[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Simple telnet server
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| 4 | * Bjorn Wesen, Axis Communications AB (bjornw@axis.com)
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| 5 | *
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[2725] | 6 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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[821] | 7 | *
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| 8 | * ---------------------------------------------------------------------------
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| 9 | * (C) Copyright 2000, Axis Communications AB, LUND, SWEDEN
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| 10 | ****************************************************************************
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| 11 | *
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| 12 | * The telnetd manpage says it all:
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| 13 | *
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[2725] | 14 | * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for
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| 15 | * a client, then creating a login process which has the slave side of the
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| 16 | * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
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| 17 | * master side of the pseudo-terminal, implementing the telnet protocol and
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| 18 | * passing characters between the remote client and the login process.
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[821] | 19 | *
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| 20 | * Vladimir Oleynik <dzo@simtreas.ru> 2001
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[2725] | 21 | * Set process group corrections, initial busybox port
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[821] | 22 | */
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[3232] | 23 |
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| 24 | //usage:#define telnetd_trivial_usage
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| 25 | //usage: "[OPTIONS]"
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| 26 | //usage:#define telnetd_full_usage "\n\n"
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| 27 | //usage: "Handle incoming telnet connections"
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| 28 | //usage: IF_NOT_FEATURE_TELNETD_STANDALONE(" via inetd") "\n"
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| 29 | //usage: "\n -l LOGIN Exec LOGIN on connect"
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| 30 | //usage: "\n -f ISSUE_FILE Display ISSUE_FILE instead of /etc/issue"
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| 31 | //usage: "\n -K Close connection as soon as login exits"
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| 32 | //usage: "\n (normally wait until all programs close slave pty)"
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| 33 | //usage: IF_FEATURE_TELNETD_STANDALONE(
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| 34 | //usage: "\n -p PORT Port to listen on"
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| 35 | //usage: "\n -b ADDR[:PORT] Address to bind to"
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| 36 | //usage: "\n -F Run in foreground"
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| 37 | //usage: "\n -i Inetd mode"
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| 38 | //usage: IF_FEATURE_TELNETD_INETD_WAIT(
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| 39 | //usage: "\n -w SEC Inetd 'wait' mode, linger time SEC"
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| 40 | //usage: "\n -S Log to syslog (implied by -i or without -F and -w)"
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| 41 | //usage: )
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| 42 | //usage: )
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| 43 |
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[1765] | 44 | #define DEBUG 0
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[821] | 45 |
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[1765] | 46 | #include "libbb.h"
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[2725] | 47 | #include <syslog.h>
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[1765] | 48 |
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| 49 | #if DEBUG
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[2725] | 50 | # define TELCMDS
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| 51 | # define TELOPTS
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[821] | 52 | #endif
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| 53 | #include <arpa/telnet.h>
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| 54 |
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| 55 |
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| 56 | struct tsession {
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[1765] | 57 | struct tsession *next;
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[2725] | 58 | pid_t shell_pid;
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| 59 | int sockfd_read;
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| 60 | int sockfd_write;
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| 61 | int ptyfd;
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| 62 |
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[821] | 63 | /* two circular buffers */
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[2725] | 64 | /*char *buf1, *buf2;*/
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| 65 | /*#define TS_BUF1(ts) ts->buf1*/
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| 66 | /*#define TS_BUF2(ts) TS_BUF2(ts)*/
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| 67 | #define TS_BUF1(ts) ((unsigned char*)(ts + 1))
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| 68 | #define TS_BUF2(ts) (((unsigned char*)(ts + 1)) + BUFSIZE)
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[821] | 69 | int rdidx1, wridx1, size1;
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| 70 | int rdidx2, wridx2, size2;
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| 71 | };
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| 72 |
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[1765] | 73 | /* Two buffers are directly after tsession in malloced memory.
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| 74 | * Make whole thing fit in 4k */
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[2725] | 75 | enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 };
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[1765] | 76 |
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[821] | 77 |
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[2725] | 78 | /* Globals */
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| 79 | struct globals {
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| 80 | struct tsession *sessions;
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| 81 | const char *loginpath;
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| 82 | const char *issuefile;
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| 83 | int maxfd;
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| 84 | } FIX_ALIASING;
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| 85 | #define G (*(struct globals*)&bb_common_bufsiz1)
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| 86 | #define INIT_G() do { \
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| 87 | G.loginpath = "/bin/login"; \
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| 88 | G.issuefile = "/etc/issue.net"; \
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| 89 | } while (0)
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[821] | 90 |
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| 91 |
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| 92 | /*
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[2725] | 93 | Remove all IAC's from buf1 (received IACs are ignored and must be removed
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| 94 | so as to not be interpreted by the terminal). Make an uninterrupted
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| 95 | string of characters fit for the terminal. Do this by packing
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| 96 | all characters meant for the terminal sequentially towards the end of buf.
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[821] | 97 |
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[2725] | 98 | Return a pointer to the beginning of the characters meant for the terminal
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[821] | 99 | and make *num_totty the number of characters that should be sent to
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| 100 | the terminal.
