main/openssh: security fix for CVE-2016-6210

2 files changed, 227 insertions, 4 deletions

diff --git a/main/openssh/APKBUILD b/main/openssh/APKBUILD
index 93977fbe77..ee7f675779 100644
--- a/main/openssh/APKBUILD
+++ b/main/openssh/APKBUILD
@@ -3,7 +3,7 @@
 pkgname=openssh
 pkgver=7.2_p2
 _myver=${pkgver%_*}${pkgver#*_}
-pkgrel=0
+pkgrel=1
 pkgdesc="Port of OpenBSD's free SSH release"
 url="http://www.openssh.org/portable.html"
 arch="all"
@@ -23,6 +23,7 @@ source="http://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/$pkgname-$_myver.tar
 	sshd.initd
 	sshd.confd
 	openssh-sftp-interactive.diff
+	CVE-2016-6210.patch
 	"
 # HPN patches are from: http://www.psc.edu/index.php/hpn-ssh
 
@@ -116,7 +117,8 @@ cd52fe99cb4b7d0d847bf5d710d93564  openssh6.5-peaktput.diff
 e21243d6ddff1bb929eed3676b4b9a2a  bsd-compatible-realpath.patch
 8590e08286f47a777725655873dd318f  sshd.initd
 b35e9f3829f4cfca07168fcba98749c7  sshd.confd
-2dd7e366607e95f9762273067309fd6e  openssh-sftp-interactive.diff"
+2dd7e366607e95f9762273067309fd6e  openssh-sftp-interactive.diff
+baccdaf19767102c91343742cc09ebc9  CVE-2016-6210.patch"
 sha256sums="a72781d1a043876a224ff1b0032daa4094d87565a68528759c1c2cab5482548c  openssh-7.2p2.tar.gz
 bf49212e47a86d10650f739532cea514a310925e6445b4f8011031b6b55f3249  openssh6.5-peaktput.diff
 861132af07c18f5e0ac7b64f389a929e61a051887bf44bda770a97e3afd9bfb6  openssh7.1-dynwindows.diff
@@ -124,7 +126,8 @@ bf49212e47a86d10650f739532cea514a310925e6445b4f8011031b6b55f3249  openssh6.5-pea
 a843cacd7002a68e9d09b5d8ea1466c9980fa35fa3ccd8d9357ac793017de2a6  bsd-compatible-realpath.patch
 c31a116bba900c6c4795b061766169e6455d6e1b7cf9aa2ee5ba4eaa1afa76b0  sshd.initd
 29c6d57ac3ec6018cadc6ba6cd9b90c9ed46e20049b970fdcc68ee2481a2ee41  sshd.confd
-4ce1ad5f767c0f4e854a0cfeef0e2e400f333c649e552df1ecc317e6a6557376  openssh-sftp-interactive.diff"
+4ce1ad5f767c0f4e854a0cfeef0e2e400f333c649e552df1ecc317e6a6557376  openssh-sftp-interactive.diff
+53ee8c957e9dd3bb51fe629d04e6373c6e4b62026352463bad916a4e66c00f37  CVE-2016-6210.patch"
 sha512sums="44f62b3a7bc50a0735d496a5aedeefb71550d8c10ad8f22b94e29fcc8084842db96e8c4ca41fced17af69e1aab09ed1182a12ad8650d9a46fd8743a0344df95b  openssh-7.2p2.tar.gz
 e041398e177674f698480e23be037160bd07b751c754956a3ddf1b964da24c85e826fb75e7c23c9826d36761da73d08db9583c047d58a08dc7b2149a949075b1  openssh6.5-peaktput.diff
 72a7dc21d18388c635d14dda762ac50caeefd38f0153d8ea36d18e9d7c982e104f7b7a3af8c18fd479c31201fbdee1639f3a1ec60d035d4ca8721a8563fa11a0  openssh7.1-dynwindows.diff
@@ -132,4 +135,5 @@ f35fffcd26635249ce5d820e7b3e406e586f2d2d7f6a045f221e2f9fb53aebc1ab1dd1e603b33894
 f2b8daa537ea3f32754a4485492cc6eb3f40133ed46c0a5a29a89e4bcf8583d82d891d94bf2e5eb1c916fa68ec094abf4e6cd641e9737a6c05053808012b3a73  bsd-compatible-realpath.patch
 7e4378daebd8f5df0cd2f0709af806a0d4a78c948b8fc3baaf3585e5f5ec5d0793f7e4d0a450bc43bbcb92daa09bfab482cbceb396b993c0545adfe56573cd44  sshd.initd
 b9ae816af54a55e134a9307e376f05367b815f1b3fd545c2a2c312d18aedcf907f413e8bad8db980cdd9aad4011a72a79e1e94594f69500939a9cb46287f2f81  sshd.confd
-c1d09c65dbc347f0904edc30f91aa9a24b0baee50309536182455b544f1e3f85a8cecfa959e32be8b101d8282ef06dde3febbbc3f315489339dcf04155c859a9  openssh-sftp-interactive.diff"
+c1d09c65dbc347f0904edc30f91aa9a24b0baee50309536182455b544f1e3f85a8cecfa959e32be8b101d8282ef06dde3febbbc3f315489339dcf04155c859a9  openssh-sftp-interactive.diff
+202ae2ca83c0caeb0099ca22e7a248053d29cc7751c5b5865004108e4b998d7bf738df8cc0aa138a2b770748e5f90835e707434acd4719ce388181db1dc81ccd  CVE-2016-6210.patch"
diff --git a/main/openssh/CVE-2016-6210.patch b/main/openssh/CVE-2016-6210.patch
new file mode 100644
index 0000000000..c543af3e3a
--- /dev/null
+++ b/main/openssh/CVE-2016-6210.patch
@@ -0,0 +1,219 @@
+From 9286875a73b2de7736b5e50692739d314cd8d9dc Mon Sep 17 00:00:00 2001
+From: Darren Tucker <dtucker@zip.com.au>
+Date: Fri, 15 Jul 2016 13:32:45 +1000
+Subject: Determine appropriate salt for invalid users.
