1 files changed, 303 insertions, 0 deletions
diff --git a/gss-genr.c b/gss-genr.c
new file mode 100644
index 0000000..2cd695e
--- /dev/null
+++ b/gss-genr.c
@@ -0,0 +1,303 @@
+/* $OpenBSD: gss-genr.c,v 1.28 2021/01/27 10:05:28 djm Exp $ */
+
+/*
+ * Copyright (c) 2001-2007 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 <sys/types.h>
+
+#include <limits.h>
+#include <stdarg.h>
+#include <string.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "xmalloc.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+#include "log.h"
+#include "ssh2.h"
+
+#include "ssh-gss.h"
+
+/* sshbuf_get for gss_buffer_desc */
+int
+ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
+{
+	int r;
+	u_char *p;
+	size_t len;
+
+	if ((r = sshbuf_get_string(b, &p, &len)) != 0)
+		return r;
+	g->value = p;
+	g->length = len;
+	return 0;
+}
+
+/* Check that the OID in a data stream matches that in the context */
+int
+ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
+{
+	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
+	    ctx->oid->length == len &&
+	    memcmp(ctx->oid->elements, data, len) == 0);
+}
+
+/* Set the contexts OID from a data stream */
+void
+ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
+{
+	if (ctx->oid != GSS_C_NO_OID) {
+		free(ctx->oid->elements);
+		free(ctx->oid);
+	}
+	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
+	ctx->oid->length = len;
+	ctx->oid->elements = xmalloc(len);
+	memcpy(ctx->oid->elements, data, len);
+}
+
+/* Set the contexts OID */
+void
+ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
+{
+	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
+}
+
+/* All this effort to report an error ... */
+void
+ssh_gssapi_error(Gssctxt *ctxt)
+{
+	char *s;
+
+	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
+	debug("%s", s);
+	free(s);
+}
+
+char *
+ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
+    OM_uint32 *minor_status)
+{
+	OM_uint32 lmin;
+	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
+	OM_uint32 ctx;
+	struct sshbuf *b;
+	char *ret;
+	int r;
+
+	if ((b = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+
+	if (major_status != NULL)
+		*major_status = ctxt->major;
+	if (minor_status != NULL)
+		*minor_status = ctxt->minor;
+
+	ctx = 0;
+	/* The GSSAPI error */
+	do {
+		gss_display_status(&lmin, ctxt->major,
+		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
+
+		if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
+		    (r = sshbuf_put_u8(b, '\n')) != 0)
+			fatal_fr(r, "assemble GSS_CODE");
+
+		gss_release_buffer(&lmin, &msg);
+	} while (ctx != 0);
+
+	/* The mechanism specific error */
+	do {
+		gss_display_status(&lmin, ctxt->minor,
+		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
+
+		if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
+		    (r = sshbuf_put_u8(b, '\n')) != 0)
+			fatal_fr(r, "assemble MECH_CODE");
+
+		gss_release_buffer(&lmin, &msg);
+	} while (ctx != 0);
+
+	if ((r = sshbuf_put_u8(b, '\n')) != 0)
+		fatal_fr(r, "assemble newline");
+	ret = xstrdup((const char *)sshbuf_ptr(b));
+	sshbuf_free(b);
+	return (ret);
+}
+
+/*
+ * Initialise our GSSAPI context. We use this opaque structure to contain all
+ * of the data which both the client and server need to persist across
+ * {accept,init}_sec_context calls, so that when we do it from the userauth
+ * stuff life is a little easier
+ */
+void
+ssh_gssapi_build_ctx(Gssctxt **ctx)
+{
+	*ctx = xcalloc(1, sizeof (Gssctxt));
+	(*ctx)->context = GSS_C_NO_CONTEXT;
+	(*ctx)->name = GSS_C_NO_NAME;
+	(*ctx)->oid = GSS_C_NO_OID;
