From e2551012993ea913e23012774330da926366487f Mon Sep 17 00:00:00 2001 From: Kevin Darbyshire-Bryant Date: Mon, 29 May 2017 10:25:09 +0100 Subject: dropbear server: support -T max auth tries Add support for '-T n' for a run-time specification for maximum number of authentication attempts where 'n' is between 1 and compile time option MAX_AUTH_TRIES. A default number of tries can be specified at compile time using 'DEFAULT_AUTH_TRIES' which itself defaults to MAX_AUTH_TRIES for backwards compatibility. Signed-off-by: Kevin Darbyshire-Bryant --- default_options.h | 6 ++++++ default_options.h.in | 4 ++++ dropbear.8 | 3 +++ runopts.h | 1 + svr-auth.c | 2 +- svr-runopts.c | 17 +++++++++++++++++ 6 files changed, 32 insertions(+), 1 deletion(-) diff --git a/default_options.h b/default_options.h index e7fad80..84adfab 100644 --- a/default_options.h +++ b/default_options.h @@ -385,6 +385,12 @@ Homedir is prepended unless path begins with / */ #define MAX_AUTH_TRIES 10 #endif +/* Default maximum number of failed authentication tries. + * defaults to MAX_AUTH_TRIES */ +#ifndef DEFAULT_AUTH_TRIES +#define DEFAULT_AUTH_TRIES MAX_AUTH_TRIES +#endif + /* The default file to store the daemon's process ID, for shutdown scripts etc. This can be overridden with the -P flag */ #ifndef DROPBEAR_PIDFILE diff --git a/default_options.h.in b/default_options.h.in index 3a55731..d4b6b8b 100644 --- a/default_options.h.in +++ b/default_options.h.in @@ -261,6 +261,10 @@ Homedir is prepended unless path begins with / */ /* Maximum number of failed authentication tries (server option) */ #define MAX_AUTH_TRIES 10 +/* Default maximum number of failed authentication tries. + * defaults to MAX_AUTH_TRIES */ +#define DEFAULT_AUTH_TRIES MAX_AUTH_TRIES + /* The default file to store the daemon's process ID, for shutdown scripts etc. This can be overridden with the -P flag */ #define DROPBEAR_PIDFILE "/var/run/dropbear.pid" diff --git a/dropbear.8 b/dropbear.8 index be73372..2d5f32a 100644 --- a/dropbear.8 +++ b/dropbear.8 @@ -91,6 +91,9 @@ if 0 disables keepalives. If no response is received for 3 consecutive keepalive .B \-I \fIidle_timeout Disconnect the session if no traffic is transmitted or received for \fIidle_timeout\fR seconds. .TP +.B \-T \fImax_authentication_attempts +Disconnect the session if number of authentication attempts is exceeded. default is set at compile time to DEFAULT_AUTH_TRIES which itself defaults to MAX_AUTH_TRIES (10) +.TP .B \-c \fIforced_command Disregard the command provided by the user and always run \fIforced_command\fR. This also overrides any authorized_keys command= option. diff --git a/runopts.h b/runopts.h index cecdc22..47c12f0 100644 --- a/runopts.h +++ b/runopts.h @@ -96,6 +96,7 @@ typedef struct svr_runopts { int noauthpass; int norootpass; int allowblankpass; + unsigned int maxauthtries; #if DROPBEAR_SVR_REMOTETCPFWD int noremotetcp; diff --git a/svr-auth.c b/svr-auth.c index 4dc280c..9636e12 100644 --- a/svr-auth.c +++ b/svr-auth.c @@ -362,7 +362,7 @@ void send_msg_userauth_failure(int partial, int incrfail) { ses.authstate.failcount++; } - if (ses.authstate.failcount >= MAX_AUTH_TRIES) { + if (ses.authstate.failcount >= svr_opts.maxauthtries) { char * userstr; /* XXX - send disconnect ? */ TRACE(("Max auth tries reached, exiting")) diff --git a/svr-runopts.c b/svr-runopts.c index dea4a55..1966f26 100644 --- a/svr-runopts.c +++ b/svr-runopts.c @@ -73,6 +73,7 @@ static void printhelp(const char * progname) { "-g Disable password logins for root\n" "-B Allow blank password logins\n" #endif + "-T <1 to %d> Maximum authentication tries (default %d)\n" #if DROPBEAR_SVR_LOCALTCPFWD "-j Disable local port forwarding\n" #endif @@ -107,6 +108,7 @@ static void printhelp(const char * progname) { #if DROPBEAR_ECDSA ECDSA_PRIV_FILENAME, #endif + MAX_AUTH_TRIES, DEFAULT_AUTH_TRIES, DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE, DEFAULT_RECV_WINDOW, DEFAULT_KEEPALIVE, DEFAULT_IDLE_TIMEOUT); } @@ -119,6 +121,7 @@ void svr_getopts(int argc, char ** argv) { char* recv_window_arg = NULL; char* keepalive_arg = NULL; char* idle_timeout_arg = NULL; + char* maxauthtries_arg = NULL; char* keyfile = NULL; char c; @@ -132,6 +135,7 @@ void svr_getopts(int argc, char ** argv) { svr_opts.noauthpass = 0; svr_opts.norootpass = 0; svr_opts.allowblankpass = 0; + svr_opts.maxauthtries = DEFAULT_AUTH_TRIES; svr_opts.inetdmode = 0; svr_opts.portcount = 0; svr_opts.hostkey = NULL; @@ -235,6 +239,9 @@ void svr_getopts(int argc, char ** argv) { case 'I': next = &idle_timeout_arg; break; + case 'T': + next = &maxauthtries_arg; + break; #if DROPBEAR_SVR_PASSWORD_AUTH || DROPBEAR_SVR_PAM_AUTH case 's': svr_opts.noauthpass = 1; @@ -331,6 +338,16 @@ void svr_getopts(int argc, char ** argv) { dropbear_exit("Bad recv window '%s'", recv_window_arg); } } + + if (maxauthtries_arg) { + unsigned int val = 0; + if (m_str_to_uint(maxauthtries_arg, &val) == DROPBEAR_FAILURE || + val == 0 || val > MAX_AUTH_TRIES) { + dropbear_exit("Bad maxauthtries '%s'", maxauthtries_arg); + } + svr_opts.maxauthtries = val; + } + if (keepalive_arg) { unsigned int val; -- cgit v1.2.3