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| 101 |
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[2725] | 102 | Note - if an IAC (3 byte quantity) starts before (bf + len) but extends
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| 103 | past (bf + len) then that IAC will be left unprocessed and *processed
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| 104 | will be less than len.
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[821] | 105 |
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[2725] | 106 | CR-LF ->'s CR mapping is also done here, for convenience.
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[821] | 107 |
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[2725] | 108 | NB: may fail to remove iacs which wrap around buffer!
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[1765] | 109 | */
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[2725] | 110 | static unsigned char *
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[1765] | 111 | remove_iacs(struct tsession *ts, int *pnum_totty)
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| 112 | {
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[2725] | 113 | unsigned char *ptr0 = TS_BUF1(ts) + ts->wridx1;
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[821] | 114 | unsigned char *ptr = ptr0;
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| 115 | unsigned char *totty = ptr;
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| 116 | unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
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| 117 | int num_totty;
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| 118 |
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| 119 | while (ptr < end) {
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| 120 | if (*ptr != IAC) {
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[2725] | 121 | char c = *ptr;
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| 122 |
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| 123 | *totty++ = c;
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| 124 | ptr++;
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| 125 | /* We map \r\n ==> \r for pragmatic reasons.
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[821] | 126 | * Many client implementations send \r\n when
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| 127 | * the user hits the CarriageReturn key.
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[3232] | 128 | * See RFC 1123 3.3.1 Telnet End-of-Line Convention.
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[821] | 129 | */
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[2725] | 130 | if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0'))
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[821] | 131 | ptr++;
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[2725] | 132 | continue;
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| 133 | }
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[821] | 134 |
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[2725] | 135 | if ((ptr+1) >= end)
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| 136 | break;
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| 137 | if (ptr[1] == NOP) { /* Ignore? (putty keepalive, etc.) */
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| 138 | ptr += 2;
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| 139 | continue;
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| 140 | }
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| 141 | if (ptr[1] == IAC) { /* Literal IAC? (emacs M-DEL) */
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| 142 | *totty++ = ptr[1];
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| 143 | ptr += 2;
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| 144 | continue;
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| 145 | }
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| 146 |
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| 147 | /*
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| 148 | * TELOPT_NAWS support!
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| 149 | */
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| 150 | if ((ptr+2) >= end) {
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| 151 | /* Only the beginning of the IAC is in the
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| 152 | buffer we were asked to process, we can't
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| 153 | process this char */
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| 154 | break;
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| 155 | }
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| 156 | /*
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| 157 | * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE
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| 158 | */
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| 159 | if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) {
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| 160 | struct winsize ws;
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| 161 | if ((ptr+8) >= end)
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| 162 | break; /* incomplete, can't process */
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| 163 | ws.ws_col = (ptr[3] << 8) | ptr[4];
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| 164 | ws.ws_row = (ptr[5] << 8) | ptr[6];
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| 165 | ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
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| 166 | ptr += 9;
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| 167 | continue;
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| 168 | }
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| 169 | /* skip 3-byte IAC non-SB cmd */
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[1765] | 170 | #if DEBUG
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[2725] | 171 | fprintf(stderr, "Ignoring IAC %s,%s\n",
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| 172 | TELCMD(ptr[1]), TELOPT(ptr[2]));
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[821] | 173 | #endif
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[2725] | 174 | ptr += 3;
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[821] | 175 | }
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| 176 |
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| 177 | num_totty = totty - ptr0;
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| 178 | *pnum_totty = num_totty;
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[2725] | 179 | /* The difference between ptr and totty is number of iacs
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| 180 | we removed from the stream. Adjust buf1 accordingly */
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| 181 | if ((ptr - totty) == 0) /* 99.999% of cases */
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| 182 | return ptr0;
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| 183 | ts->wridx1 += ptr - totty;
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| 184 | ts->size1 -= ptr - totty;
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| 185 | /* Move chars meant for the terminal towards the end of the buffer */
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[821] | 186 | return memmove(ptr - num_totty, ptr0, num_totty);
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| 187 | }
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| 188 |
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[2725] | 189 | /*
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| 190 | * Converting single IAC into double on output
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| 191 | */
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| 192 | static size_t iac_safe_write(int fd, const char *buf, size_t count)
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[821] | 193 | {
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[2725] | 194 | const char *IACptr;
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| 195 | size_t wr, rc, total;
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[821] | 196 |
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[2725] | 197 | total = 0;
