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openssh: backport Debian patch for CVE-2023-48795

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import patches from ubuntu to fix
 CVE-2023-48795

Upstream-Status: Backport [import from ubuntu https://git.launchpad.net/ubuntu/+source/openssh/tree/debian/patches?h=ubuntu%2Ffocal-security
Upstream commit 1edb00c58f]

Reference: https://ubuntu.com/security/CVE-2023-48795

(From OE-Core rev: 4026a1cc3aa242a80c306b34b030f05d41b55dda)

Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
This commit is contained in:
Vijay Anusuri
2023-12-22 20:07:20 +05:30
committed by Steve Sakoman
parent 0aa12e4919
commit fc412fa80d
2 changed files with 469 additions and 0 deletions
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468
meta/recipes-connectivity/openssh/openssh/CVE-2023-48795.patch Normal file
View File

@@ -0,0 +1,468 @@
(modified to not remove ssh_packet_read_expect(), to add to
KexAlgorithms in sshd.c and sshconnect2.c as this version pre-dates
kex_proposal_populate_entries(), replace debug*_f() with debug*(),
error*_f() with error*(), and fatal_f() with fatal())
Backport of:
From 1edb00c58f8a6875fad6a497aa2bacf37f9e6cd5 Mon Sep 17 00:00:00 2001
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Mon, 18 Dec 2023 14:45:17 +0000
Subject: [PATCH] upstream: implement "strict key exchange" in ssh and sshd
This adds a protocol extension to improve the integrity of the SSH
transport protocol, particular in and around the initial key exchange
(KEX) phase.
Full details of the extension are in the PROTOCOL file.
with markus@
OpenBSD-Commit-ID: 2a66ac962f0a630d7945fee54004ed9e9c439f14
Upstream-Status: Backport [import from ubuntu https://git.launchpad.net/ubuntu/+source/openssh/tree/debian/patches/CVE-2023-48795.patch?h=ubuntu/focal-security
Upstream commit https://github.com/openssh/openssh-portable/commit/1edb00c58f8a6875fad6a497aa2bacf37f9e6cd5]
CVE: CVE-2023-48795
Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
---
PROTOCOL | 26 +++++++++++++++++
kex.c | 68 +++++++++++++++++++++++++++++++++-----------
kex.h | 1 +
packet.c | 78 ++++++++++++++++++++++++++++++++++++++-------------
sshconnect2.c | 14 +++------
sshd.c | 7 +++--
6 files changed, 146 insertions(+), 48 deletions(-)
diff --git a/PROTOCOL b/PROTOCOL
index f75c1c0..89bddfe 100644
--- a/PROTOCOL
+++ b/PROTOCOL
@@ -102,6 +102,32 @@ OpenSSH supports the use of ECDH in Curve25519 for key exchange as
described at:
http://git.libssh.org/users/aris/libssh.git/plain/doc/curve25519-sha256@libssh.org.txt?h=curve25519
+1.9 transport: strict key exchange extension
+
+OpenSSH supports a number of transport-layer hardening measures under
+a "strict KEX" feature. This feature is signalled similarly to the
+RFC8308 ext-info feature: by including a additional algorithm in the
+initiial SSH2_MSG_KEXINIT kex_algorithms field. The client may append
+"kex-strict-c-v00@openssh.com" to its kex_algorithms and the server
+may append "kex-strict-s-v00@openssh.com". These pseudo-algorithms
+are only valid in the initial SSH2_MSG_KEXINIT and MUST be ignored
+if they are present in subsequent SSH2_MSG_KEXINIT packets.
+
+When an endpoint that supports this extension observes this algorithm
+name in a peer's KEXINIT packet, it MUST make the following changes to
+the the protocol:
+
+a) During initial KEX, terminate the connection if any unexpected or
+ out-of-sequence packet is received. This includes terminating the
+ connection if the first packet received is not SSH2_MSG_KEXINIT.
+ Unexpected packets for the purpose of strict KEX include messages
+ that are otherwise valid at any time during the connection such as
+ SSH2_MSG_DEBUG and SSH2_MSG_IGNORE.
