new file mode 100644
@@ -0,0 +1,466 @@
+From d4634630432594b139b3af6b9f254b890c0f275d Mon Sep 17 00:00:00 2001
+From: Michael Buckley <michael@buckleyisms.com>
+Date: Thu, 30 Nov 2023 15:08:02 -0800
+Subject: [PATCH] src: add 'strict KEX' to fix CVE-2023-48795 "Terrapin Attack"
+
+Refs:
+https://terrapin-attack.com/
+https://seclists.org/oss-sec/2023/q4/292
+https://osv.dev/list?ecosystem=&q=CVE-2023-48795
+https://github.com/advisories/GHSA-45x7-px36-x8w8
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-48795
+
+Fixes #1290
+Closes #1291
+
+CVE: CVE-2023-48795
+Upstream-Status: Backport
+Signed-off-by: Ross Burton <ross.burton@arm.com>
+---
+ src/kex.c | 63 +++++++++++++++++++++++------------
+ src/libssh2_priv.h | 18 +++++++---
+ src/packet.c | 83 +++++++++++++++++++++++++++++++++++++++++++---
+ src/packet.h | 2 +-
+ src/session.c | 3 ++
+ src/transport.c | 12 ++++++-
+ 6 files changed, 149 insertions(+), 32 deletions(-)
+
+diff --git a/src/kex.c b/src/kex.c
+index d4034a0a..b4b748ca 100644
+--- a/src/kex.c
++++ b/src/kex.c
+@@ -3037,6 +3037,13 @@ kex_method_extension_negotiation = {
+ 0,
+ };
+
++static const LIBSSH2_KEX_METHOD
++kex_method_strict_client_extension = {
++ "kex-strict-c-v00@openssh.com",
++ NULL,
++ 0,
++};
++
+ static const LIBSSH2_KEX_METHOD *libssh2_kex_methods[] = {
+ #if LIBSSH2_ED25519
+ &kex_method_ssh_curve25519_sha256,
+@@ -3055,6 +3062,7 @@ static const LIBSSH2_KEX_METHOD *libssh2_kex_methods[] = {
+ &kex_method_diffie_helman_group1_sha1,
+ &kex_method_diffie_helman_group_exchange_sha1,
+ &kex_method_extension_negotiation,
++ &kex_method_strict_client_extension,
+ NULL
+ };
+
+@@ -3307,13 +3315,13 @@ static int kexinit(LIBSSH2_SESSION * session)
+ return 0;
+ }
+
+-/* kex_agree_instr
++/* _libssh2_kex_agree_instr
+ * Kex specific variant of strstr()
+ * Needle must be preceded by BOL or ',', and followed by ',' or EOL
+ */
+-static unsigned char *
+-kex_agree_instr(unsigned char *haystack, size_t haystack_len,
+- const unsigned char *needle, size_t needle_len)
++unsigned char *
++_libssh2_kex_agree_instr(unsigned char *haystack, size_t haystack_len,
++ const unsigned char *needle, size_t needle_len)
+ {
+ unsigned char *s;
+ unsigned char *end_haystack;
+@@ -3398,7 +3406,7 @@ static int kex_agree_hostkey(LIBSSH2_SESSION * session,
+ while(s && *s) {
+ unsigned char *p = (unsigned char *) strchr((char *) s, ',');
+ size_t method_len = (p ? (size_t)(p - s) : strlen((char *) s));
+- if(kex_agree_instr(hostkey, hostkey_len, s, method_len)) {
++ if(_libssh2_kex_agree_instr(hostkey, hostkey_len, s, method_len)) {
+ const LIBSSH2_HOSTKEY_METHOD *method =
