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Reply-To: marc@destek.net
To: freebsd-questions@FreeBSD.ORG
Subject: getpwent() question
Date: Thu, 19 Nov 1998 17:14:54 -0500
From: Marc Evans <marc@destek.net>
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Hello -

I am working with a customer that we would like to move over to using
FreeBSD for e-mail purposes (amoung other things). Part of what we have to
deal with here is that there a re several thousand users with greater then
UT_NAMESIZE login names. Having the users change these names is not an
option. Therefore, I have started looking at the sources to determine if
they may be able to be changed to address this limitation.

On the surface, what I found was that getpwnam() seems to be the function
that for most e-mail purposes imposes the limitation. Interrestingly
enough, I found that if I change getpwnam() to the following code for
sendmail, mail.local, and qpopper, the limitation was eliminated (for
those specific programs):

struct passwd *Getpwnam(const char *login)
{
  struct passwd *p = NULL;
  setpassent(1);
  do { p = getpwent(); } while (p && strcmp(p->pw_name,login));
  return(p);
}

Clearly this is non-optimal, but it does at least illistrate one of the
required concepts.

I next dug into the libc code itself, specifically thet getpwnam()
function. I am considering changing the code to the following:

struct passwd *
getpwnam(name)
        const char *name;
{
        DBT key;
        int rval;
        int len = strlen(name) + 2;
        char *bf = malloc(MAX(len,UT_NAMESIZE) + 2);

	if (bf == NULL)
		return((struct passwd *)NULL);

        if (!_pw_db && !__initdb())
                return((struct passwd *)NULL);

        bf[0] = _PW_KEYBYNAME;
        strcpy(&bf[1],name);
        key.data = (u_char *)bf;
        key.size = len + 1;
        rval = __hashpw(&key);
                
#ifdef YP       
        if (!rval && _yp_enabled)
                rval = _getyppass(&_pw_passwd, name, "passwd.byname");
#endif                  
        /* 
         * Prevent login attempts when YP is not enabled but YP entries
         * are in /etc/master.passwd.
         */
        if (rval && (_pw_passwd.pw_name[0] == '+'||
                        _pw_passwd.pw_name[0] == '-')) rval = 0;

        endpwent();
        /* if (rval) _pw_passwd[UT_NAMESIZE] = '\0';    /* Backward compatible */
        return(rval ? &_pw_passwd : (struct passwd *)NULL);
}

Now, my question for this forum is, what will this likely break, e.g.,
what programs are people aware of that assume that pw_name is UT_NAMESIZE
truncated? The vast majority of the references I have located seem to do
dynamic memory allocation or have other fail-safe tests.

Probably the most important program that I would like to get this type of
change rolled into is passwd, though chown is not far behind.

Has anyone else looked at this?

Please reply directly to me, marc@destek.net, because I am not a
subscriber to this list. I will however summarize if people are
interrested.

Thanks in advance - Marc

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