b6d421b63
Denys Vlasenko
2016-10-12
Subject
telnetd: treat all 2-byte IACs in 240..249 range as NOPs.
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networking/telnetd.c+24 -18
| @@ -169,12 +169,10 @@ safe_write_to_pty_decode_iac(struct tsession *ts) | |
| handle_iac: | |
| /* 2-byte commands (240..250 and 255): | |
| * IAC IAC (255) Literal 255. Supported. | |
| + | * IAC SE (240) End of subnegotiation. Treated as NOP. |
| * 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). | |
| @@ -182,8 +180,11 @@ safe_write_to_pty_decode_iac(struct tsession *ts) | |
| * 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". | |
| + | * Implemented only as part of NAWS: |
| + | * IAC SB (250) Subnegotiation of an option follows. |
| */ | |
| - | if (buf[1] == IAC) { /* Literal 255 (emacs M-DEL) */ |
| + | if (buf[1] == IAC) { |
| + | /* Literal 255 (emacs M-DEL) */ |
| //bb_error_msg("255!"); | |
| rc = safe_write(ts->ptyfd, &buf[1], 1); | |
| if (rc <= 0) | |
| @@ -191,7 +192,9 @@ safe_write_to_pty_decode_iac(struct tsession *ts) | |
| rc = 2; | |
| goto update_and_return; | |
| } | |
| - | if (buf[1] == NOP) { /* NOP (241). Ignore (putty keepalive, etc) */ |
| + | if (buf[1] >= 240 && buf[1] <= 249) { |
| + | /* NOP (241). Ignore (putty keepalive, etc) */ |
| + | /* All other 2-byte commands also treated as NOPs here */ |
| rc = 2; | |
| goto update_and_return; | |
| } | |
| @@ -205,24 +208,27 @@ safe_write_to_pty_decode_iac(struct tsession *ts) | |
| goto update_and_return; | |
| } | |
| - | /* TELOPT_NAWS support */ |
| - | /* IAC SB, TELOPT_NAWS, 4-byte, IAC SE */ |
| - | if (buf[1] == SB && buf[2] == TELOPT_NAWS) { |
| - | struct winsize ws; |
| - | if (wr <= 8) { |
| + | if (buf[1] == SB) { |
| + | if (buf[2] == TELOPT_NAWS) { |
| + | /* IAC SB, TELOPT_NAWS, 4-byte, IAC SE */ |
| + | struct winsize ws; |
| + | if (wr <= 6) { |
| /* BUG: incomplete, can't process */ | |
| - | rc = wr; |
| + | rc = wr; |
| + | goto update_and_return; |
| + | } |
| + | memset(&ws, 0, sizeof(ws)); /* pixel sizes are set to 0 */ |
| + | ws.ws_col = (buf[3] << 8) | buf[4]; |
| + | ws.ws_row = (buf[5] << 8) | buf[6]; |
| + | ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); |
| + | rc = 7; |
| + | /* trailing IAC SE will be eaten separately, as 2-byte NOP */ |
| goto update_and_return; | |
| } | |
| - | memset(&ws, 0, sizeof(ws)); |
| - | ws.ws_col = (buf[3] << 8) | buf[4]; |
| - | ws.ws_row = (buf[5] << 8) | buf[6]; |
| - | ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); |
| - | rc = 9; |
| - | goto update_and_return; |
| + | /* else: other subnegs not supported yet */ |
| } | |
| - | /* Skip 3-byte cmds (assume they are WILL/WONT/DO/DONT 251..254 codes) */ |
| + | /* Assume it is a 3-byte WILL/WONT/DO/DONT 251..254 command and skip it */ |
| #if DEBUG | |
| fprintf(stderr, "Ignoring IAC %s,%s\n", | |
| TELCMD(buf[1]), TELOPT(buf[2])); | |