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| 198 | while (1) {
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| 199 | if (count == 0)
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| 200 | return total;
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| 201 | if (*buf == (char)IAC) {
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| 202 | static const char IACIAC[] ALIGN1 = { IAC, IAC };
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| 203 | rc = safe_write(fd, IACIAC, 2);
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| 204 | if (rc != 2)
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| 205 | break;
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| 206 | buf++;
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| 207 | total++;
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| 208 | count--;
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[821] | 209 | continue;
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| 210 | }
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[2725] | 211 | /* count != 0, *buf != IAC */
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| 212 | IACptr = memchr(buf, IAC, count);
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| 213 | wr = count;
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| 214 | if (IACptr)
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| 215 | wr = IACptr - buf;
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| 216 | rc = safe_write(fd, buf, wr);
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| 217 | if (rc != wr)
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| 218 | break;
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| 219 | buf += rc;
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| 220 | total += rc;
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| 221 | count -= rc;
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[821] | 222 | }
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[2725] | 223 | /* here: rc - result of last short write */
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| 224 | if ((ssize_t)rc < 0) { /* error? */
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| 225 | if (total == 0)
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| 226 | return rc;
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| 227 | rc = 0;
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| 228 | }
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| 229 | return total + rc;
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[821] | 230 | }
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| 231 |
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[2725] | 232 | /* Must match getopt32 string */
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| 233 | enum {
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| 234 | OPT_WATCHCHILD = (1 << 2), /* -K */
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| 235 | OPT_INETD = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */
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| 236 | OPT_PORT = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p PORT */
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| 237 | OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */
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| 238 | OPT_SYSLOG = (1 << 7) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -S */
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| 239 | OPT_WAIT = (1 << 8) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -w SEC */
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| 240 | };
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[821] | 241 |
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| 242 | static struct tsession *
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[1765] | 243 | make_new_session(
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[2725] | 244 | IF_FEATURE_TELNETD_STANDALONE(int sock)
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| 245 | IF_NOT_FEATURE_TELNETD_STANDALONE(void)
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[1765] | 246 | ) {
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[2725] | 247 | #if !ENABLE_FEATURE_TELNETD_STANDALONE
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| 248 | enum { sock = 0 };
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| 249 | #endif
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[1765] | 250 | const char *login_argv[2];
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[821] | 251 | struct termios termbuf;
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[1765] | 252 | int fd, pid;
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[2725] | 253 | char tty_name[GETPTY_BUFSIZE];
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[821] | 254 | struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2);
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| 255 |
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[2725] | 256 | /*ts->buf1 = (char *)(ts + 1);*/
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| 257 | /*ts->buf2 = ts->buf1 + BUFSIZE;*/
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[821] | 258 |
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[2725] | 259 | /* Got a new connection, set up a tty */
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| 260 | fd = xgetpty(tty_name);
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| 261 | if (fd > G.maxfd)
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| 262 | G.maxfd = fd;
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| 263 | ts->ptyfd = fd;
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| 264 | ndelay_on(fd);
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| 265 | close_on_exec_on(fd);
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| 266 |
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| 267 | /* SO_KEEPALIVE by popular demand */
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| 268 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
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| 269 | #if ENABLE_FEATURE_TELNETD_STANDALONE
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| 270 | ts->sockfd_read = sock;
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| 271 | ndelay_on(sock);
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| 272 | if (sock == 0) { /* We are called with fd 0 - we are in inetd mode */
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| 273 | sock++; /* so use fd 1 for output */
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| 274 | ndelay_on(sock);
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[1765] | 275 | }
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[2725] | 276 | ts->sockfd_write = sock;
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| 277 | if (sock > G.maxfd)
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| 278 | G.maxfd = sock;
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[1765] | 279 | #else
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[2725] | 280 | /* ts->sockfd_read = 0; - done by xzalloc */
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[821] | 281 | ts->sockfd_write = 1;
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[1765] | 282 | ndelay_on(0);
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| 283 | ndelay_on(1);
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| 284 | #endif
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[2725] | 285 |
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[821] | 286 | /* Make the telnet client understand we will echo characters so it
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| 287 | * should not do it locally. We don't tell the client to run linemode,
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| 288 | * because we want to handle line editing and tab completion and other
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[1765] | 289 | * stuff that requires char-by-char support. */
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[2725] | 290 | {
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| 291 | static const char iacs_to_send[] ALIGN1 = {
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| 292 | IAC, DO, TELOPT_ECHO,
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| 293 | IAC, DO, TELOPT_NAWS,
