diff options
| -rw-r--r-- | auth.h | 6 | ||||
| -rw-r--r-- | svr-auth.c | 19 | ||||
| -rw-r--r-- | svr-authpam.c | 26 | ||||
| -rw-r--r-- | svr-authpasswd.c | 27 | ||||
| -rw-r--r-- | svr-authpubkey.c | 11 |
5 files changed, 54 insertions, 35 deletions
@@ -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); @@ -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); |