+ (const LIBSSH2_HOSTKEY_METHOD *)
+ kex_get_method_by_name((char *) s, method_len,
+@@ -3432,9 +3440,9 @@ static int kex_agree_hostkey(LIBSSH2_SESSION * session,
+ }
+
+ while(hostkeyp && (*hostkeyp) && (*hostkeyp)->name) {
+- s = kex_agree_instr(hostkey, hostkey_len,
+- (unsigned char *) (*hostkeyp)->name,
+- strlen((*hostkeyp)->name));
++ s = _libssh2_kex_agree_instr(hostkey, hostkey_len,
++ (unsigned char *) (*hostkeyp)->name,
++ strlen((*hostkeyp)->name));
+ if(s) {
+ /* So far so good, but does it suit our purposes? (Encrypting vs
+ Signing) */
+@@ -3468,6 +3476,12 @@ static int kex_agree_kex_hostkey(LIBSSH2_SESSION * session, unsigned char *kex,
+ {
+ const LIBSSH2_KEX_METHOD **kexp = libssh2_kex_methods;
+ unsigned char *s;
++ const unsigned char *strict =
++ (unsigned char *)"kex-strict-s-v00@openssh.com";
++
++ if(_libssh2_kex_agree_instr(kex, kex_len, strict, 28)) {
++ session->kex_strict = 1;
++ }
+
+ if(session->kex_prefs) {
+ s = (unsigned char *) session->kex_prefs;
+@@ -3475,7 +3489,7 @@ static int kex_agree_kex_hostkey(LIBSSH2_SESSION * session, unsigned char *kex,
+ while(s && *s) {
+ unsigned char *q, *p = (unsigned char *) strchr((char *) s, ',');
+ size_t method_len = (p ? (size_t)(p - s) : strlen((char *) s));
+- q = kex_agree_instr(kex, kex_len, s, method_len);
++ q = _libssh2_kex_agree_instr(kex, kex_len, s, method_len);
+ if(q) {
+ const LIBSSH2_KEX_METHOD *method = (const LIBSSH2_KEX_METHOD *)
+ kex_get_method_by_name((char *) s, method_len,
+@@ -3509,9 +3523,9 @@ static int kex_agree_kex_hostkey(LIBSSH2_SESSION * session, unsigned char *kex,
+ }
+
+ while(*kexp && (*kexp)->name) {
+- s = kex_agree_instr(kex, kex_len,
+- (unsigned char *) (*kexp)->name,
+- strlen((*kexp)->name));
++ s = _libssh2_kex_agree_instr(kex, kex_len,
++ (unsigned char *) (*kexp)->name,
++ strlen((*kexp)->name));
+ if(s) {
+ /* We've agreed on a key exchange method,
+ * Can we agree on a hostkey that works with this kex?
+@@ -3555,7 +3569,7 @@ static int kex_agree_crypt(LIBSSH2_SESSION * session,
+ unsigned char *p = (unsigned char *) strchr((char *) s, ',');
+ size_t method_len = (p ? (size_t)(p - s) : strlen((char *) s));
+
+- if(kex_agree_instr(crypt, crypt_len, s, method_len)) {
++ if(_libssh2_kex_agree_instr(crypt, crypt_len, s, method_len)) {
+ const LIBSSH2_CRYPT_METHOD *method =
+ (const LIBSSH2_CRYPT_METHOD *)
+ kex_get_method_by_name((char *) s, method_len,
+@@ -3577,9 +3591,9 @@ static int kex_agree_crypt(LIBSSH2_SESSION * session,
+ }
+
+ while(*cryptp && (*cryptp)->name) {
+- s = kex_agree_instr(crypt, crypt_len,
+- (unsigned char *) (*cryptp)->name,
+- strlen((*cryptp)->name));