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| 294 | /* This requires telnetd.ctrlSQ.patch (incomplete) */
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| 295 | /*IAC, DO, TELOPT_LFLOW,*/
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| 296 | IAC, WILL, TELOPT_ECHO,
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| 297 | IAC, WILL, TELOPT_SGA
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| 298 | };
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| 299 | /* This confuses iac_safe_write(), it will try to duplicate
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| 300 | * each IAC... */
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| 301 | //memcpy(TS_BUF2(ts), iacs_to_send, sizeof(iacs_to_send));
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| 302 | //ts->rdidx2 = sizeof(iacs_to_send);
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| 303 | //ts->size2 = sizeof(iacs_to_send);
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| 304 | /* So just stuff it into TCP stream! (no error check...) */
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| 305 | #if ENABLE_FEATURE_TELNETD_STANDALONE
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| 306 | safe_write(sock, iacs_to_send, sizeof(iacs_to_send));
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| 307 | #else
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| 308 | safe_write(1, iacs_to_send, sizeof(iacs_to_send));
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| 309 | #endif
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| 310 | /*ts->rdidx2 = 0; - xzalloc did it */
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| 311 | /*ts->size2 = 0;*/
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| 312 | }
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[821] | 313 |
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[2725] | 314 | fflush_all();
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| 315 | pid = vfork(); /* NOMMU-friendly */
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[1765] | 316 | if (pid < 0) {
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| 317 | free(ts);
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| 318 | close(fd);
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[2725] | 319 | /* sock will be closed by caller */
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| 320 | bb_perror_msg("vfork");
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[1765] | 321 | return NULL;
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[821] | 322 | }
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[1765] | 323 | if (pid > 0) {
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[2725] | 324 | /* Parent */
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[1765] | 325 | ts->shell_pid = pid;
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| 326 | return ts;
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| 327 | }
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[821] | 328 |
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[2725] | 329 | /* Child */
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| 330 | /* Careful - we are after vfork! */
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[821] | 331 |
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[2725] | 332 | /* Restore default signal handling ASAP */
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| 333 | bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL);
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| 334 |
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[3232] | 335 | pid = getpid();
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| 336 |
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[2725] | 337 | if (ENABLE_FEATURE_UTMP) {
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| 338 | len_and_sockaddr *lsa = get_peer_lsa(sock);
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| 339 | char *hostname = NULL;
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| 340 | if (lsa) {
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| 341 | hostname = xmalloc_sockaddr2dotted(&lsa->u.sa);
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| 342 | free(lsa);
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| 343 | }
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| 344 | write_new_utmp(pid, LOGIN_PROCESS, tty_name, /*username:*/ "LOGIN", hostname);
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| 345 | free(hostname);
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| 346 | }
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| 347 |
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| 348 | /* Make new session and process group */
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[1765] | 349 | setsid();
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[821] | 350 |
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[2725] | 351 | /* Open the child's side of the tty */
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[1765] | 352 | /* NB: setsid() disconnects from any previous ctty's. Therefore
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| 353 | * we must open child's side of the tty AFTER setsid! */
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[2725] | 354 | close(0);
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| 355 | xopen(tty_name, O_RDWR); /* becomes our ctty */
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| 356 | xdup2(0, 1);
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| 357 | xdup2(0, 2);
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| 358 | tcsetpgrp(0, pid); /* switch this tty's process group to us */
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[821] | 359 |
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[2725] | 360 | /* The pseudo-terminal allocated to the client is configured to operate
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| 361 | * in cooked mode, and with XTABS CRMOD enabled (see tty(4)) */
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[1765] | 362 | tcgetattr(0, &termbuf);
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| 363 | termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */
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[2725] | 364 | termbuf.c_oflag |= ONLCR | XTABS;
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[1765] | 365 | termbuf.c_iflag |= ICRNL;
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| 366 | termbuf.c_iflag &= ~IXOFF;
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| 367 | /*termbuf.c_lflag &= ~ICANON;*/
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[2725] | 368 | tcsetattr_stdin_TCSANOW(&termbuf);
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[821] | 369 |
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[2725] | 370 | /* Uses FILE-based I/O to stdout, but does fflush_all(),
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| 371 | * so should be safe with vfork.
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| 372 | * I fear, though, that some users will have ridiculously big
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| 373 | * issue files, and they may block writing to fd 1,
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| 374 | * (parent is supposed to read it, but parent waits
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| 375 | * for vforked child to exec!) */
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| 376 | print_login_issue(G.issuefile, tty_name);
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[821] | 377 |
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[2725] | 378 | /* Exec shell / login / whatever */
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| 379 | login_argv[0] = G.loginpath;
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[1765] | 380 | login_argv[1] = NULL;
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[2725] | 381 | /* exec busybox applet (if PREFER_APPLETS=y), if that fails,
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| 382 | * exec external program.
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| 383 | * NB: sock is either 0 or has CLOEXEC set on it.
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| 384 | * fd has CLOEXEC set on it too. These two fds will be closed here.
