166 lines
4.9 KiB
Diff
166 lines
4.9 KiB
Diff
Fix CVE-2018-15473, a method by which remote clients can enumerate
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usernames on the server:
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http://seclists.org/oss-sec/2018/q3/124
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https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-15473
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Patch adapted from upstream source repository:
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https://anongit.mindrot.org/openssh.git/commit/?id=74287f5df9966a0648b4a68417451dd18f079ab8
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From 74287f5df9966a0648b4a68417451dd18f079ab8 Mon Sep 17 00:00:00 2001
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From: "djm@openbsd.org" <djm@openbsd.org>
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Date: Tue, 31 Jul 2018 03:10:27 +0000
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Subject: [PATCH] upstream: delay bailout for invalid authentic
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=?UTF-8?q?ating=20user=20until=20after=20the=20packet=20containing=20the?=
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=?UTF-8?q?=20request=20has=20been=20fully=20parsed.=20Reported=20by=20Dar?=
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=?UTF-8?q?iusz=20Tytko=20and=20Micha=C5=82=20Sajdak;=20ok=20deraadt?=
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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OpenBSD-Commit-ID: b4891882fbe413f230fe8ac8a37349b03bd0b70d
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---
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auth2-gss.c | 11 +++++++----
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auth2-hostbased.c | 11 ++++++-----
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auth2-pubkey.c | 25 +++++++++++++++----------
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3 files changed, 28 insertions(+), 19 deletions(-)
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# Adapted from upstream to apply to OpenSSH 7.7p1.
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diff --git a/auth2-gss.c b/auth2-gss.c
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index 589283b7..1d7cfb39 100644
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--- a/auth2-gss.c
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+++ b/auth2-gss.c
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@@ -69,9 +69,6 @@ userauth_gssapi(struct ssh *ssh)
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u_int len;
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u_char *doid = NULL;
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- if (!authctxt->valid || authctxt->user == NULL)
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- return (0);
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-
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mechs = packet_get_int();
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if (mechs == 0) {
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debug("Mechanism negotiation is not supported");
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diff --git a/auth2-gss.c b/auth2-gss.c
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index 47308c5c..9351e042 100644
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--- a/auth2-gss.c
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+++ b/auth2-gss.c
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@@ -106,6 +103,12 @@ userauth_gssapi(struct ssh *ssh)
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return (0);
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}
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+ if (!authctxt->valid || authctxt->user == NULL) {
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+ debug2("%s: disabled because of invalid user", __func__);
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+ free(doid);
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+ return (0);
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+ }
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+
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if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
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if (ctxt != NULL)
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ssh_gssapi_delete_ctx(&ctxt);
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diff --git a/auth2-hostbased.c b/auth2-hostbased.c
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index 60159a56..35939329 100644
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--- a/auth2-hostbased.c
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+++ b/auth2-hostbased.c
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@@ -67,10 +67,6 @@ userauth_hostbased(struct ssh *ssh)
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size_t alen, blen, slen;
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int r, pktype, authenticated = 0;
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- if (!authctxt->valid) {
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- debug2("%s: disabled because of invalid user", __func__);
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- return 0;
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- }
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/* XXX use sshkey_froms() */
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if ((r = sshpkt_get_cstring(ssh, &pkalg, &alen)) != 0 ||
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(r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
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@@ -117,6 +113,11 @@ userauth_hostbased(struct ssh *ssh)
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goto done;
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}
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+ if (!authctxt->valid || authctxt->user == NULL) {
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+ debug2("%s: disabled because of invalid user", __func__);
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+ goto done;
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+ }
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+
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if ((b = sshbuf_new()) == NULL)
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fatal("%s: sshbuf_new failed", __func__);
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/* reconstruct packet */
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diff --git a/auth2-pubkey.c b/auth2-pubkey.c
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index c4d0f790..e1c15040 100644
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--- a/auth2-pubkey.c
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+++ b/auth2-pubkey.c
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@@ -89,19 +89,15 @@ userauth_pubkey(struct ssh *ssh)
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{
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Authctxt *authctxt = ssh->authctxt;
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struct passwd *pw = authctxt->pw;
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- struct sshbuf *b;
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+ struct sshbuf *b = NULL;
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struct sshkey *key = NULL;
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- char *pkalg, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
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- u_char *pkblob, *sig, have_sig;
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+ char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
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+ u_char *pkblob = NULL, *sig = NULL, have_sig;
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size_t blen, slen;
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int r, pktype;
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int authenticated = 0;
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struct sshauthopt *authopts = NULL;
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- if (!authctxt->valid) {
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- debug2("%s: disabled because of invalid user", __func__);
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- return 0;
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- }
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if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
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(r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
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(r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
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@@ -167,6 +163,11 @@ userauth_pubkey(struct ssh *ssh)
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fatal("%s: sshbuf_put_string session id: %s",
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__func__, ssh_err(r));
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}
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+ if (!authctxt->valid || authctxt->user == NULL) {
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+ debug2("%s: disabled because of invalid user",
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+ __func__);
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+ goto done;
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+ }
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/* reconstruct packet */
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xasprintf(&userstyle, "%s%s%s", authctxt->user,
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authctxt->style ? ":" : "",
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@@ -183,7 +184,6 @@ userauth_pubkey(struct ssh *ssh)
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#ifdef DEBUG_PK
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sshbuf_dump(b, stderr);
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#endif
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-
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/* test for correct signature */
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authenticated = 0;
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if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
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@@ -194,7 +194,6 @@ userauth_pubkey(struct ssh *ssh)
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authenticated = 1;
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}
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sshbuf_free(b);
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- free(sig);
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auth2_record_key(authctxt, authenticated, key);
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} else {
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debug("%s: test pkalg %s pkblob %s%s%s",
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@@ -205,6 +204,11 @@ userauth_pubkey(struct ssh *ssh)
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if ((r = sshpkt_get_end(ssh)) != 0)
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fatal("%s: %s", __func__, ssh_err(r));
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+ if (!authctxt->valid || authctxt->user == NULL) {
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+ debug2("%s: disabled because of invalid user",
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+ __func__);
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+ goto done;
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+ }
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/* XXX fake reply and always send PK_OK ? */
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/*
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* XXX this allows testing whether a user is allowed
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@@ -238,6 +242,7 @@ done:
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free(pkblob);
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free(key_s);
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free(ca_s);
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+ free(sig);
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return authenticated;
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}
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--
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2.18.0
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