- isolate telnet protocol. moved from mbbsd.c

git-svn-id: http://opensvn.csie.org/pttbbs/trunk/pttbbs@3679 63ad8ddf-47c3-0310-b6dd-a9e9d9715204

1 files changed, 327 insertions, 0 deletions

diff --git a/mbbsd/telnet.c b/mbbsd/telnet.c
new file mode 100644
index 00000000..aa985471
--- /dev/null
+++ b/mbbsd/telnet.c
@@ -0,0 +1,327 @@
+/*
+ * piaip's simplified implementation of TELNET protocol
+ */
+#ifdef DEBUG
+#define TELOPTS
+#define TELCMDS
+#endif
+
+#include "bbs.h"
+
+#ifdef DETECT_CLIENT
+void UpdateClientCode(unsigned char c); // see mbbsd.c
+#endif
+
+unsigned int telnet_handler(unsigned char c) ;
+void	telnet_init(void);
+ssize_t tty_read(unsigned char *buf, size_t max);
+
+enum TELNET_IAC_STATES {
+	IAC_NONE,
+	IAC_COMMAND,
+	IAC_WAIT_OPT,
+	IAC_WAIT_SE,
+	IAC_PROCESS_OPT,
+	IAC_ERROR
+};
+
+static unsigned char iac_state = 0; /* as byte to reduce memory */
+
+#define TELNET_IAC_MAXLEN (16)
+/* We don't reply to most commands, so this maxlen can be minimal.
+ * Warning: if you want to support ENV passing or other long commands,
+ * remember to increase this value. Howver, some poorly implemented
+ * terminals like xxMan may not follow the protocols and user will hang
+ * on those terminals when IACs were sent.
+ */
+
+void
+telnet_init(void)
+{
+    /* We are the boss. We don't respect to client.
+     * It's client's responsibility to follow us.
+     * Please write these codes in i-dont-care opt handlers.
+     */
+    const char telnet_init_cmds[] = {
+	/* retrieve terminal type and throw away.
+	 * why? because without this, clients enter line mode.
+	 */
+	IAC, DO, TELOPT_TTYPE,
+	IAC, SB, TELOPT_TTYPE, TELQUAL_SEND, IAC, SE,
+
+	/* i'm a smart term with resize ability. */
+	IAC, DO, TELOPT_NAWS,
+
+	/* i will echo. */
+	IAC, WILL, TELOPT_ECHO,
+	/* supress ga. */
+	IAC, WILL, TELOPT_SGA,
+	/* 8 bit binary. */
+	IAC, WILL, TELOPT_BINARY,
+	IAC, DO,   TELOPT_BINARY,
+    };
+
+    raw_connection = 1;
+    write(0, telnet_init_cmds, sizeof(telnet_init_cmds));
+}
+
+/* tty_read
+ * read from tty, process telnet commands if raw connection.
+ * return: >0 = length, <=0 means read more, abort/eof is automatically processed.
+ */
+ssize_t
+tty_read(unsigned char *buf, size_t max)
+{
+    ssize_t l = read(0, buf, max);
+
+    if(l == 0 || (l < 0 && !(errno == EINTR || errno == EAGAIN)))
+	abort_bbs(0);
+
+    if(!raw_connection)
+	return l;
+
+    /* process buffer */
+    if (l > 0) {
+	unsigned char *buf2 = buf;
+	size_t i = 0, i2 = 0;
+
+	/* prescan. because IAC is rare, 
+	 * this cost is worthy. */
+	if (iac_state == IAC_NONE && memchr(buf, IAC, l) == NULL)
+	    return l;
+
+	/* we have to look into the buffer. */
+	for (i = 0; i < l; i++, buf++)
+	    if(telnet_handler(*buf) == 0)
+		*(buf2++) = *buf;
+	    else
+		i2 ++;
+	l = (i2 == l) ? -1L : l - i2;
+    }
+    return l;
+}
+
+/* input:  raw character
+ * output: telnet command if c was handled, otherwise zero.
+ */
+unsigned int 
+telnet_handler(unsigned char c) 
+{
+    static unsigned char iac_quote = 0; /* as byte to reduce memory */
+    static unsigned char iac_opt_req = 0;
+
+    static unsigned char iac_buf[TELNET_IAC_MAXLEN];
+    static unsigned int  iac_buflen = 0;
+
+    /* we have to quote all IACs. */
+    if(c == IAC && !iac_quote) {
+	iac_quote = 1;
+	return NOP;
+    }
+
+#ifdef DETECT_CLIENT
+    /* hash client telnet sequences */
+    if(cuser.userid[0]==0) {
+	if(iac_state == IAC_WAIT_SE) {
+	    // skip suboption
+	} else {
+	    if(iac_quote)
+		UpdateClientCode(IAC);
+	    UpdateClientCode(c);
+	}
+    }
+#endif
+
+    /* a special case is the top level iac. otherwise, iac is just a quote. */
+    if (iac_quote) {
+	if(iac_state == IAC_NONE)
+	    iac_state = IAC_COMMAND;
+	if(iac_state == IAC_WAIT_SE && c == SE)
+	    iac_state = IAC_PROCESS_OPT;
+	iac_quote = 0;
+    }
+
+    /* now, let's process commands by state */
+    switch(iac_state) {
+
+	case IAC_NONE:
+	    return 0;
+
+	case IAC_COMMAND:
+#if 0 // def DEBUG
+	    {
+		int cx = c; /* to make compiler happy */
+		write(0, "-", 1);
+		if(TELCMD_OK(cx))
+		    write(0, TELCMD(c), strlen(TELCMD(c)));
+		write(0, " ", 1);
+	    }
+#endif
+	    iac_state = IAC_NONE; /* by default we restore state. */
+	    switch(c) {
+		case IAC:
+		    return 0;
+
+		/* we don't want to process these. or maybe in future. */
+		case BREAK:           /* break */
+		case ABORT:           /* Abort process */
+		case SUSP:            /* Suspend process */
