contrib: introduce simple highlighter library

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

contrib/highlighter/Makefile

@@ -0,0 +1,25 @@
+CFLAGS ?= -O3 -march=native
+CFLAGS += -std=gnu99
+CFLAGS += -Wall
+CFLAGS += -MMD -MP
+
+highlight: highlight.o highlighter.o
+
+fuzz: CC := clang
+fuzz: CFLAGS += -fsanitize=fuzzer
+fuzz: fuzz.c highlighter.c
+
+gui/Makefile: gui/highlight.pro
+	cd gui && qmake
+gui: gui/Makefile
+	@$(MAKE) -C gui
+
+clean:
+	rm -f highlight fuzz *.o *.d
+	@if [ -f gui/Makefile ]; then $(MAKE) -C gui distclean; fi
+
+.PHONY: clean gui
+.DEFAULT_GOAL: highlight
+MAKEFLAGS += --no-print-directory
+
+-include *.d

contrib/highlighter/README

@@ -0,0 +1,22 @@
+wg(8) and wg-quick(8) syntax highlighter library
+================================================
+
+highlighter.c contains a simple portable highlighter for the wg(8) and
+wg-quick(8) configuration files. Simply copy `highlight.c` and
+`highlight.h` into your project wholesale.
+
+As a demo, a simple console highlighter program is included, alongside a
+simple Qt5 GUI app to show its usage in realtime.
+
+There is also a basic fuzzer, because why not?
+
+Usage:
+
+    $ make
+    $ ./highlight < path/to/tunnel.conf
+
+    $ make gui
+    $ ./gui/highlight
+
+    $ make fuzz
+    $ ./fuzz -workers=$(nproc) -jobs=$(nproc) ./corpus

contrib/highlighter/fuzz.c

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include "highlighter.h"
+
+int LLVMFuzzerTestOneInput(const char *data, size_t size)
+{
+	char *str = strndup(data, size);
+	if (!str)
+		return 0;
+	struct highlight_span *spans = highlight_config(str);
+	if (!spans)
+		return 0;
+	for (struct highlight_span *span = spans; span->type != HighlightEnd; ++span);
+	free(spans);
+	free(str);
+	return 0;
+}

