Resolve KASM-4489 "Feature/ watermark time"

CMakeLists.txt

@@ -154,6 +154,9 @@ find_package(PNG REQUIRED)
 # Check for libjpeg
 find_package(JPEG REQUIRED)
 
+find_package(Freetype REQUIRED)
+include_directories(${FREETYPE_INCLUDE_DIRS})
+
 # Staticly link libjpeg-turbo
 set(JPEG_LIBRARIES "-Wl,-Bstatic -lturbojpeg -Wl,-Bdynamic")
 # Warn if it doesn't seem to be the accelerated libjpeg that's found

builder/dockerfile.ubuntu_focal.vncserver_devenv.test

@@ -58,7 +58,8 @@ RUN echo 'alias tv="./run-specs spec/vncserver_yaml_validation_spec.py"' >> ~/.b
 RUN echo 'alias ty="./run-specs spec/vncserver_*spec.py"' >> ~/.bashrc
 RUN echo 'alias ta="./run-specs"' >> ~/.bashrc
 RUN echo 'alias vd="vncserver -dry-run"' >> ~/.bashrc
-ENV SET_PASSWORD_FUNC 'sp() { echo -e "$VNC_PW\\n$VNC_PW\\n" | kasmvncpasswd -w -u $USER $HOME/.kasmpasswd; }'
+RUN echo 'alias ss="sp; vncserver -select-de xfce"' >> ~/.bashrc
+ENV SET_PASSWORD_FUNC 'sp() { echo -e "$VNC_PW\\n$VNC_PW\\n" | kasmvncpasswd -w -u $VNC_USER $HOME/.kasmpasswd; }'
 RUN echo $SET_PASSWORD_FUNC >> ~/.bashrc
 
 ENV LC_ALL=C.UTF-8

centos/kasmvncserver.spec

@@ -7,7 +7,7 @@ License: GPLv2+
 URL: https://github.com/kasmtech/KasmVNC
 
 BuildRequires: rsync
-Requires: xorg-x11-xauth, xorg-x11-xkb-utils, xkeyboard-config, xorg-x11-server-utils, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny
+Requires: xorg-x11-xauth, xorg-x11-xkb-utils, xkeyboard-config, xorg-x11-server-utils, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, perl-DateTime-TimeZone
 Conflicts: tigervnc-server, tigervnc-server-minimal
 
 %description

cmake/Modules/FindFreetype.cmake

@@ -0,0 +1,17 @@
+# - Find freetype
+# Find the freetype libraries
+#
+#  This module defines the following variables:
+#     FREETYPE_FOUND        - True if freetype is found
+#     FREETYPE_INCLUDE_DIRS - include directories
+#
+
+find_package(PkgConfig)
+pkg_check_modules(PC_FREETYPE freetype2)
+find_path(FREETYPE_INCLUDE_DIRS NAMES ft2build.h HINTS ${PC_FREETYPE_INCLUDE_DIRS})
+
+include(FindPackageHandleStandardArgs)
+set(FPHSA_NAME_MISMATCHED 1)
+find_package_handle_standard_args(freetype DEFAULT_MSG FREETYPE_INCLUDE_DIRS)
+unset(FPHSA_NAME_MISMATCHED)
+mark_as_advanced(FREETYPE_INCLUDE_DIRS)