+
+When sshd is processing a non-PAM login for a non-existent user it uses
+the string from the fakepw structure as the salt for crypt(3)ing the
+password supplied by the client.  That string has a Blowfish prefix, so on
+systems that don't understand that crypt will fail fast due to an invalid
+salt, and even on those that do it may have significantly different timing
+from the hash methods used for real accounts (eg sha512).  This allows
+user enumeration by, eg, sending large password strings.  This was noted
+by EddieEzra.Harari at verint.com (CVE-2016-6210).
+
+To mitigate, use the same hash algorithm that root uses for hashing
+passwords for users that do not exist on the system.  ok djm@
+---
+ auth-passwd.c           | 12 ++++++++----
+ openbsd-compat/xcrypt.c | 34 ++++++++++++++++++++++++++++++++++
+ 2 files changed, 42 insertions(+), 4 deletions(-)
+
+diff --git a/auth-passwd.c b/auth-passwd.c
+index 63ccf3c..530b5d4 100644
+--- a/auth-passwd.c
++++ b/auth-passwd.c
+@@ -193,7 +193,7 @@ int
+ sys_auth_passwd(Authctxt *authctxt, const char *password)
+ {
+ 	struct passwd *pw = authctxt->pw;
+-	char *encrypted_password;
++	char *encrypted_password, *salt = NULL;
+ 
+ 	/* Just use the supplied fake password if authctxt is invalid */
+ 	char *pw_password = authctxt->valid ? shadow_pw(pw) : pw->pw_passwd;
+@@ -202,9 +202,13 @@ sys_auth_passwd(Authctxt *authctxt, const char *password)
+ 	if (strcmp(pw_password, "") == 0 && strcmp(password, "") == 0)
+ 		return (1);
+ 
+-	/* Encrypt the candidate password using the proper salt. */
+-	encrypted_password = xcrypt(password,
+-	    (pw_password[0] && pw_password[1]) ? pw_password : "xx");
++	/*
++	 * Encrypt the candidate password using the proper salt, or pass a
++	 * NULL and let xcrypt pick one.
++	 */
++	if (authctxt->valid && pw_password[0] && pw_password[1])
++		salt = pw_password;
++	encrypted_password = xcrypt(password, salt);
+ 
+ 	/*
+ 	 * Authentication is accepted if the encrypted passwords
+diff --git a/openbsd-compat/xcrypt.c b/openbsd-compat/xcrypt.c
+index 8577cbd..8913bb8 100644
+--- a/openbsd-compat/xcrypt.c
++++ b/openbsd-compat/xcrypt.c
+@@ -25,6 +25,7 @@
+ #include "includes.h"
+ 
+ #include <sys/types.h>
++#include <string.h>
+ #include <unistd.h>
+ #include <pwd.h>
+ 
+@@ -62,11 +63,44 @@
+ #  define crypt DES_crypt
+ # endif
+ 
++/*
++ * Pick an appropriate password encryption type and salt for the running
++ * system.
++ */
++static const char *
++pick_salt(void)
++{
++	struct passwd *pw;
++	char *passwd, *p;
++	size_t typelen;
++	static char salt[32];
++
++	if (salt[0] != '\0')
++		return salt;
++	strlcpy(salt, "xx", sizeof(salt));
++	if ((pw = getpwuid(0)) == NULL)
++		return salt;
++	passwd = shadow_pw(pw);
++	if (passwd[0] != '$' || (p = strrchr(passwd + 1, '$')) == NULL)
++		return salt;  /* no $, DES */
++	typelen = p - passwd + 1;
++	strlcpy(salt, passwd, MIN(typelen, sizeof(salt)));
++	explicit_bzero(passwd, strlen(passwd));
++	return salt;
++}
++
+ char *
+ xcrypt(const char *password, const char *salt)
+ {
+ 	char *crypted;
+ 
++	/*
++	 * If we don't have a salt we are encrypting a fake password for
++	 * for timing purposes.  Pick an appropriate salt.