++ s = _libssh2_kex_agree_instr(crypt, crypt_len,
++ (unsigned char *) (*cryptp)->name,
++ strlen((*cryptp)->name));
+ if(s) {
+ endpoint->crypt = *cryptp;
+ return 0;
+@@ -3619,7 +3633,7 @@ static int kex_agree_mac(LIBSSH2_SESSION * session,
+ unsigned char *p = (unsigned char *) strchr((char *) s, ',');
+ size_t method_len = (p ? (size_t)(p - s) : strlen((char *) s));
+
+- if(kex_agree_instr(mac, mac_len, s, method_len)) {
++ if(_libssh2_kex_agree_instr(mac, mac_len, s, method_len)) {
+ const LIBSSH2_MAC_METHOD *method = (const LIBSSH2_MAC_METHOD *)
+ kex_get_method_by_name((char *) s, method_len,
+ (const LIBSSH2_COMMON_METHOD **)
+@@ -3640,8 +3654,9 @@ static int kex_agree_mac(LIBSSH2_SESSION * session,
+ }
+
+ while(*macp && (*macp)->name) {
+- s = kex_agree_instr(mac, mac_len, (unsigned char *) (*macp)->name,
+- strlen((*macp)->name));
++ s = _libssh2_kex_agree_instr(mac, mac_len,
++ (unsigned char *) (*macp)->name,
++ strlen((*macp)->name));
+ if(s) {
+ endpoint->mac = *macp;
+ return 0;
+@@ -3672,7 +3687,7 @@ static int kex_agree_comp(LIBSSH2_SESSION *session,
+ unsigned char *p = (unsigned char *) strchr((char *) s, ',');
+ size_t method_len = (p ? (size_t)(p - s) : strlen((char *) s));
+
+- if(kex_agree_instr(comp, comp_len, s, method_len)) {
++ if(_libssh2_kex_agree_instr(comp, comp_len, s, method_len)) {
+ const LIBSSH2_COMP_METHOD *method =
+ (const LIBSSH2_COMP_METHOD *)
+ kex_get_method_by_name((char *) s, method_len,
+@@ -3694,8 +3709,9 @@ static int kex_agree_comp(LIBSSH2_SESSION *session,
+ }
+
+ while(*compp && (*compp)->name) {
+- s = kex_agree_instr(comp, comp_len, (unsigned char *) (*compp)->name,
+- strlen((*compp)->name));
++ s = _libssh2_kex_agree_instr(comp, comp_len,
++ (unsigned char *) (*compp)->name,
++ strlen((*compp)->name));
+ if(s) {
+ endpoint->comp = *compp;
+ return 0;
+@@ -3876,6 +3892,7 @@ _libssh2_kex_exchange(LIBSSH2_SESSION * session, int reexchange,
+ session->local.kexinit = key_state->oldlocal;
+ session->local.kexinit_len = key_state->oldlocal_len;
+ key_state->state = libssh2_NB_state_idle;
++ session->state &= ~LIBSSH2_STATE_INITIAL_KEX;
+ session->state &= ~LIBSSH2_STATE_KEX_ACTIVE;
+ session->state &= ~LIBSSH2_STATE_EXCHANGING_KEYS;
+ return -1;
+@@ -3901,6 +3918,7 @@ _libssh2_kex_exchange(LIBSSH2_SESSION * session, int reexchange,
+ session->local.kexinit = key_state->oldlocal;
+ session->local.kexinit_len = key_state->oldlocal_len;
+ key_state->state = libssh2_NB_state_idle;
++ session->state &= ~LIBSSH2_STATE_INITIAL_KEX;
+ session->state &= ~LIBSSH2_STATE_KEX_ACTIVE;
+ session->state &= ~LIBSSH2_STATE_EXCHANGING_KEYS;
+ return -1;