+		case AO:              /* abort output--but let prog finish */
+		case IP:              /* interrupt process--permanently */
+		case EOR:             /* end of record (transparent mode) */
+		case DM:              /* data mark--for connect. cleaning */
+		case xEOF:            /* End of file: EOF is already used... */
+		    return NOP;
+
+		case NOP:             /* nop */
+		    return NOP;
+
+		/* we should process these, but maybe in future. */
+		case GA:              /* you may reverse the line */
+		case EL:              /* erase the current line */
+		case EC:              /* erase the current character */
+		    return NOP;
+
+		/* good */
+		case AYT:             /* are you there */
+		    {
+			    const char *alive = "I'm still alive, loading: ";
+			    char buf[STRLEN];
+
+			    /* respond as fast as we can */
+			    write(0, alive, strlen(alive));
+			    cpuload(buf);
+			    write(0, buf, strlen(buf));
+			    write(0, "\r\n", 2);
+		    }
+		    return NOP;
+
+		case DONT:            /* you are not to use option */
+		case DO:              /* please, you use option */
+		case WONT:            /* I won't use option */
+		case WILL:            /* I will use option */
+		    iac_opt_req = c;
+		    iac_state = IAC_WAIT_OPT;
+		    return NOP;
+
+		case SB:              /* interpret as subnegotiation */
+		    iac_state = IAC_WAIT_SE;
+		    iac_buflen = 0;
+		    return NOP;
+
+		case SE:              /* end sub negotiation */
+		default:
+		    return NOP;
+	    }
+	    return 1;
+
+	case IAC_WAIT_OPT:
+#if 0 // def DEBUG
+	    write(0, "-", 1);
+	    if(TELOPT_OK(c))
+		write(0, TELOPT(c), strlen(TELOPT(c)));
+	    write(0, " ", 1);
+#endif
+	    iac_state = IAC_NONE;
+	    /*
+	     * According to RFC, there're some tricky steps to prevent loop.
+	     * However because we have a poor term which does not allow 
+	     * most abilities, let's be a strong boss here.
+	     *
+	     * Although my old imeplementation worked, it's even better to follow this:
+	     * http://www.tcpipguide.com/free/t_TelnetOptionsandOptionNegotiation-3.htm
+	     */
+	    switch(c) {
+		/* i-dont-care: i don't care about what client is. 
+		 * these should be clamed in init and
+		 * client must follow me. */
+		case TELOPT_TTYPE:	/* termtype or line. */
+		case TELOPT_NAWS:       /* resize terminal */
+		case TELOPT_SGA:	/* supress GA */
+		case TELOPT_ECHO:       /* echo */
+		case TELOPT_BINARY:	/* we are CJK. */
+		    break;
+
+		/* i-dont-agree: i don't understand/agree these.
+		 * according to RFC, saying NO stopped further
+		 * requests so there'll not be endless loop. */
+		case TELOPT_RCP:         /* prepare to reconnect */
+		default:
+		    if (iac_opt_req == WILL || iac_opt_req == DO)
+		    {
+			/* unknown option, reply with won't */
+			unsigned char cmd[3] = { IAC, DONT, 0 };
+			if(iac_opt_req == DO) cmd[1] = WONT;
+			cmd[2] = c;
+			write(0, cmd, sizeof(cmd));
+		    }
+		    break;
+	    }
+	    return 1;
+
+	case IAC_WAIT_SE:
+	    iac_buf[iac_buflen++] = c;
+	    /* no need to convert state because previous quoting will do. */
+		    
+	    if(iac_buflen == TELNET_IAC_MAXLEN) {
+		/* may be broken protocol?
+		 * whether finished or not, break for safety 
+		 * or user may be frozen.
+		 */
+		iac_state = IAC_NONE;
+		return 0;
+	    }
+	    return 1;
+
+	case IAC_PROCESS_OPT:
+	    iac_state = IAC_NONE;
+#if 0 // def DEBUG
+	    write(0, "-", 1);
+	    if(TELOPT_OK(iac_buf[0]))
+		write(0, TELOPT(iac_buf[0]), strlen(TELOPT(iac_buf[0])));
+	    write(0, " ", 1);
+#endif
+	    switch(iac_buf[0]) {
+
+		/* resize terminal */
+		case TELOPT_NAWS:
+		    {
+			int w = (iac_buf[1] << 8) + (iac_buf[2]);
+			int h = (iac_buf[3] << 8) + (iac_buf[4]);
+			term_resize(w, h);
+#ifdef DETECT_CLIENT
+			if(cuser.userid[0]==0) {
+			    UpdateClientCode(iac_buf[0]);
+			    if(w==80 && h==24)
+				UpdateClientCode(1);
+			    else if(w==80)
+				UpdateClientCode(2);
+			    else if(h==24)
+				UpdateClientCode(3);
+			    else
+				UpdateClientCode(4);
+			    UpdateClientCode(IAC);
+			    UpdateClientCode(SE);
+			}
+#endif
+		    }
+		    break;
+
+		default:
+#ifdef DETECT_CLIENT
+		    if(cuser.userid[0]==0) {
+			int i;
+			for(i=0;i<iac_buflen;i++)
+			    UpdateClientCode(iac_buf[i]);
+			UpdateClientCode(IAC);
+			UpdateClientCode(SE);
+		    }
+#endif
+		    break;
+	    }
+	    return 1;
+    }
+    return 1; /* never reached */
+}
+
+// vim: sw=4