diff options
| -rw-r--r-- | usr.sbin/inetd/builtins.c | 76 |
1 files changed, 65 insertions, 11 deletions
diff --git a/usr.sbin/inetd/builtins.c b/usr.sbin/inetd/builtins.c index e3d2013..2ad656c 100644 --- a/usr.sbin/inetd/builtins.c +++ b/usr.sbin/inetd/builtins.c @@ -23,7 +23,7 @@ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * - * $Id: builtins.c,v 1.11 1999/07/24 17:06:05 green Exp $ + * $Id: builtins.c,v 1.12 1999/07/25 23:15:03 green Exp $ * */ @@ -307,15 +307,9 @@ echo_stream(s, sep) /* Echo service -- echo data back */ * support. */ -/* - * NOTE: If any of the asprintf()s here fail, rest assured that faulting - * in the buffers for using snprintf() would have also failed. - * Asprintf() is the proper way to do what we do. - */ - /* ARGSUSED */ void -iderror(lport, fport, s, er) +iderror(lport, fport, s, er) /* Generic ident_stream error-sending func */ int lport, fport, s, er; { char *p; @@ -334,7 +328,7 @@ iderror(lport, fport, s, er) /* ARGSUSED */ void -ident_stream(s, sep) /* Ident service */ +ident_stream(s, sep) /* Ident service (AKA "auth") */ int s; struct servtab *sep; { @@ -353,8 +347,17 @@ ident_stream(s, sep) /* Ident service */ u_short lport, fport; inetd_setproctitle(sep->se_service, s); + /* + * Reset getopt() since we are a fork() but not an exec() from + * a parent which used getopt() already. + */ optind = 1; optreset = 1; + /* + * Take the internal argument vector and count it out to make an + * argument count for getopt. This can be used for any internal + * service to read arguments and use getopt() easily. + */ for (av = sep->se_argv; *av; av++) argc++; if (argc) { @@ -402,6 +405,12 @@ ident_stream(s, sep) /* Ident service */ len = sizeof(sin[1]); if (getpeername(s, (struct sockaddr *)&sin[1], &len) == -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 + * "local_port , foreign_port\r\n" (with local being the + * server's port and foreign being the client's.) + */ FD_ZERO(&fdset); FD_SET(s, &fdset); if (select(s + 1, &fdset, NULL, NULL, &tv) == -1) @@ -416,17 +425,30 @@ ident_stream(s, sep) /* Ident service */ buf[len] = '\0'; if (sscanf(buf, "%hu , %hu", &lport, &fport) != 2) iderror(0, 0, s, 0); - if (!rflag) + if (!rflag) /* Send HIDDEN-USER immediately if not "real" */ iderror(lport, fport, s, -1); + /* + * 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 + * arrays have been filled in above via get{peer,sock}name(), + * so right here we are only setting the ports. + */ sin[0].sin_port = htons(lport); sin[1].sin_port = htons(fport); len = sizeof(uc); if (sysctlbyname("net.inet.tcp.getcred", &uc, &len, sin, sizeof(sin)) == -1) iderror(lport, fport, s, errno); - pw = getpwuid(uc.cr_uid); + pw = getpwuid(uc.cr_uid); /* Look up the pw to get the username */ if (pw == NULL) iderror(lport, fport, s, errno); + /* + * If enabled, we check for a file named ".noident" in the user's + * home directory. If found, we return HIDDEN-USER. + */ if (nflag) { if (asprintf(&p, "%s/.noident", pw->pw_dir) == -1) iderror(lport, fport, s, errno); @@ -436,13 +458,30 @@ ident_stream(s, sep) /* Ident service */ } 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) { FILE *fakeid = NULL; 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. + */ seteuid(pw->pw_uid); setegid(pw->pw_gid); + /* + * If we were to lstat() here, it would do no good, since it + * would introduce a race condition and could be defeated. + * Therefore, we open the file we have permissions to open + * and if it's not a regular file, we close it and end up + * returning the user's real username. + */ fakeid = fopen(p, "r"); free(p); if (fakeid != NULL && @@ -454,13 +493,27 @@ ident_stream(s, sep) /* Ident service */ goto printit; } fclose(fakeid); + /* + * Usually, the file will have the desired identity + * in the form "identity\n", so we use strtok() to + * end the string (which fgets() doesn't do.) + */ strtok(buf, "\r\n"); + /* User names of >16 characters are invalid */ if (strlen(buf) > 16) buf[16] = '\0'; cp = buf; + /* Allow for beginning white space... */ while (isspace(*cp)) cp++; + /* ...and ending white space. */ strtok(cp, " \t"); + /* + * 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 || getpwnam(cp)) cp = getpwuid(uc.cr_uid)->pw_name; } else @@ -468,6 +521,7 @@ ident_stream(s, sep) /* Ident service */ } else cp = pw->pw_name; printit: + /* Finally, we make and send the reply. */ if (asprintf(&p, "%d , %d : USERID : %s : %s\r\n", lport, fport, osname, cp) == -1) { syslog(LOG_ERR, "asprintf: %m"); |
