Commit 8c2d71dd authored by Leonardo Arena's avatar Leonardo Arena
Browse files

main/dropbear: security fix (CVE-2018-15599)

Fixes #9351
parent 2c95720d
......@@ -3,7 +3,7 @@
# Maintainer: Natanael Copa <ncopa@alpinelinux.org>
pkgname=dropbear
pkgver=2017.75
pkgrel=0
pkgrel=1
pkgdesc="small SSH 2 client/server designed for small memory environments"
url="http://matt.ucc.asn.au/dropbear/dropbear.html"
arch="all"
......@@ -21,11 +21,14 @@ source="http://matt.ucc.asn.au/dropbear/releases/${pkgname}-${pkgver}.tar.bz2
dropbear.confd
dropbear-0.53.1-static_build_fix.patch
dropbear-options_sftp-server_path.patch
CVE-2018-15599.patch
"
builddir="$srcdir"/$pkgname-$pkgver
_progs="dropbear dropbearkey dbclient dropbearconvert scp"
# secfixes:
# 2017.75-r1:
# - CVE-2018-15599
# 2017.75-r0:
# - CVE-2017-9078
# - CVE-2017-9079
......@@ -96,4 +99,5 @@ sha512sums="9c2f2a5e718339f83abc0ad7719bda12bfc75e5bcb87a7c0eec0afefc743e5c0a157
9c55ab3d8b61955cde1ccc1b8acbd3d2ef123feb9489e92737304c35315d07b7f85fad8a12ac7b0ec2c1dcee3d76b8bc4aa18518f4ddd963917805db33e48826 dropbear.initd
83f2c1eaf7687917a4b2bae7d599d4378c4bd64f9126ba42fc5d235f2b3c9a474d1b3168d70ed64bb4101cc251d30bc9ae20604da9b5d819fcd635ee4d0ebb0f dropbear.confd
c9b0f28eb9653de21da4e8646fc27870a156112bce3d8a13baa6154ebf4baada3dee4f75bd5fdf5b6cd24a43fb80fb009e917d139d9e65d35118b082de0ebfbf dropbear-0.53.1-static_build_fix.patch
7fed3e2566f56f0445df185437afaddf7a029df0e4d5f265c1e97a89ce4a8d61b1b4aaae8ecaf25d94251fa9d14bb5b01b4cf7afa1a52289a4f8c7d042029d3c dropbear-options_sftp-server_path.patch"
7fed3e2566f56f0445df185437afaddf7a029df0e4d5f265c1e97a89ce4a8d61b1b4aaae8ecaf25d94251fa9d14bb5b01b4cf7afa1a52289a4f8c7d042029d3c dropbear-options_sftp-server_path.patch
51ba4866bf42aeb4ab756f7a3f9f425362ae74184ae3ae327e0c55c4cd29311aa6b9831126f2238cd88f2fda624e8494230efda3dbec5828c0259b3a93ade102 CVE-2018-15599.patch"
commit 52adbb34c32d3e2e1bcdb941e20a6f81138b8248
Author: Matt Johnston <matt@ucc.asn.au>
Date: Thu Aug 23 23:43:12 2018 +0800
Wait to fail invalid usernames
---
auth.h | 6 +++---
svr-auth.c | 19 +++++--------------
svr-authpam.c | 26 ++++++++++++++++++++++----
svr-authpasswd.c | 27 ++++++++++++++-------------
svr-authpubkey.c | 11 ++++++++++-
5 files changed, 54 insertions(+), 35 deletions(-)
diff --git a/auth.h b/auth.h
index da498f5..98f5468 100644
--- a/auth.h
+++ b/auth.h
