Re: use getpwuid_r in doas

[Ted Unangst]

Ted Unangst wrote:
> I have a coming change which will need to access both the calling user and
> target users' passwd entries. In order to accomplish this, we need to switch
> to the reentrant flavor of getpwuid. No behaviorial change, but I think this
> is clearer and less error prone as well, versus reusing a pointer to static
> storage.

Improve a few more things noticed by martijn. We don't need to copy strings
that have long lifetimes. Also, fix some error checks to be more precise.

Index: doas.c
===================================================================
RCS file: /cvs/src/usr.bin/doas/doas.c,v
retrieving revision 1.75
diff -u -p -r1.75 doas.c
--- doas.c      10 Jun 2019 18:11:27 -0000      1.75
+++ doas.c      10 Jun 2019 18:15:34 -0000
@@ -288,7 +288,6 @@ main(int argc, char **argv)
        char *sh;
        const char *cmd;
        char cmdline[LINE_MAX];
-       char myname[_PW_NAME_LEN + 1];
        char mypwbuf[_PW_BUF_LEN], targpwbuf[_PW_BUF_LEN];
        struct passwd mypwstore, targpwstore;
        struct passwd *mypw, *targpw;
@@ -349,10 +348,10 @@ main(int argc, char **argv)
                usage();
 
        rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw);
-       if (rv != 0 || mypw == NULL)
+       if (rv != 0)
                err(1, "getpwuid_r failed");
-       if (strlcpy(myname, mypw->pw_name, sizeof(myname)) >= sizeof(myname))
-               errx(1, "pw_name too long");
+       if (mypw == NULL)
+               errx(1, "no passwd entry for self");
        ngroups = getgroups(NGROUPS_MAX, groups);
        if (ngroups == -1)
                err(1, "can't get groups");
@@ -361,9 +360,7 @@ main(int argc, char **argv)
        if (sflag) {
                sh = getenv("SHELL");
                if (sh == NULL || *sh == '\0') {
-                       shargv[0] = strdup(mypw->pw_shell);
-                       if (shargv[0] == NULL)
-                               err(1, NULL);
+                       shargv[0] = mypw->pw_shell;
                } else
                        shargv[0] = sh;
                argv = shargv;
@@ -394,7 +391,7 @@ main(int argc, char **argv)
        if (!permit(uid, groups, ngroups, &rule, target, cmd,
            (const char **)argv + 1)) {
                syslog(LOG_AUTHPRIV | LOG_NOTICE,
-                   "failed command for %s: %s", myname, cmdline);
+                   "failed command for %s: %s", mypw->pw_name, cmdline);
                errc(1, EPERM, NULL);
        }
 
@@ -402,7 +399,7 @@ main(int argc, char **argv)
                if (nflag)
                        errx(1, "Authorization required");
 
-               authuser(myname, login_style, rule->options & PERSIST);
+               authuser(mypw->pw_name, login_style, rule->options & PERSIST);
        }
 
        if (unveil(_PATH_LOGIN_CONF, "r") == -1)
@@ -418,7 +415,9 @@ main(int argc, char **argv)
                err(1, "pledge");
 
        rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), 
&targpw);
-       if (rv != 0 || targpw == NULL)
+       if (rv != 0)
+               err(1, "getpwuid_r failed");
+       if (targpw == NULL)
                errx(1, "no passwd entry for target");
 
        if (setusercontext(NULL, targpw, target, LOGIN_SETGROUP |
@@ -438,7 +437,7 @@ main(int argc, char **argv)
                err(1, "pledge");
 
        syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s",
-           myname, cmdline, targpw->pw_name, cwd);
+           mypw->pw_name, cmdline, targpw->pw_name, cwd);
 
        envp = prepenv(rule);