dropbear: wait to fail invalid usernames

fixes CVE-2018-15599 (same patch as 2211ee0037)

cherry-pick upstream commit 52adbb34c32d3e2e1bcdb941e20a6f81138b8248

Signed-off-by: Konstantin Demin <rockdrilla@gmail.com>

diff --git a/package/network/services/dropbear/patches/010-wait-to-fail-invalid-usernames.patch b/package/network/services/dropbear/patches/010-wait-to-fail-invalid-usernames.patch
new file mode 100644 (file)
index 0000000..3b6c1a0
--- /dev/null
+++ b/package/network/services/dropbear/patches/010-wait-to-fail-invalid-usernames.patch
@@ -0,0 +1,191 @@
+--- 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);
+--- 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
+--- 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;
+ 
+@@ -207,9 +208,15 @@ void svr_auth_pam() {
+       /* 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 +249,7 @@ 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 +260,16 @@ 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) {
++              send_msg_userauth_failure(0, 1);
++      }
++
+       /* successful authentication */
+       dropbear_log(LOG_NOTICE, "PAM password auth succeeded for '%s' from %s",
+                       ses.authstate.pw_name,
+--- a/svr-authpasswd.c
++++ b/svr-authpasswd.c
+@@ -48,22 +48,14 @@ static int constant_time_strcmp(const ch
+ 
+ /* 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 +65,18 @@ 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) {
++              passwdcrypt = ses.authstate.pw_passwd;
++              testcrypt = crypt(password, passwdcrypt);
++      }
+       m_burn(password, passwordlen);
+       m_free(password);
+ 
++      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",
+--- 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 +102,11 @@ void svr_auth_pubkey() {
+       keybloblen = buf_getint(ses.payload);
+       keyblob = buf_getptr(ses.payload, keybloblen);
+ 
++      if (!valid_user) {
++              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);

diff --git a/package/network/services/dropbear/patches/100-pubkey_path.patch b/package/network/services/dropbear/patches/100-pubkey_path.patch
index 280606be03d14d53bfb45f98abf1bfb488be1227..9743b1ed690768475945fe7a529fc15154aa53ac 100644 (file)
--- a/package/network/services/dropbear/patches/100-pubkey_path.patch
+++ b/package/network/services/dropbear/patches/100-pubkey_path.patch
@@ -1,6 +1,6 @@
 --- a/svr-authpubkey.c
 +++ b/svr-authpubkey.c
-@@ -327,14 +327,20 @@ static int checkpubkey(const char* algo,
+@@ -332,14 +332,20 @@ static int checkpubkey(const char* algo,
                goto out;
        }
  
@@ -29,7 +29,7 @@
  
        /* open the file as the authenticating user. */
        origuid = getuid();
-@@ -411,26 +417,35 @@ static int checkpubkeyperms() {
+@@ -416,26 +422,35 @@ static int checkpubkeyperms() {
                goto out;
        }