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NetBSD/libexec/identd/identd.c

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/* $NetBSD: identd.c,v 1.24 2004/11/05 21:56:01 dsl Exp $ */
/*
* identd.c - TCP/IP Ident protocol server.
*
* This software is in the public domain.
* Written by Peter Postma <peter@pointless.nl>
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <netdb.h>
#include <poll.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
__RCSID("$NetBSD: identd.c,v 1.24 2004/11/05 21:56:01 dsl Exp $");
#define OPSYS_NAME "UNIX"
#define IDENT_SERVICE "auth"
#define TIMEOUT 30 /* seconds */
static int idhandle(int, const char *, const char *, const char *,
const char *, int);
static void idparse(int, int, int, const char *, const char *, const char *);
static void iderror(int, int, int, const char *);
static const char *gethost(struct sockaddr_storage *);
static int *socketsetup(const char *, const char *, int);
static int sysctl_getuid(struct sockaddr_storage *, socklen_t, uid_t *);
static int check_noident(const char *);
static int check_userident(const char *, char *, size_t);
static void random_string(char *, size_t);
static void change_format(const char *, struct passwd *, char *, size_t);
static void timeout_handler(int);
static void waitchild(int);
static void fatal(const char *);
static int bflag, eflag, fflag, Fflag, iflag, Iflag;
static int lflag, Lflag, nflag, Nflag, rflag;
int
main(int argc, char *argv[])
{
int IPv4or6, ch, *socks, timeout;
char *address, *charset, *fmt;
const char *osname, *portno;
char *p;
char user[LOGIN_NAME_MAX];
struct group *grp;
struct passwd *pw;
gid_t gid;
uid_t uid;
IPv4or6 = AF_UNSPEC;
osname = OPSYS_NAME;
portno = IDENT_SERVICE;
timeout = TIMEOUT;
address = NULL;
charset = NULL;
fmt = NULL;
socks = NULL;
gid = uid = 0;
bflag = eflag = fflag = Fflag = iflag = Iflag = 0;
lflag = Lflag = nflag = Nflag = rflag = 0;
/* Started from a tty? then run as daemon */
if (isatty(0))
bflag = 1;
/* Parse arguments */
while ((ch = getopt(argc, argv, "46a:bceF:f:g:IiL:lNno:p:rt:u:")) != -1)
switch (ch) {
case '4':
IPv4or6 = AF_INET;
break;
case '6':
IPv4or6 = AF_INET6;
break;
case 'a':
address = optarg;
break;
case 'b':
bflag = 1;
break;
case 'c':
charset = optarg;
break;
case 'e':
eflag = 1;
break;
case 'F':
Fflag = 1;
fmt = optarg;
break;
case 'f':
fflag = 1;
(void)strlcpy(user, optarg, sizeof(user));
break;
case 'g':
gid = (gid_t)strtol(optarg, &p, 0);
if (*p != '\0') {
if ((grp = getgrnam(optarg)) != NULL)
gid = grp->gr_gid;
else
errx(1, "No such group '%s'", optarg);
}
break;
case 'I':
Iflag = 1;
/* FALLTHROUGH */
case 'i':
iflag = 1;
break;
case 'L':
Lflag = 1;
(void)strlcpy(user, optarg, sizeof(user));
break;
case 'l':
lflag = 1;
break;
case 'N':
Nflag = 1;
break;
case 'n':
nflag = 1;
break;
case 'o':
osname = optarg;
break;
case 'p':
portno = optarg;
break;
case 'r':
rflag = 1;
break;
case 't':
timeout = (int)strtol(optarg, &p, 0);
if (*p != '\0')
errx(1, "Invalid timeout value '%s'", optarg);
break;
case 'u':
uid = (uid_t)strtol(optarg, &p, 0);
if (*p != '\0') {