+@@ -3949,6 +3967,7 @@ _libssh2_kex_exchange(LIBSSH2_SESSION * session, int reexchange,
+ session->remote.kexinit = NULL;
+ }
+
++ session->state &= ~LIBSSH2_STATE_INITIAL_KEX;
+ session->state &= ~LIBSSH2_STATE_KEX_ACTIVE;
+ session->state &= ~LIBSSH2_STATE_EXCHANGING_KEYS;
+
+diff --git a/src/libssh2_priv.h b/src/libssh2_priv.h
+index 82c3afe2..ee1d8b5c 100644
+--- a/src/libssh2_priv.h
++++ b/src/libssh2_priv.h
+@@ -699,6 +699,9 @@ struct _LIBSSH2_SESSION
+ /* key signing algorithm preferences -- NULL yields server order */
+ char *sign_algo_prefs;
+
++ /* Whether to use the OpenSSH Strict KEX extension */
++ int kex_strict;
++
+ /* (remote as source of data -- packet_read ) */
+ libssh2_endpoint_data remote;
+
+@@ -870,6 +873,7 @@ struct _LIBSSH2_SESSION
+ int fullpacket_macstate;
+ size_t fullpacket_payload_len;
+ int fullpacket_packet_type;
++ uint32_t fullpacket_required_type;
+
+ /* State variables used in libssh2_sftp_init() */
+ libssh2_nonblocking_states sftpInit_state;
+@@ -910,10 +914,11 @@ struct _LIBSSH2_SESSION
+ };
+
+ /* session.state bits */
+-#define LIBSSH2_STATE_EXCHANGING_KEYS 0x00000001
+-#define LIBSSH2_STATE_NEWKEYS 0x00000002
+-#define LIBSSH2_STATE_AUTHENTICATED 0x00000004
+-#define LIBSSH2_STATE_KEX_ACTIVE 0x00000008
++#define LIBSSH2_STATE_INITIAL_KEX 0x00000001
++#define LIBSSH2_STATE_EXCHANGING_KEYS 0x00000002
++#define LIBSSH2_STATE_NEWKEYS 0x00000004
++#define LIBSSH2_STATE_AUTHENTICATED 0x00000008
++#define LIBSSH2_STATE_KEX_ACTIVE 0x00000010
+
+ /* session.flag helpers */
+ #ifdef MSG_NOSIGNAL
+@@ -1144,6 +1149,11 @@ ssize_t _libssh2_send(libssh2_socket_t socket, const void *buffer,
+ int _libssh2_kex_exchange(LIBSSH2_SESSION * session, int reexchange,
+ key_exchange_state_t * state);
+
++unsigned char *_libssh2_kex_agree_instr(unsigned char *haystack,
++ size_t haystack_len,
++ const unsigned char *needle,
++ size_t needle_len);
++
+ /* Let crypt.c/hostkey.c expose their method structs */
+ const LIBSSH2_CRYPT_METHOD **libssh2_crypt_methods(void);
+ const LIBSSH2_HOSTKEY_METHOD **libssh2_hostkey_methods(void);
+diff --git a/src/packet.c b/src/packet.c
+index b5b41981..35d4d39e 100644
+--- a/src/packet.c
++++ b/src/packet.c
+@@ -605,14 +605,13 @@ authagent_exit:
+ * layer when it has received a packet.
+ *
+ * The input pointer 'data' is pointing to allocated data that this function
+- * is asked to deal with so on failure OR success, it must be freed fine.
+- * The only exception is when the return code is LIBSSH2_ERROR_EAGAIN.
++ * will be freed unless return the code is LIBSSH2_ERROR_EAGAIN.
+ *
+ * This function will always be called with 'datalen' greater than zero.
