dropbear: Fix CVE-2018-15599

Wait to fail invalid usernames to fix
CVE-2018-15599

Rework 0006-dropbear-configuration-file.patch
to fix fuzz warnings

(From OE-Core rev: f017715120b67ff02f56ed5db131436ee62aeffb)

Signed-off-by: Mingli Yu <Mingli.Yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

3 files changed, 254 insertions, 6 deletions

diff --git a/meta/recipes-core/dropbear/dropbear.inc b/meta/recipes-core/dropbear/dropbear.inc
index b634e0e53e..dc24ea71bf 100644
--- a/meta/recipes-core/dropbear/dropbear.inc
+++ b/meta/recipes-core/dropbear/dropbear.inc
@@ -13,6 +13,7 @@ RPROVIDES_${PN} = "ssh sshd"
 DEPENDS += "${@bb.utils.contains('DISTRO_FEATURES', 'pam', 'libpam', '', d)}"
 
 SRC_URI = "http://matt.ucc.asn.au/dropbear/releases/dropbear-${PV}.tar.bz2 \
+           file://CVE-2018-15599.patch \
            file://0001-urandom-xauth-changes-to-options.h.patch \
            file://0007-fix-localoptions-search-path.patch \
            file://init \
diff --git a/meta/recipes-core/dropbear/dropbear/0006-dropbear-configuration-file.patch b/meta/recipes-core/dropbear/dropbear/0006-dropbear-configuration-file.patch
index fa4c8d0a67..deed78ffb9 100644
--- a/meta/recipes-core/dropbear/dropbear/0006-dropbear-configuration-file.patch
+++ b/meta/recipes-core/dropbear/dropbear/0006-dropbear-configuration-file.patch
@@ -1,4 +1,7 @@
-Subject: [PATCH 6/6] dropbear configuration file
+From e3a5db1b6d3f6382a15b2266458c26c645a10f18 Mon Sep 17 00:00:00 2001
+From: Mingli Yu <Mingli.Yu@windriver.com>
+Date: Thu, 6 Sep 2018 15:54:00 +0800
+Subject: [PATCH] dropbear configuration file
 
 dropbear: Change the path ("/etc/pam.d/sshd" as default) to find a pam configuration file \
 to "/etc/pam.d/dropbear for dropbear when enabling pam supporting"
@@ -7,12 +10,17 @@ Upstream-Status: Inappropriate [configuration]
 
 Signed-off-by: Maxin B. John <maxin.john@enea.com>
 Signed-off-by: Xiaofeng Yan <xiaofeng.yan@windriver.com>
+Signed-off-by: Mingli Yu <Mingli.Yu@windriver.com>
 ---
-diff -Naur dropbear-2013.60-orig/svr-authpam.c dropbear-2013.60/svr-authpam.c
---- dropbear-2013.60-orig/svr-authpam.c 2013-10-16 16:34:53.000000000 +0200
-+++ dropbear-2013.60/svr-authpam.c      2013-10-21 17:04:04.969416055 +0200
-@@ -211,7 +211,7 @@
-        userData.passwd = password;
+ svr-authpam.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/svr-authpam.c b/svr-authpam.c
+index d201bc9..165ec5c 100644
+--- a/svr-authpam.c
++++ b/svr-authpam.c
+@@ -223,7 +223,7 @@ void svr_auth_pam(int valid_user) {
+        }
  
         /* Init pam */
 -       if ((rc = pam_start("sshd", NULL, &pamConv, &pamHandlep)) != PAM_SUCCESS) {
@@ -20,3 +28,6 @@ diff -Naur dropbear-2013.60-orig/svr-authpam.c dropbear-2013.60/svr-authpam.c
                 dropbear_log(LOG_WARNING, "pam_start() failed, rc=%d, %s", 
                                 rc, pam_strerror(pamHandlep, rc));
                 goto cleanup;
+-- 
+2.7.4
+
diff --git a/meta/recipes-core/dropbear/dropbear/CVE-2018-15599.patch b/meta/recipes-core/dropbear/dropbear/CVE-2018-15599.patch
new file mode 100644
index 0000000000..912545c957
--- /dev/null
+++ b/meta/recipes-core/dropbear/dropbear/CVE-2018-15599.patch
@@ -0,0 +1,236 @@
+From 256e2abb8150f9fea33cd026597dbe70f0379296 Mon Sep 17 00:00:00 2001
+From: Matt Johnston <matt@ucc.asn.au>
+Date: Thu, 23 Aug 2018 23:43:12 +0800
+Subject: [PATCH] Wait to fail invalid usernames
+
+Wait to fail invalid usernames
+
+Upstream-Status: Backport [https://secure.ucc.asn.au/hg/dropbear/rev/5d2d1021ca00]
+CVE: CVE-2018-15599
+Signed-off-by: Mingli Yu <Mingli.Yu@windriver.com>
+---
+ 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);
+ void send_msg_userauth_banner(const 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);
+ 
+ #if DROPBEAR_SVR_PUBKEY_OPTIONS_BUILT
+ int svr_pubkey_allows_agentfwd(void);
+diff --git a/svr-auth.c b/svr-auth.c
+index 64d97aa..1f364ca 100644
+--- a/svr-auth.c
++++ b/svr-auth.c
+@@ -149,10 +149,8 @@ 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
+@@ -164,10 +162,8 @@ 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
+@@ -177,12 +173,7 @@ 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", 
+@@ -242,7 +254,7 @@ 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;
+@@ -253,12 +265,18 @@ 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
+@@ -48,22 +48,14 @@ 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;
++       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) {
+@@ -73,12 +65,21 @@ 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(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 */
+        char* algo = NULL; /* pubkey algo */
+@@ -102,6 +102,15 @@ 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);