This patch cleans up the ident stuff in inetd. The code which has

been patched so many times it was a bit of a mess. There are style,
code and man page cleanups. The following are the functional changes:

	The RFC only permits the returning of 4 possible error
	codes, make sure we only return these (PR 27636).

	Use MAXLOGNAME to determine the longest usernames.

	Add a -i flag, which returns the uid instead of the username
	(this is from a PR 25787, which also contained alot of the
	cleanups in this patch).

PR:		25787, 27636
Partially Submitted by:	Arne.Dag.Fidjestol@idi.ntnu.no
Reviewed by:	Arne.Dag.Fidjestol@idi.ntnu.no, green
MFC after:	3 weeks

usr.sbin/inetd/builtins.c

@@ -306,15 +306,21 @@ echo_stream(s, sep)		/* Echo service -- echo data back */
  * support.
  */
 
+/* RFC 1413 says the following are the only errors you can return. */
+#define ID_INVALID	"INVALID-PORT"	/* Port number improperly specified. */
+#define ID_NOUSER	"NO-USER"	/* Port not in use/not identifable. */
+#define ID_HIDDEN	"HIDDEN-USER"	/* Hiden at user's request. */
+#define ID_UNKNOWN	"UNKNOWN-ERROR"	/* Everything else. */
+
 /* ARGSUSED */
 void
 iderror(lport, fport, s, er)	/* Generic ident_stream error-sending func */
-	int lport, fport, s, er;
+	int lport, fport, s;
+	char *er;
 {
 	char *p;
 
-	asprintf(&p, "%d , %d : ERROR : %s\r\n", lport, fport, 
+	asprintf(&p, "%d , %d : ERROR : %s\r\n", lport, fport, er);
-	    er == -1 ? "HIDDEN-USER" : er ? strerror(er) : "UNKNOWN-ERROR");
 	if (p == NULL) {
 		syslog(LOG_ERR, "asprintf: %m");
 		exit(EX_OSERR);
@@ -345,13 +351,13 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 	}, to;
 	struct passwd *pw = NULL;
 	fd_set fdset;
-	char buf[BUFSIZE], *cp = NULL, *p, **av, *osname = NULL, garbage[7], e;
+	char buf[BUFSIZE], *p, **av, *osname = NULL, e;
-	char *fallback = NULL;
+	char idbuf[MAXLOGNAME] = ""; /* Big enough to hold uid in decimal. */
 	socklen_t socklen;
 	ssize_t ssize;
 	size_t size, bufsiz;
-	int c, fflag = 0, nflag = 0, rflag = 0, argc = 0, usedfallback = 0;
+	int c, fflag = 0, nflag = 0, rflag = 0, argc = 0;
-	int gflag = 0, Fflag = 0, getcredfail = 0, onreadlen;
+	int gflag = 0, iflag = 0, Fflag = 0, getcredfail = 0, onreadlen;
 	u_short lport, fport;
 
 	inetd_setproctitle(sep->se_service, s);
@@ -373,10 +379,11 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 		size_t i;
 		u_int32_t random;
 
