- markus@cvs.openbsd.org 2003/08/22 10:56:09

     [auth2.c auth2-gss.c auth.h compat.c compat.h gss-genr.c gss-serv-krb5.c
     gss-serv.c monitor.c monitor.h monitor_wrap.c monitor_wrap.h readconf.c
     readconf.h servconf.c servconf.h session.c session.h ssh-gss.h
     ssh_config.5 sshconnect2.c sshd_config sshd_config.5]
     support GSS API user authentication; patches from Simon Wilkinson,
     stripped down and tested by Jakob and myself.

1 files changed, 291 insertions, 0 deletions

diff --git a/gss-serv.c b/gss-serv.c
new file mode 100644
index 00000000..42718177
--- /dev/null
+++ b/gss-serv.c
@@ -0,0 +1,291 @@
+/*	$OpenBSD: gss-serv.c,v 1.1 2003/08/22 10:56:09 markus Exp $	*/
+
+/*
+ * Copyright (c) 2001-2003 Simon Wilkinson. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `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 AUTHOR 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"
+
+#ifdef GSSAPI
+
+#include "bufaux.h"
+#include "compat.h"
+#include "auth.h"
+#include "log.h"
+#include "channels.h"
+#include "session.h"
+#include "servconf.h"
+#include "monitor_wrap.h"
+#include "xmalloc.h"
+#include "getput.h"
+
+#include "ssh-gss.h"
+
+extern ServerOptions options;
+
+static ssh_gssapi_client gssapi_client =
+    { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
+    GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
+
+ssh_gssapi_mech gssapi_null_mech =
+    { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
+
+#ifdef KRB5
+extern ssh_gssapi_mech gssapi_kerberos_mech;
+#endif
+
+ssh_gssapi_mech* supported_mechs[]= {
+#ifdef KRB5
+	&gssapi_kerberos_mech,
+#endif
+	&gssapi_null_mech,
+};
+
+/* Unpriviledged */
+void
+ssh_gssapi_supported_oids(gss_OID_set *oidset)
+{
+	int i = 0;
+	OM_uint32 min_status;
+	int present;
+	gss_OID_set supported;
+
+	gss_create_empty_oid_set(&min_status, oidset);
+	gss_indicate_mechs(&min_status, &supported);
+
+	while (supported_mechs[i]->name != NULL) {
+		if (GSS_ERROR(gss_test_oid_set_member(&min_status,
+		    &supported_mechs[i]->oid, supported, &present)))
+			present = 0;
+		if (present)
+			gss_add_oid_set_member(&min_status,
+			    &supported_mechs[i]->oid, oidset);
+		i++;
+	}
+}
+
+
+/* Wrapper around accept_sec_context
+ * Requires that the context contains:
+ *    oid
+ *    credentials	(from ssh_gssapi_acquire_cred)
+ */
+/* Priviledged */
+OM_uint32
+ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
+    gss_buffer_desc *send_tok, OM_uint32 *flags)
+{
+	OM_uint32 status;
+	gss_OID mech;
+
+	ctx->major = gss_accept_sec_context(&ctx->minor,
+	    &ctx->context, ctx->creds, recv_tok,
+	    GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
+	    send_tok, flags, NULL, &ctx->client_creds);
+
+	if (GSS_ERROR(ctx->major))
+		ssh_gssapi_error(ctx);
+
+	if (ctx->client_creds)
+		debug("Received some client credentials");
+	else
+		debug("Got no client credentials");
+
+	status = ctx->major;
+
+	/* Now, if we're complete and we have the right flags, then
+	 * we flag the user as also having been authenticated
+	 */
+
+	if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
+	    (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
+		if (ssh_gssapi_getclient(ctx, &gssapi_client))
+			fatal("Couldn't convert client name");
+	}
+
+	return (status);
+}
+
+/*
+ * This parses an exported name, extracting the mechanism specific portion
+ * to use for ACL checking. It verifies that the name belongs the mechanism
+ * originally selected.
+ */
+static OM_uint32
+ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
+{
+	char *tok;
+	OM_uint32 offset;
+	OM_uint32 oidl;
+	
+	tok=ename->value;
+	
+	/* 
+	 * Check that ename is long enough for all of the fixed length 
+	 * header, and that the initial ID bytes are correct
+	 */
+
+	if (ename->length<6 || memcmp(tok,"\x04\x01", 2)!=0) 
