nupas auth: incompatibility and error messaging

nupas auth: incompatibility and error messaging

[inkswinc]

Nupas' smtp.c file uses a different var in the 'server=' part of the
string it queries from factotum than upas did: where upas used
'server=smtp.gmail.com' (from the dialstring passed on the
commandline), nupas uses 'server=gmail-smtp-msa.l.google.com' (result
of some lookup, I presume) Not only does this break backwards
compatibility, but it also feels a little more brittle to me; the
latter name seems likely to change.

Not sure where else this difference occurs; it doesn't seem to in
imaps, which I also use, but it does seem to in /sys/lib/tls/smtp
(though with gmail that needs to change all the time anyways, so...)

It also doesn't do a good job of error messaging when auth fails; it
just shows up as an error in the 'hello' phase, which sucks.

Following patch is an attempt at resolving those issues; it works for
me.  This is the first time I've ever given anyone else any C code
I've written, so feel free to be ruthless if you see anything
suboptimal.

diff -r a01d0802d023 sys/src/cmd/upas/smtp/smtp.c
--- a/sys/src/cmd/upas/smtp/smtp.c	Mon Mar 20 19:15:40 2017 +0100
+++ b/sys/src/cmd/upas/smtp/smtp.c	Tue Mar 21 23:49:01 2017 +0000
@@ -493,20 +493,27 @@
 static char *
 doauth(char *methods)
 {
-	char *buf, *err;
+	char *buf, *err, *factstring;
 	UserPasswd *p;
 	int n;
 	DS ds;
 
-	dialstringparse(ddomain, &ds);
+	dialstringparse(farend, &ds);
 	if(strstr(methods, "CRAM-MD5"))
 		return smtpcram(&ds);
 
-	p = auth_getuserpasswd(nil,
-		user?"proto=pass service=smtp server=%q user=%q":"proto=pass service=smtp server=%q",
+	factstring = smprint(user?
+		"proto=pass service=smtp server=%q user=%q":
+		"proto=pass service=smtp server=%q",
 		ds.host, user);
-	if (p == nil)
+
+	p = auth_getuserpasswd(nil,factstring);
+	if (p == nil) {
+		syslog(0, "smtp.fail", "failed to get userpasswd for %s", factstring);
+		free(factstring);
 		return Giveup;
+	}
+	free(factstring);
 
 	err = Retry;
 	if (strstr(methods, "LOGIN")){


Thanks,
sam-d

Re: [9front] nupas auth: incompatibility and error messaging

[Benjamin Purcell]

At the very least you should check that the char* returned from
smprint is not nil.

But if this were me I would avoid the memory allocation entirely since
we can estimate a reasonable bound on the auth string. In that case I
like to use a static buf instead and print into it sequentially. That
way you also avoid an arguably ugly ternary expression and avoid
another memory allocation that is found below:
http://okturing.com/src/1190/body

Re: [9front] nupas auth: incompatibility and error messaging

[Benjamin Purcell]

If no one objects to the change sam-d wants to make with switching
ddomain to farend, I'll apply the patch I posted soon.

-spew