if ((pw = getpwnam(optarg)) != NULL) {
uid = pw->pw_uid;
gid = pw->pw_gid;
} else
errx(1, "No such user '%s'", optarg);
}
break;
default:
exit(1);
}
if (lflag)
openlog("identd", LOG_PID, LOG_DAEMON);
/* Setup sockets if -b flag */
if (bflag) {
socks = socketsetup(address, portno, IPv4or6);
if (socks == NULL)
return 1;
}
/* Switch to another uid/gid ? */
if (gid && setgid(gid) == -1) {
if (lflag)
syslog(LOG_ERR, "setgid: %m");
if (bflag)
warn("setgid");
exit(1);
}
if (uid && setuid(uid) == -1) {
if (lflag)
syslog(LOG_ERR, "setuid: %m");
if (bflag)
warn("setuid");
exit(1);
}
/* Daemonize, setup pollfds and start mainloop if -b flag */
if (bflag) {
int fd, i, nfds, rv;
struct pollfd *rfds;
(void)signal(SIGCHLD, waitchild);
(void)daemon(0, 0);
rfds = malloc(*socks * sizeof(struct pollfd));
if (rfds == NULL)
fatal("malloc");
nfds = *socks;
for (i = 0; i < nfds; i++) {
rfds[i].fd = socks[i+1];
rfds[i].events = POLLIN;
rfds[i].revents = 0;
}
/* Mainloop for daemon */
for (;;) {
rv = poll(rfds, nfds, INFTIM);
if (rv < 0 && errno == EINTR)
continue;
if (rv < 0)
fatal("poll");
for (i = 0; i < nfds; i++) {
if (rfds[i].revents & POLLIN) {
fd = accept(rfds[i].fd, NULL, NULL);
if (fd < 0) {
if (lflag)
syslog(LOG_ERR,
"accept: %m");
continue;
}
switch (fork()) {
case -1: /* error */
if (lflag)
syslog(LOG_ERR,
"fork: %m");
(void)sleep(1);
break;
case 0: /* child */
(void)idhandle(fd, charset,
fmt, osname, user, timeout);
_exit(0);
default: /* parent */
(void)close(fd);
}
}
}
}
} else
(void)idhandle(STDIN_FILENO, charset, fmt, osname, user,
timeout);
return 0;
}
static int
idhandle(int fd, const char *charset, const char *fmt, const char *osname,
const char *user, int timeout)
{
struct sockaddr_storage ss[2];
char userbuf[LOGIN_NAME_MAX]; /* actual user name (or numeric uid) */
char idbuf[LOGIN_NAME_MAX]; /* name to be used in response */
char buf[BUFSIZ], *p;
int n, lport, fport;
struct passwd *pw;
socklen_t len;
uid_t uid;
lport = fport = 0;
(void)strlcpy(idbuf, user, sizeof(idbuf));
(void)signal(SIGALRM, timeout_handler);
(void)alarm(timeout);
/* Get foreign internet address */
len = sizeof(ss[0]);
if (getpeername(fd, (struct sockaddr *)&ss[0], &len) < 0)
fatal("getpeername");
if (lflag)
syslog(LOG_INFO, "Connection from %s", gethost(&ss[0]));
/* Get local internet address */
len = sizeof(ss[1]);
if (getsockname(fd, (struct sockaddr *)&ss[1], &len) < 0)
fatal("getsockname");
/* Be sure to have the same address family's */
if (ss[0].ss_family != ss[1].ss_family) {
if (lflag)
syslog(LOG_ERR, "Foreign/local AF are different!");
return 1;
}
/* Receive data from the client */
if ((n = recv(fd, buf, sizeof(buf) - 1, 0)) < 0) {
fatal("recv");
} else if (n == 0) {
if (lflag)
syslog(LOG_NOTICE, "recv: EOF");
iderror(fd, 0, 0, "UNKNOWN-ERROR");
return 1;
}
buf[n] = '\0';
/* Get local and remote ports from the received data */
p = buf;
while (*p != '\0' && isspace((unsigned char)*p))
p++;
if ((p = strtok(p, " \t,")) != NULL) {
lport = atoi(p);
if ((p = strtok(NULL, " \t,")) != NULL)
fport = atoi(p);
}
/* Are the ports valid? */
if (lport < 1 || lport > 65535 || fport < 1 || fport > 65535) {
