GUACAMOLE-2237: Server-side terminal multiline paste fix.

[bbennett-ks]

For terminal-based protocols, pasted terminal contents are now normalized on the server before being written to stdin: line endings are converted so \n and \r\n become \r. This applies to both terminal paste shortcuts (Ctrl+Shift+V & Cmd+V) as well as for mouse click (middle & right). Doing this server-side is required because these paths ultimately paste from the terminal’s server-side clipboard buffer & mouse paste in particular does not give the client an normalize at paste time.

This does not change clipboard synchronization itself: Clipboard contents are still stored and exchanged as before, only the terminal-emulator paste path is normalized immediately before pasting.

Similar client-side changes are under review: GUACAMOLE-2237 (client 1201). Both sets of changes are independent, addressing different core issues.

Unit Tests

Added the following unit tests:

PASS: test_terminal 1 - [selection_point] enclose_text: OK
PASS: test_terminal 2 - [selection_point] enclose_wide_text: OK
PASS: test_terminal 3 - [selection_point] is_point_after: OK
PASS: test_terminal 4 - [selection_point] rounding: OK
PASS: test_terminal 5 - [selection_point] rounding_wide: OK
PASS: test_terminal 6 - [paste] lf_to_cr: OK                 New!
PASS: test_terminal 7 - [paste] crlf_to_single_cr: OK        New!
PASS: test_terminal 8 - [paste] bare_cr_passthrough: OK      New!
PASS: test_terminal 9 - [paste] mixed_endings: OK            New!
PASS: test_terminal 10 - [paste] consecutive_endings: OK     New!
PASS: test_terminal 11 - [paste] trailing_cr: OK             New!
PASS: test_terminal 12 - [paste] no_endings: OK              New!
PASS: test_terminal 13 - [paste] empty: OK                   New!
PASS: test_terminal 14 - [paste] embedded_nul: OK            New!
============================================================================
Testsuite summary for guacamole-server 1.6.1
============================================================================

Manual Tests

Copying the following (Linux/Chrome Browser):

• Via Ctrl+V/Click/Right Click
• Via Browser Paste Menu

[mike-jumper]

Doesn't the terminal emulator already normalize line endings in the server-side clipboard via:

guacamole-server/src/terminal/terminal.c

Lines 2796 to 2798 in d304ad3

	/* Convert clipboard contents */
	guac_iconv(GUAC_READ_UTF8_NORMALIZED, &data, length,
	GUAC_WRITE_UTF8, &output, output_buf_size);

?

[bbennett-ks]

Doesn't the terminal emulator already normalize line endings in the server-side clipboard via:

guacamole-server/src/terminal/terminal.c

Lines 2796 to 2798 in d304ad3

	/* Convert clipboard contents */
	guac_iconv(GUAC_READ_UTF8_NORMALIZED, &data, length,
	GUAC_WRITE_UTF8, &output, output_buf_size);

Yeah, this are is confusing. I updated the function header to clarify. We normalize to LF when we ingest clipboard data and we (re)normalize to CR when sending to keyboard as LF isn't universally treated (e.g. Windows) as the Enter key.

[necouchman]

Looks good to me. @mike-jumper Any further concerns?