-		while ((c = getopt(argc, sep->se_argv, "d:fFgno:rt:")) != -1)
+		while ((c = getopt(argc, sep->se_argv, "d:fFgino:rt:")) != -1)
 			switch (c) {
 			case 'd':
-				fallback = optarg;
+				if (!gflag)
+					strlcpy(idbuf, optarg, sizeof(idbuf));
 				break;
 			case 'f':
 				fflag = 1;
@@ -394,21 +401,22 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 				 * gives a more optimal way to reload the
 				 * random number only when necessary.
 				 *
-				 * I'm using base-36, so I need at least 6
+				 * 32 bits from arc4random corrisponds to
-				 * bits; round it up to 8 bits to make it
+				 * about 6 base-36 digits, so we reseed evey 6.
-				 * easier.
 				 */
-				for (i = 0; i < sizeof(garbage) - 1; i++) {
+				for (i = 0; i < sizeof(idbuf) - 1; i++) {
-					const char *const base36 =
+					static const char *const base36 =
 					    "0123456789"
 					    "abcdefghijklmnopqrstuvwxyz";
-					if (i % (sizeof(random) * 8 / 8) == 0)
+					if (i % 6 == 0)
 						random = arc4random();
-					garbage[i] =
+					idbuf[i] = base36[random % 36];
-					    base36[(random & 0xff) % 36];
+					random /= 36;
-					random >>= 8;
 				}
-				garbage[i] = '\0';
+				idbuf[i] = '\0';
+				break;
+			case 'i':
+				iflag = 1;
 				break;
 			case 'n':
 				nflag = 1;
@@ -423,6 +431,7 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 				switch (sscanf(optarg, "%d.%d", &sec, &usec)) {
 				case 2:
 					tv.tv_usec = usec;
+					/* FALLTHROUGH */
 				case 1:
 					tv.tv_sec = sec;
 					break;
@@ -438,15 +447,10 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 	}
 	if (osname == NULL) {
 		if (uname(&un) == -1)
-			iderror(0, 0, s, errno);
+			iderror(0, 0, s, ID_UNKNOWN);
 		osname = un.sysname;
 	}
-	socklen = sizeof(ss[0]);
+
-	if (getsockname(s, (struct sockaddr *)&ss[0], &socklen) == -1)
-		iderror(0, 0, s, errno);
-	socklen = sizeof(ss[1]);
-	if (getpeername(s, (struct sockaddr *)&ss[1], &socklen) == -1)
-		iderror(0, 0, s, errno);
 	/*
 	 * We're going to prepare for and execute reception of a
 	 * packet of data from the user. The data is in the format
@@ -476,14 +480,14 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 			break;
 		FD_SET(s, &fdset);
 		if (select(s + 1, &fdset, NULL, NULL, &tv) == -1)
-			iderror(0, 0, s, errno);
+			iderror(0, 0, s, ID_UNKNOWN);
 		if (ioctl(s, FIONREAD, &onreadlen) == -1)
-			iderror(0, 0, s, errno);
+			iderror(0, 0, s, ID_UNKNOWN);
 		if (onreadlen > bufsiz)
 			onreadlen = bufsiz;
 		ssize = read(s, &buf[size], (size_t)onreadlen);
 		if (ssize == -1)
-			iderror(0, 0, s, errno);
+			iderror(0, 0, s, ID_UNKNOWN);
 		else if (ssize == 0)
 			break;
 		bufsiz -= ssize;
@@ -494,37 +498,38 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 	buf[size] = '\0';
 	/* Read two characters, and check for a delimiting character */
 	if (sscanf(buf, "%hu , %hu%c", &lport, &fport, &e) != 3 || isdigit(e))
-		iderror(0, 0, s, 0);
+		iderror(0, 0, s, ID_INVALID);
-	if (gflag) {
+
-		cp = garbage;
+	/* Send garbage? */
+	if (gflag)
 		goto printit;
-	}
+
-		
 	/*
 	 * If not "real" (-r), send a HIDDEN-USER error for everything.
 	 * If -d is used to set a fallback username, this is used to
 	 * override it, and the fallback is returned instead.
 	 */
 	if (!rflag) {
-		if (fallback == NULL)
+		if (*idbuf == '\0')
-			iderror(lport, fport, s, -1);
+			iderror(lport, fport, s, ID_HIDDEN);
-		else {
+		goto printit;
-			cp = fallback;
-			goto printit;
-		}
 	}
-		
+
 	/*
 	 * We take the input and construct an array of two sockaddr_ins
 	 * which contain the local address information and foreign
 	 * address information, respectively, used to look up the
 	 * credentials for the socket (which are returned by the
-	 * sysctl "net.inet.tcp.getcred" when we call it.) The
+	 * sysctl "net.inet.tcp.getcred" when we call it.)
-	 * arrays have been filled in above via get{peer,sock}name(),
-	 * so right here we are only setting the ports.
 	 */
+	socklen = sizeof(ss[0]);
+	if (getsockname(s, (struct sockaddr *)&ss[0], &socklen) == -1)
+		iderror(lport, fport, s, ID_UNKNOWN);
+	socklen = sizeof(ss[1]);
+	if (getpeername(s, (struct sockaddr *)&ss[1], &socklen) == -1)
+		iderror(lport, fport, s, ID_UNKNOWN);
 	if (ss[0].ss_family != ss[1].ss_family)
-		iderror(lport, fport, s, EINVAL);
+		iderror(lport, fport, s, ID_UNKNOWN);
 	size = sizeof(uc);
 	switch (ss[0].ss_family) {
 	case AF_INET:
@@ -552,48 +557,54 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 		break;
 	}
 	if (getcredfail != 0) {
-		if (fallback == NULL)		/* Use a default, if asked to */
+		if (*idbuf == '\0')
-			iderror(lport, fport, s, getcredfail);
+			iderror(lport, fport, s,
-		usedfallback = 1;
+			    getcredfail == ENOENT ? ID_NOUSER : ID_UNKNOWN);
-	} else {
+		goto printit;
-		/* Look up the pw to get the username */
-		errno = 0;
-		pw = getpwuid(uc.cr_uid);
 	}
-	if (pw == NULL && !usedfallback)		/* No such user... */
+
-		iderror(lport, fport, s, errno != 0 ? errno : ENOENT);
+	/* Look up the pw to get the username and home directory*/
+	errno = 0;
+	pw = getpwuid(uc.cr_uid);
+	if (pw == NULL)
+		iderror(lport, fport, s, errno == 0 ? ID_NOUSER : ID_UNKNOWN);
+
+	if (iflag)
+		snprintf(idbuf, sizeof(idbuf), "%u", (unsigned)pw->pw_uid);
+	else
+		strlcpy(idbuf, pw->pw_name, sizeof(idbuf));
+
 	/*
 	 * If enabled, we check for a file named ".noident" in the user's
 	 * home directory. If found, we return HIDDEN-USER.
 	 */
-	if (nflag && !usedfallback) {
+	if (nflag) {
 		if (asprintf(&p, "%s/.noident", pw->pw_dir) == -1)
-			iderror(lport, fport, s, errno);
+			iderror(lport, fport, s, ID_UNKNOWN);
 		if (lstat(p, &sb) == 0) {
 			free(p);
-			iderror(lport, fport, s, -1);
+			iderror(lport, fport, s, ID_HIDDEN);
 		}
 		free(p);
 	}
+
 	/*
 	 * Here, if enabled, we read a user's ".fakeid" file in their
 	 * home directory. It consists of a line containing the name
 	 * they want.
 	 */
-	if (fflag && !usedfallback) {
+	if (fflag) {
-		FILE *fakeid = NULL;
 		int fakeid_fd;
 