+b) After sending or receiving a SSH2_MSG_NEWKEYS message, reset the
+ packet sequence number to zero. This behaviour persists for the
+ duration of the connection (i.e. not just the first
+ SSH2_MSG_NEWKEYS).
+
2. Connection protocol changes
2.1. connection: Channel write close extension "eow@openssh.com"
diff --git a/kex.c b/kex.c
index ce85f04..3129a4e 100644
--- a/kex.c
+++ b/kex.c
@@ -63,7 +63,7 @@
#include "digest.h"
/* prototype */
-static int kex_choose_conf(struct ssh *);
+static int kex_choose_conf(struct ssh *, uint32_t seq);
static int kex_input_newkeys(int, u_int32_t, struct ssh *);
static const char *proposal_names[PROPOSAL_MAX] = {
@@ -173,6 +173,18 @@ kex_names_valid(const char *names)
return 1;
}
+/* returns non-zero if proposal contains any algorithm from algs */
+static int
+has_any_alg(const char *proposal, const char *algs)
+{
+ char *cp;
+
+ if ((cp = match_list(proposal, algs, NULL)) == NULL)
+ return 0;
+ free(cp);
+ return 1;
+}
+
/*
* Concatenate algorithm names, avoiding duplicates in the process.
* Caller must free returned string.
@@ -180,7 +192,7 @@ kex_names_valid(const char *names)
char *
kex_names_cat(const char *a, const char *b)
{
- char *ret = NULL, *tmp = NULL, *cp, *p, *m;
+ char *ret = NULL, *tmp = NULL, *cp, *p;
size_t len;
if (a == NULL || *a == '\0')
@@ -197,10 +209,8 @@ kex_names_cat(const char *a, const char *b)
}
strlcpy(ret, a, len);
for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
- if ((m = match_list(ret, p, NULL)) != NULL) {
- free(m);
+ if (has_any_alg(ret, p))
continue; /* Algorithm already present */
- }
if (strlcat(ret, ",", len) >= len ||
strlcat(ret, p, len) >= len) {
free(tmp);
@@ -409,7 +419,12 @@ kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
{
int r;
- error("kex protocol error: type %d seq %u", type, seq);
+ /* If in strict mode, any unexpected message is an error */
+ if ((ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict) {
+ ssh_packet_disconnect(ssh, "strict KEX violation: "
+ "unexpected packet type %u (seqnr %u)", type, seq);
+ }
+ error("type %u seq %u", type, seq);
if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
(r = sshpkt_put_u32(ssh, seq)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
@@ -481,6 +496,11 @@ kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh)
ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error);
if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0)
return r;
+ if (ninfo >= 1024) {
+ error("SSH2_MSG_EXT_INFO with too many entries, expected "
+ "<=1024, received %u", ninfo);
+ return dispatch_protocol_error(type, seq, ssh);
+ }
for (i = 0; i < ninfo; i++) {
if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
return r;
@@ -581,7 +601,7 @@ kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
error("%s: no hex", __func__);
return SSH_ERR_INTERNAL_ERROR;
}
- ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
+ ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_protocol_error);
ptr = sshpkt_ptr(ssh, &dlen);
if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
return r;
@@ -617,7 +637,7 @@ kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh)
if (!(kex->flags & KEX_INIT_SENT))
if ((r = kex_send_kexinit(ssh)) != 0)
return r;
- if ((r = kex_choose_conf(ssh)) != 0)
+ if ((r = kex_choose_conf(ssh, seq)) != 0)
return r;
if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
@@ -880,7 +900,13 @@ proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