if (lflag)
syslog(LOG_NOTICE, "Invalid port(s): %d, %d from %s",
lport, fport, gethost(&ss[0]));
iderror(fd, 0, 0, eflag ? "UNKNOWN-ERROR" : "INVALID-PORT");
return 1;
}
/* If there is a 'lie' user enabled, then handle it now and quit */
if (Lflag) {
if (lflag)
syslog(LOG_NOTICE, "Lying with name %s to %s",
idbuf, gethost(&ss[0]));
idparse(fd, lport, fport, charset, osname, idbuf);
return 0;
}
/* Protocol dependent stuff */
switch (ss[0].ss_family) {
case AF_INET:
((struct sockaddr_in *)&ss[0])->sin_port = htons(fport);
((struct sockaddr_in *)&ss[1])->sin_port = htons(lport);
break;
case AF_INET6:
((struct sockaddr_in6 *)&ss[0])->sin6_port = htons(fport);
((struct sockaddr_in6 *)&ss[1])->sin6_port = htons(lport);
break;
default:
if (lflag)
syslog(LOG_ERR, "Unsupported protocol, proto no. %d",
ss[0].ss_family);
return 1;
}
/* Do sysctl call */
if (sysctl_getuid(ss, sizeof(ss), &uid) == -1) {
if (lflag)
syslog(LOG_ERR, "sysctl: %m");
if (fflag) {
if (lflag)
syslog(LOG_NOTICE, "Using fallback name %s "
"to %s", idbuf, gethost(&ss[0]));
idparse(fd, lport, fport, charset, osname, idbuf);
return 0;
}
iderror(fd, lport, fport, eflag ? "UNKNOWN-ERROR" : "NO-USER");
return 1;
}
/* Fill in userbuf with user name if possible, else numeric uid */
if ((pw = getpwuid(uid)) == NULL) {
if (lflag)
syslog(LOG_ERR, "Couldn't map uid (%u) to name", uid);
(void)snprintf(userbuf, sizeof(userbuf), "%u", uid);
} else {
if (lflag)
syslog(LOG_INFO, "Successfull lookup: %d, %d: %s for %s",
lport, fport, pw->pw_name, gethost(&ss[0]));
(void)strlcpy(userbuf, pw->pw_name, sizeof(userbuf));
}
/* No ident enabled? */
if (Nflag && pw && check_noident(pw->pw_dir)) {
if (lflag)
syslog(LOG_NOTICE, "Returning HIDDEN-USER for user %s"
" to %s", pw->pw_name, gethost(&ss[0]));
iderror(fd, lport, fport, "HIDDEN-USER");
return 1;
}
/* User ident enabled ? */
if (iflag && pw && check_userident(pw->pw_dir, idbuf, sizeof(idbuf))) {
if (!Iflag) {
if ((strspn(idbuf, "0123456789") &&
getpwuid(atoi(idbuf)) != NULL)
|| (getpwnam(idbuf) != NULL)) {
if (lflag)
syslog(LOG_NOTICE,
"Ignoring user-specified '%s' for "
"user %s", idbuf, userbuf);
(void)strlcpy(idbuf, userbuf, sizeof(idbuf));
}
}
if (lflag)
syslog(LOG_NOTICE, "Returning user-specified '%s' for "
"user %s to %s", idbuf, userbuf, gethost(&ss[0]));
idparse(fd, lport, fport, charset, osname, idbuf);
return 0;
}
/* Send random crap? */
if (rflag) {
/* Random number or string? */
if (nflag)
(void)snprintf(idbuf, sizeof(idbuf), "%u",
(unsigned int)(arc4random() % 65535));
else
random_string(idbuf, sizeof(idbuf));
if (lflag)
syslog(LOG_NOTICE, "Returning random '%s' for user %s"
" to %s", idbuf, userbuf, gethost(&ss[0]));
idparse(fd, lport, fport, charset, osname, idbuf);
return 0;
}
/* Return number? */
if (nflag)
(void)snprintf(idbuf, sizeof(idbuf), "%u", uid);
else
(void)strlcpy(idbuf, userbuf, sizeof(idbuf));
if (Fflag) {
/* RFC 1413 says that 512 is the limit */
change_format(fmt, pw, buf, 512);
idparse(fd, lport, fport, charset, osname, buf);
} else
idparse(fd, lport, fport, charset, osname, idbuf);
return 0;
