diff options
Diffstat (limited to 'meta/recipes-connectivity/openssh/openssh/CVE-2023-38408-05.patch')
| -rw-r--r-- | meta/recipes-connectivity/openssh/openssh/CVE-2023-38408-05.patch | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/meta/recipes-connectivity/openssh/openssh/CVE-2023-38408-05.patch b/meta/recipes-connectivity/openssh/openssh/CVE-2023-38408-05.patch new file mode 100644 index 0000000000..0ddbdc68d4 --- /dev/null +++ b/meta/recipes-connectivity/openssh/openssh/CVE-2023-38408-05.patch @@ -0,0 +1,194 @@ +From a6cee3905edf070c0de135d3f2ee5b74da1dbd28 Mon Sep 17 00:00:00 2001 +From: "djm@openbsd.org" <djm@openbsd.org> +Date: Tue, 26 May 2020 01:26:58 +0000 +Subject: [PATCH 05/12] upstream: Restrict ssh-agent from signing web + challenges for FIDO + +keys. + +When signing messages in ssh-agent using a FIDO key that has an +application string that does not start with "ssh:", ensure that the +message being signed is one of the forms expected for the SSH protocol +(currently pubkey authentication and sshsig signatures). + +This prevents ssh-agent forwarding on a host that has FIDO keys +attached granting the ability for the remote side to sign challenges +for web authentication using those keys too. + +Note that the converse case of web browsers signing SSH challenges is +already precluded because no web RP can have the "ssh:" prefix in the +application string that we require. + +ok markus@ + +OpenBSD-Commit-ID: 9ab6012574ed0352d2f097d307f4a988222d1b19 + +Upstream-Status: Backport [https://github.com/openssh/openssh-portable/commit/0c111eb84efba7c2a38b2cc3278901a0123161b9] +CVE: CVE-2023-38408 +Signed-off-by: Shubham Kulkarni <skulkarni@mvista.com> +--- + ssh-agent.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++----- + 1 file changed, 100 insertions(+), 10 deletions(-) + +diff --git a/ssh-agent.c b/ssh-agent.c +index ceb348c..1794f35 100644 +--- a/ssh-agent.c ++++ b/ssh-agent.c +@@ -1,4 +1,4 @@ +-/* $OpenBSD: ssh-agent.c,v 1.255 2020/02/06 22:30:54 naddy Exp $ */ ++/* $OpenBSD: ssh-agent.c,v 1.258 2020/05/26 01:26:58 djm Exp $ */ + /* + * Author: Tatu Ylonen <ylo@cs.hut.fi> + * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland +@@ -77,6 +77,7 @@ + + #include "xmalloc.h" + #include "ssh.h" ++#include "ssh2.h" + #include "sshbuf.h" + #include "sshkey.h" + #include "authfd.h" +@@ -167,6 +168,9 @@ static long lifetime = 0; + + static int fingerprint_hash = SSH_FP_HASH_DEFAULT; + ++/* Refuse signing of non-SSH messages for web-origin FIDO keys */ ++static int restrict_websafe = 1; ++ + static void + close_socket(SocketEntry *e) + { +@@ -282,6 +286,80 @@ agent_decode_alg(struct sshkey *key, u_int flags) + return NULL; + } + ++/* ++ * This function inspects a message to be signed by a FIDO key that has a ++ * web-like application string (i.e. one that does not begin with "ssh:". ++ * It checks that the message is one of those expected for SSH operations ++ * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges ++ * for the web. ++ */ ++static int ++check_websafe_message_contents(struct sshkey *key, ++ const u_char *msg, size_t len) ++{ ++ int matched = 0; ++ struct sshbuf *b; ++ u_char m, n; ++ char *cp1 = NULL, *cp2 = NULL; ++ int r; ++ struct sshkey *mkey = NULL; ++ ++ if ((b = sshbuf_from(msg, len)) == NULL) ++ fatal("%s: sshbuf_new", __func__); ++ ++ /* SSH userauth request */ ++ if ((r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* sess_id */ ++ (r = sshbuf_get_u8(b, &m)) == 0 && /* SSH2_MSG_USERAUTH_REQUEST */ ++ (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* server user */ ++ (r = sshbuf_get_cstring(b, &cp1, NULL)) == 0 && /* service */ ++ (r = sshbuf_get_cstring(b, &cp2, NULL)) == 0 && /* method */ ++ (r = sshbuf_get_u8(b, &n)) == 0 && /* sig-follows */ ++ (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* alg */ ++ (r = sshkey_froms(b, &mkey)) == 0 && /* key */ ++ sshbuf_len(b) == 0) { ++ debug("%s: parsed userauth", __func__); ++ if (m == SSH2_MSG_USERAUTH_REQUEST && n == 1 && ++ strcmp(cp1, "ssh-connection") == 0 && ++ strcmp(cp2, "publickey") == 0 && ++ sshkey_equal(key, mkey)) { ++ debug("%s: well formed userauth", __func__); ++ matched = 1; ++ } ++ } ++ free(cp1); ++ free(cp2); ++ sshkey_free(mkey); ++ sshbuf_free(b); ++ if (matched) ++ return 1; ++ ++ if ((b = sshbuf_from(msg, len)) == NULL) ++ fatal("%s: sshbuf_new", __func__); ++ cp1 = cp2 = NULL; ++ mkey = NULL; ++ ++ /* SSHSIG */ ++ if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) == 0 && ++ (r = sshbuf_consume(b, 6)) == 0 && ++ (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* namespace */ ++ (r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* reserved */ ++ (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* hashalg */ ++ (r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* H(msg) */ ++ sshbuf_len(b) == 0) { ++ debug("%s: parsed sshsig", __func__); ++ matched = 1; ++ } ++ ++ sshbuf_free(b); ++ if (matched) ++ return 1; ++ ++ /* XXX CA signature operation */ ++ ++ error("web-origin key attempting to sign non-SSH message"); ++ return 0; ++} ++ + /* ssh2 only */ + static void + process_sign_request2(SocketEntry *e) +@@ -314,14 +392,20 @@ process_sign_request2(SocketEntry *e) + verbose("%s: user refused key", __func__); + goto send; + } +- if (sshkey_is_sk(id->key) && +- (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) { +- if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, +- SSH_FP_DEFAULT)) == NULL) +- fatal("%s: fingerprint failed", __func__); +- notifier = notify_start(0, +- "Confirm user presence for key %s %s", +- sshkey_type(id->key), fp); ++ if (sshkey_is_sk(id->key)) { ++ if (strncmp(id->key->sk_application, "ssh:", 4) != 0 && ++ !check_websafe_message_contents(key, data, dlen)) { ++ /* error already logged */ ++ goto send; ++ } ++ if ((id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) { ++ if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, ++ SSH_FP_DEFAULT)) == NULL) ++ fatal("%s: fingerprint failed", __func__); ++ notifier = notify_start(0, ++ "Confirm user presence for key %s %s", ++ sshkey_type(id->key), fp); ++ } + } + if ((r = sshkey_sign(id->key, &signature, &slen, + data, dlen, agent_decode_alg(key, flags), +@@ -1214,7 +1298,7 @@ main(int ac, char **av) + __progname = ssh_get_progname(av[0]); + seed_rng(); + +- while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) { ++ while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) { + switch (ch) { + case 'E': + fingerprint_hash = ssh_digest_alg_by_name(optarg); +@@ -1229,6 +1313,12 @@ main(int ac, char **av) + case 'k': + k_flag++; + break; ++ case 'O': ++ if (strcmp(optarg, "no-restrict-websafe") == 0) ++ restrict_websafe = 0; ++ else ++ fatal("Unknown -O option"); ++ break; + case 'P': + if (provider_whitelist != NULL) + fatal("-P option already specified"); +-- +2.41.0 |