contrib/highlighter/gui/highlight.cpp

@@ -0,0 +1,90 @@
+#include <QApplication>
+#include <QPlainTextEdit>
+#include <QPalette>
+#include <QFontDatabase>
+#include <QVBoxLayout>
+#include <QPushButton>
+
+extern "C" {
+#include "../highlighter.h"
+}
+
+static QColor colormap[] = {
+	[HighlightSection] = QColor("#ababab"),
+	[HighlightField] = QColor("#70c0b1"),
+	[HighlightPrivateKey] = QColor("#7aa6da"),
+	[HighlightPublicKey] = QColor("#7aa6da"),
+	[HighlightPresharedKey] = QColor("#7aa6da"),
+	[HighlightIP] = QColor("#b9ca4a"),
+	[HighlightCidr] = QColor("#e78c45"),
+	[HighlightHost] = QColor("#b9ca4a"),
+	[HighlightPort] = QColor("#e78c45"),
+	[HighlightMTU] = QColor("#c397d8"),
+	[HighlightKeepalive] = QColor("#c397d8"),
+	[HighlightComment] = QColor("#969896"),
+	[HighlightDelimiter] = QColor("#7aa6da"),
+#ifndef MOBILE_WGQUICK_SUBSET
+	[HighlightTable] = QColor("#c397d8"),
+	[HighlightFwMark] = QColor("#c397d8"),
+	[HighlightSaveConfig] = QColor("#c397d8"),
+	[HighlightCmd] = QColor("#969896"),
+#endif
+	[HighlightError] = QColor("#d54e53")
+};
+
+int main(int argc, char *argv[])
+{
+	QApplication a(argc, argv);
+	QWidget w;
+	w.setWindowTitle(QObject::tr("WireGuard Configuration Highlighter"));
+	QVBoxLayout v;
+	w.setLayout(&v);
+	QPlainTextEdit e;
+	v.addWidget(&e);
+	QPalette p(e.palette());
+	p.setColor(QPalette::Base, QColor("#010101"));
+	p.setColor(QPalette::Text, QColor("#eaeaea"));
+	e.setPalette(p);
+	QFont f(QFontDatabase::systemFont(QFontDatabase::FixedFont));
+	f.setPointSize(16);
+	e.setFont(f);
+	e.setMinimumSize(400, 500);
+	bool guard = false;
+	QObject::connect(&e, &QPlainTextEdit::textChanged, [&]() {
+		if (guard)
+			return;
+		struct highlight_span *spans = highlight_config(e.toPlainText().toLatin1().data());
+		if (!spans)
+			return;
+		QTextCursor cursor(e.document());
+		QTextCharFormat format;
+		cursor.beginEditBlock();
+		cursor.movePosition(QTextCursor::Start, QTextCursor::MoveAnchor);
+		cursor.movePosition(QTextCursor::End, QTextCursor::KeepAnchor);
+		format.setForeground(p.color(QPalette::Text));
+		format.setUnderlineStyle(QTextCharFormat::NoUnderline);
+		cursor.mergeCharFormat(format);
+		for (struct highlight_span *span = spans; span->type != HighlightEnd; ++span) {
+			cursor.movePosition(QTextCursor::Start, QTextCursor::MoveAnchor);
+			cursor.movePosition(QTextCursor::NextCharacter, QTextCursor::MoveAnchor, span->start);
+			cursor.movePosition(QTextCursor::NextCharacter, QTextCursor::KeepAnchor, span->len);
+			format.setForeground(colormap[span->type]);
+			format.setUnderlineStyle(span->type == HighlightError ? QTextCharFormat::SpellCheckUnderline : QTextCharFormat::NoUnderline);
+			cursor.mergeCharFormat(format);
+		}
+		free(spans);
+		guard = true;
+		cursor.endEditBlock();
+		guard = false;
+	});
+	QPushButton b;
+	v.addWidget(&b);
+	b.setText(QObject::tr("&Randomize colors"));
+	QObject::connect(&b, &QPushButton::clicked, [&]() {
+		for (size_t i = 0; i < sizeof(colormap) / sizeof(colormap[0]); ++i)
+			colormap[i] = QColor::fromHsl(qrand() % 360, qrand() % 192 + 64, qrand() % 128 + 128);
+		e.setPlainText(e.toPlainText());
+	});
+	w.show();
+	return a.exec();
+}

contrib/highlighter/gui/highlight.pro

@@ -0,0 +1,5 @@
+QT += core gui widgets
+TEMPLATE = app
+TARGET = highlight
+SOURCES += highlight.cpp ../highlighter.c
+HEADERS += ../highlighter.h

