[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * A fake identd server
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| 4 | *
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| 5 | * Adapted to busybox by Thomas Lundquist <thomasez@zelow.no>
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| 6 | * Original Author: Tomi Ollila <too@iki.fi>
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| 7 | * http://www.guru-group.fi/~too/sw/
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| 8 | *
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| 9 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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| 10 | */
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| 11 |
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| 12 | #include "busybox.h"
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| 13 |
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| 14 | #include <unistd.h>
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| 15 | #include <string.h>
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| 16 | #include <fcntl.h>
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| 17 | #include <signal.h>
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| 18 | #include <sys/syslog.h>
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| 19 |
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| 20 | #include <pwd.h>
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| 21 |
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| 22 | #include <sys/syslog.h>
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| 23 | #include <time.h>
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| 24 | #include <sys/socket.h>
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| 25 | #include <errno.h>
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| 26 | #include <sys/uio.h>
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| 27 |
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| 28 |
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| 29 | #define IDENT_PORT 113
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| 30 | #define MAXCONNS 20
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| 31 | #define MAXIDLETIME 45
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| 32 |
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| 33 | static const char ident_substr[] = " : USERID : UNIX : ";
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| 34 | enum { ident_substr_len = sizeof(ident_substr) - 1 };
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| 35 | #define PIDFILE "/var/run/identd.pid"
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| 36 |
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| 37 | /*
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| 38 | * We have to track the 'first connection socket' so that we
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| 39 | * don't go around closing file descriptors for non-clients.
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| 40 | *
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| 41 | * descriptor setup normally
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| 42 | * 0 = server socket
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| 43 | * 1 = syslog fd (hopefully -- otherwise this won't work)
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| 44 | * 2 = connection socket after detached from tty. standard error before that
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| 45 | * 3 - 2 + MAXCONNS = rest connection sockets
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| 46 | *
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| 47 | * To try to make sure that syslog fd is what is "requested", the that fd
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| 48 | * is closed before openlog() call. It can only severely fail if fd 0
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| 49 | * is initially closed.
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| 50 | */
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| 51 | #define FCS 2
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| 52 |
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| 53 | /*
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| 54 | * FD of the connection is always the index of the connection structure
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| 55 | * in `conns' array + FCS
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| 56 | */
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| 57 | static struct {
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| 58 | char buf[20];
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| 59 | int len;
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| 60 | time_t lasttime;
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| 61 | } conns[MAXCONNS];
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| 62 |
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| 63 | /* When using global variables, bind those at least to a structure. */
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| 64 | static struct {
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| 65 | const char *identuser;
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| 66 | fd_set readfds;
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| 67 | int conncnt;
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| 68 | } G;
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| 69 |
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| 70 | /*
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| 71 | * Prototypes
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| 72 | */
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| 73 | static void reply(int s, char *buf);
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| 74 | static void replyError(int s, char *buf);
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| 75 |
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| 76 | static const char *nobodystr = "nobody"; /* this needs to be declared like this */
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| 77 | static char *bind_ip_address = "0.0.0.0";
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| 78 |
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| 79 | static inline void movefd(int from, int to)
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| 80 | {
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| 81 | if (from != to) {
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| 82 | dup2(from, to);
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| 83 | close(from);
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| 84 | }
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| 85 | }
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| 86 |
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| 87 | static void inetbind(void)
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| 88 | {
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| 89 | int s, port;
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| 90 | struct sockaddr_in addr;
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| 91 | int len = sizeof(addr);
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| 92 | int one = 1;
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| 93 | struct servent *se;
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| 94 |
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| 95 | if ((se = getservbyname("identd", "tcp")) == NULL)
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| 96 | port = IDENT_PORT;
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| 97 | else
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| 98 | port = se->s_port;
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| 99 |
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| 100 | s = bb_xsocket(AF_INET, SOCK_STREAM, 0);
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| 101 |