+	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
+	(*ctx)->client = GSS_C_NO_NAME;
+	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
+}
+
+/* Delete our context, providing it has been built correctly */
+void
+ssh_gssapi_delete_ctx(Gssctxt **ctx)
+{
+	OM_uint32 ms;
+
+	if ((*ctx) == NULL)
+		return;
+	if ((*ctx)->context != GSS_C_NO_CONTEXT)
+		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
+	if ((*ctx)->name != GSS_C_NO_NAME)
+		gss_release_name(&ms, &(*ctx)->name);
+	if ((*ctx)->oid != GSS_C_NO_OID) {
+		free((*ctx)->oid->elements);
+		free((*ctx)->oid);
+		(*ctx)->oid = GSS_C_NO_OID;
+	}
+	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
+		gss_release_cred(&ms, &(*ctx)->creds);
+	if ((*ctx)->client != GSS_C_NO_NAME)
+		gss_release_name(&ms, &(*ctx)->client);
+	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
+		gss_release_cred(&ms, &(*ctx)->client_creds);
+
+	free(*ctx);
+	*ctx = NULL;
+}
+
+/*
+ * Wrapper to init_sec_context
+ * Requires that the context contains:
+ *	oid
+ *	server name (from ssh_gssapi_import_name)
+ */
+OM_uint32
+ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
+    gss_buffer_desc* send_tok, OM_uint32 *flags)
+{
+	int deleg_flag = 0;
+
+	if (deleg_creds) {
+		deleg_flag = GSS_C_DELEG_FLAG;
+		debug("Delegating credentials");
+	}
+
+	ctx->major = gss_init_sec_context(&ctx->minor,
+	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
+	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
+	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
+
+	if (GSS_ERROR(ctx->major))
+		ssh_gssapi_error(ctx);
+
+	return (ctx->major);
+}
+
+/* Create a service name for the given host */
+OM_uint32
+ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
+{
+	gss_buffer_desc gssbuf;
+	char *val;
+
+	xasprintf(&val, "host@%s", host);
+	gssbuf.value = val;
+	gssbuf.length = strlen(gssbuf.value);
+
+	if ((ctx->major = gss_import_name(&ctx->minor,
+	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
+		ssh_gssapi_error(ctx);
+
+	free(gssbuf.value);
+	return (ctx->major);
+}
+
+OM_uint32
+ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
+{
+	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
+	    GSS_C_QOP_DEFAULT, buffer, hash)))
+		ssh_gssapi_error(ctx);
+
+	return (ctx->major);
+}
+
+void
+ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
+    const char *context, const struct sshbuf *session_id)
+{
+	int r;
+
+	sshbuf_reset(b);
+	if ((r = sshbuf_put_stringb(b, session_id)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
+	    (r = sshbuf_put_cstring(b, user)) != 0 ||
+	    (r = sshbuf_put_cstring(b, service)) != 0 ||
+	    (r = sshbuf_put_cstring(b, context)) != 0)
+		fatal_fr(r, "assemble buildmic");
+}
+
+int
+ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
+{
+	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
+	OM_uint32 major, minor;
+	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
+
+	/* RFC 4462 says we MUST NOT do SPNEGO */
+	if (oid->length == spnego_oid.length && 
+	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
+		return 0; /* false */
+
+	ssh_gssapi_build_ctx(ctx);
+	ssh_gssapi_set_oid(*ctx, oid);
+	major = ssh_gssapi_import_name(*ctx, host);
+	if (!GSS_ERROR(major)) {
+		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, 
+		    NULL);
+		gss_release_buffer(&minor, &token);
+		if ((*ctx)->context != GSS_C_NO_CONTEXT)
+			gss_delete_sec_context(&minor, &(*ctx)->context,
+			    GSS_C_NO_BUFFER);
+	}
+
+	if (GSS_ERROR(major)) 
+		ssh_gssapi_delete_ctx(ctx);
+
+	return (!GSS_ERROR(major));
+}
+
+#endif /* GSSAPI */