common/rfb/ServerCore.cxx

@@ -189,6 +189,18 @@ rfb::IntParameter rfb::Server::DLP_WatermarkRepeatSpace
 ("DLP_WatermarkRepeatSpace",
  "Number of pixels between repeats of the watermark",
  0, 0, 4096);
+rfb::IntParameter rfb::Server::DLP_WatermarkFontSize
+("DLP_WatermarkFontSize",
+ "Font size for -DLP_WatermarkText",
+ 48, 8, 256);
+rfb::IntParameter rfb::Server::DLP_WatermarkTimeOffset
+("DLP_WatermarkTimeOffset",
+ "Offset from UTC for -DLP_WatermarkText",
+ 0, -24, 24);
+rfb::IntParameter rfb::Server::DLP_WatermarkTimeOffsetMinutes
+("DLP_WatermarkTimeOffsetMinutes",
+ "Offset from UTC for -DLP_WatermarkText, minutes",
+ 0, -24 * 60, 24 * 60);
 rfb::StringParameter rfb::Server::DLP_WatermarkImage
 ("DLP_WatermarkImage",
  "PNG file to use as a watermark",
@@ -201,6 +213,14 @@ rfb::StringParameter rfb::Server::DLP_WatermarkTint
 ("DLP_WatermarkTint",
  "Tint the greyscale watermark by this color.",
  "255,255,255,255");
+rfb::StringParameter rfb::Server::DLP_WatermarkText
+("DLP_WatermarkText",
+ "Use this text instead of an image for the watermark, with strftime time formatting",
+ "");
+rfb::StringParameter rfb::Server::DLP_WatermarkFont
+("DLP_WatermarkFont",
+ "Use this font for -DLP_WatermarkText instead of the bundled one",
+ "");
 
 rfb::StringParameter rfb::Server::maxVideoResolution
 ("MaxVideoResolution",

common/rfb/ServerCore.h

@@ -49,12 +49,17 @@ namespace rfb {
     static IntParameter DLP_ClipDelay;
     static IntParameter DLP_KeyRateLimit;
     static IntParameter DLP_WatermarkRepeatSpace;
+    static IntParameter DLP_WatermarkFontSize;
+    static IntParameter DLP_WatermarkTimeOffset;
+    static IntParameter DLP_WatermarkTimeOffsetMinutes;
     static StringParameter DLP_ClipLog;
     static StringParameter DLP_Region;
     static StringParameter DLP_Clip_Types;
     static StringParameter DLP_WatermarkImage;
     static StringParameter DLP_WatermarkLocation;
     static StringParameter DLP_WatermarkTint;
+    static StringParameter DLP_WatermarkText;
+    static StringParameter DLP_WatermarkFont;
     static BoolParameter DLP_RegionAllowClick;
     static BoolParameter DLP_RegionAllowRelease;
     static IntParameter jpegVideoQuality;

common/rfb/VNCServerST.cxx

@@ -974,6 +974,11 @@ void VNCServerST::writeUpdate()
     blackOut();
   }
 
+  if (watermarkData && Server::DLP_WatermarkText[0] && watermarkTextNeedsUpdate(true)) {
+    // If using a text watermark, we have to mark everything as changed...
+    refreshClients();
+  }
+
   comparer->getUpdateInfo(&ui, pb->getRect());
   toCheck = ui.changed.union_(ui.copied);
 

common/rfb/Watermark.cxx

@@ -20,10 +20,14 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <zlib.h>
 #include <rfb/LogWriter.h>
 #include <rfb/ServerCore.h>
 #include <rfb/VNCServerST.h>
+#include "font.h"
+#include <ft2build.h>
+#include FT_FREETYPE_H
 
 #include "Watermark.h"
 
@@ -36,6 +40,10 @@ watermarkInfo_t watermarkInfo;
 uint8_t *watermarkData, *watermarkUnpacked, *watermarkTmp;
 uint32_t watermarkDataLen;
 static uint16_t rw, rh;
+static time_t lastUpdate;
+
+static FT_Library ft = NULL;
+static FT_Face face;
 
 #define MAXW 4096
 #define MAXH 4096
@@ -92,15 +100,151 @@ static bool loadimage(const char path[]) {
 	return true;
 }
 