|
---|
| 385 | */
|
---|
| 386 | BB_EXECVP(G.loginpath, (char **)login_argv);
|
---|
| 387 | /* _exit is safer with vfork, and we shouldn't send message
|
---|
| 388 | * to remote clients anyway */
|
---|
| 389 | _exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", G.loginpath);*/
|
---|
[1765] | 390 | }
|
---|
[821] | 391 |
|
---|
[1765] | 392 | #if ENABLE_FEATURE_TELNETD_STANDALONE
|
---|
[821] | 393 |
|
---|
| 394 | static void
|
---|
| 395 | free_session(struct tsession *ts)
|
---|
| 396 | {
|
---|
[2725] | 397 | struct tsession *t;
|
---|
[821] | 398 |
|
---|
[2725] | 399 | if (option_mask32 & OPT_INETD)
|
---|
| 400 | exit(EXIT_SUCCESS);
|
---|
| 401 |
|
---|
| 402 | /* Unlink this telnet session from the session list */
|
---|
| 403 | t = G.sessions;
|
---|
[821] | 404 | if (t == ts)
|
---|
[2725] | 405 | G.sessions = ts->next;
|
---|
[821] | 406 | else {
|
---|
[1765] | 407 | while (t->next != ts)
|
---|
[821] | 408 | t = t->next;
|
---|
| 409 | t->next = ts->next;
|
---|
| 410 | }
|
---|
| 411 |
|
---|
[2725] | 412 | #if 0
|
---|
| 413 | /* It was said that "normal" telnetd just closes ptyfd,
|
---|
| 414 | * doesn't send SIGKILL. When we close ptyfd,
|
---|
| 415 | * kernel sends SIGHUP to processes having slave side opened. */
|
---|
[821] | 416 | kill(ts->shell_pid, SIGKILL);
|
---|
[2725] | 417 | waitpid(ts->shell_pid, NULL, 0);
|
---|
| 418 | #endif
|
---|
[821] | 419 | close(ts->ptyfd);
|
---|
[1765] | 420 | close(ts->sockfd_read);
|
---|
[2725] | 421 | /* We do not need to close(ts->sockfd_write), it's the same
|
---|
| 422 | * as sockfd_read unless we are in inetd mode. But in inetd mode
|
---|
| 423 | * we do not reach this */
|
---|
[821] | 424 | free(ts);
|
---|
| 425 |
|
---|
[2725] | 426 | /* Scan all sessions and find new maxfd */
|
---|
| 427 | G.maxfd = 0;
|
---|
| 428 | ts = G.sessions;
|
---|
[1765] | 429 | while (ts) {
|
---|
[2725] | 430 | if (G.maxfd < ts->ptyfd)
|
---|
| 431 | G.maxfd = ts->ptyfd;
|
---|
| 432 | if (G.maxfd < ts->sockfd_read)
|
---|
| 433 | G.maxfd = ts->sockfd_read;
|
---|
| 434 | #if 0
|
---|
| 435 | /* Again, sockfd_write == sockfd_read here */
|
---|
| 436 | if (G.maxfd < ts->sockfd_write)
|
---|
| 437 | G.maxfd = ts->sockfd_write;
|
---|
| 438 | #endif
|
---|
[1765] | 439 | ts = ts->next;
|
---|
[821] | 440 | }
|
---|
[1765] | 441 | }
|
---|
[821] | 442 |
|
---|
[1765] | 443 | #else /* !FEATURE_TELNETD_STANDALONE */
|
---|
[821] | 444 |
|
---|
[2725] | 445 | /* Used in main() only, thus "return 0" actually is exit(EXIT_SUCCESS). */
|
---|
| 446 | #define free_session(ts) return 0
|
---|
[821] | 447 |
|
---|
[1765] | 448 | #endif
|
---|
[821] | 449 |
|
---|
[2725] | 450 | static void handle_sigchld(int sig UNUSED_PARAM)
|
---|
| 451 | {
|
---|
| 452 | pid_t pid;
|
---|
| 453 | struct tsession *ts;
|
---|
| 454 | int save_errno = errno;
|
---|
[821] | 455 |
|
---|
[2725] | 456 | /* Looping: more than one child may have exited */
|
---|
| 457 | while (1) {
|
---|
| 458 | pid = wait_any_nohang(NULL);
|
---|
| 459 | if (pid <= 0)
|
---|
| 460 | break;
|
---|
| 461 | ts = G.sessions;
|
---|
| 462 | while (ts) {
|
---|
| 463 | if (ts->shell_pid == pid) {
|
---|
| 464 | ts->shell_pid = -1;
|
---|
| 465 | // man utmp:
|
---|
| 466 | // When init(8) finds that a process has exited, it locates its utmp entry
|
---|
| 467 | // by ut_pid, sets ut_type to DEAD_PROCESS, and clears ut_user, ut_host
|
---|
| 468 | // and ut_time with null bytes.
