (ret == -1) {
+                rval = 2;
+                goto cleanup;
+            }
+        else
+            atrealm = strcpy(atrealm, realm);
+    }
+
+    krberr = krb5_kt_resolve(context, ktname, &ktid);
+    if (krberr) {
+        fprintf(stderr, "Failed to open keytab '%s'\n", keytab);
+        rval = 3;
+        goto cleanup;
+    }
+
+    if (principal)
+        rval = remove_principal(context, ktid, principal, debug);
+    else if (realm)
+        rval = remove_realm(context, ktid, atrealm, debug);
+
+cleanup:
+    if (rval == 0 || rval > 3) {
+        krberr = krb5_kt_close(context, ktid);
+        if (krberr) {
+            fprintf(stderr, "Closing keytab failed\n");
+            if (debug)
+                fprintf(stderr, "krb5_kt_close %d: %s\n", krberr, error_message(krberr));
+        }
+    }
+
+    krb5_free_context(context);
+
+    poptFreeContext(pc);
+
+    return rval;
+}
diff --git a/ipa-client/man/Makefile.am b/ipa-client/man/Makefile.am
index eee7144c1..bf11e39a8 100644
--- a/ipa-client/man/Makefile.am
+++ b/ipa-client/man/Makefile.am
@@ -6,6 +6,7 @@ NULL =
 
 man_MANS = 				\
 		ipa-getkeytab.1		\
+		ipa-rmkeytab.1		\
 		ipa-client-install.1	\
 		ipa-join.1
 	
diff --git a/ipa-client/man/ipa-rmkeytab.1 b/ipa-client/man/ipa-rmkeytab.1
new file mode 100644
index 000000000..a60f45cf9
--- /dev/null
+++ b/ipa-client/man/ipa-rmkeytab.1
@@ -0,0 +1,90 @@
+.\" A man page for ipa-rmkeytab
+.\" Copyright (C) 2009 Red Hat, Inc.
+.\"
+.\" This is free software; you can redistribute it and/or modify it under
+.\" the terms of the GNU Library General Public License as published by
+.\" the Free Software Foundation; version 2 only
+.\"
+.\" This program is distributed in the hope that it will be useful, but
+.\" WITHOUT ANY WARRANTY; without even the implied warranty of
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+.\" General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU Library General Public
+.\" License along with this program; if not, write to the Free Software
+.\" Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+.\"
+.\" Author: Rob Crittenden <rcritten@redhat.com>
+.\"
+.\"
+.TH "ipa-rmkeytab" "1" "Oct 30 2009" "freeipa" ""
+.SH "NAME"
+ipa\-rmkeytab \- Remove a kerberos principal from a keytab
+.SH "SYNOPSIS"
+ipa\-rmkeytab [ \fB\-p\fR principal\-name ] [ \fB\-k\fR keytab\-file ] [ \fB\-r\fR realm ] [ \fB\-d\fR ]
+
+.SH "DESCRIPTION"
+Removes a kerberos principal from a \fIkeytab\fR.
+
+Kerberos keytabs are used for services (like sshd) to
+perform kerberos authentication. A keytab is a file
+with one or more secrets (or keys) for a kerberos
+principal.
+
+A kerberos service principal is a kerberos identity
+that can be used for authentication. Service principals
+contain the name of the service, the hostname of the
+server, and the realm name.
+
+ipa\-rmkeytab provides two ways to remove principals.
+A specific principal can be removed or all principals for all
+principals for a given realm can be removed.
+
+All encryption types and versions of a principal are removed.
+
+The realm may be included when removing a specific principal but
+it is not required.
+
+\fBNOTE:\fR removing a principal from the keytab does not affect
+the Kerberos principal stored in the IPA server. It merely removes
+the entry from the local keytab.
+.SH "OPTIONS"
+.TP
+\fB\-p principal\-name\fR
+The non\-realm part of the full principal name.
+.TP
+\fB\-k keytab\-file\fR
+The keytab file where to append the new key (will be
+created if it does not exist).
+.TP
+\fB\-r realm\fR
+A realm to remove all principals for.
+.TP
+\fB\-d\fR
+Debug mode. Additional information is displayed.
+.SH "EXAMPLES"
+Remove the NFS service principal on the host foo.example.com from /tmp/nfs.keytab.
+
+   # ipa\-rmkeytab \-p nfs/foo.example.com \-k /tmp/nfs.keytab
+
+Remove the ldap service principal onthe host foo.example.com from /etc/krb5.keytab.
+
+   # ipa\-rmkeytab \-p ldap/foo.example.com \-k /tmp/ldap.keytab
+
+Remove all principals for the realm EXAMPLE.COM.
+
+  # ipa\-rmkeytab \-r EXAMPLE.COM \-k /tmp/ldap.keytab
+.SH "EXIT STATUS"
+The exit status is 0 on success, nonzero on error.
+
+1 Kerberos initialization failed
+
+2 Memory allocation error
+
+3 Unable to open keytab
+
+4 Unable to parse the principal name
+
+5 Principal name not found in keytab
+
+6 Unable to remove principal from keytab