+// Note: w and h are absolute
+static void str(uint8_t *buf, const char *txt, const uint32_t x_, const uint32_t y_,
+		const uint32_t w, const uint32_t h,
+		const uint32_t stride) {
+
+	unsigned ucs[256], i, ucslen;
+	unsigned len = strlen(txt);
+	i = 0;
+	ucslen = 0;
+	while (len > 0 && txt[i]) {
+		size_t ret = rfb::utf8ToUCS4(&txt[i], len, &ucs[ucslen]);
+		i += ret;
+		len -= ret;
+		ucslen++;
+	}
+
+	uint32_t x, y;
+
+	x = x_;
+	y = y_;
+	for (i = 0; i < ucslen; i++) {
+		if (FT_Load_Char(face, ucs[i], FT_LOAD_RENDER))
+			continue;
+		const FT_Bitmap * const map = &(face->glyph->bitmap);
+
+		if (FT_HAS_KERNING(face) && i) {
+			FT_Vector delta;
+			FT_Get_Kerning(face, ucs[i - 1], ucs[i], ft_kerning_default, &delta);
+			x += delta.x >> 6;
+		}
+
+		uint32_t row, col;
+		for (row = 0; row < (uint32_t) map->rows; row++) {
+			int ny = row + y - face->glyph->bitmap_top;
+			if (ny < 0)
+				continue;
+			if ((unsigned) ny >= h)
+				continue;
+
+			uint8_t *dst = (uint8_t *) buf;
+			dst += ny * stride + x;
+
+			const uint8_t *src = map->buffer + map->pitch * row;
+			for (col = 0; col < (uint32_t) map->width; col++) {
+				if (col + x >= w)
+					continue;
+				const uint8_t out = (src[col] + 8) >> 4;
+				dst[col] = out < 16 ? out : 15;
+			}
+		}
+
+		x += face->glyph->advance.x >> 6;
+	}
+}
+
+static uint32_t drawnwidth(const char *txt) {
+
+	unsigned ucs[256], i, ucslen;
+	unsigned len = strlen(txt);
+	i = 0;
+	ucslen = 0;
+	while (len > 0 && txt[i]) {
+		size_t ret = rfb::utf8ToUCS4(&txt[i], len, &ucs[ucslen]);
+		i += ret;
+		len -= ret;
+		ucslen++;
+	}
+
+	uint32_t x;
+
+	x = 0;
+	for (i = 0; i < ucslen; i++) {
+		if (FT_Load_Char(face, ucs[i], FT_LOAD_DEFAULT))
+			continue;
+
+		if (FT_HAS_KERNING(face) && i) {
+			FT_Vector delta;
+			FT_Get_Kerning(face, ucs[i - 1], ucs[i], ft_kerning_default, &delta);
+			x += delta.x >> 6;
+		}
+
+		x += face->glyph->advance.x >> 6;
+	}
+
+	return x;
+}
+
+static bool drawtext(const char fmt[], const int16_t utcOff, const char fontpath[],
+			const uint8_t fontsize) {
+	char buf[PATH_MAX];
+
+	if (!ft) {
+		if (FT_Init_FreeType(&ft))
+			abort();
+		if (fontpath[0]) {
+			if (FT_New_Face(ft, fontpath, 0, &face))
+				abort();
+		} else {
+			if (FT_New_Memory_Face(ft, font_otf, sizeof(font_otf), 0, &face))
+				abort();
+		}
+		FT_Set_Pixel_Sizes(face, fontsize, fontsize);
+	}
+
+	time_t now = lastUpdate = time(NULL);
+	now += utcOff * 60;
+
+	struct tm *tm = gmtime(&now);
+	size_t len = strftime(buf, PATH_MAX, fmt, tm);
+	if (!len)
+		return false;
+
+	free(watermarkInfo.src);
+	const uint32_t h = fontsize + 4;
+	const uint32_t w = drawnwidth(buf);
+
+	watermarkInfo.w = w;
+	watermarkInfo.h = h;
+	watermarkInfo.src = (uint8_t *) calloc(w, h);
+
+	str(watermarkInfo.src, buf, 0, fontsize, w, h, w);
+
+	return true;
+}
+
 bool watermarkInit() {
 	memset(&watermarkInfo, 0, sizeof(watermarkInfo_t));
 	watermarkData = watermarkUnpacked = watermarkTmp = NULL;
 	rw = rh = 0;
 
-	if (!Server::DLP_WatermarkImage[0])
+	if (!Server::DLP_WatermarkImage[0] && !Server::DLP_WatermarkText[0])
 		return true;
 