-		if (asprintf(&p, "%s/.fakeid", pw->pw_dir) == -1)
-			iderror(lport, fport, s, errno);
 		/*
 		 * Here we set ourself to effectively be the user, so we don't
 		 * open any files we have no permission to open, especially
 		 * symbolic links to sensitive root-owned files or devices.
 		 */
 		if (initgroups(pw->pw_name, pw->pw_gid) == -1)
-			iderror(lport, fport, s, errno);
+			iderror(lport, fport, s, ID_UNKNOWN);
-		seteuid(pw->pw_uid);
+		if (seteuid(pw->pw_uid) == -1)
+			iderror(lport, fport, s, ID_UNKNOWN);
 		/*
 		 * We can't stat() here since that would be a race
 		 * condition.
@@ -601,60 +612,58 @@ ident_stream(s, sep)		/* Ident service (AKA "auth") */
 		 * and if it's not a regular file, we close it and end up
 		 * returning the user's real username.
 		 */
+		if (asprintf(&p, "%s/.fakeid", pw->pw_dir) == -1)
+			iderror(lport, fport, s, ID_UNKNOWN);
 		fakeid_fd = open(p, O_RDONLY | O_NONBLOCK);
 		free(p);
-		if (fakeid_fd != -1 && fstat(fakeid_fd, &sb) != -1 &&
+		if (fakeid_fd == -1 || fstat(fakeid_fd, &sb) == -1 ||
-		    S_ISREG(sb.st_mode) &&
+		    !S_ISREG(sb.st_mode))
-		    (fakeid = fdopen(fakeid_fd, "r")) != NULL) {
+			goto fakeid_fail;
-			buf[sizeof(buf) - 1] = '\0';
+
-			if (fgets(buf, sizeof(buf), fakeid) == NULL) {
+		if ((ssize = read(fakeid_fd, buf, sizeof(buf) - 1)) < 0)
-				cp = pw->pw_name;
+			goto fakeid_fail;
-				fclose(fakeid);
+		buf[ssize] = '\0';
-				goto printit;
+
+		/*
+		 * Usually, the file will have the desired identity
+		 * in the form "identity\n". Allow for leading white
+		 * space and trailing white space/end of line.
+		 */
+		p = buf;
+		p += strspn(p, " \t");
+		p[strcspn(p, " \t\r\n")] = '\0';
+		if (strlen(p) > MAXLOGNAME - 1) /* Too long (including nul)? */
+			p[MAXLOGNAME - 1] = '\0';
+
+		/*
+		 * If the name is a zero-length string or matches it
+		 * the id or name of another user (unless permitted by -F)
+		 * then it is invalid.
+		 */
+		if (*p == '\0')
+			goto fakeid_fail;
+		if (!Fflag) {
+			if (iflag) {
+				if (p[strspn(p, "0123456789")] == '\0' &&
+				    getpwuid(atoi(p)) != NULL)
+					goto fakeid_fail;
+			} else {
+				if (getpwnam(p) != NULL)
+					goto fakeid_fail;
 			}
-			/*
+		}
-			 * Usually, the file will have the desired identity
+
-			 * in the form "identity\n", so we use strcspn() to
+		strlcpy(idbuf, p, sizeof(idbuf));
-			 * end the string (which fgets() doesn't do.)
+
-			 */
+fakeid_fail:
-			buf[strcspn(buf, "\r\n")] = '\0';
+		if (fakeid_fd != -1)
-			cp = buf;
-			/* Allow for beginning white space... */
-			while (isspace(*cp))
-				cp++;
-			/* ...and ending white space. */
-			cp[strcspn(cp, " \t")] = '\0';
-			/* User names of >16 characters are invalid */
-			if (strlen(cp) > 16)
-				cp[16] = '\0';
-			/*
-			 * If the name is a zero-length string or matches
-			 * the name of another user, it's invalid, so
-			 * we will return their real identity instead.
-			 */
-			
-			if (!*cp || (!Fflag && getpwnam(cp))) {
-				errno = 0;
-				pw = getpwuid(uc.cr_uid);
-				if (pw == NULL)
-					iderror(lport, fport, s,
-					    errno != 0 ? errno : ENOENT);
-				cp = pw->pw_name;
-			}
-		} else
-			cp = pw->pw_name;
-		if (fakeid != NULL)
-			fclose(fakeid);
-		else if (fakeid_fd != -1)
 			close(fakeid_fd);
-	} else if (!usedfallback)
+	}
-		cp = pw->pw_name;
+
-	else
-		cp = fallback;
 printit:
 	/* Finally, we make and send the reply. */
 	if (asprintf(&p, "%d , %d : USERID : %s : %s\r\n", lport, fport, osname,
-	    cp) == -1) {
+	    idbuf) == -1) {
 		syslog(LOG_ERR, "asprintf: %m");
 		exit(EX_OSERR);
 	}

