diff options
Diffstat (limited to 'networking')
| -rw-r--r-- | networking/telnetd.c | 49 |
1 files changed, 35 insertions, 14 deletions
diff --git a/networking/telnetd.c b/networking/telnetd.c index 68fccdc..fa618a9 100644 --- a/networking/telnetd.c +++ b/networking/telnetd.c @@ -125,48 +125,67 @@ safe_write_to_pty_decode_iac(struct tsession *ts) rc = safe_write(ts->ptyfd, buf, rc); if (rc <= 0) return rc; - if (rc < wr && (buf[rc] == '\n' || buf[rc] == '\0')) + if (rc < wr /* don't look past available data */ + && buf[rc-1] == '\r' /* need this: imagine that write was _short_ */ + && (buf[rc] == '\n' || buf[rc] == '\0') + ) { rc++; - + } goto update_and_return; } /* buf starts with IAC char. Process that sequence. * Example: we get this from our own (bbox) telnet client: - * read(5, "\377\374\1""\377\373\37""\377\372\37\0\262\0@\377\360""\377\375\1""\377\375\3") = 21 + * read(5, "\377\374\1""\377\373\37""\377\372\37\0\262\0@\377\360""\377\375\1""\377\375\3"): + * IAC WONT ECHO, IAC WILL NAWS, IAC SB NAWS <cols> <rows> IAC SE, IAC DO SGA */ if (wr <= 1) { - /* Only the beginning of the IAC is in the - * buffer we were asked to process, we can't - * process this char */ +/* BUG: only the single IAC byte is in the buffer, we just eat IAC */ rc = 1; goto update_and_return; } - if (buf[1] == IAC) { /* Literal IAC (emacs M-DEL) */ + /* 2-byte commands (240..250 and 255): + * IAC IAC (255) Literal 255. Supported. + * IAC NOP (241) NOP. Supported. + * IAC BRK (243) Break. Like serial line break. TODO via tcsendbreak()? + * IAC AYT (246) Are you there. Send back evidence that AYT was seen. TODO (send NOP back)? + * Implemented only as part of NAWS: + * IAC SB (250) Subnegotiation of an option follows. + * IAC SE (240) End of subnegotiation. + * These don't look useful: + * IAC DM (242) Data mark. What is this? + * IAC IP (244) Suspend, interrupt or abort the process. (Ancient cousin of ^C). + * IAC AO (245) Abort output. "You can continue running, but do not send me the output". + * IAC EC (247) Erase character. The receiver should delete the last received char. + * IAC EL (248) Erase line. The receiver should delete everything up tp last newline. + * IAC GA (249) Go ahead. For half-duplex lines: "now you talk". + */ + if (buf[1] == IAC) { /* Literal 255 (emacs M-DEL) */ rc = safe_write(ts->ptyfd, buf, 1); if (rc <= 0) return rc; rc = 2; goto update_and_return; } - - if (buf[1] == NOP) { /* NOP. Ignore (putty keepalive, etc) */ + if (buf[1] == NOP) { /* NOP (241). Ignore (putty keepalive, etc) */ rc = 2; goto update_and_return; } if (wr <= 2) { +/* BUG: only 2 bytes of the IAC is in the buffer, we just eat them */ rc = 2; goto update_and_return; } /* TELOPT_NAWS support */ - /* IAC, SB, TELOPT_NAWS, 4-byte, IAC, SE */ + /* IAC SB, TELOPT_NAWS, 4-byte, IAC SE */ if (buf[1] == SB && buf[2] == TELOPT_NAWS) { struct winsize ws; if (wr <= 8) { - rc = wr; /* incomplete, can't process */ +/* BUG: incomplete, can't process */ + rc = wr; goto update_and_return; } memset(&ws, 0, sizeof(ws)); @@ -176,7 +195,8 @@ safe_write_to_pty_decode_iac(struct tsession *ts) rc = 9; goto update_and_return; } - /* Skip 3-byte IAC non-SB cmds */ + + /* Skip 3-byte cmds (assume they are WILL/WONT/DO/DONT 251..254 codes) */ #if DEBUG fprintf(stderr, "Ignoring IAC %s,%s\n", TELCMD(buf[1]), TELOPT(buf[2])); @@ -189,10 +209,10 @@ safe_write_to_pty_decode_iac(struct tsession *ts) ts->wridx1 = 0; ts->size1 -= rc; /* - * Hack. We cannot process iacs which wrap around buffer's end. + * Hack. We cannot process IACs which wrap around buffer's end. * Since properly fixing it requires writing bigger code, * we rely instead on this code making it virtually impossible - * to have wrapped iac (people don't type at 2k/second). + * to have wrapped IAC (people don't type at 2k/second). * It also allows for bigger reads in common case. */ if (ts->size1 == 0) { /* very typical */ @@ -229,6 +249,7 @@ static size_t safe_write_double_iac(int fd, const char *buf, size_t count) if (*buf == (char)IAC) { static const char IACIAC[] ALIGN1 = { IAC, IAC }; rc = safe_write(fd, IACIAC, 2); +/* BUG: if partial write was only 1 byte long, we end up emitting just one IAC */ if (rc != 2) break; buf++; |