@@ -37,9 +37,9 @@ void recv_msg_userauth_request(void);
void send_msg_userauth_failure(int partial, int incrfail);
void send_msg_userauth_success();
void send_msg_userauth_banner(buffer *msg);
-void svr_auth_password(void);
-void svr_auth_pubkey(void);
-void svr_auth_pam(void);
+void svr_auth_password(int valid_user);
+void svr_auth_pubkey(int valid_user);
+void svr_auth_pam(int valid_user);
#ifdef ENABLE_SVR_PUBKEY_OPTIONS
int svr_pubkey_allows_agentfwd();
diff --git a/svr-auth.c b/svr-auth.c
index c19c090..edde86b 100644
--- a/svr-auth.c
+++ b/svr-auth.c
@@ -176,10 +176,8 @@ void recv_msg_userauth_request() {
if (methodlen == AUTH_METHOD_PASSWORD_LEN &&
strncmp(methodname, AUTH_METHOD_PASSWORD,
AUTH_METHOD_PASSWORD_LEN) == 0) {
- if (valid_user) {
- svr_auth_password();
- goto out;
- }
+ svr_auth_password(valid_user);
+ goto out;
}
}
#endif
@@ -191,10 +189,8 @@ void recv_msg_userauth_request() {
if (methodlen == AUTH_METHOD_PASSWORD_LEN &&
strncmp(methodname, AUTH_METHOD_PASSWORD,
AUTH_METHOD_PASSWORD_LEN) == 0) {
- if (valid_user) {
- svr_auth_pam();
- goto out;
- }
+ svr_auth_pam(valid_user);
+ goto out;
}
}
#endif
@@ -204,12 +200,7 @@ void recv_msg_userauth_request() {
if (methodlen == AUTH_METHOD_PUBKEY_LEN &&
strncmp(methodname, AUTH_METHOD_PUBKEY,
AUTH_METHOD_PUBKEY_LEN) == 0) {
- if (valid_user) {
- svr_auth_pubkey();
- } else {
- /* pubkey has no failure delay */
- send_msg_userauth_failure(0, 0);
- }
+ svr_auth_pubkey(valid_user);
goto out;
}
#endif
diff --git a/svr-authpam.c b/svr-authpam.c
index 05e4f3e..d201bc9 100644
--- a/svr-authpam.c
+++ b/svr-authpam.c
@@ -178,13 +178,14 @@ pamConvFunc(int num_msg,
* Keyboard interactive would be a lot nicer, but since PAM is synchronous, it
* gets very messy trying to send the interactive challenges, and read the
* interactive responses, over the network. */
-void svr_auth_pam() {
+void svr_auth_pam(int valid_user) {
struct UserDataS userData = {NULL, NULL};
struct pam_conv pamConv = {
pamConvFunc,
&userData /* submitted to pamvConvFunc as appdata_ptr */
};
+ const char* printable_user = NULL;
pam_handle_t* pamHandlep = NULL;
@@ -204,12 +205,23 @@ void svr_auth_pam() {
password = buf_getstring(ses.payload, &passwordlen);
+ /* We run the PAM conversation regardless of whether the username is valid
+ in case the conversation function has an inherent delay.
+ Use ses.authstate.username rather than ses.authstate.pw_name.
