Nuno Carvalho <[EMAIL PROTECTED]> writes: > Hi, > > I'm trying to, using socket programming, ask the remote user for login > and password. I would like that password won't appears on remote machine > when user is typing it. I already saw RFC's but it doesn't worked ! :((( > > Could someone send me such part of code !? > Should IAC + DONT + TELOPT_ECHO sent to socket or client descriptor !?
You're misunderstanding the RFCs. In terms of telnet options, the "ECHO" refers to whether the local or remote end of the connection should handle echoing the characters back to the user. The way telnet does what it does is by having the server send "IAC WILL ECHO" and then having the server only echo those characters that should be echoed. I have attached below a transcript of a simple telnet session to show you what's going on. You may also need to send the telnet option that means "one character at a time" transmission and not "line-by-line" mode. I'm not quite certain how to do this; I believe it has something to do with manipulating the "go-ahead" option, and supressing it. I'd try to do the following: Server> IAC WILL SUPRESS-GO-AHEAD Client> IAC DO SUPRESS-GO-AHEAD Server> <present login prompt> Client> <send username> Server> IAC WILL ECHO Client> IAC DO ECHO Server> <present password prompt> Client> <send password> Server> IAC WONT ECHO I'm not certain what you should get if the client isn't willing to do the supress-go-ahead stuff; if the client responds with a "don't echo", then there's really no way to prevent the password from being displayed. Looking at your mail again, it appears that you are writing both the client and the server part of this application - if so, then you shouldn't be touching telnet options at all - you should only deal with the telnet options if you expect people to be using telnet to connect to your server. If you are writing the client as well as the server, look at the getpass function that someone else mentioned, or look at the termios(3) manpage for how to turn terminal echoing off. Here's the transcript of a telnet session to my machine - the CLIENT or SERVER refers to the machine which sent each bunch of data. Note that this transcript is complicated by many other options, but I think that only the echo and supress-go-ahead options are relevant. (These begin around record number 5, below). Record number 1 (SERVER), length 12 FFFD18FF FD20FFFD 23FFFD27 xxxxxxxx .ý..ý .ý#.ý' 000001 Record number 2 (CLIENT), length 12 FFFB18FF FB20FFFC 23FFFB27 xxxxxxxx .û..û .ü#.û' 000001 Record number 3 (SERVER), length 18 FFFA2001 FFF0FFFA 2701FFF0 FFFA1801 .ú ..ð.ú'..ð.ú.. 000001 FFF0xxxx xxxxxxxx xxxxxxxx xxxxxxxx .ð 000002 Record number 4 (CLIENT), length 38 FFFA2000 33383430 302C3338 343030FF .ú .38400,38400. 000001 F0FFFA27 00FFF0FF FA180068 79706572 ð.ú'..ð.ú..hyper 000002 7465726D FFF0xxxx xxxxxxxx xxxxxxxx term.ð 000003 Record number 5 (SERVER), length 15 FFFB03FF FD01FFFD 1FFFFB05 FFFD21xx .û..ý..ý..û..ý! 000001 Record number 6 (CLIENT), length 24 FFFD03FF FC01FFFB 1FFFFA1F 00500018 .ý..ü..û..ú..P.. 000001 FFF0FFFD 05FFFB21 xxxxxxxx xxxxxxxx .ð.ý..û! 000002 Record number 7 (SERVER), length 43 FFFB0144 65626961 6E20474E 552F4C69 .û.Debian GNU/Li 000001 6E757820 736C696E 6B206375 73682E64 nux slink cush.d 000002 796E2E6D 6C2E6F72 670D0Axx xxxxxxxx yn.ml.org.. 000003 Record number 8 (CLIENT), length 3 FFFD01xx xxxxxxxx xxxxxxxx xxxxxxxx .ý. 000001 Record number 9 (SERVER), length 14 0D0A6375 7368206C 6F67696E 3A20xxxx ..cush login: 000001 Record number 10 (CLIENT), length 1 75xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx u 000001 Record number 11 (SERVER), length 1 75xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx u 000001 Record number 12 (CLIENT), length 1 73xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx s 000001 Record number 13 (SERVER), length 1 73xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx s 000001 Record number 14 (CLIENT), length 1 65xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx e 000001 Record number 15 (SERVER), length 1 65xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx e 000001 Record number 16 (CLIENT), length 1 72xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx r 000001 Record number 17 (SERVER), length 1 72xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx r 000001 Record number 18 (CLIENT), length 1 6Exxxxxx xxxxxxxx xxxxxxxx xxxxxxxx n 000001 Record number 19 (SERVER), length 1 6Exxxxxx xxxxxxxx xxxxxxxx xxxxxxxx n 000001 Record number 20 (CLIENT), length 1 61xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx a 000001 Record number 21 (SERVER), length 1 61xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx a 000001 Record number 22 (CLIENT), length 1 6Dxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx m 000001 Record number 23 (SERVER), length 1 6Dxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx m 000001 Record number 24 (CLIENT), length 1 65xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx e 000001 Record number 25 (SERVER), length 1 65xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx e 000001 Record number 26 (CLIENT), length 2 0D00xxxx xxxxxxxx xxxxxxxx xxxxxxxx .. 000001 Record number 27 (SERVER), length 12 0D0A5061 7373776F 72643A20 xxxxxxxx ..Password: 000001 Record number 28 (CLIENT), length 10 70617373 776F7264 0D00xxxx xxxxxxxx password.. 000001 Record number 29 (SERVER), length 33 0D0A4C6F 67696E20 696E636F 72726563 ..Login incorrec 000001 740D0A0D 0A637573 68206C6F 67696E3A t....cush login: 000002 20xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx 000003 Record number 30 (CLIENT), length 1 04xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx . 000001 *** Disconnect ***