}
static int
-kex_choose_conf(struct ssh *ssh)
+kexalgs_contains(char **peer, const char *ext)
+{
+ return has_any_alg(peer[PROPOSAL_KEX_ALGS], ext);
+}
+
+static int
+kex_choose_conf(struct ssh *ssh, uint32_t seq)
{
struct kex *kex = ssh->kex;
struct newkeys *newkeys;
@@ -905,13 +931,23 @@ kex_choose_conf(struct ssh *ssh)
sprop=peer;
}
- /* Check whether client supports ext_info_c */
- if (kex->server && (kex->flags & KEX_INITIAL)) {
- char *ext;
-
- ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
- kex->ext_info_c = (ext != NULL);
- free(ext);
+ /* Check whether peer supports ext_info/kex_strict */
+ if ((kex->flags & KEX_INITIAL) != 0) {
+ if (kex->server) {
+ kex->ext_info_c = kexalgs_contains(peer, "ext-info-c");
+ kex->kex_strict = kexalgs_contains(peer,
+ "kex-strict-c-v00@openssh.com");
+ } else {
+ kex->kex_strict = kexalgs_contains(peer,
+ "kex-strict-s-v00@openssh.com");
+ }
+ if (kex->kex_strict) {
+ debug3("will use strict KEX ordering");
+ if (seq != 0)
+ ssh_packet_disconnect(ssh,
+ "strict KEX violation: "
+ "KEXINIT was not the first packet");
+ }
}
/* Algorithm Negotiation */
diff --git a/kex.h b/kex.h
index a5ae6ac..cae38f7 100644
--- a/kex.h
+++ b/kex.h
@@ -145,6 +145,7 @@ struct kex {
u_int kex_type;
char *server_sig_algs;
int ext_info_c;
+ int kex_strict;
struct sshbuf *my;
struct sshbuf *peer;
struct sshbuf *client_version;
diff --git a/packet.c b/packet.c
index 6d3e917..43139f9 100644
--- a/packet.c
+++ b/packet.c
@@ -1203,8 +1203,13 @@ ssh_packet_send2_wrapped(struct ssh *ssh)
sshbuf_dump(state->output, stderr);
#endif
/* increment sequence number for outgoing packets */
- if (++state->p_send.seqnr == 0)
+ if (++state->p_send.seqnr == 0) {
+ if ((ssh->kex->flags & KEX_INITIAL) != 0) {
+ ssh_packet_disconnect(ssh, "outgoing sequence number "
+ "wrapped during initial key exchange");
+ }
logit("outgoing seqnr wraps around");
+ }
if (++state->p_send.packets == 0)
if (!(ssh->compat & SSH_BUG_NOREKEY))
return SSH_ERR_NEED_REKEY;
@@ -1212,6 +1217,11 @@ ssh_packet_send2_wrapped(struct ssh *ssh)
state->p_send.bytes += len;
sshbuf_reset(state->outgoing_packet);
+ if (type == SSH2_MSG_NEWKEYS && ssh->kex->kex_strict) {
+ debug("resetting send seqnr %u", state->p_send.seqnr);
+ state->p_send.seqnr = 0;
+ }
+
if (type == SSH2_MSG_NEWKEYS)
r = ssh_set_newkeys(ssh, MODE_OUT);
else if (type == SSH2_MSG_USERAUTH_SUCCESS && state->server_side)
@@ -1345,8 +1355,7 @@ ssh_packet_read_seqnr(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
/* Stay in the loop until we have received a complete packet. */
for (;;) {
/* Try to read a packet from the buffer. */
- r = ssh_packet_read_poll_seqnr(ssh, typep, seqnr_p);
- if (r != 0)
+ if ((r = ssh_packet_read_poll_seqnr(ssh, typep, seqnr_p)) != 0)
break;
/* If we got a packet, return it. */
if (*typep != SSH_MSG_NONE)
@@ -1633,10 +1642,16 @@ ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
if ((r = sshbuf_consume(state->input, mac->mac_len)) != 0)
goto out;
}
+
if (seqnr_p != NULL)
*seqnr_p = state->p_read.seqnr;
- if (++state->p_read.seqnr == 0)
+ if (++state->p_read.seqnr == 0) {
+ if ((ssh->kex->flags & KEX_INITIAL) != 0) {
+ ssh_packet_disconnect(ssh, "incoming sequence number "
+ "wrapped during initial key exchange");
+ }
logit("incoming seqnr wraps around");
+ }
if (++state->p_read.packets == 0)
if (!(ssh->compat & SSH_BUG_NOREKEY))
return SSH_ERR_NEED_REKEY;