+ After PAM succeeds we then check the valid_user flag too */
+
/* used to pass data to the PAM conversation function - don't bother with
* strdup() etc since these are touched only by our own conversation
* function (above) which takes care of it */
- userData.user = ses.authstate.pw_name;
+ userData.user = ses.authstate.username;
userData.passwd = password;
+ if (ses.authstate.pw_name) {
+ printable_user = ses.authstate.pw_name;
+ } else {
+ printable_user = "<invalid username>";
+ }
+
/* Init pam */
if ((rc = pam_start("sshd", NULL, &pamConv, &pamHandlep)) != PAM_SUCCESS) {
dropbear_log(LOG_WARNING, "pam_start() failed, rc=%d, %s",
@@ -236,7 +248,7 @@ void svr_auth_pam() {
rc, pam_strerror(pamHandlep, rc));
dropbear_log(LOG_WARNING,
"Bad PAM password attempt for '%s' from %s",
- ses.authstate.pw_name,
+ printable_user,
svr_ses.addrstring);
send_msg_userauth_failure(0, 1);
goto cleanup;
@@ -247,12 +259,18 @@ void svr_auth_pam() {
rc, pam_strerror(pamHandlep, rc));
dropbear_log(LOG_WARNING,
"Bad PAM password attempt for '%s' from %s",
- ses.authstate.pw_name,
+ printable_user,
svr_ses.addrstring);
send_msg_userauth_failure(0, 1);
goto cleanup;
}
+ if (!valid_user) {
+ /* PAM auth succeeded but the username isn't allowed in for another reason
+ (checkusername() failed) */
+ send_msg_userauth_failure(0, 1);
+ }
+
/* successful authentication */
dropbear_log(LOG_NOTICE, "PAM password auth succeeded for '%s' from %s",
ses.authstate.pw_name,
diff --git a/svr-authpasswd.c b/svr-authpasswd.c
index bdee2aa..69c7d8a 100644
--- a/svr-authpasswd.c
+++ b/svr-authpasswd.c
@@ -46,22 +46,14 @@ static int constant_time_strcmp(const char* a, const char* b) {
/* Process a password auth request, sending success or failure messages as
* appropriate */
-void svr_auth_password() {
+void svr_auth_password(int valid_user) {
char * passwdcrypt = NULL; /* the crypt from /etc/passwd or /etc/shadow */
char * testcrypt = NULL; /* crypt generated from the user's password sent */
- char * password;
+ unsigned char * password = NULL;
unsigned int passwordlen;
-
unsigned int changepw;
- passwdcrypt = ses.authstate.pw_passwd;
-
-#ifdef DEBUG_HACKCRYPT
- /* debugging crypt for non-root testing with shadows */
- passwdcrypt = DEBUG_HACKCRYPT;
-#endif
-
/* check if client wants to change password */
changepw = buf_getbool(ses.payload);
if (changepw) {
@@ -71,12 +63,21 @@ void svr_auth_password() {
}
password = buf_getstring(ses.payload, &passwordlen);
-
- /* the first bytes of passwdcrypt are the salt */
- testcrypt = crypt(password, passwdcrypt);
+ if (valid_user) {
+ /* the first bytes of passwdcrypt are the salt */
+ passwdcrypt = ses.authstate.pw_passwd;
+ testcrypt = crypt((char*)password, passwdcrypt);
+ }
m_burn(password, passwordlen);
m_free(password);
+ /* After we have got the payload contents we can exit if the username
+ is invalid. Invalid users have already been logged. */
+ if (!valid_user) {
+ send_msg_userauth_failure(0, 1);
+ return;
+ }
+
if (testcrypt == NULL) {
/* crypt() with an invalid salt like "!!" */
dropbear_log(LOG_WARNING, "User account '%s' is locked",
diff --git a/svr-authpubkey.c b/svr-authpubkey.c
index aa6087c..ff481c8 100644
--- a/svr-authpubkey.c
+++ b/svr-authpubkey.c
@@ -79,7 +79,7 @@ static int checkfileperm(char * filename);
/* process a pubkey auth request, sending success or failure message as
* appropriate */
-void svr_auth_pubkey() {
+void svr_auth_pubkey(int valid_user) {
unsigned char testkey; /* whether we're just checking if a key is usable */
unsigned char* algo = NULL; /* pubkey algo */
@@ -101,6 +101,15 @@ void svr_auth_pubkey() {
keybloblen = buf_getint(ses.payload);
keyblob = buf_getptr(ses.payload, keybloblen);
+ if (!valid_user) {
+ /* Return failure once we have read the contents of the packet
+ required to validate a public key.
+ Avoids blind user enumeration though it isn't possible to prevent
+ testing for user existence if the public key is known */
+ send_msg_userauth_failure(0, 0);
+ goto out;
+ }
+
/* check if the key is valid */
if (checkpubkey(algo, algolen, keyblob, keybloblen) == DROPBEAR_FAILURE) {
send_msg_userauth_failure(0, 0);
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