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