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Do a better job at determining the username of the login session.

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When multiple users share the same UID, the old code will simply pick an
arbitrary username to attach to the utmpx entries. Make the code a bit
more accurate by first checking whether getlogin() returns a username
which corresponds to the uid of the calling process. If this fails,
simply fall back to picking an arbitrary username.

Reported by:	saurik on GitHub
MFC after:	2 weeks
This commit is contained in:
Ed Schouten 2012-04-19 21:12:08 +00:00
parent 52116a1cb9
commit 1d2276c873
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=234469
1 changed files with 23 additions and 1 deletions
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24
libexec/ulog-helper/ulog-helper.c
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@ -46,6 +46,28 @@ __FBSDID("$FreeBSD$");
* username. It does allow users to log arbitrary hostnames.
*/
static const char *
get_username(void)
{
const struct passwd *pw;
const char *login;
uid_t uid;
/*
* Attempt to determine the username corresponding to this login
* session. First, validate the results of getlogin() against
* the password database. If getlogin() returns invalid data,
* return an arbitrary username corresponding to this uid.
*/
uid = getuid();
if ((login = getlogin()) != NULL && (pw = getpwnam(login)) != NULL &&
pw->pw_uid == uid)
return (login);
if ((pw = getpwuid(uid)) != NULL)
return (pw->pw_name);
return (NULL);
}
int
main(int argc, char *argv[])
{
@ -57,7 +79,7 @@ main(int argc, char *argv[])
if ((argc == 2 || argc == 3) && strcmp(argv[1], "login") == 0) {
/* Username. */
user = user_from_uid(getuid(), 1);
user = get_username();
if (user == NULL)
return (EX_OSERR);