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| 102 | setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
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| 103 |
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| 104 | memset(&addr, 0, sizeof(addr));
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| 105 | addr.sin_addr.s_addr = inet_addr(bind_ip_address);
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| 106 | addr.sin_family = AF_INET;
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| 107 | addr.sin_port = htons(port);
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| 108 |
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| 109 | bb_xbind(s, (struct sockaddr *)&addr, len);
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| 110 | bb_xlisten(s, 5);
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| 111 |
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| 112 | movefd(s, 0);
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| 113 | }
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| 114 |
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| 115 | static void handlexitsigs(int signum)
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| 116 | {
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| 117 | if (unlink(PIDFILE) < 0)
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| 118 | close(open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0644));
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| 119 | exit(0);
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| 120 | }
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| 121 |
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| 122 | /* May succeed. If not, won't care. */
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| 123 | static inline void writepid(uid_t nobody, uid_t nogrp)
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| 124 | {
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| 125 | char buf[24];
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| 126 | int fd = open(PIDFILE, O_WRONLY|O_CREAT|O_TRUNC, 0664);
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| 127 |
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| 128 | if (fd < 0)
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| 129 | return;
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| 130 |
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| 131 | snprintf(buf, 23, "%d\n", getpid());
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| 132 | write(fd, buf, strlen(buf));
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| 133 | fchown(fd, nobody, nogrp);
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| 134 | close(fd);
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| 135 |
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| 136 | /* should this handle ILL, ... (see signal(7)) */
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| 137 | signal(SIGTERM, handlexitsigs);
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| 138 | signal(SIGINT, handlexitsigs);
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| 139 | signal(SIGQUIT, handlexitsigs);
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| 140 | }
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| 141 |
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| 142 | /* return 0 as parent, 1 as child */
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| 143 | static int godaemon(void)
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| 144 | {
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| 145 | uid_t nobody, nogrp;
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| 146 | struct passwd *pw;
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| 147 |
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| 148 | switch (fork()) {
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| 149 | case -1:
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| 150 | bb_perror_msg_and_die("Could not fork");
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| 151 |
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| 152 | case 0:
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| 153 | pw = getpwnam(nobodystr);
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| 154 | if (pw == NULL)
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| 155 | bb_error_msg_and_die("Cannot find uid/gid of user '%s'", nobodystr);
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| 156 | nobody = pw->pw_uid;
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| 157 | nogrp = pw->pw_gid;
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| 158 | writepid(nobody, nogrp);
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| 159 |
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| 160 | close(0);
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| 161 | inetbind();
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| 162 | xsetgid(nogrp);
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| 163 | xsetuid(nobody);
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| 164 | close(1);
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| 165 | close(2);
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| 166 |
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| 167 | signal(SIGHUP, SIG_IGN);
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| 168 | signal(SIGPIPE, SIG_IGN); /* connection closed when writing (raises ???) */
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| 169 |
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| 170 | setsid();
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| 171 |
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| 172 | openlog(bb_applet_name, 0, LOG_DAEMON);
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| 173 | return 1;
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| 174 | }
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| 175 |
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| 176 | return 0;
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| 177 | }
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| 178 |
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| 179 | static void deleteConn(int s)
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| 180 | {
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| 181 | int i = s - FCS;
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| 182 |
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| 183 | close(s);
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| 184 |
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| 185 | G.conncnt--;
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| 186 |
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| 187 | /*
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| 188 | * Most of the time there is 0 connections. Most often that there
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| 189 | * is connections, there is just one connection. When this one connection
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| 190 | * closes, i == G.conncnt = 0 -> no copying.
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| 191 | * When there is more than one connection, the oldest connections closes
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| 192 | * earlier on average. When this happens, the code below starts copying
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| 193 | * the connection structure w/ highest index to the place which which is
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| 194 | * just deleted. This means that the connection structures are no longer
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| 195 | * in chronological order. I'd quess this means that when there is more
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| 196 | * than 1 connection, on average every other connection structure needs
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| 197 | * to be copied over the time all these connections are deleted.
