diff options
| -rw-r--r-- | networking/telnetd.c | 231 |
1 files changed, 120 insertions, 111 deletions
diff --git a/networking/telnetd.c b/networking/telnetd.c index 2fbdc3bb3..68fccdca8 100644 --- a/networking/telnetd.c +++ b/networking/telnetd.c @@ -91,107 +91,133 @@ struct globals { } while (0) -/* - Remove all IAC's from buf1 (received IACs are ignored and must be removed - so as to not be interpreted by the terminal). Make an uninterrupted - string of characters fit for the terminal. Do this by packing - all characters meant for the terminal sequentially towards the end of buf. +/* Write some buf1 data to pty, processing IAC's. + * Update wridx1 and size1. Return < 0 on error. + * Buggy if IAC is present but incomplete: skips them. + */ +static ssize_t +safe_write_to_pty_decode_iac(struct tsession *ts) +{ + unsigned wr; + ssize_t rc; + unsigned char *buf; + unsigned char *found; + + buf = TS_BUF1(ts) + ts->wridx1; + wr = MIN(BUFSIZE - ts->wridx1, ts->size1); + found = memchr(buf, IAC, wr); + if (found != buf) { + /* There is a "prefix" of non-IAC chars. + * Write only them, and return. + */ + if (found) + wr = found - buf; - Return a pointer to the beginning of the characters meant for the terminal - and make *num_totty the number of characters that should be sent to - the terminal. + /* We map \r\n ==> \r for pragmatic reasons: + * many client implementations send \r\n when + * the user hits the CarriageReturn key. + * See RFC 1123 3.3.1 Telnet End-of-Line Convention. + */ + rc = wr; + found = memchr(buf, '\r', wr); + if (found) + rc = found - buf + 1; + rc = safe_write(ts->ptyfd, buf, rc); + if (rc <= 0) + return rc; + if (rc < wr && (buf[rc] == '\n' || buf[rc] == '\0')) + rc++; - Note - if an IAC (3 byte quantity) starts before (bf + len) but extends - past (bf + len) then that IAC will be left unprocessed and *processed - will be less than len. + goto update_and_return; + } - CR-LF ->'s CR mapping is also done here, for convenience. + /* 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 + */ + if (wr <= 1) { + /* Only the beginning of the IAC is in the + * buffer we were asked to process, we can't + * process this char */ + rc = 1; + goto update_and_return; + } - NB: may fail to remove iacs which wrap around buffer! - */ -static unsigned char * -remove_iacs(struct tsession *ts, int *pnum_totty) -{ - unsigned char *ptr0 = TS_BUF1(ts) + ts->wridx1; - unsigned char *ptr = ptr0; - unsigned char *totty = ptr; - unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1); - int num_totty; - - while (ptr < end) { - if (*ptr != IAC) { - char c = *ptr; - - *totty++ = c; - ptr++; - /* We map \r\n ==> \r for pragmatic reasons. - * Many client implementations send \r\n when - * the user hits the CarriageReturn key. - * See RFC 1123 3.3.1 Telnet End-of-Line Convention. - */ - if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0')) - ptr++; - continue; - } + if (buf[1] == IAC) { /* Literal IAC (emacs M-DEL) */ + rc = safe_write(ts->ptyfd, buf, 1); + if (rc <= 0) + return rc; + rc = 2; + goto update_and_return; + } - if ((ptr+1) >= end) - break; - if (ptr[1] == NOP) { /* Ignore? (putty keepalive, etc.) */ - ptr += 2; - continue; - } - if (ptr[1] == IAC) { /* Literal IAC? (emacs M-DEL) */ - *totty++ = ptr[1]; - ptr += 2; - continue; - } + if (buf[1] == NOP) { /* NOP. Ignore (putty keepalive, etc) */ + rc = 2; + goto update_and_return; + } - /* - * TELOPT_NAWS support! - */ - if ((ptr+2) >= end) { - /* Only the beginning of the IAC is in the - buffer we were asked to process, we can't - process this char */ - break; - } - /* - * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE - */ - if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) { - struct winsize ws; - if ((ptr+8) >= end) - break; /* incomplete, can't process */ - ws.ws_col = (ptr[3] << 8) | ptr[4]; - ws.ws_row = (ptr[5] << 8) | ptr[6]; - ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); - ptr += 9; - continue; + if (wr <= 2) { + rc = 2; + 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) { + rc = wr; /* incomplete, can't process */ + goto update_and_return; } - /* skip 3-byte IAC non-SB cmd */ + 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; + } + /* Skip 3-byte IAC non-SB cmds */ #if DEBUG - fprintf(stderr, "Ignoring IAC %s,%s\n", - TELCMD(ptr[1]), TELOPT(ptr[2])); + fprintf(stderr, "Ignoring IAC %s,%s\n", + TELCMD(buf[1]), TELOPT(buf[2])); #endif - ptr += 3; + rc = 3; + + update_and_return: + ts->wridx1 += rc; + if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */ + ts->wridx1 = 0; + ts->size1 -= rc; + /* + * 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). + * It also allows for bigger reads in common case. + */ + if (ts->size1 == 0) { /* very typical */ + //bb_error_msg("zero size1"); + ts->rdidx1 = 0; + ts->wridx1 = 0; + return rc; } - - num_totty = totty - ptr0; - *pnum_totty = num_totty; - /* The difference between ptr and totty is number of iacs - we removed from the stream. Adjust buf1 accordingly */ - if ((ptr - totty) == 0) /* 99.999% of cases */ - return ptr0; - ts->wridx1 += ptr - totty; - ts->size1 -= ptr - totty; - /* Move chars meant for the terminal towards the end of the buffer */ - return memmove(ptr - num_totty, ptr0, num_totty); + wr = ts->wridx1; + if (wr != 0 && wr < ts->rdidx1) { + /* Buffer is not wrapped yet. + * We can easily move it to the beginning. + */ + //bb_error_msg("moved %d", wr); + memmove(TS_BUF1(ts), TS_BUF1(ts) + wr, ts->size1); + ts->rdidx1 -= wr; + ts->wridx1 = 0; + } + return rc; } /* * Converting single IAC into double on output */ -static size_t iac_safe_write(int fd, const char *buf, size_t count) +static size_t safe_write_double_iac(int fd, const char *buf, size_t count) { const char *IACptr; size_t wr, rc, total; @@ -298,7 +324,7 @@ make_new_session( IAC, WILL, TELOPT_ECHO, IAC, WILL, TELOPT_SGA }; - /* This confuses iac_safe_write(), it will try to duplicate + /* This confuses safe_write_double_iac(), it will try to duplicate * each IAC... */ //memcpy(TS_BUF2(ts), iacs_to_send, sizeof(iacs_to_send)); //ts->rdidx2 = sizeof(iacs_to_send); @@ -649,51 +675,34 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv) struct tsession *next = ts->next; /* in case we free ts */ if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) { - int num_totty; - unsigned char *ptr; /* Write to pty from buffer 1 */ - ptr = remove_iacs(ts, &num_totty); - count = safe_write(ts->ptyfd, ptr, num_totty); + count = safe_write_to_pty_decode_iac(ts); if (count < 0) { if (errno == EAGAIN) goto skip1; goto kill_session; } - ts->size1 -= count; - ts->wridx1 += count; - if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */ - ts->wridx1 = 0; } skip1: if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) { /* Write to socket from buffer 2 */ count = MIN(BUFSIZE - ts->wridx2, ts->size2); - count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count); + count = safe_write_double_iac(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count); if (count < 0) { if (errno == EAGAIN) goto skip2; goto kill_session; } - ts->size2 -= count; ts->wridx2 += count; if (ts->wridx2 >= BUFSIZE) /* actually == BUFSIZE */ ts->wridx2 = 0; + ts->size2 -= count; + if (ts->size2 == 0) { + ts->rdidx2 = 0; + ts->wridx2 = 0; + } } skip2: - /* Should not be needed, but... remove_iacs is actually buggy - * (it 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). - * It also allows for bigger reads in common case. */ - if (ts->size1 == 0) { - ts->rdidx1 = 0; - ts->wridx1 = 0; - } - if (ts->size2 == 0) { - ts->rdidx2 = 0; - ts->wridx2 = 0; - } if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) { /* Read from socket to buffer 1 */ |