+		return GSS_S_FAILURE;
+
+	/*
+	 * Extract the OID, and check it. Here GSSAPI breaks with tradition
+	 * and does use the OID type and length bytes. To confuse things
+	 * there are two lengths - the first including these, and the
+	 * second without.
+	 */
+
+	oidl = GET_16BIT(tok+2); /* length including next two bytes */
+	oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
+
+	/*
+	 * Check the BER encoding for correct type and length, that the
+	 * string is long enough and that the OID matches that in our context
+	 */
+	if (tok[4] != 0x06 || tok[5] != oidl ||
+	    ename->length < oidl+6 ||        
+	   !ssh_gssapi_check_oid(ctx,tok+6,oidl))
+		return GSS_S_FAILURE;
+
+	offset = oidl+6;
+	
+	if (ename->length < offset+4)
+		return GSS_S_FAILURE;
+		
+	name->length = GET_32BIT(tok+offset);
+	offset += 4;
+	
+	if (ename->length < offset+name->length)
+        	return GSS_S_FAILURE;
+	
+	name->value = xmalloc(name->length);
+	memcpy(name->value,tok+offset,name->length);
+	
+	return GSS_S_COMPLETE;
+} 
+
+/* Extract the client details from a given context. This can only reliably
+ * be called once for a context */
+
+/* Priviledged (called from accept_secure_ctx) */
+OM_uint32
+ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
+{
+	int i = 0;
+
+	gss_buffer_desc ename;
+	
+	client->mech = NULL;
+
+	while (supported_mechs[i]->name != NULL) {
+		if (supported_mechs[i]->oid.length == ctx->oid->length &&
+		    (memcmp(supported_mechs[i]->oid.elements,
+		    ctx->oid->elements, ctx->oid->length) == 0))
+			client->mech = supported_mechs[i];
+		i++;
+	}
+
+	if (client->mech == NULL) 
+		return GSS_S_FAILURE;
+	
+	if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 
+	    &client->displayname, NULL))) {
+	        ssh_gssapi_error(ctx);
+	        return (ctx->major);
+	}
+	
+	if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 
+	    &ename))) {
+		ssh_gssapi_error(ctx);
+		return (ctx->major);
+	}
+	
+	if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
+	    &client->exportedname))) {
+		return (ctx->major);
+	}
+
+	/* We can't copy this structure, so we just move the pointer to it */
+	client->creds = ctx->client_creds;
+	ctx->client_creds = GSS_C_NO_CREDENTIAL;
+	return (ctx->major);
+}
+
+/* As user - called through fatal cleanup hook */
+void
+ssh_gssapi_cleanup_creds(void *ignored)
+{
+	if (gssapi_client.store.filename != NULL) {
+		/* Unlink probably isn't sufficient */
+		debug("removing gssapi cred file\"%s\"", gssapi_client.store.filename);
+		unlink(gssapi_client.store.filename);
+	}
+}
+
+/* As user */
+void
+ssh_gssapi_storecreds(void)
+{
+	if (gssapi_client.mech && gssapi_client.mech->storecreds) {
+		(*gssapi_client.mech->storecreds)(&gssapi_client);
+		if (options.gss_cleanup_creds)
+			fatal_add_cleanup(ssh_gssapi_cleanup_creds, NULL);
+	} else
+		debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
+}
+
+/* This allows GSSAPI methods to do things to the childs environment based
+ * on the passed authentication process and credentials.
+ */
+/* As user */
+void
+ssh_gssapi_do_child(char ***envp, u_int *envsizep)
+{
+
+	if (gssapi_client.store.envvar != NULL &&
+	    gssapi_client.store.envval != NULL) {
+
+		debug("Setting %s to %s", gssapi_client.store.envvar,
+		gssapi_client.store.envval);
+		child_set_env(envp, envsizep, gssapi_client.store.envvar,
+		     gssapi_client.store.envval);
+	}
+}
+
+/* Priviledged */
+int
+ssh_gssapi_userok(char *user)
+{
+	if (gssapi_client.exportedname.length == 0 ||
+	    gssapi_client.exportedname.value == NULL) {
+		debug("No suitable client data");
+		return 0;
+	}
+	if (gssapi_client.mech && gssapi_client.mech->userok)
+		return ((*gssapi_client.mech->userok)(&gssapi_client, user));
+	else
+		debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
+	return (0);
+}
+
+#endif