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| 198 | */
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| 199 | if (i != G.conncnt) {
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| 200 | memcpy(&conns[i], &conns[G.conncnt], sizeof(conns[0]));
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| 201 | movefd(G.conncnt + FCS, s);
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| 202 | }
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| 203 |
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| 204 | FD_CLR(G.conncnt + FCS, &G.readfds);
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| 205 | }
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| 206 |
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| 207 | static int closeOldest(void)
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| 208 | {
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| 209 | time_t min = conns[0].lasttime;
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| 210 | int idx = 0;
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| 211 | int i;
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| 212 |
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| 213 | for (i = 1; i < MAXCONNS; i++)
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| 214 | if (conns[i].lasttime < min)
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| 215 | idx = i;
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| 216 |
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| 217 | replyError(idx + FCS, "X-SERVER-TOO-BUSY");
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| 218 | close(idx + FCS);
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| 219 |
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| 220 | return idx;
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| 221 | }
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| 222 |
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| 223 | static int checkInput(char *buf, int len, int l)
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| 224 | {
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| 225 | int i;
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| 226 | for (i = len; i < len + l; ++i)
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| 227 | if (buf[i] == '\n')
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| 228 | return 1;
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| 229 | return 0;
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| 230 | }
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| 231 |
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| 232 | int fakeidentd_main(int argc, char **argv)
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| 233 | {
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| 234 | memset(conns, 0, sizeof(conns));
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| 235 | memset(&G, 0, sizeof(G));
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| 236 | FD_ZERO(&G.readfds);
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| 237 | FD_SET(0, &G.readfds);
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| 238 |
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| 239 | /* handle -b <ip> parameter */
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| 240 | bb_getopt_ulflags(argc, argv, "b:", &bind_ip_address);
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| 241 | /* handle optional REPLY STRING */
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| 242 | if (optind < argc)
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| 243 | G.identuser = argv[optind];
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| 244 | else
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| 245 | G.identuser = nobodystr;
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| 246 |
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| 247 | /* daemonize and have the parent return */
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| 248 | if (godaemon() == 0)
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| 249 | return 0;
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| 250 |
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| 251 | /* main loop where we process all events and never exit */
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| 252 | while (1) {
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| 253 | fd_set rfds = G.readfds;
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| 254 | struct timeval tv = { 15, 0 };
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| 255 | int i;
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| 256 | int tim = time(NULL);
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| 257 |
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| 258 | select(G.conncnt + FCS, &rfds, NULL, NULL, G.conncnt? &tv: NULL);
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| 259 |
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| 260 | for (i = G.conncnt - 1; i >= 0; i--) {
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| 261 | int s = i + FCS;
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| 262 |
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| 263 | if (FD_ISSET(s, &rfds)) {
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| 264 | char *buf = conns[i].buf;
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| 265 | unsigned int len = conns[i].len;
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| 266 | unsigned int l;
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| 267 |
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| 268 | if ((l = read(s, buf + len, sizeof(conns[0].buf) - len)) > 0) {
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| 269 | if (checkInput(buf, len, l)) {
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| 270 | reply(s, buf);
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| 271 | goto deleteconn;
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| 272 | } else if (len + l >= sizeof(conns[0].buf)) {
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| 273 | replyError(s, "X-INVALID-REQUEST");
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| 274 | goto deleteconn;
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| 275 | } else {
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| 276 | conns[i].len += l;
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| 277 | }
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| 278 | } else {
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| 279 | goto deleteconn;
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| 280 | }
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| 281 |
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| 282 | conns[i].lasttime = tim;
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| 283 | continue;
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| 284 |
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| 285 | deleteconn:
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| 286 | deleteConn(s);
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| 287 | } else {
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| 288 | /* implement as time_after() in linux kernel sources ... */
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| 289 | if (conns[i].lasttime + MAXIDLETIME <= tim) {
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| 290 | replyError(s, "X-TIMEOUT");
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| 291 | deleteConn(s);
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| 292 | }
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| 293 | }
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| 294 | }
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| 295 |
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| 296 | if (FD_ISSET(0, &rfds)) {
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| 297 | int s = accept(0, NULL, 0);
