diff options
| author | djm@openbsd.org <djm@openbsd.org> | 2022-01-06 22:55:23 +0100 |
|---|---|---|
| committer | Damien Miller <djm@mindrot.org> | 2022-01-06 23:21:38 +0100 |
| commit | 0fa33683223c76289470a954404047bc762be84c (patch) | |
| tree | db67fda0913f4d40d102eb9c5f6a6c58d91e5ee8 /serverloop.c | |
| parent | upstream: convert ssh, sshd mainloops from select() to poll(); (diff) | |
| download | openssh-0fa33683223c76289470a954404047bc762be84c.tar.xz openssh-0fa33683223c76289470a954404047bc762be84c.zip | |
upstream: Fix signature algorithm selection logic for
UpdateHostkeys on the server side. The previous code tried to prefer RSA/SHA2
for hostkey proofs of RSA keys, but missed some cases. This will use RSA/SHA2
signatures for RSA keys if the client proposed these algorithms in initial
KEX. bz3375
Mostly by Dmitry Belyavskiy with some tweaks by me.
ok markus@
OpenBSD-Commit-ID: c17ba0c3236340d2c6a248158ebed042ac6a8029
Diffstat (limited to 'serverloop.c')
| -rw-r--r-- | serverloop.c | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/serverloop.c b/serverloop.c index 1a744e1e6..e31dbed55 100644 --- a/serverloop.c +++ b/serverloop.c @@ -1,4 +1,4 @@ -/* $OpenBSD: serverloop.c,v 1.229 2022/01/06 21:48:38 djm Exp $ */ +/* $OpenBSD: serverloop.c,v 1.230 2022/01/06 21:55:23 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland @@ -685,16 +685,17 @@ server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) struct sshbuf *resp = NULL; struct sshbuf *sigbuf = NULL; struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; - int r, ndx, kexsigtype, use_kexsigtype, success = 0; + int r, ndx, success = 0; const u_char *blob; + const char *sigalg, *kex_rsa_sigalg = NULL; u_char *sig = 0; size_t blen, slen; if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); - - kexsigtype = sshkey_type_plain( - sshkey_type_from_name(ssh->kex->hostkey_alg)); + if (sshkey_type_plain(sshkey_type_from_name( + ssh->kex->hostkey_alg)) == KEY_RSA) + kex_rsa_sigalg = ssh->kex->hostkey_alg; while (ssh_packet_remaining(ssh) > 0) { sshkey_free(key); key = NULL; @@ -727,16 +728,24 @@ server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) * For RSA keys, prefer to use the signature type negotiated * during KEX to the default (SHA1). */ - use_kexsigtype = kexsigtype == KEY_RSA && - sshkey_type_plain(key->type) == KEY_RSA; + sigalg = NULL; + if (sshkey_type_plain(key->type) == KEY_RSA) { + if (kex_rsa_sigalg != NULL) + sigalg = kex_rsa_sigalg; + else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) + sigalg = "rsa-sha2-512"; + else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) + sigalg = "rsa-sha2-256"; + } + debug3_f("sign %s key (index %d) using sigalg %s", + sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); if ((r = sshbuf_put_cstring(sigbuf, "hostkeys-prove-00@openssh.com")) != 0 || (r = sshbuf_put_stringb(sigbuf, ssh->kex->session_id)) != 0 || (r = sshkey_puts(key, sigbuf)) != 0 || (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, - sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), - use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || + sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || (r = sshbuf_put_string(resp, sig, slen)) != 0) { error_fr(r, "assemble signature"); goto out; |