-	if (!loadimage(Server::DLP_WatermarkImage))
+	if (Server::DLP_WatermarkImage[0] && Server::DLP_WatermarkText[0]) {
+		vlog.error("WatermarkImage and WatermarkText can't be used together");
+		return false;
+	}
+
+	if (Server::DLP_WatermarkImage[0] && !loadimage(Server::DLP_WatermarkImage))
+		return false;
+
+	if (Server::DLP_WatermarkText[0] &&
+		!drawtext(Server::DLP_WatermarkText,
+				Server::DLP_WatermarkTimeOffset * 60 + Server::DLP_WatermarkTimeOffsetMinutes,
+				Server::DLP_WatermarkFont, Server::DLP_WatermarkFontSize))
 		return false;
 
 	if (Server::DLP_WatermarkRepeatSpace && Server::DLP_WatermarkLocation[0]) {
@@ -136,10 +280,22 @@ bool watermarkInit() {
 }
 
 // update the screen-size rendered watermark whenever the screen is resized
+// or if using text, every frame
 void VNCServerST::updateWatermark() {
 	if (rw == pb->width() &&
-		rh == pb->height())
+		rh == pb->height()) {
+
+		if (Server::DLP_WatermarkImage[0])
 			return;
+		if (!watermarkTextNeedsUpdate(false))
+			return;
+	}
+
+	if (Server::DLP_WatermarkText[0] && watermarkTextNeedsUpdate(false)) {
+		drawtext(Server::DLP_WatermarkText,
+				Server::DLP_WatermarkTimeOffset * 60 + Server::DLP_WatermarkTimeOffsetMinutes,
+				Server::DLP_WatermarkFont, Server::DLP_WatermarkFontSize);
+	}
 
 	rw = pb->width();
 	rh = pb->height();
@@ -246,3 +402,15 @@ void packWatermark(const Region &changed) {
 
 	watermarkDataLen = destLen;
 }
+
+// Limit changes to once per second
+bool watermarkTextNeedsUpdate(const bool early) {
+	static time_t now;
+
+	// We're called a couple times per frame, only grab the
+	// time on the first time so it doesn't change inside a frame
+	if (early)
+		now = time(NULL);
+
+	return now != lastUpdate;
+}

common/rfb/Watermark.h

@@ -36,6 +36,7 @@ extern watermarkInfo_t watermarkInfo;
 
 bool watermarkInit();
 void packWatermark(const rfb::Region &changed); // filter and pack the watermark for sending
+bool watermarkTextNeedsUpdate(const bool early);
 
 extern uint8_t *watermarkData;
 extern uint32_t watermarkDataLen;

debian/control

@@ -14,7 +14,7 @@ Architecture: amd64 arm64
 Depends: ${shlibs:Depends}, ${misc:Depends}, ${perl:Depends}, ssl-cert, xauth,
   x11-xkb-utils, xkb-data, procps, libswitch-perl, libyaml-tiny-perl,
   libhash-merge-simple-perl, libscalar-list-utils-perl, liblist-moreutils-perl,
-  libtry-tiny-perl, libgbm1
+  libtry-tiny-perl, libdatetime-timezone-perl, libgbm1
 Provides: vnc-server
 Description: KasmVNC provides remote web-based access to a Desktop or application.
   While VNC is in the name, KasmVNC differs from other VNC variants such

fedora/kasmvncserver.spec

@@ -7,7 +7,7 @@ License: GPLv2+
 URL: https://github.com/kasmtech/KasmVNC
 
 BuildRequires: rsync
-Requires: xorg-x11-xauth, xkeyboard-config, xkbcomp, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, mesa-libgbm, libxshmfence
+Requires: xorg-x11-xauth, xkeyboard-config, xkbcomp, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, perl-DateTime-TimeZone, mesa-libgbm, libxshmfence
 Conflicts: tigervnc-server, tigervnc-server-minimal
 