+ */
+ int
+ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
+- size_t datalen, int macstate)
++ size_t datalen, int macstate, uint32_t seq)
+ {
+ int rc = 0;
+ unsigned char *message = NULL;
+@@ -657,6 +656,70 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
+ break;
+ }
+
++ if(session->state & LIBSSH2_STATE_INITIAL_KEX) {
++ if(msg == SSH_MSG_KEXINIT) {
++ if(!session->kex_strict) {
++ if(datalen < 17) {
++ LIBSSH2_FREE(session, data);
++ session->packAdd_state = libssh2_NB_state_idle;
++ return _libssh2_error(session,
++ LIBSSH2_ERROR_BUFFER_TOO_SMALL,
++ "Data too short extracting kex");
++ }
++ else {
++ const unsigned char *strict =
++ (unsigned char *)"kex-strict-s-v00@openssh.com";
++ struct string_buf buf;
++ unsigned char *algs = NULL;
++ size_t algs_len = 0;
++
++ buf.data = (unsigned char *)data;
++ buf.dataptr = buf.data;
++ buf.len = datalen;
++ buf.dataptr += 17; /* advance past type and cookie */
++
++ if(_libssh2_get_string(&buf, &algs, &algs_len)) {
++ LIBSSH2_FREE(session, data);
++ session->packAdd_state = libssh2_NB_state_idle;
++ return _libssh2_error(session,
++ LIBSSH2_ERROR_BUFFER_TOO_SMALL,
++ "Algs too short");
++ }
++
++ if(algs_len == 0 ||
++ _libssh2_kex_agree_instr(algs, algs_len, strict, 28)) {
++ session->kex_strict = 1;
++ }
++ }
++ }
++
++ if(session->kex_strict && seq) {
++ LIBSSH2_FREE(session, data);
++ session->socket_state = LIBSSH2_SOCKET_DISCONNECTED;
++ session->packAdd_state = libssh2_NB_state_idle;
++ libssh2_session_disconnect(session, "strict KEX violation: "
++ "KEXINIT was not the first packet");
++
++ return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_DISCONNECT,
++ "strict KEX violation: "
++ "KEXINIT was not the first packet");
++ }
++ }
++
++ if(session->kex_strict && session->fullpacket_required_type &&
++ session->fullpacket_required_type != msg) {
++ LIBSSH2_FREE(session, data);
++ session->socket_state = LIBSSH2_SOCKET_DISCONNECTED;
++ session->packAdd_state = libssh2_NB_state_idle;
++ libssh2_session_disconnect(session, "strict KEX violation: "
++ "unexpected packet type");
++
++ return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_DISCONNECT,
++ "strict KEX violation: "
++ "unexpected packet type");
++ }
++ }
++
+ if(session->packAdd_state == libssh2_NB_state_allocated) {
+ /* A couple exceptions to the packet adding rule: */
+ switch(msg) {
+@@ -1341,6 +1404,15 @@ _libssh2_packet_ask(LIBSSH2_SESSION * session, unsigned char packet_type,
+
+ return 0;
+ }
++ else if(session->kex_strict &&
++ (session->state & LIBSSH2_STATE_INITIAL_KEX)) {
++ libssh2_session_disconnect(session, "strict KEX violation: "
++ "unexpected packet type");
++
++ return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_DISCONNECT,
++ "strict KEX violation: "
++ "unexpected packet type");
++ }
+ packet = _libssh2_list_next(&packet->node);
+ }
+ return -1;
+@@ -1402,7 +1474,10 @@ _libssh2_packet_require(LIBSSH2_SESSION * session, unsigned char packet_type,
+ }
+
+ while(session->socket_state == LIBSSH2_SOCKET_CONNECTED) {
+- int ret = _libssh2_transport_read(session);
++ int ret;
++ session->fullpacket_required_type = packet_type;
++ ret = _libssh2_transport_read(session);
++ session->fullpacket_required_type = 0;