|
---|
| 469 | // [same applies to other processes which maintain utmp entries, like telnetd]
|
---|
| 470 | //
|
---|
| 471 | // We do not bother actually clearing fields:
|
---|
| 472 | // it might be interesting to know who was logged in and from where
|
---|
| 473 | update_utmp(pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL);
|
---|
| 474 | break;
|
---|
| 475 | }
|
---|
| 476 | ts = ts->next;
|
---|
| 477 | }
|
---|
| 478 | }
|
---|
| 479 |
|
---|
| 480 | errno = save_errno;
|
---|
| 481 | }
|
---|
| 482 |
|
---|
| 483 | int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
| 484 | int telnetd_main(int argc UNUSED_PARAM, char **argv)
|
---|
[1765] | 485 | {
|
---|
| 486 | fd_set rdfdset, wrfdset;
|
---|
| 487 | unsigned opt;
|
---|
[2725] | 488 | int count;
|
---|
[1765] | 489 | struct tsession *ts;
|
---|
| 490 | #if ENABLE_FEATURE_TELNETD_STANDALONE
|
---|
| 491 | #define IS_INETD (opt & OPT_INETD)
|
---|
[2725] | 492 | int master_fd = master_fd; /* for compiler */
|
---|
| 493 | int sec_linger = sec_linger;
|
---|
[1765] | 494 | char *opt_bindaddr = NULL;
|
---|
| 495 | char *opt_portnbr;
|
---|
| 496 | #else
|
---|
| 497 | enum {
|
---|
| 498 | IS_INETD = 1,
|
---|
| 499 | master_fd = -1,
|
---|
| 500 | };
|
---|
| 501 | #endif
|
---|
[2725] | 502 | INIT_G();
|
---|
[821] | 503 |
|
---|
[2725] | 504 | /* -w NUM, and implies -F. -w and -i don't mix */
|
---|
| 505 | IF_FEATURE_TELNETD_INETD_WAIT(opt_complementary = "wF:w+:i--w:w--i";)
|
---|
| 506 | /* Even if !STANDALONE, we accept (and ignore) -i, thus people
|
---|
| 507 | * don't need to guess whether it's ok to pass -i to us */
|
---|
| 508 | opt = getopt32(argv, "f:l:Ki"
|
---|
| 509 | IF_FEATURE_TELNETD_STANDALONE("p:b:F")
|
---|
| 510 | IF_FEATURE_TELNETD_INETD_WAIT("Sw:"),
|
---|
| 511 | &G.issuefile, &G.loginpath
|
---|
| 512 | IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr)
|
---|
| 513 | IF_FEATURE_TELNETD_INETD_WAIT(, &sec_linger)
|
---|
| 514 | );
|
---|
| 515 | if (!IS_INETD /*&& !re_execed*/) {
|
---|
| 516 | /* inform that we start in standalone mode?
|
---|
| 517 | * May be useful when people forget to give -i */
|
---|
| 518 | /*bb_error_msg("listening for connections");*/
|
---|
| 519 | if (!(opt & OPT_FOREGROUND)) {
|
---|
| 520 | /* DAEMON_CHDIR_ROOT was giving inconsistent
|
---|
| 521 | * behavior with/without -F, -i */
|
---|
| 522 | bb_daemonize_or_rexec(0 /*was DAEMON_CHDIR_ROOT*/, argv);
|
---|
| 523 | }
|
---|
| 524 | }
|
---|
[1765] | 525 | /* Redirect log to syslog early, if needed */
|
---|
[2725] | 526 | if (IS_INETD || (opt & OPT_SYSLOG) || !(opt & OPT_FOREGROUND)) {
|
---|
| 527 | openlog(applet_name, LOG_PID, LOG_DAEMON);
|
---|
[1765] | 528 | logmode = LOGMODE_SYSLOG;
|
---|
| 529 | }
|
---|
| 530 | #if ENABLE_FEATURE_TELNETD_STANDALONE
|
---|
| 531 | if (IS_INETD) {
|
---|
[2725] | 532 | G.sessions = make_new_session(0);
|
---|
| 533 | if (!G.sessions) /* pty opening or vfork problem, exit */
|
---|
| 534 | return 1; /* make_new_session printed error message */
|
---|
[1765] | 535 | } else {
|
---|
[2725] | 536 | master_fd = 0;
|
---|
| 537 | if (!(opt & OPT_WAIT)) {
|
---|
| 538 | unsigned portnbr = 23;
|
---|
| 539 | if (opt & OPT_PORT)
|
---|
| 540 | portnbr = xatou16(opt_portnbr);
|
---|
| 541 | master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr);
|
---|
| 542 | xlisten(master_fd, 1);
|
---|
| 543 | }
|
---|
| 544 | close_on_exec_on(master_fd);
|
---|
[1765] | 545 | }
|
---|
[821] | 546 | #else
|
---|
[2725] | 547 | G.sessions = make_new_session();
|
---|
| 548 | if (!G.sessions) /* pty opening or vfork problem, exit */
|
---|
| 549 | return 1; /* make_new_session printed error message */
|
---|
[821] | 550 | #endif
|
---|
| 551 |
|
---|
[1765] | 552 | /* We don't want to die if just one session is broken */
|
---|
| 553 | signal(SIGPIPE, SIG_IGN);
|
---|
[821] | 554 |
|
---|
[2725] | 555 | if (opt & OPT_WATCHCHILD)
|
---|
| 556 | signal(SIGCHLD, handle_sigchld);
|
---|
| 557 | else /* prevent dead children from becoming zombies */
|
---|
| 558 | signal(SIGCHLD, SIG_IGN);
|
---|
| 559 |
|
---|
| 560 | /*
|
---|
| 561 | This is how the buffers are used. The arrows indicate data flow.
|
---|
| 562 |
|
---|
| 563 | +-------+ wridx1++ +------+ rdidx1++ +----------+
|
---|
| 564 | | | <-------------- | buf1 | <-------------- | |
|
---|
| 565 | | | size1-- +------+ size1++ | |
|
---|
| 566 | | pty | | socket |
|
---|
| 567 | | | rdidx2++ +------+ wridx2++ | |
|
---|
| 568 | | | --------------> | buf2 | --------------> | |
|
---|
| 569 | +-------+ size2++ +------+ size2-- +----------+
|
---|
| 570 |
|
---|
| 571 | size1: "how many bytes are buffered for pty between rdidx1 and wridx1?"