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| 298 |
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| 299 | if (s < 0) {
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| 300 | if (errno != EINTR) /* EINTR */
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| 301 | syslog(LOG_ERR, "accept: %s", strerror(errno));
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| 302 | } else {
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| 303 | if (G.conncnt == MAXCONNS)
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| 304 | i = closeOldest();
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| 305 | else
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| 306 | i = G.conncnt++;
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| 307 |
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| 308 | movefd(s, i + FCS); /* move if not already there */
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| 309 | FD_SET(i + FCS, &G.readfds);
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| 310 |
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| 311 | conns[i].len = 0;
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| 312 | conns[i].lasttime = time(NULL);
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| 313 | }
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| 314 | }
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| 315 | } /* end of while(1) */
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| 316 |
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| 317 | return 0;
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| 318 | }
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| 319 |
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| 320 | static int parseAddrs(char *ptr, char **myaddr, char **heraddr);
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| 321 | static void reply(int s, char *buf)
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| 322 | {
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| 323 | char *myaddr, *heraddr;
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| 324 |
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| 325 | myaddr = heraddr = NULL;
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| 326 |
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| 327 | if (parseAddrs(buf, &myaddr, &heraddr))
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| 328 | replyError(s, "X-INVALID-REQUEST");
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| 329 | else {
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| 330 | struct iovec iv[6];
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| 331 | iv[0].iov_base = myaddr; iv[0].iov_len = strlen(myaddr);
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| 332 | iv[1].iov_base = ", "; iv[1].iov_len = 2;
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| 333 | iv[2].iov_base = heraddr; iv[2].iov_len = strlen(heraddr);
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| 334 | iv[3].iov_base = (void *)ident_substr; iv[3].iov_len = ident_substr_len;
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| 335 | iv[4].iov_base = (void *)G.identuser; iv[4].iov_len = strlen(G.identuser);
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| 336 | iv[5].iov_base = "\r\n"; iv[5].iov_len = 2;
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| 337 | writev(s, iv, 6);
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| 338 | }
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| 339 | }
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| 340 |
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| 341 | static void replyError(int s, char *buf)
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| 342 | {
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| 343 | struct iovec iv[3];
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| 344 | iv[0].iov_base = "0, 0 : ERROR : "; iv[0].iov_len = 15;
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| 345 | iv[1].iov_base = buf; iv[1].iov_len = strlen(buf);
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| 346 | iv[2].iov_base = "\r\n"; iv[2].iov_len = 2;
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| 347 | writev(s, iv, 3);
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| 348 | }
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| 349 |
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| 350 | static int chmatch(char c, char *chars)
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| 351 | {
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| 352 | for (; *chars; chars++)
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| 353 | if (c == *chars)
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| 354 | return 1;
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| 355 | return 0;
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| 356 | }
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| 357 |
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| 358 | static int skipchars(char **p, char *chars)
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| 359 | {
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| 360 | while (chmatch(**p, chars))
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| 361 | (*p)++;
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| 362 | if (**p == '\r' || **p == '\n')
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| 363 | return 0;
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| 364 | return 1;
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| 365 | }
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| 366 |
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| 367 | static int parseAddrs(char *ptr, char **myaddr, char **heraddr)
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| 368 | {
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| 369 | /* parse <port-on-server> , <port-on-client> */
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| 370 |
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| 371 | if (!skipchars(&ptr, " \t"))
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| 372 | return -1;
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| 373 |
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| 374 | *myaddr = ptr;
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| 375 |
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| 376 | if (!skipchars(&ptr, "1234567890"))
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| 377 | return -1;
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| 378 |
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| 379 | if (!chmatch(*ptr, " \t,"))
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| 380 | return -1;
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| 381 |
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| 382 | *ptr++ = '\0';
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| 383 |
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| 384 | if (!skipchars(&ptr, " \t,") )
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| 385 | return -1;
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| 386 |
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| 387 | *heraddr = ptr;
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| 388 |
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| 389 | skipchars(&ptr, "1234567890");
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| 390 |
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| 391 | if (!chmatch(*ptr, " \n\r"))
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| 392 | return -1;
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| 393 |
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| 394 | *ptr = '\0';
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| 395 |
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| 396 | return 0;
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| 397 | }
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