crash seen on minooka:

	acid; stk()
	strlen(p=0x0)+0xc /sys/src/libc/386/strlen.s:11
	login(dest=0x24eb0,pass_nvram=0x0,pass_stdin=0x0,id=0x242f0)+0x544 /sys/src/cmd/auth/secstore/secstore.c:426
	main(argv=0xdf7fef8c,argc=0x0)+0x1e6 /sys/src/cmd/auth/secstore/secstore.c:559
	_main+0x31 /sys/src/libc/386/main9.s:16

Reference: /n/atom/patch/applied2013/secstorecrash
Date: Tue Jun 18 07:48:19 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/auth/secstore/secstore.c	Tue Jun 18 07:47:40 2013
+++ /sys/src/cmd/auth/secstore/secstore.c	Tue Jun 18 07:47:40 2013
@@ -423,6 +423,10 @@
 		ntry++;
 		if(!pass_stdin && !pass_nvram){
 			pass = getpassm("secstore password: ");
+			if(pass == nil){
+				fprint(2, "secstore: getpassm failed\n");
+				exits("password");
+			}
 			if(strlen(pass) >= sizeof c->pass){
 				fprint(2, "secstore: password too long, skipping secstore login\n");
 				exits("password too long");
@@ -465,6 +469,8 @@
 			free(PINSTA);
 		}else{
 			pass = getpassm("STA PIN+SecureID: ");
+			if(pass == nil)
+				exits("password: interrupted");
 			strncpy(s+3, pass, sizeof s - 4);
 			memset(pass, 0, strlen(pass));
 			free(pass);