usr.sbin/inetd/inetd.8

@@ -455,6 +455,21 @@ If the real
 service is disabled,
 return this username for every request.
 This is primarily useful when running this service on a NAT machine.
+.It Fl g
+Instead of returning
+the user's name to the ident requester,
+report a
+username made up of random alphanumeric characters,
+e.g.
+.Dq c0c993 .
+The
+.Fl g
+flag overrides not only the user names,
+but also any fallback name,
+.Pa .fakeid
+or
+.Pa .noident
+files.
 .It Fl t Xo
 .Ar sec Ns Op . Ns Ar usec
 .Xc
@@ -465,6 +480,8 @@ Offer a real
 .Dq auth
 service, as per RFC 1413.
 All the remaining flags apply only in this case.
+.It Fl i
+Return numeric user IDs instead of usernames.
 .It Fl f
 If the file
 .Pa .fakeid
@@ -474,29 +491,25 @@ If the the username found in
 .Pa .fakeid
 is that of an existing user,
 then the real username is reported.
+If the
+.Fl i
+flag is also given then the username in
+.Pa .fakeid
+is checked against existing user IDs instead.
 .It Fl F
 same as 
 .Fl f
 but without the restriction that the username in
 .Pa .fakeid
 must not match an existing user.
-.It Fl g
-Instead of returning the user's name to the ident requester, report a
-username made up of random alphanumeric characters, e.g.
-.Dq c0c993 .
-The
-.Fl g
-flag overrides not only the user names, but also any
-.Pa .fakeid
-or
-.Pa .noident
-files.
 .It Fl n
 If the file
 .Pa .noident
 exists in the home directory of the identified user, return
 .Dq ERROR\ : HIDDEN-USER .
-instead.
+This overrides any
+.Pa fakeid
+file which might exist.
 .It Fl o Ar osname
 Use
 .Ar osname

usr.sbin/inetd/inetd.h

@@ -122,7 +122,7 @@ void		endconfig __P((void));
 struct servtab *enter __P((struct servtab *));
 void		freeconfig __P((struct servtab *));
 struct servtab *getconfigent __P((void));
-void		iderror __P((int, int, int, int));
+void		iderror __P((int, int, int, char *));
 void		ident_stream __P((int, struct servtab *));
 void		machtime_dg __P((int, struct servtab *));
 void		machtime_stream __P((int, struct servtab *));