[Freeipa-devel] Password Maxlife 0 causes expiration of 90 days

[Drew Erny]

https://fedorahosted.org/freeipa/ticket/2795

I've tracked down the source of this bug; it's nutty C stuff.

So, in daemons/ipa-slapi-plugins/ipa-pwd-extop/common.c, when you update 
password, the expiration time appears to be set in the function 
ipapwd_CheckPolicy on line 631, which looks like

	data->expireTime = data->timeNow + pol.max_pwd_life;

So the bug has to be in how pol.max_pwd_life gets is value. So I check 
around, pol is initialized like this:

	struct ipapwd_policy pol = {0};
	...
	pol.max_pwd_life = IPAPWD_DEFAULT_PWDLIFE;

And IPAPWD_DEFAULT_PWDLIFE is a constant 90 days.

But then the actual value of max_pwd_life is obtained by passing pol 
into the function ipapwd_getPolicy on line 577 or 590, depending on the 
password change type.

Inside of ipapwd_getPolicy, there's a couple of lines starting at line 393

	tmpint = slapi_entry_attr_get_int(pe, "krbMaxPwdLife");
	if (tmpint != 0) {
		policy->max_pwd_life = tmpint;
	}:

Which sets the max password life to the returned value, unless this 
function returns 0. However, the documentation from 
/usr/include/dirsrv/slapi-plugin.h says that that function, 
slapi_entry_attr_get_int, returns 0 if the entry does not contain that 
attribute. So, since the value 0 is returned, an error is assumed to 
have occurred that member of the struct is left untouched... which means 
it's still set to the value it was set to when it was initialized, 90 days.

So, when the expireTime is set at line 631, it's set to 90 days because 
the value returned by slapi_entry_attr_get_int is 0.

I've checked to see if we can get some error context out of the pe 
variable passed in, but it appears to be an opaque struct that the user 
isn't meant to see the internals of.

I'm not really sure what to do with this knowledge. The only thing I can 
think would be to use another sentinel value, like -1, to indicate that 
the password does not expire; or, otherwise, to document that there is 
no way to have non-expiring passwords, and administrators can only set 
value to some far-future date, and then close this bug. Or, we could 
just set the default expiration date to be somewhere far in the future. 
I'm not really qualified to make a call on how to proceed with this, but 
I'm capable of making the change if someone more senior decides.

I can also totally see this issue with the interface of slapi-plugin 
being the possible cause of many bugs.

Opinions?