forked from pool/openssh
9778084948
Added openssh-cve-2023-48795.patch OBS-URL: https://build.opensuse.org/request/show/1133932 OBS-URL: https://build.opensuse.org/package/show/network/openssh?expand=0&rev=254
400 lines
14 KiB
Diff
400 lines
14 KiB
Diff
Index: openssh-9.3p2/PROTOCOL
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===================================================================
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--- openssh-9.3p2.orig/PROTOCOL
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+++ openssh-9.3p2/PROTOCOL
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@@ -104,6 +104,25 @@ http://git.libssh.org/users/aris/libssh.
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This is identical to curve25519-sha256 as later published in RFC8731.
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+1.9 transport: strict key exchange extension
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+
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+OpenSSH supports a number of transport-layer hardening measures under
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+a "strict KEX" feature. This feature is signalled similarly to the
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+RFC8305 ext-info feature: by including a additional algorithm in the
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+SSH2_MSG_KEXINIT kex_algorithms field. The client may append
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+"kex-strict-c-v00@openssh.com" to its kex_algorithms and the server
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+may append "kex-strict-s-v00@openssh.com".
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+
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+When endpoint that supports this extension observes this algorithm
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+name in a peer's KEXINIT packet, it MUST make the following changes to
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+the the protocol:
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+
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+a) During initial KEX, terminate the connection if any unexpected or
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+ out-of-sequence packet is received. This includes terminating the
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+ connection if the first packet received is not SSH2_MSG_KEXINIT.
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+b) At each SSH2_MSG_NEWKEYS message, reset the packet sequence number
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+ to zero.
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+
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2. Connection protocol changes
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2.1. connection: Channel write close extension "eow@openssh.com"
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Index: openssh-9.3p2/kex.c
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===================================================================
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--- openssh-9.3p2.orig/kex.c
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+++ openssh-9.3p2/kex.c
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@@ -76,7 +76,7 @@
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#include "fips.h"
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/* prototype */
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-static int kex_choose_conf(struct ssh *);
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+static int kex_choose_conf(struct ssh *, uint32_t seq);
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static int kex_input_newkeys(int, u_int32_t, struct ssh *);
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static const char * const proposal_names[PROPOSAL_MAX] = {
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@@ -261,6 +261,18 @@ kex_names_valid(const char *names)
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return 1;
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}
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+/* returns non-zero if proposal contains any algorithm from algs */
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+static int
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+has_any_alg(const char *proposal, const char *algs)
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+{
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+ char *cp;
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+
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+ if ((cp = match_list(proposal, algs, NULL)) == NULL)
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+ return 0;
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+ free(cp);
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+ return 1;
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+}
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+
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/*
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* Concatenate algorithm names, avoiding duplicates in the process.
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* Caller must free returned string.
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@@ -268,7 +280,7 @@ kex_names_valid(const char *names)
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char *
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kex_names_cat(const char *a, const char *b)
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{
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- char *ret = NULL, *tmp = NULL, *cp, *p, *m;
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+ char *ret = NULL, *tmp = NULL, *cp, *p;
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size_t len;
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if (a == NULL || *a == '\0')
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@@ -285,10 +297,8 @@ kex_names_cat(const char *a, const char
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}
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strlcpy(ret, a, len);
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for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {
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- if ((m = match_list(ret, p, NULL)) != NULL) {
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- free(m);
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+ if (has_any_alg(ret, p))
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continue; /* Algorithm already present */
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- }
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if (strlcat(ret, ",", len) >= len ||
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strlcat(ret, p, len) >= len) {
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free(tmp);
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@@ -441,15 +451,23 @@ kex_proposal_populate_entries(struct ssh
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const char *defpropclient[PROPOSAL_MAX] = { KEX_CLIENT };
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const char **defprop = ssh->kex->server ? defpropserver : defpropclient;
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u_int i;
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+ char *cp;
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if (prop == NULL)
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fatal_f("proposal missing");
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+ /* Append EXT_INFO signalling to KexAlgorithms */
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+ if (kexalgos == NULL)
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+ kexalgos = defprop[PROPOSAL_KEX_ALGS];
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+ if ((cp = kex_names_cat(kexalgos, ssh->kex->server ?