 %description

opensuse/kasmvncserver.spec

@@ -7,7 +7,7 @@ License: GPLv2+
 URL: https://github.com/kasmtech/KasmVNC
 
 BuildRequires: rsync
-Requires: xauth, hostname, libxkbcommon-x11-0, xkeyboard-config, x11-tools, openssl, perl, libpixman-1-0, libjpeg8, libgomp1, libXfont2-2, libXdmcp6, libglvnd, xkbcomp, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, libgbm1, libxshmfence1
+Requires: xauth, hostname, libxkbcommon-x11-0, xkeyboard-config, x11-tools, openssl, perl, libpixman-1-0, libjpeg8, libgomp1, libXfont2-2, libXdmcp6, libglvnd, xkbcomp, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, perl-DateTime-TimeZone, libgbm1, libxshmfence1
 Conflicts: tigervnc, tigervnc-x11vnc
 
 %description

oracle/kasmvncserver.spec

@@ -7,7 +7,7 @@ License: GPLv2+
 URL: https://github.com/kasmtech/KasmVNC
 
 BuildRequires: rsync
-Requires: xorg-x11-xauth, xorg-x11-xkb-utils, xkeyboard-config, xorg-x11-server-utils, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, hostname, mesa-libgbm, libxshmfence
+Requires: xorg-x11-xauth, xorg-x11-xkb-utils, xkeyboard-config, xorg-x11-server-utils, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, perl-DateTime-TimeZone, hostname, mesa-libgbm, libxshmfence
 Conflicts: tigervnc-server, tigervnc-server-minimal
 
 %description

oracle/kasmvncserver9.spec

@@ -7,7 +7,7 @@ License: GPLv2+
 URL: https://github.com/kasmtech/KasmVNC
 
 BuildRequires: rsync
-Requires: xorg-x11-xauth, xkeyboard-config, xorg-x11-server-utils, xkbcomp, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, hostname, mesa-libgbm, libxshmfence
+Requires: xorg-x11-xauth, xkeyboard-config, xorg-x11-server-utils, xkbcomp, openssl, perl, perl-Switch, perl-YAML-Tiny, perl-Hash-Merge-Simple, perl-Scalar-List-Utils, perl-List-MoreUtils, perl-Try-Tiny, perl-DateTime-TimeZone, hostname, mesa-libgbm, libxshmfence
 Conflicts: tigervnc-server, tigervnc-server-minimal
 
 %description

spec/vncserver_yaml_to_cli_spec.py

@@ -2,7 +2,7 @@ import os
 import re
 import shutil
 from os.path import expanduser
-from mamba import description, context, fcontext, it, fit, before, after
+from mamba import description, context, fcontext, it, fit, _it, before, after
 from expects import expect, equal, contain, match
 
 from helper.spec_helper import start_xvnc, kill_xvnc, run_cmd, clean_env, \
@@ -268,6 +268,18 @@ with description('YAML to CLI') as self:
                                      completed_process.stdout)
         expect(cli_option).to(equal("-geometry '1024x768'"))
 
+    with it("allows wide utf characters"):
+        write_config('''
+        data_loss_prevention:
+            watermark:
+                text:
+                    template: "星街すいせい"
+        ''')
+        completed_process = run_vncserver()
+        cli_option = pick_cli_option('DLP_WatermarkText',
+                                     completed_process.stdout)
+        expect(cli_option).to(equal("-DLP_WatermarkText '星街すいせい'"))
+
     with it("ignores empty section override"):
         write_config('''
         security:

t

@@ -0,0 +1,9 @@
+use DateTime::TimeZone;
+
+my $timezone = $ARGV[0];
+
+if (DateTime::TimeZone->is_valid_name($timezone)) {
+    print "Valid timezone\n";
+} else {
+    print "Invalid timezone\n";
+}

t2

@@ -0,0 +1,11 @@
+use DateTime;
+use DateTime::TimeZone;
+
+#my $timezone_name = 'America/New_York';
+my $timezone_name = 'UTC';
+
+my $dt = DateTime->now(time_zone => $timezone_name);
+my $offset = $dt->offset();
+
+print "Timezone: $timezone_name\n";
+print "Offset: $offset seconds\n";

