From 04828a09ca88f7afc0f844a73968c84aed8bc6b3 Mon Sep 17 00:00:00 2001 From: djm Date: Sun, 19 Dec 2021 22:13:12 +0000 Subject: [PATCH] EXT_INFO negotiation of hostbound pubkey auth the EXT_INFO packet gets a new publickey-hostbound@openssh.com to advertise the hostbound public key method. Client side support to parse this feature flag and set the kex->flags indicator if the expected version is offered (currently "0"). ok markus@ --- usr.bin/ssh/kex.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/usr.bin/ssh/kex.c b/usr.bin/ssh/kex.c index 3f9c1851dcc..d3fe4ad828e 100644 --- a/usr.bin/ssh/kex.c +++ b/usr.bin/ssh/kex.c @@ -1,4 +1,4 @@ -/* $OpenBSD: kex.c,v 1.169 2021/12/19 22:08:06 djm Exp $ */ +/* $OpenBSD: kex.c,v 1.170 2021/12/19 22:13:12 djm Exp $ */ /* * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. * @@ -421,9 +421,12 @@ kex_send_ext_info(struct ssh *ssh) return SSH_ERR_ALLOC_FAIL; /* XXX filter algs list by allowed pubkey/hostbased types */ if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 || - (r = sshpkt_put_u32(ssh, 1)) != 0 || + (r = sshpkt_put_u32(ssh, 2)) != 0 || (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 || (r = sshpkt_put_cstring(ssh, algs)) != 0 || + (r = sshpkt_put_cstring(ssh, + "publickey-hostbound@openssh.com")) != 0 || + (r = sshpkt_put_cstring(ssh, "0")) != 0 || (r = sshpkt_send(ssh)) != 0) { error_fr(r, "compose"); goto out; @@ -483,6 +486,21 @@ kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh) debug_f("%s=<%s>", name, val); kex->server_sig_algs = val; val = NULL; + } else if (strcmp(name, + "publickey-hostbound@openssh.com") == 0) { + /* XXX refactor */ + /* Ensure no \0 lurking in value */ + if (memchr(val, '\0', vlen) != NULL) { + error_f("nul byte in %s", name); + return SSH_ERR_INVALID_FORMAT; + } + debug_f("%s=<%s>", name, val); + if (strcmp(val, "0") == 0) + kex->flags |= KEX_HAS_PUBKEY_HOSTBOUND; + else { + debug_f("unsupported version of %s extension", + name); + } } else debug_f("%s (unrecognised)", name); free(name); -- 2.20.1