++	 */
++	if (salt == NULL)
++		salt = pick_salt();
++
+ # ifdef HAVE_MD5_PASSWORDS
+         if (is_md5_salt(salt))
+                 crypted = md5_crypt(password, salt);
+-- 
+cgit v0.12
+
+From 283b97ff33ea2c641161950849931bd578de6946 Mon Sep 17 00:00:00 2001
+From: Darren Tucker <dtucker@zip.com.au>
+Date: Fri, 15 Jul 2016 13:49:44 +1000
+Subject: Mitigate timing of disallowed users PAM logins.
+
+When sshd decides to not allow a login (eg PermitRootLogin=no) and
+it's using PAM, it sends a fake password to PAM so that the timing for
+the failure is not noticeably different whether or not the password
+is correct.  This behaviour can be detected by sending a very long
+password string which is slower to hash than the fake password.
+
+Mitigate by constructing an invalid password that is the same length
+as the one from the client and thus takes the same time to hash.
+Diff from djm@
+---
+ auth-pam.c | 35 +++++++++++++++++++++++++++++++----
+ 1 file changed, 31 insertions(+), 4 deletions(-)
+
+diff --git a/auth-pam.c b/auth-pam.c
+index 451de78..465b5a7 100644
+--- a/auth-pam.c
++++ b/auth-pam.c
+@@ -232,7 +232,6 @@ static int sshpam_account_status = -1;
+ static char **sshpam_env = NULL;
+ static Authctxt *sshpam_authctxt = NULL;
+ static const char *sshpam_password = NULL;
+-static char badpw[] = "\b\n\r\177INCORRECT";
+ 
+ /* Some PAM implementations don't implement this */
+ #ifndef HAVE_PAM_GETENVLIST
+@@ -795,12 +794,35 @@ sshpam_query(void *ctx, char **name, char **info,
+ 	return (-1);
+ }
+ 
++/*
++ * Returns a junk password of identical length to that the user supplied.
++ * Used to mitigate timing attacks against crypt(3)/PAM stacks that
++ * vary processing time in proportion to password length.
++ */
++static char *
++fake_password(const char *wire_password)
++{
++	const char junk[] = "\b\n\r\177INCORRECT";
++	char *ret = NULL;
++	size_t i, l = wire_password != NULL ? strlen(wire_password) : 0;
++
++	if (l >= INT_MAX)
++		fatal("%s: password length too long: %zu", __func__, l);
++
++	ret = malloc(l + 1);
++	for (i = 0; i < l; i++)
++		ret[i] = junk[i % (sizeof(junk) - 1)];
++	ret[i] = '\0';
++	return ret;
++}
++
+ /* XXX - see also comment in auth-chall.c:verify_response */
+ static int
+ sshpam_respond(void *ctx, u_int num, char **resp)
+ {
+ 	Buffer buffer;
+ 	struct pam_ctxt *ctxt = ctx;
++	char *fake;
+ 
+ 	debug2("PAM: %s entering, %u responses", __func__, num);
+ 	switch (ctxt->pam_done) {
+@@ -821,8 +843,11 @@ sshpam_respond(void *ctx, u_int num, char **resp)
+ 	    (sshpam_authctxt->pw->pw_uid != 0 ||
+ 	    options.permit_root_login == PERMIT_YES))
+ 		buffer_put_cstring(&buffer, *resp);
+-	else
+-		buffer_put_cstring(&buffer, badpw);
++	else {
++		fake = fake_password(*resp);
++		buffer_put_cstring(&buffer, fake);
++		free(fake);
++	}
+ 	if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
+ 		buffer_free(&buffer);
+ 		return (-1);
+@@ -1166,6 +1191,7 @@ sshpam_auth_passwd(Authctxt *authctxt, const char *password)
+ {
+ 	int flags = (options.permit_empty_passwd == 0 ?
+ 	    PAM_DISALLOW_NULL_AUTHTOK : 0);
++	char *fake = NULL;
+ 
+ 	if (!options.use_pam || sshpam_handle == NULL)
+ 		fatal("PAM: %s called when PAM disabled or failed to "
+@@ -1181,7 +1207,7 @@ sshpam_auth_passwd(Authctxt *authctxt, const char *password)
+ 	 */
+ 	if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
+ 	    options.permit_root_login != PERMIT_YES))
+-		sshpam_password = badpw;
++		sshpam_password = fake = fake_password(password);
+ 
+ 	sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
+ 	    (const void *)&passwd_conv);
+@@ -1191,6 +1217,7 @@ sshpam_auth_passwd(Authctxt *authctxt, const char *password)
+ 
+ 	sshpam_err = pam_authenticate(sshpam_handle, flags);
+ 	sshpam_password = NULL;
++	free(fake);
+ 	if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
+ 		debug("PAM: password authentication accepted for %.100s",
+ 		    authctxt->user);
+-- 
+cgit v0.12
+