|
---|
| 572 | size2: "how many bytes are buffered for socket between rdidx2 and wridx2?"
|
---|
| 573 |
|
---|
| 574 | Each session has got two buffers. Buffers are circular. If sizeN == 0,
|
---|
| 575 | buffer is empty. If sizeN == BUFSIZE, buffer is full. In both these cases
|
---|
| 576 | rdidxN == wridxN.
|
---|
| 577 | */
|
---|
[1765] | 578 | again:
|
---|
| 579 | FD_ZERO(&rdfdset);
|
---|
| 580 | FD_ZERO(&wrfdset);
|
---|
[2725] | 581 |
|
---|
| 582 | /* Select on the master socket, all telnet sockets and their
|
---|
| 583 | * ptys if there is room in their session buffers.
|
---|
| 584 | * NB: scalability problem: we recalculate entire bitmap
|
---|
| 585 | * before each select. Can be a problem with 500+ connections. */
|
---|
| 586 | ts = G.sessions;
|
---|
| 587 | while (ts) {
|
---|
| 588 | struct tsession *next = ts->next; /* in case we free ts */
|
---|
| 589 | if (ts->shell_pid == -1) {
|
---|
| 590 | /* Child died and we detected that */
|
---|
| 591 | free_session(ts);
|
---|
| 592 | } else {
|
---|
| 593 | if (ts->size1 > 0) /* can write to pty */
|
---|
| 594 | FD_SET(ts->ptyfd, &wrfdset);
|
---|
| 595 | if (ts->size1 < BUFSIZE) /* can read from socket */
|
---|
| 596 | FD_SET(ts->sockfd_read, &rdfdset);
|
---|
| 597 | if (ts->size2 > 0) /* can write to socket */
|
---|
| 598 | FD_SET(ts->sockfd_write, &wrfdset);
|
---|
| 599 | if (ts->size2 < BUFSIZE) /* can read from pty */
|
---|
| 600 | FD_SET(ts->ptyfd, &rdfdset);
|
---|
| 601 | }
|
---|
| 602 | ts = next;
|
---|
| 603 | }
|
---|
[1765] | 604 | if (!IS_INETD) {
|
---|
| 605 | FD_SET(master_fd, &rdfdset);
|
---|
| 606 | /* This is needed because free_session() does not
|
---|
[2725] | 607 | * take master_fd into account when it finds new
|
---|
| 608 | * maxfd among remaining fd's */
|
---|
| 609 | if (master_fd > G.maxfd)
|
---|
| 610 | G.maxfd = master_fd;
|
---|
[1765] | 611 | }
|
---|
[821] | 612 |
|
---|
[2725] | 613 | {
|
---|
| 614 | struct timeval *tv_ptr = NULL;
|
---|
| 615 | #if ENABLE_FEATURE_TELNETD_INETD_WAIT
|
---|
| 616 | struct timeval tv;
|
---|
| 617 | if ((opt & OPT_WAIT) && !G.sessions) {
|
---|
| 618 | tv.tv_sec = sec_linger;
|
---|
| 619 | tv.tv_usec = 0;
|
---|
| 620 | tv_ptr = &tv;
|
---|
| 621 | }
|
---|
| 622 | #endif
|
---|
| 623 | count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, tv_ptr);
|
---|
[1765] | 624 | }
|
---|
[2725] | 625 | if (count == 0) /* "telnetd -w SEC" timed out */
|
---|
[1765] | 626 | return 0;
|
---|
[2725] | 627 | if (count < 0)
|
---|
| 628 | goto again; /* EINTR or ENOMEM */
|
---|
[821] | 629 |
|
---|
[1765] | 630 | #if ENABLE_FEATURE_TELNETD_STANDALONE
|
---|
[2725] | 631 | /* Check for and accept new sessions */
|
---|
[1765] | 632 | if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) {
|
---|
| 633 | int fd;
|
---|
| 634 | struct tsession *new_ts;
|
---|
[821] | 635 |
|
---|
[2725] | 636 | fd = accept(master_fd, NULL, NULL);
|
---|
[1765] | 637 | if (fd < 0)
|
---|
| 638 | goto again;
|
---|
[2725] | 639 | close_on_exec_on(fd);
|
---|
| 640 |
|
---|
| 641 | /* Create a new session and link it into active list */
|
---|
| 642 | new_ts = make_new_session(fd);
|
---|
[1765] | 643 | if (new_ts) {
|
---|
[2725] | 644 | new_ts->next = G.sessions;
|
---|
| 645 | G.sessions = new_ts;
|
---|
[1765] | 646 | } else {
|
---|
| 647 | close(fd);
|
---|
[821] | 648 | }
|
---|
[1765] | 649 | }
|
---|
| 650 | #endif
|
---|
[821] | 651 |
|
---|
[2725] | 652 | /* Then check for data tunneling */
|
---|
| 653 | ts = G.sessions;
|
---|
[1765] | 654 | while (ts) { /* For all sessions... */
|
---|
[2725] | 655 | struct tsession *next = ts->next; /* in case we free ts */
|
---|
[821] | 656 |
|
---|
[2725] | 657 | if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) {
|
---|
[1765] | 658 | int num_totty;
|
---|