+ if(ret == LIBSSH2_ERROR_EAGAIN)
+ return ret;
+ else if(ret < 0) {
+diff --git a/src/packet.h b/src/packet.h
+index 79018bcf..6ea100a5 100644
+--- a/src/packet.h
++++ b/src/packet.h
+@@ -71,6 +71,6 @@ int _libssh2_packet_burn(LIBSSH2_SESSION * session,
+ int _libssh2_packet_write(LIBSSH2_SESSION * session, unsigned char *data,
+ unsigned long data_len);
+ int _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
+- size_t datalen, int macstate);
++ size_t datalen, int macstate, uint32_t seq);
+
+ #endif /* __LIBSSH2_PACKET_H */
+diff --git a/src/session.c b/src/session.c
+index a4d602ba..f4bafb57 100644
+--- a/src/session.c
++++ b/src/session.c
+@@ -464,6 +464,8 @@ libssh2_session_init_ex(LIBSSH2_ALLOC_FUNC((*my_alloc)),
+ session->abstract = abstract;
+ session->api_timeout = 0; /* timeout-free API by default */
+ session->api_block_mode = 1; /* blocking API by default */
++ session->state = LIBSSH2_STATE_INITIAL_KEX;
++ session->fullpacket_required_type = 0;
+ session->packet_read_timeout = LIBSSH2_DEFAULT_READ_TIMEOUT;
+ session->flag.quote_paths = 1; /* default behavior is to quote paths
+ for the scp subsystem */
+@@ -1186,6 +1188,7 @@ libssh2_session_disconnect_ex(LIBSSH2_SESSION *session, int reason,
+ const char *desc, const char *lang)
+ {
+ int rc;
++ session->state &= ~LIBSSH2_STATE_INITIAL_KEX;
+ session->state &= ~LIBSSH2_STATE_EXCHANGING_KEYS;
+ BLOCK_ADJUST(rc, session,
+ session_disconnect(session, reason, desc, lang));
+diff --git a/src/transport.c b/src/transport.c
+index 6d902d33..3b30ff84 100644
+--- a/src/transport.c
++++ b/src/transport.c
+@@ -187,6 +187,7 @@ fullpacket(LIBSSH2_SESSION * session, int encrypted /* 1 or 0 */ )
+ struct transportpacket *p = &session->packet;
+ int rc;
+ int compressed;
++ uint32_t seq = session->remote.seqno;
+
+ if(session->fullpacket_state == libssh2_NB_state_idle) {
+ session->fullpacket_macstate = LIBSSH2_MAC_CONFIRMED;
+@@ -318,7 +319,7 @@ fullpacket(LIBSSH2_SESSION * session, int encrypted /* 1 or 0 */ )
+ if(session->fullpacket_state == libssh2_NB_state_created) {
+ rc = _libssh2_packet_add(session, p->payload,
+ session->fullpacket_payload_len,
+- session->fullpacket_macstate);
++ session->fullpacket_macstate, seq);
+ if(rc == LIBSSH2_ERROR_EAGAIN)
+ return rc;
+ if(rc) {
+@@ -329,6 +330,11 @@ fullpacket(LIBSSH2_SESSION * session, int encrypted /* 1 or 0 */ )
+
+ session->fullpacket_state = libssh2_NB_state_idle;
+
++ if(session->kex_strict &&
++ session->fullpacket_packet_type == SSH_MSG_NEWKEYS) {
++ session->remote.seqno = 0;
++ }
++
+ return session->fullpacket_packet_type;
+ }
+
+@@ -1091,6 +1097,10 @@ int _libssh2_transport_send(LIBSSH2_SESSION *session,
+
+ session->local.seqno++;
+
++ if(session->kex_strict && data[0] == SSH_MSG_NEWKEYS) {
++ session->local.seqno = 0;
++ }
++
+ ret = LIBSSH2_SEND(session, p->outbuf, total_length,
+ LIBSSH2_SOCKET_SEND_FLAGS(session));
+ if(ret < 0)
+--
+2.34.1
+
@@ -9,6 +9,7 @@ LIC_FILES_CHKSUM = "file://COPYING;md5=24a33237426720395ebb1dd1349ca225"
SRC_URI = "http://www.libssh2.org/download/${BP}.tar.gz \
file://run-ptest \
+ file://CVE-2023-48795.patch \
"
SRC_URI[sha256sum] = "3736161e41e2693324deb38c26cfdc3efe6209d634ba4258db1cecff6a5ad461"