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+ "kex-strict-s-v00@openssh.com" :
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+ "ext-info-c,kex-strict-c-v00@openssh.com")) == NULL)
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+ fatal_f("kex_names_cat");
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+
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for (i = 0; i < PROPOSAL_MAX; i++) {
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switch(i) {
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case PROPOSAL_KEX_ALGS:
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- prop[i] = compat_kex_proposal(ssh,
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- kexalgos ? kexalgos : defprop[i]);
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+ prop[i] = compat_kex_proposal(ssh, cp);
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break;
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case PROPOSAL_ENC_ALGS_CTOS:
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case PROPOSAL_ENC_ALGS_STOC:
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@@ -470,6 +488,7 @@ kex_proposal_populate_entries(struct ssh
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prop[i] = xstrdup(defprop[i]);
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}
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}
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+ free(cp);
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}
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void
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@@ -573,7 +592,12 @@ kex_protocol_error(int type, u_int32_t s
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{
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int r;
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- error("kex protocol error: type %d seq %u", type, seq);
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+ /* If in strict mode, any unexpected message is an error */
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+ if ((ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict) {
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+ ssh_packet_disconnect(ssh, "strict KEX violation: "
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+ "unexpected packet type %u (seqnr %u)", type, seq);
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+ }
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+ error_f("type %u seq %u", type, seq);
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if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 ||
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(r = sshpkt_put_u32(ssh, seq)) != 0 ||
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(r = sshpkt_send(ssh)) != 0)
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@@ -651,7 +675,7 @@ kex_input_ext_info(int type, u_int32_t s
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if (ninfo >= 1024) {
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error("SSH2_MSG_EXT_INFO with too many entries, expected "
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"<=1024, received %u", ninfo);
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- return SSH_ERR_INVALID_FORMAT;
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+ return dispatch_protocol_error(type, seq, ssh);
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}
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for (i = 0; i < ninfo; i++) {
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if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0)
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@@ -767,7 +791,7 @@ kex_input_kexinit(int type, u_int32_t se
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error_f("no kex");
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return SSH_ERR_INTERNAL_ERROR;
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}
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- ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL);
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+ ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_protocol_error);
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ptr = sshpkt_ptr(ssh, &dlen);
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if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0)
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return r;
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@@ -803,7 +827,7 @@ kex_input_kexinit(int type, u_int32_t se
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if (!(kex->flags & KEX_INIT_SENT))
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if ((r = kex_send_kexinit(ssh)) != 0)
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return r;
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- if ((r = kex_choose_conf(ssh)) != 0)
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+ if ((r = kex_choose_conf(ssh, seq)) != 0)
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return r;
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if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL)
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@@ -1082,20 +1106,14 @@ proposals_match(char *my[PROPOSAL_MAX],
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return (1);
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}
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-/* returns non-zero if proposal contains any algorithm from algs */
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static int
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-has_any_alg(const char *proposal, const char *algs)
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+kexalgs_contains(char **peer, const char *ext)
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{
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- char *cp;
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-
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- if ((cp = match_list(proposal, algs, NULL)) == NULL)
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- return 0;
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- free(cp);
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- return 1;
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+ return has_any_alg(peer[PROPOSAL_KEX_ALGS], ext);
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}
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static int
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-kex_choose_conf(struct ssh *ssh)
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+kex_choose_conf(struct ssh *ssh, uint32_t seq)
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{
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struct kex *kex = ssh->kex;
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struct newkeys *newkeys;
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@@ -1120,13 +1138,23 @@ kex_choose_conf(struct ssh *ssh)
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sprop=peer;
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}
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- /* Check whether client supports ext_info_c */
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- if (kex->server && (kex->flags & KEX_INITIAL)) {
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- char *ext;
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-
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- ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL);
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- kex->ext_info_c = (ext != NULL);
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- free(ext);
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+ /* Check whether peer supports ext_info/kex_strict */
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+ if ((kex->flags & KEX_INITIAL) != 0) {
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+ if (kex->server) {
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+ kex->ext_info_c = kexalgs_contains(peer, "ext-info-c");
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+ kex->kex_strict = kexalgs_contains(peer,
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+ "kex-strict-c-v00@openssh.com");
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+ } else {
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+ kex->kex_strict = kexalgs_contains(peer,
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+ "kex-strict-s-v00@openssh.com");
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+ }
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+ if (kex->kex_strict) {
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+ debug3_f("will use strict KEX ordering");
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+ if (seq != 0)
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+ ssh_packet_disconnect(ssh,
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+ "strict KEX violation: "
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+ "KEXINIT was not the first packet");
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+ }
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}
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/* Check whether client supports rsa-sha2 algorithms */
