On Wed, Apr 17, 2002 at 10:59:48AM -0700, Sumeet Malhotra wrote:
> Thanks Steve,
>=20
> I ran the program as root and it passes that point now! But was wondering
> how does the passwd program change its effective uid to 0. setuid (or
> seteuid) to 0 can only be done if you are a super user. Am I right?

/home/juli$ ls -l /usr/bin/passwd
-r-sr-xr-x  2 root  wheel  18120 Apr 14 14:49 /usr/bin/passwd

It has the set-uid bit set so, when it is run, it becomes root automaticall=
y.

HTH

>=20
> Sumeet
>=20
> -----Original Message-----
> From: Steven M. Bellovin [mailto:smb@research.att.com]
> Sent: Wednesday, April 17, 2002 10:30 AM
> To: Sumeet Malhotra
> Cc: 'netbsd-users@netbsd.org'
> Subject: Re: Changing user passwd thru a program=20
>=20
>=20
> In message
> <45BEF1D68145D51186C100B0D0AABE659FEB1D@med.corp.rhapsodynetworks.co
> m>, Sumeet Malhotra writes:
> >Hi all,
> >
> >I'm trying to write an API to provide user passwd change facility. It
> should
> >work exactly the same way a normal "passwd" program works, except that it
> >takes the 3 arguments - username, oldpass and newpass as function args.
> >
> >I modelled the program exactly on the lines of the NetBSD passwd source
> >code, but the program fails when trying to compare the oldpass with the
> >existing one in the /etc/passwd file. The code to compare the oldpass wi=
th
> >existing one is :
> >
> >if (strcmp(crypt(oldpw, pw->pw_passwd), pw->pw_passwd) !=3D 0)
> >        return ACCESS_DENIED;
> >
> >Here pw->pw_passwd is the password entry from /etc/passwd file.
> >
> >The /etc/passwd file uses "*" as the passwd entries which means that the
> >passwords are to be looked up somewhere else (possibly master.passwd
> file?).
> >The string compare tries to compare the encrypted password with "*" and
> >fails.
> >
>=20
> See getpwent(3) -- unless you're running as root, you get the '*'.  If=20
> you are running as root, you get the real hashed password.
>=20
> 		--Steve Bellovin, http://www.research.att.com/~smb
> 		Full text of "Firewalls" book now at
> http://www.wilyhacker.com

--=20
Of course it runs NetBSD - http://www.netbsd.org
HispaBSD member - http://www.hispabsd.org
Julio Merino <jmmv@hispabsd.org>