unix/KasmVNC/CallbackValidator.pm

@@ -0,0 +1,37 @@
+package KasmVNC::CallbackValidator;
+
+use strict;
+use warnings;
+use v5.10;
+use Data::Dumper;
+
+use KasmVNC::Utils;
+
+sub new {
+    my ($class, $args) = @_;
+    my $self = bless {
+      isValidCallback => $args->{isValidCallback},
+      errorMessage => $args->{errorMessage}
+    }, $class;
+}
+
+sub validate {
+  my $self = shift;
+  $self->{configKey} = shift;
+  my @values = @{ listify($self->{configKey}->value()) };
+
+  foreach my $value (@values) {
+    $self->validateValue($value);
+  }
+}
+
+sub validateValue {
+  my $self = shift;
+  my $value = shift;
+
+  unless ($self->{isValidCallback}($value)) {
+    $self->{configKey}->addErrorMessage($self->{errorMessage});
+  }
+}
+
+1;

unix/KasmVNC/Utils.pm

@@ -45,6 +45,8 @@ sub isPresent {
 sub deriveBoolean {
   my $value = shift;
 
+  return $value if containsWideSymbols($value);
+
   switch($value) {
     case 'true' {
       return 1;
@@ -63,4 +65,12 @@ sub printStackTrace {
   print { *STDERR } $trace->as_string;
 }
 
+sub containsWideSymbols {
+	my $string = shift;
+
+  return 1 unless defined($string);
+
+	$string =~ /[^\x00-\xFF]/;
+}
+
 1;

unix/kasmvnc_defaults.yaml

@@ -92,6 +92,11 @@ data_loss_prevention:
     # location: 10,10
     # tint: 255,20,20,128
     # repeat_spacing: 10
+    text:
+      template: "${USER} %H:%M"
+      font: auto
+      font_size: 48
+      timezone_name: Australia/Adelaide
   logging:
     # "verbose" SETTING LOGS YOUR PRIVATE INFORMATION. Keypresses and clipboard content
     level: off

unix/vncserver

@@ -27,6 +27,7 @@
 
 use v5.10;
 use warnings;
+use utf8;
 
 sub DEVENV() { $ENV{KASMVNC_DEVELOPMENT} };
 use if DEVENV, Devel::StackTrace;
@@ -38,11 +39,14 @@ use List::Util qw(first);
 use List::MoreUtils qw(any uniq);
 use Data::Dumper;
 use Try::Tiny;
+use DateTime;
+use DateTime::TimeZone;
 
 use KasmVNC::CliOption;
 use KasmVNC::ConfigKey;
 use KasmVNC::PatternValidator;
 use KasmVNC::EnumValidator;
+use KasmVNC::CallbackValidator;
 use KasmVNC::Config;
 use KasmVNC::Users;
 use KasmVNC::TextOption;
@@ -56,6 +60,7 @@ use constant {
   OPTIONAL_ARG_VALUE => 2
 };
 
+UseUtfStdio();
 InitLogger();
 