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Index: openssh-9.3p2/kex.h
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===================================================================
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--- openssh-9.3p2.orig/kex.h
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+++ openssh-9.3p2/kex.h
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@@ -157,6 +157,7 @@ struct kex {
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u_int kex_type;
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char *server_sig_algs;
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int ext_info_c;
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+ int kex_strict;
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struct sshbuf *my;
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struct sshbuf *peer;
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struct sshbuf *client_version;
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Index: openssh-9.3p2/packet.c
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===================================================================
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--- openssh-9.3p2.orig/packet.c
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+++ openssh-9.3p2/packet.c
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@@ -1236,6 +1236,11 @@ ssh_packet_send2_wrapped(struct ssh *ssh
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state->p_send.bytes += len;
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sshbuf_reset(state->outgoing_packet);
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+ if (type == SSH2_MSG_NEWKEYS && ssh->kex->kex_strict) {
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+ debug_f("resetting send seqnr %u", state->p_send.seqnr);
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+ state->p_send.seqnr = 0;
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+ }
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+
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if (type == SSH2_MSG_NEWKEYS)
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r = ssh_set_newkeys(ssh, MODE_OUT);
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else if (type == SSH2_MSG_USERAUTH_SUCCESS && state->server_side)
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@@ -1364,8 +1369,7 @@ ssh_packet_read_seqnr(struct ssh *ssh, u
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/* Stay in the loop until we have received a complete packet. */
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for (;;) {
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/* Try to read a packet from the buffer. */
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- r = ssh_packet_read_poll_seqnr(ssh, typep, seqnr_p);
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- if (r != 0)
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+ if ((r = ssh_packet_read_poll_seqnr(ssh, typep, seqnr_p)) != 0)
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break;
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/* If we got a packet, return it. */
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if (*typep != SSH_MSG_NONE)
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@@ -1649,6 +1630,7 @@ ssh_packet_read_poll2(struct ssh *ssh, u
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if ((r = sshbuf_consume(state->input, mac->mac_len)) != 0)
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goto out;
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}
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+
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if (seqnr_p != NULL)
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*seqnr_p = state->p_read.seqnr;
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if (++state->p_read.seqnr == 0)
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@@ -1718,6 +1700,10 @@ ssh_packet_read_poll2(struct ssh *ssh, u
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#endif
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/* reset for next packet */
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state->packlen = 0;
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+ if (*typep == SSH2_MSG_NEWKEYS && ssh->kex->kex_strict) {
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+ debug_f("resetting read seqnr %u", state->p_read.seqnr);
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+ state->p_read.seqnr = 0;
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+ }
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if ((r = ssh_packet_check_rekey(ssh)) != 0)
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return r;
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@@ -1738,10 +1724,39 @@ ssh_packet_read_poll_seqnr(struct ssh *s
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r = ssh_packet_read_poll2(ssh, typep, seqnr_p);
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if (r != 0)
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return r;
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- if (*typep) {
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- state->keep_alive_timeouts = 0;
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- DBG(debug("received packet type %d", *typep));
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+ if (*typep == 0) {
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+ /* no message ready */
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+ return 0;
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}
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+ state->keep_alive_timeouts = 0;
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+ DBG(debug("received packet type %d", *typep));
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+
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+ /* Always process disconnect messages */
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+ if (*typep == SSH2_MSG_DISCONNECT) {
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+ if ((r = sshpkt_get_u32(ssh, &reason)) != 0 ||
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+ (r = sshpkt_get_string(ssh, &msg, NULL)) != 0)
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+ return r;
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+ /* Ignore normal client exit notifications */
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+ do_log2(ssh->state->server_side &&
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+ reason == SSH2_DISCONNECT_BY_APPLICATION ?
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+ SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_ERROR,
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+ "Received disconnect from %s port %d:"
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+ "%u: %.400s", ssh_remote_ipaddr(ssh),
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+ ssh_remote_port(ssh), reason, msg);
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+ free(msg);
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+ return SSH_ERR_DISCONNECTED;
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+ }
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+
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+ /*
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+ * Do not implicitly handle any messages here during initial
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+ * KEX when in strict mode. They will be need to be allowed
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+ * explicitly by the KEX dispatch table or they will generate
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+ * protocol errors.
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+ */
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+ if (ssh->kex != NULL &&
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+ (ssh->kex->flags & KEX_INITIAL) && ssh->kex->kex_strict)
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+ return 0;
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+ /* Implicitly handle transport-level messages */
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switch (*typep) {
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case SSH2_MSG_IGNORE:
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debug3("Received SSH2_MSG_IGNORE");
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@@ -1756,19 +1771,6 @@ ssh_packet_read_poll_seqnr(struct ssh *s
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debug("Remote: %.900s", msg);
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free(msg);
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break;
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- case SSH2_MSG_DISCONNECT:
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- if ((r = sshpkt_get_u32(ssh, &reason)) != 0 ||
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- (r = sshpkt_get_string(ssh, &msg, NULL)) != 0)
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- return r;
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- /* Ignore normal client exit notifications */
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- do_log2(ssh->state->server_side &&
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- reason == SSH2_DISCONNECT_BY_APPLICATION ?