}
/* Send/parse the ident result */
static void
idparse(int fd, int lport, int fport, const char *charset, const char *osname,
const char *user)
{
char *p;
if (asprintf(&p, "%d,%d:USERID:%s%s%s:%s\r\n", lport, fport,
osname, charset ? "," : "", charset ? charset : "", user) < 0)
fatal("asprintf");
if (send(fd, p, strlen(p), 0) < 0) {
free(p);
fatal("send");
}
free(p);
}
/* Return a specified ident error */
static void
iderror(int fd, int lport, int fport, const char *error)
{
char *p;
if (asprintf(&p, "%d,%d:ERROR:%s\r\n", lport, fport, error) < 0)
fatal("asprintf");
if (send(fd, p, strlen(p), 0) < 0) {
free(p);
fatal("send");
}
free(p);
}
/* Return the IP address of the connecting host */
static const char *
gethost(struct sockaddr_storage *ss)
{
static char host[NI_MAXHOST];
if (getnameinfo((struct sockaddr *)ss, ss->ss_len, host,
sizeof(host), NULL, 0, NI_NUMERICHOST) == 0)
return host;
return "UNKNOWN";
}
/* Setup sockets, for daemon mode */
static int *
socketsetup(const char *address, const char *port, int af)
{
struct addrinfo hints, *res, *res0;
int error, maxs, *s, *socks, y = 1;
const char *cause = NULL;
(void)memset(&hints, 0, sizeof(hints));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = af;
hints.ai_socktype = SOCK_STREAM;
error = getaddrinfo(address, port, &hints, &res0);
if (error) {
if (lflag)
syslog(LOG_ERR, "getaddrinfo: %s", gai_strerror(error));
errx(1, "%s", gai_strerror(error));
/*NOTREACHED*/
}
/* Count max number of sockets we may open */
for (maxs = 0, res = res0; res != NULL; res = res->ai_next)
maxs++;
socks = malloc((maxs + 1) * sizeof(int));
if (socks == NULL) {
if (lflag)
syslog(LOG_ERR, "malloc: %m");
err(1, "malloc");
/* NOTREACHED */
}
*socks = 0;
s = socks + 1;
for (res = res0; res != NULL; res = res->ai_next) {
*s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (*s < 0) {
cause = "socket";
continue;
}
(void)setsockopt(*s, SOL_SOCKET, SO_REUSEADDR, &y, sizeof(y));
if (bind(*s, res->ai_addr, res->ai_addrlen) < 0) {
cause = "bind";
(void)close(*s);
continue;
}
if (listen(*s, 5) < 0) {
cause = "listen";
(void)close(*s);
continue;
}
*socks = *socks + 1;
s++;
}
if (*socks == 0) {
free(socks);
if (lflag)
syslog(LOG_ERR, "%s: %m", cause);
err(1, "%s", cause);
/* NOTREACHED */
}
if (res0)
freeaddrinfo(res0);
return socks;
}
/* Return the UID for the connection owner */
static int
sysctl_getuid(struct sockaddr_storage *ss, socklen_t len, uid_t *uid)
{
int mib[4];
uid_t myuid;
size_t uidlen;
uidlen = sizeof(myuid);
mib[0] = CTL_NET;
mib[1] = ss->ss_family;
mib[2] = IPPROTO_TCP;
mib[3] = TCPCTL_IDENT;
if (sysctl(mib, sizeof(mib)/ sizeof(int), &myuid, &uidlen, ss, len) < 0)
return -1;
*uid = myuid;
return 0;
}
/* Check if a .noident file exists in the user home directory */
static int
check_noident(const char *homedir)
{
struct stat sb;
char *path;
int ret;
if (homedir == NULL)
return 0;
if (asprintf(&path, "%s/.noident", homedir) < 0)
return 0;
ret = stat(path, &sb);
free(path);
return (ret == 0);
}
/*
* Check if a .ident file exists in the user home directory and
* return the contents of that file.