@@ -1702,6 +1717,10 @@ ssh_packet_read_poll2(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
#endif
/* reset for next packet */
state->packlen = 0;
+ if (*typep == SSH2_MSG_NEWKEYS && ssh->kex->kex_strict) {
+ debug("resetting read seqnr %u", state->p_read.seqnr);
+ state->p_read.seqnr = 0;
+ }
/* do we need to rekey? */
if (ssh_packet_need_rekeying(ssh, 0)) {
@@ -1726,10 +1745,39 @@ ssh_packet_read_poll_seqnr(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
r = ssh_packet_read_poll2(ssh, typep, seqnr_p);
if (r != 0)
return r;
- if (*typep) {
- state->keep_alive_timeouts = 0;
- DBG(debug("received packet type %d", *typep));
+ if (*typep == 0) {
+ /* no message ready */
+ return 0;
+ }
+ state->keep_alive_timeouts = 0;
+ DBG(debug("received packet type %d", *typep));
+
+ /* Always process disconnect messages */
+ if (*typep == SSH2_MSG_DISCONNECT) {
+ if ((r = sshpkt_get_u32(ssh, &reason)) != 0 ||
+ (r = sshpkt_get_string(ssh, &msg, NULL)) != 0)
+ return r;
+ /* Ignore normal client exit notifications */
+ do_log2(ssh->state->server_side &&
+ reason == SSH2_DISCONNECT_BY_APPLICATION ?
+ SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_ERROR,
+ "Received disconnect from %s port %d:"
+ "%u: %.400s", ssh_remote_ipaddr(ssh),
+ ssh_remote_port(ssh), reason, msg);
+ free(msg);
+ return SSH_ERR_DISCONNECTED;
}
+
+ /*
+ * Do not implicitly handle any messages here during initial
+ * KEX when in strict mode. They will be need to be allowed
+ * explicitly by the KEX dispatch table or they will generate
+ * protocol errors.
+ */
+ if (ssh->kex != NULL &&
+ (ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict)
+ return 0;
+ /* Implicitly handle transport-level messages */
switch (*typep) {
case SSH2_MSG_IGNORE:
debug3("Received SSH2_MSG_IGNORE");
@@ -1744,19 +1792,6 @@ ssh_packet_read_poll_seqnr(struct ssh *ssh, u_char *typep, u_int32_t *seqnr_p)
debug("Remote: %.900s", msg);
free(msg);
break;
- case SSH2_MSG_DISCONNECT:
- if ((r = sshpkt_get_u32(ssh, &reason)) != 0 ||
- (r = sshpkt_get_string(ssh, &msg, NULL)) != 0)
- return r;
- /* Ignore normal client exit notifications */
- do_log2(ssh->state->server_side &&
- reason == SSH2_DISCONNECT_BY_APPLICATION ?
- SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_ERROR,
- "Received disconnect from %s port %d:"
- "%u: %.400s", ssh_remote_ipaddr(ssh),
- ssh_remote_port(ssh), reason, msg);
- free(msg);
- return SSH_ERR_DISCONNECTED;
case SSH2_MSG_UNIMPLEMENTED:
if ((r = sshpkt_get_u32(ssh, &seqnr)) != 0)
return r;
@@ -2235,6 +2270,7 @@ kex_to_blob(struct sshbuf *m, struct kex *kex)
(r = sshbuf_put_u32(m, kex->hostkey_type)) != 0 ||
(r = sshbuf_put_u32(m, kex->hostkey_nid)) != 0 ||
(r = sshbuf_put_u32(m, kex->kex_type)) != 0 ||
+ (r = sshbuf_put_u32(m, kex->kex_strict)) != 0 ||
(r = sshbuf_put_stringb(m, kex->my)) != 0 ||
(r = sshbuf_put_stringb(m, kex->peer)) != 0 ||
(r = sshbuf_put_stringb(m, kex->client_version)) != 0 ||
@@ -2397,6 +2433,7 @@ kex_from_blob(struct sshbuf *m, struct kex **kexp)
(r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_type)) != 0 ||
(r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_nid)) != 0 ||
(r = sshbuf_get_u32(m, &kex->kex_type)) != 0 ||
+ (r = sshbuf_get_u32(m, &kex->kex_strict)) != 0 ||
(r = sshbuf_get_stringb(m, kex->my)) != 0 ||
(r = sshbuf_get_stringb(m, kex->peer)) != 0 ||
(r = sshbuf_get_stringb(m, kex->client_version)) != 0 ||
@@ -2724,6 +2761,7 @@ sshpkt_disconnect(struct ssh *ssh, const char *fmt,...)