 CheckWeCanRunInThisEnvironment();
@@ -1765,6 +1770,79 @@ sub DefineConfigToCLIConversion {
           })
         ]
     }),
+    KasmVNC::CliOption->new({
+        name => 'DLP_WatermarkText',
+        configKeys => [
+          KasmVNC::ConfigKey->new({
+            name => "data_loss_prevention.watermark.text.template",
+            validator => KasmVNC::CallbackValidator->new({
+              isValidCallback => sub {
+                my $value = shift;
+
+                isBlank(ConfigValue("data_loss_prevention.watermark.image"));
+              },
+              errorMessage => "Watermark image and text can't be used at the same time"
+            }),
+          })
+        ]
+    }),
+    KasmVNC::CliOption->new({
+        name => 'DLP_WatermarkFont',
+        configKeys => [
+          KasmVNC::ConfigKey->new({
+            name => "data_loss_prevention.watermark.text.font",
+            type => KasmVNC::ConfigKey::ANY
+          })
+        ],
+        isActiveSub => sub {
+          $self = shift;
+
+          my $value = $self->configValue();
+          isPresent($value) && $value ne "auto";
+        }
+    }),
+    KasmVNC::CliOption->new({
+        name => 'DLP_WatermarkFontSize',
+        configKeys => [
+          KasmVNC::ConfigKey->new({
+            name => "data_loss_prevention.watermark.text.font_size",
+            validator => KasmVNC::CallbackValidator->new({
+              isValidCallback => sub {
+                my $value = shift;
+
+                return 0 unless $value =~ /^\d+$/;
+
+                $value >= 8 && $value <= 256;
+              },
+              errorMessage => "must be in range 8..256"
+            }),
+          })
+        ]
+    }),
+    KasmVNC::CliOption->new({
+        name => 'DLP_WatermarkTimeOffsetMinutes',
+        configKeys => [
+          KasmVNC::ConfigKey->new({
+            name => "data_loss_prevention.watermark.text.timezone_name",
+            validator => KasmVNC::CallbackValidator->new({
+              isValidCallback => sub {
+                my $timezone_name = shift;
+
+                DateTime::TimeZone->is_valid_name($timezone_name);
+              },
+              errorMessage => "must be a valid timezone name like Australia/Adelaide"
+            })
+          })
+        ],
+        deriveValueSub => sub {
+          my $self = shift;
+          my $timezone_name = $self->configValue();
+          my $dt = DateTime->now(time_zone => $timezone_name);
+          my $offset_in_seconds = $dt->offset();
+
+          $offset_in_seconds/60;
+        }
+    }),
     KasmVNC::CliOption->new({
         name => 'DLP_Log',
         configKeys => [
@@ -2835,3 +2913,7 @@ sub InitLogger {
   my $debugEnabled = any { $_ eq "-debug" } @ARGV;
   $logger = KasmVNC::Logger->new({ level => $debugEnabled ? "debug" : "warn" });
 }
+
+sub UseUtfStdio {
+  use open qw( :std :encoding(UTF-8) );
+}

unix/xserver/hw/vnc/Makefile.am

@@ -52,7 +52,8 @@ Xvnc_CPPFLAGS = $(XVNC_CPPFLAGS) -DKASMVNC -DNO_MODULE_EXTS \
 	-I$(top_srcdir)/dri3 @LIBDRM_CFLAGS@
 
 Xvnc_LDADD = $(XVNC_LIBS) libvnccommon.la $(COMMON_LIBS) \
-	$(XSERVER_LIBS) $(XSERVER_SYS_LIBS) $(XVNC_SYS_LIBS) -lX11 -lwebp -lssl -lcrypto -lcrypt
+	$(XSERVER_LIBS) $(XSERVER_SYS_LIBS) $(XVNC_SYS_LIBS) -lX11 -lwebp -lssl -lcrypto -lcrypt \
+	-lfreetype
 
 Xvnc_LDFLAGS = $(LD_EXPORT_SYMBOLS_FLAG) -fopenmp
 

unix/xserver/hw/vnc/Xvnc.man

@@ -243,6 +243,8 @@ Default \fB-1\fP.
 .B \-WebpVideoQuality \fInum\fP
 The WEBP quality to use when in video mode.
 Default \fB-1\fP.
+.
+.TP
 .B \-MaxVideoResolution \fI1920x1080\fP
 When in video mode, downscale the screen to max this size. Keeps aspect ratio.
 Default \fB1920x1080\fP.
@@ -372,6 +374,28 @@ The color components can be used to colorize the greyscale watermark, and the al
 can be used to make it fainter.
 .
 .TP
+.B \-DLP_WatermarkText \fI"foo %H:%M"\fP
+Instead of an image, render this text as the watermark. Takes time formatting options
+for \fBstrftime\fP.
+.
+.TP
+.B \-DLP_WatermarkFont \fI/path/to/font.ttf\fP
+Use a different font for -DLP_WatermarkText than the bundled one. TTF and OTF fonts
+are accepted.
+.
+.TP
+.B \-DLP_WatermarkFontSize \fI48\fP
+Font size for -DLP_WatermarkText. Default \fI48\fP.
+.
+.TP
+.B \-DLP_WatermarkTimeOffset \fI0\fP
+Time offset from UTC, hours. Default \fI0\fP.
+.
+.TP
+.B \-DLP_WatermarkTimeOffsetMinutes \fI0\fP
+Time offset from UTC, minutes. Default \fI0\fP.
+.
+.TP
 .B \-selfBench
 Run a set of self-benchmarks and exit.
 .