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authorSimon Wilkinson <simon@sxw.org.uk>2014-02-09 16:09:48 +0000
committerColin Watson <cjwatson@debian.org>2019-10-09 23:06:20 +0100
commit9da806e67101afdc0d3a1d304659927acf18f5c5 (patch)
tree4cb56e13b3b3b14147366a04a7ff691f76908bf7 /auth2-gss.c
parent4213eec74e74de6310c27a40c3e9759a08a73996 (diff)
GSSAPI key exchange support
This patch has been rejected upstream: "None of the OpenSSH developers are in favour of adding this, and this situation has not changed for several years. This is not a slight on Simon's patch, which is of fine quality, but just that a) we don't trust GSSAPI implementations that much and b) we don't like adding new KEX since they are pre-auth attack surface. This one is particularly scary, since it requires hooks out to typically root-owned system resources." However, quite a lot of people rely on this in Debian, and it's better to have it merged into the main openssh package rather than having separate -krb5 packages (as we used to have). It seems to have a generally good security history. Origin: other, https://github.com/openssh-gsskex/openssh-gsskex/commits/debian/master Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1242 Last-Updated: 2019-10-09 Patch-Name: gssapi.patch
Diffstat (limited to 'auth2-gss.c')
-rw-r--r--auth2-gss.c56
1 files changed, 53 insertions, 3 deletions
diff --git a/auth2-gss.c b/auth2-gss.c
index 9351e0428..d6446c0cf 100644
--- a/auth2-gss.c
+++ b/auth2-gss.c
@@ -1,7 +1,7 @@
1/* $OpenBSD: auth2-gss.c,v 1.29 2018/07/31 03:10:27 djm Exp $ */ 1/* $OpenBSD: auth2-gss.c,v 1.29 2018/07/31 03:10:27 djm Exp $ */
2 2
3/* 3/*
4 * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. 4 * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
5 * 5 *
6 * Redistribution and use in source and binary forms, with or without 6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions 7 * modification, are permitted provided that the following conditions
@@ -55,6 +55,48 @@ static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *
55static int input_gssapi_errtok(int, u_int32_t, struct ssh *); 55static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
56 56
57/* 57/*
58 * The 'gssapi_keyex' userauth mechanism.
59 */
60static int
61userauth_gsskeyex(struct ssh *ssh)
62{
63 Authctxt *authctxt = ssh->authctxt;
64 int r, authenticated = 0;
65 struct sshbuf *b = NULL;
66 gss_buffer_desc mic, gssbuf;
67 u_char *p;
68 size_t len;
69
70 if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
71 (r = sshpkt_get_end(ssh)) != 0)
72 fatal("%s: %s", __func__, ssh_err(r));
73
74 if ((b = sshbuf_new()) == NULL)
75 fatal("%s: sshbuf_new failed", __func__);
76
77 mic.value = p;
78 mic.length = len;
79
80 ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
81 "gssapi-keyex");
82
83 if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
84 fatal("%s: sshbuf_mutable_ptr failed", __func__);
85 gssbuf.length = sshbuf_len(b);
86
87 /* gss_kex_context is NULL with privsep, so we can't check it here */
88 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gss_kex_context,
89 &gssbuf, &mic))))
90 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
91 authctxt->pw, 1));
92
93 sshbuf_free(b);
94 free(mic.value);
95
96 return (authenticated);
97}
98
99/*
58 * We only support those mechanisms that we know about (ie ones that we know 100 * We only support those mechanisms that we know about (ie ones that we know
59 * how to check local user kuserok and the like) 101 * how to check local user kuserok and the like)
60 */ 102 */
@@ -260,7 +302,8 @@ input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
260 if ((r = sshpkt_get_end(ssh)) != 0) 302 if ((r = sshpkt_get_end(ssh)) != 0)
261 fatal("%s: %s", __func__, ssh_err(r)); 303 fatal("%s: %s", __func__, ssh_err(r));
262 304
263 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 305 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
306 authctxt->pw, 1));
264 307
265 if ((!use_privsep || mm_is_monitor()) && 308 if ((!use_privsep || mm_is_monitor()) &&
266 (displayname = ssh_gssapi_displayname()) != NULL) 309 (displayname = ssh_gssapi_displayname()) != NULL)
@@ -306,7 +349,8 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
306 gssbuf.length = sshbuf_len(b); 349 gssbuf.length = sshbuf_len(b);
307 350
308 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 351 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
309 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 352 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
353 authctxt->pw, 0));
310 else 354 else
311 logit("GSSAPI MIC check failed"); 355 logit("GSSAPI MIC check failed");
312 356
@@ -326,6 +370,12 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
326 return 0; 370 return 0;
327} 371}
328 372
373Authmethod method_gsskeyex = {
374 "gssapi-keyex",
375 userauth_gsskeyex,
376 &options.gss_authentication
377};
378
329Authmethod method_gssapi = { 379Authmethod method_gssapi = {
330 "gssapi-with-mic", 380 "gssapi-with-mic",
331 userauth_gssapi, 381 userauth_gssapi,