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- SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_ERROR,
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- "Received disconnect from %s port %d:"
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- "%u: %.400s", ssh_remote_ipaddr(ssh),
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- ssh_remote_port(ssh), reason, msg);
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- free(msg);
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- return SSH_ERR_DISCONNECTED;
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case SSH2_MSG_UNIMPLEMENTED:
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if ((r = sshpkt_get_u32(ssh, &seqnr)) != 0)
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return r;
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@@ -2300,6 +2302,7 @@ kex_to_blob(struct sshbuf *m, struct kex
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(r = sshbuf_put_u32(m, kex->hostkey_type)) != 0 ||
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(r = sshbuf_put_u32(m, kex->hostkey_nid)) != 0 ||
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(r = sshbuf_put_u32(m, kex->kex_type)) != 0 ||
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+ (r = sshbuf_put_u32(m, kex->kex_strict)) != 0 ||
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(r = sshbuf_put_stringb(m, kex->my)) != 0 ||
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(r = sshbuf_put_stringb(m, kex->peer)) != 0 ||
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(r = sshbuf_put_stringb(m, kex->client_version)) != 0 ||
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@@ -2462,6 +2465,7 @@ kex_from_blob(struct sshbuf *m, struct k
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(r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_type)) != 0 ||
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(r = sshbuf_get_u32(m, (u_int *)&kex->hostkey_nid)) != 0 ||
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(r = sshbuf_get_u32(m, &kex->kex_type)) != 0 ||
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+ (r = sshbuf_get_u32(m, &kex->kex_strict)) != 0 ||
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(r = sshbuf_get_stringb(m, kex->my)) != 0 ||
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(r = sshbuf_get_stringb(m, kex->peer)) != 0 ||
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(r = sshbuf_get_stringb(m, kex->client_version)) != 0 ||
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@@ -2790,6 +2794,7 @@ sshpkt_disconnect(struct ssh *ssh, const
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vsnprintf(buf, sizeof(buf), fmt, args);
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va_end(args);
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+ debug2_f("sending SSH2_MSG_DISCONNECT: %s", buf);
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if ((r = sshpkt_start(ssh, SSH2_MSG_DISCONNECT)) != 0 ||
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(r = sshpkt_put_u32(ssh, SSH2_DISCONNECT_PROTOCOL_ERROR)) != 0 ||
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(r = sshpkt_put_cstring(ssh, buf)) != 0 ||
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Index: openssh-9.3p2/sshconnect2.c
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===================================================================
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--- openssh-9.3p2.orig/sshconnect2.c
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+++ openssh-9.3p2/sshconnect2.c
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@@ -420,7 +420,6 @@ struct cauthmethod {
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};
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static int input_userauth_service_accept(int, u_int32_t, struct ssh *);
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-static int input_userauth_ext_info(int, u_int32_t, struct ssh *);
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static int input_userauth_success(int, u_int32_t, struct ssh *);
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static int input_userauth_failure(int, u_int32_t, struct ssh *);
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static int input_userauth_banner(int, u_int32_t, struct ssh *);
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@@ -540,7 +539,7 @@ ssh_userauth2(struct ssh *ssh, const cha
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ssh->authctxt = &authctxt;
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ssh_dispatch_init(ssh, &input_userauth_error);
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- ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_ext_info);
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+ ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, kex_input_ext_info);
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ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_ACCEPT, &input_userauth_service_accept);
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ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt.success); /* loop until success */
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pubkey_cleanup(ssh);
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@@ -591,12 +590,6 @@ input_userauth_service_accept(int type,
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return r;
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}
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-static int
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-input_userauth_ext_info(int type, u_int32_t seqnr, struct ssh *ssh)
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-{
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- return kex_input_ext_info(type, seqnr, ssh);
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-}
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-
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void
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userauth(struct ssh *ssh, char *authlist)
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{
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@@ -675,6 +668,7 @@ input_userauth_success(int type, u_int32
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free(authctxt->methoddata);
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authctxt->methoddata = NULL;
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authctxt->success = 1; /* break out */
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+ ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, dispatch_protocol_error);
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return 0;
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}
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