*/
static int
check_userident(const char *homedir, char *username, size_t len)
{
struct stat sb;
char *path, *p;
int fd, n;
if (len == 0 || homedir == NULL)
return 0;
if (asprintf(&path, "%s/.ident", homedir) < 0)
return 0;
if ((fd = open(path, O_RDONLY|O_NONBLOCK|O_NOFOLLOW, 0)) < 0) {
free(path);
return 0;
}
if (fstat(fd, &sb) < 0 || !S_ISREG(sb.st_mode)) {
(void)close(fd);
free(path);
return 0;
}
if ((n = read(fd, username, len - 1)) < 1) {
(void)close(fd);
free(path);
return 0;
}
username[n] = '\0';
if ((p = strpbrk(username, "\r\n")))
*p = '\0';
(void)close(fd);
free(path);
return 1;
}
/* Generate a random string */
static void
random_string(char *str, size_t len)
{
static const char chars[] = "abcdefghijklmnopqrstuvwxyz1234567890";
char *p;
if (len == 0)
return;
for (p = str; len > 1; len--)
*p++ = chars[arc4random() % (sizeof(chars) - 1)];
*p = '\0';
}
/* Change the output format */
static void
change_format(const char *format, struct passwd *pw, char *dest, size_t len)
{
struct group *gr;
const char *cp;
char **gmp;
int bp;
if (len == 0)
return;
if ((gr = getgrgid(pw->pw_gid)) == NULL)
return;
for (bp = 0, cp = format; *cp != '\0' && bp < 490; cp++) {
if (*cp != '%') {
dest[bp++] = *cp;
continue;
}
if (*++cp == '\0')
break;
switch (*cp) {
case 'u':
(void)snprintf(&dest[bp], len - bp, "%.*s", 490 - bp,
pw->pw_name);
break;
case 'U':
(void)snprintf(&dest[bp], len - bp, "%d", pw->pw_uid);
break;
case 'g':
(void)snprintf(&dest[bp], len - bp, "%.*s", 490 - bp,
gr->gr_name);
break;
case 'G':
(void)snprintf(&dest[bp], len - bp, "%d", gr->gr_gid);
break;
case 'l':
(void)snprintf(&dest[bp], len - bp, "%.*s", 490 - bp,
gr->gr_name);
bp += strlen(&dest[bp]);
if (bp >= 490)
break;
setgrent();
while ((gr = getgrent()) != NULL) {
if (gr->gr_gid == pw->pw_gid)
continue;
for (gmp = gr->gr_mem; *gmp && **gmp; gmp++) {
if (strcmp(*gmp, pw->pw_name) == 0) {
(void)snprintf(&dest[bp],
len - bp, ",%.*s",
490 - bp, gr->gr_name);
bp += strlen(&dest[bp]);
break;
}
}
if (bp >= 490)
break;
}
endgrent();
break;
case 'L':
(void)snprintf(&dest[bp], len - bp, "%u", gr->gr_gid);
bp += strlen(&dest[bp]);
if (bp >= 490)
break;
setgrent();
while ((gr = getgrent()) != NULL) {
if (gr->gr_gid == pw->pw_gid)
continue;
for (gmp = gr->gr_mem; *gmp && **gmp; gmp++) {
if (strcmp(*gmp, pw->pw_name) == 0) {
(void)snprintf(&dest[bp],
len - bp, ",%u",
gr->gr_gid);
bp += strlen(&dest[bp]);
break;
}
}
if (bp >= 490)
break;
}
endgrent();
break;
default:
dest[bp] = *cp;
dest[bp+1] = '\0';
break;
}
bp += strlen(&dest[bp]);
}
if (bp >= 490) {
(void)snprintf(&dest[490], len - 490, "...");
bp = 493;
}
dest[bp] = '\0';
}
/* Just exit when we caught SIGALRM */
static void
timeout_handler(int s)
{
if (lflag)
syslog(LOG_DEBUG, "SIGALRM triggered, exiting...");
exit(1);
}
/* This is to clean up zombie processes when in daemon mode */
static void
waitchild(int s)
{
while (waitpid(-1, NULL, WNOHANG) > 0)
continue;
}
/* Report errno through syslog and quit */
static void
fatal(const char *func)
{
if (lflag)
syslog(LOG_ERR, "%s: %m", func);
exit(1);
}
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