vsnprintf(buf, sizeof(buf), fmt, args);
va_end(args);
+ debug2("sending SSH2_MSG_DISCONNECT: %s", buf);
if ((r = sshpkt_start(ssh, SSH2_MSG_DISCONNECT)) != 0 ||
(r = sshpkt_put_u32(ssh, SSH2_DISCONNECT_PROTOCOL_ERROR)) != 0 ||
(r = sshpkt_put_cstring(ssh, buf)) != 0 ||
diff --git a/sshconnect2.c b/sshconnect2.c
index 5df9477..617ed9f 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -218,7 +218,8 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port)
fatal("%s: kex_assemble_namelist", __func__);
free(all_key);
- if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
+ if ((s = kex_names_cat(options.kex_algorithms,
+ "ext-info-c,kex-strict-c-v00@openssh.com")) == NULL)
fatal("%s: kex_names_cat", __func__);
myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(s);
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
@@ -343,7 +344,6 @@ struct cauthmethod {
};
static int input_userauth_service_accept(int, u_int32_t, struct ssh *);
-static int input_userauth_ext_info(int, u_int32_t, struct ssh *);
static int input_userauth_success(int, u_int32_t, struct ssh *);
static int input_userauth_failure(int, u_int32_t, struct ssh *);
static int input_userauth_banner(int, u_int32_t, struct ssh *);
@@ -460,7 +460,7 @@ ssh_userauth2(struct ssh *ssh, const char *local_user,
ssh->authctxt = &authctxt;
ssh_dispatch_init(ssh, &input_userauth_error);
- ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_ext_info);
+ ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, kex_input_ext_info);
ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_ACCEPT, &input_userauth_service_accept);
ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt.success); /* loop until success */
pubkey_cleanup(ssh);
@@ -505,13 +505,6 @@ input_userauth_service_accept(int type, u_int32_t seq, struct ssh *ssh)
return r;
}
-/* ARGSUSED */
-static int
-input_userauth_ext_info(int type, u_int32_t seqnr, struct ssh *ssh)
-{
- return kex_input_ext_info(type, seqnr, ssh);
-}
-
void
userauth(struct ssh *ssh, char *authlist)
{
@@ -593,6 +586,7 @@ input_userauth_success(int type, u_int32_t seq, struct ssh *ssh)
free(authctxt->methoddata);
authctxt->methoddata = NULL;
authctxt->success = 1; /* break out */
+ ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, dispatch_protocol_error);
return 0;
}
diff --git a/sshd.c b/sshd.c
index 60b2aaf..ffea38c 100644
--- a/sshd.c
+++ b/sshd.c
@@ -2323,11 +2323,13 @@ static void
do_ssh2_kex(struct ssh *ssh)
{
char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
+ char *s;
struct kex *kex;
int r;
- myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(
- options.kex_algorithms);
+ if ((s = kex_names_cat(options.kex_algorithms, "kex-strict-s-v00@openssh.com")) == NULL)
+ fatal("kex_names_cat");
+ myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(s);
myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal(
options.ciphers);
myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal(
@@ -2382,6 +2384,7 @@ do_ssh2_kex(struct ssh *ssh)
packet_send();
packet_write_wait();
#endif
+ free(s);
debug("KEX done");
}
--
2.25.1

1
meta/recipes-connectivity/openssh/openssh_8.2p1.bb
View File

@@ -39,6 +39,7 @@ SRC_URI = "http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-${PV}.tar
file://CVE-2023-38408-10.patch \
file://CVE-2023-38408-11.patch \
file://CVE-2023-38408-12.patch \
file://CVE-2023-48795.patch \
"
SRC_URI[md5sum] = "3076e6413e8dbe56d33848c1054ac091"
SRC_URI[sha256sum] = "43925151e6cf6cee1450190c0e9af4dc36b41c12737619edff8bcebdff64e671"