[2725] | 659 | unsigned char *ptr;
|
---|
| 660 | /* Write to pty from buffer 1 */
|
---|
[1765] | 661 | ptr = remove_iacs(ts, &num_totty);
|
---|
[2725] | 662 | count = safe_write(ts->ptyfd, ptr, num_totty);
|
---|
| 663 | if (count < 0) {
|
---|
| 664 | if (errno == EAGAIN)
|
---|
| 665 | goto skip1;
|
---|
| 666 | goto kill_session;
|
---|
[821] | 667 | }
|
---|
[2725] | 668 | ts->size1 -= count;
|
---|
| 669 | ts->wridx1 += count;
|
---|
| 670 | if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */
|
---|
[1765] | 671 | ts->wridx1 = 0;
|
---|
[821] | 672 | }
|
---|
[2725] | 673 | skip1:
|
---|
| 674 | if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) {
|
---|
| 675 | /* Write to socket from buffer 2 */
|
---|
| 676 | count = MIN(BUFSIZE - ts->wridx2, ts->size2);
|
---|
| 677 | count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count);
|
---|
| 678 | if (count < 0) {
|
---|
| 679 | if (errno == EAGAIN)
|
---|
| 680 | goto skip2;
|
---|
| 681 | goto kill_session;
|
---|
[821] | 682 | }
|
---|
[2725] | 683 | ts->size2 -= count;
|
---|
| 684 | ts->wridx2 += count;
|
---|
| 685 | if (ts->wridx2 >= BUFSIZE) /* actually == BUFSIZE */
|
---|
[1765] | 686 | ts->wridx2 = 0;
|
---|
| 687 | }
|
---|
[2725] | 688 | skip2:
|
---|
| 689 | /* Should not be needed, but... remove_iacs is actually buggy
|
---|
| 690 | * (it cannot process iacs which wrap around buffer's end)!
|
---|
| 691 | * Since properly fixing it requires writing bigger code,
|
---|
| 692 | * we rely instead on this code making it virtually impossible
|
---|
| 693 | * to have wrapped iac (people don't type at 2k/second).
|
---|
| 694 | * It also allows for bigger reads in common case. */
|
---|
[1765] | 695 | if (ts->size1 == 0) {
|
---|
| 696 | ts->rdidx1 = 0;
|
---|
| 697 | ts->wridx1 = 0;
|
---|
| 698 | }
|
---|
| 699 | if (ts->size2 == 0) {
|
---|
| 700 | ts->rdidx2 = 0;
|
---|
| 701 | ts->wridx2 = 0;
|
---|
| 702 | }
|
---|
[2725] | 703 |
|
---|
| 704 | if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) {
|
---|
| 705 | /* Read from socket to buffer 1 */
|
---|
| 706 | count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1);
|
---|
| 707 | count = safe_read(ts->sockfd_read, TS_BUF1(ts) + ts->rdidx1, count);
|
---|
| 708 | if (count <= 0) {
|
---|
| 709 | if (count < 0 && errno == EAGAIN)
|
---|
| 710 | goto skip3;
|
---|
| 711 | goto kill_session;
|
---|
| 712 | }
|
---|
| 713 | /* Ignore trailing NUL if it is there */
|
---|
| 714 | if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) {
|
---|
| 715 | --count;
|
---|
| 716 | }
|
---|
| 717 | ts->size1 += count;
|
---|
| 718 | ts->rdidx1 += count;
|
---|
| 719 | if (ts->rdidx1 >= BUFSIZE) /* actually == BUFSIZE */
|
---|
| 720 | ts->rdidx1 = 0;
|
---|
| 721 | }
|
---|
| 722 | skip3:
|
---|
| 723 | if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
|
---|
| 724 | /* Read from pty to buffer 2 */
|
---|
| 725 | count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
|
---|
| 726 | count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
|
---|
| 727 | if (count <= 0) {
|
---|
| 728 | if (count < 0 && errno == EAGAIN)
|
---|
| 729 | goto skip4;
|
---|
| 730 | goto kill_session;
|
---|
| 731 | }
|
---|
| 732 | ts->size2 += count;
|
---|
| 733 | ts->rdidx2 += count;
|
---|
| 734 | if (ts->rdidx2 >= BUFSIZE) /* actually == BUFSIZE */
|
---|
| 735 | ts->rdidx2 = 0;
|
---|
| 736 | }
|
---|
| 737 | skip4:
|
---|
[1765] | 738 | ts = next;
|
---|
[2725] | 739 | continue;
|
---|
| 740 | kill_session:
|
---|
| 741 | if (ts->shell_pid > 0)
|
---|
| 742 | update_utmp(ts->shell_pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL);
|
---|
| 743 | free_session(ts);
|
---|
| 744 | ts = next;
|
---|
[1765] | 745 | }
|
---|
[2725] | 746 |
|
---|
[1765] | 747 | goto again;
|
---|
[821] | 748 | }
|
---|