contrib/highlighter/highlight.c

@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "highlighter.h"
+
+#define TERMINAL_FG_BLACK	"\x1b[30m"
+#define TERMINAL_FG_RED		"\x1b[31m"
+#define TERMINAL_FG_GREEN	"\x1b[32m"
+#define TERMINAL_FG_YELLOW	"\x1b[33m"
+#define TERMINAL_FG_BLUE	"\x1b[34m"
+#define TERMINAL_FG_MAGENTA	"\x1b[35m"
+#define TERMINAL_FG_CYAN	"\x1b[36m"
+#define TERMINAL_FG_WHITE	"\x1b[37m"
+#define TERMINAL_FG_DEFAULT	"\x1b[39m"
+
+#define TERMINAL_BG_BLACK	"\x1b[40m"
+#define TERMINAL_BG_RED		"\x1b[41m"
+#define TERMINAL_BG_GREEN	"\x1b[42m"
+#define TERMINAL_BG_YELLOW	"\x1b[43m"
+#define TERMINAL_BG_BLUE	"\x1b[44m"
+#define TERMINAL_BG_MAGENTA	"\x1b[45m"
+#define TERMINAL_BG_CYAN	"\x1b[46m"
+#define TERMINAL_BG_WHITE	"\x1b[47m"
+#define TERMINAL_BG_DEFAULT	"\x1b[49m"
+
+#define TERMINAL_BOLD		"\x1b[1m"
+#define TERMINAL_NO_BOLD	"\x1b[22m"
+#define TERMINAL_UNDERLINE	"\x1b[4m"
+#define TERMINAL_NO_UNDERLINE	"\x1b[24m"
+
+#define TERMINAL_RESET		"\x1b[0m"
+
+static const char *colormap[] = {
+	[HighlightSection] = TERMINAL_FG_BLACK TERMINAL_BOLD,
+	[HighlightField] = TERMINAL_FG_BLUE TERMINAL_BOLD,
+	[HighlightPrivateKey] = TERMINAL_FG_YELLOW TERMINAL_BOLD,
+	[HighlightPublicKey] = TERMINAL_FG_YELLOW TERMINAL_BOLD,
+	[HighlightPresharedKey] = TERMINAL_FG_YELLOW TERMINAL_BOLD,
+	[HighlightIP] = TERMINAL_FG_GREEN,
+	[HighlightCidr] = TERMINAL_FG_YELLOW,
+	[HighlightHost] = TERMINAL_FG_GREEN TERMINAL_BOLD,
+	[HighlightPort] = TERMINAL_FG_MAGENTA,
+	[HighlightMTU] = TERMINAL_FG_BLUE,
+	[HighlightKeepalive] = TERMINAL_FG_BLUE,
+	[HighlightComment] = TERMINAL_FG_CYAN,
+	[HighlightDelimiter] = TERMINAL_FG_CYAN,
+#ifndef MOBILE_WGQUICK_SUBSET
+	[HighlightTable] = TERMINAL_FG_BLUE,
+	[HighlightFwMark] = TERMINAL_FG_BLUE,
+	[HighlightSaveConfig] = TERMINAL_FG_BLUE,
+	[HighlightCmd] = TERMINAL_FG_WHITE,
+#endif
+	[HighlightError] = TERMINAL_FG_RED TERMINAL_UNDERLINE
+};
+
+int main(int argc, char *argv[])
+{
+	char input[1024 * 1024];
+	struct highlight_span *spans;
+	size_t last = 0, total_len;
+
+	total_len = fread(input, 1, sizeof(input) - 1, stdin);
+	input[total_len] = '\0';
+	spans = highlight_config(input);
+
+	fputs(TERMINAL_RESET, stdout);
+	for (struct highlight_span *span = spans; span->type != HighlightEnd; ++span) {
+		fwrite(input + last, 1, span->start - last, stdout);
+		fputs(colormap[span->type], stdout);
+		fwrite(input + span->start, 1, span->len, stdout);
+		fputs(TERMINAL_RESET, stdout);
+		last = span->start + span->len;
+	}
+	fwrite(input + last, 1, total_len - last, stdout);
+
+	free(spans);
+	return 0;
+}

contrib/highlighter/highlighter.c

@@ -0,0 +1,620 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include "highlighter.h"
+
+typedef struct {
+	const char *s;
+	size_t len;
+} string_span_t;
+
+static bool is_decimal(char c)
+{
+	return c >= '0' && c <= '9';
+}
+
+static bool is_hexadecimal(char c)
+{
+	return is_decimal(c) || ((c | 32) >= 'a' && (c | 32) <= 'f');
+}
+
+static bool is_alphabet(char c)
+{
+	return (c | 32) >= 'a' && (c | 32) <= 'z';
+}
+
+static bool is_same(string_span_t s, const char *c)
+{
+	size_t len = strlen(c);
+
+	if (len != s.len)
+		return false;
+	return !memcmp(s.s, c, len);
+}
+
+static bool is_caseless_same(string_span_t s, const char *c)
+{
+	size_t len = strlen(c);
+
+	if (len != s.len)
+		return false;
+	for (size_t i = 0; i < len; ++i) {
+		char a = c[i], b = s.s[i];
+		if ((unsigned)a - 'a' < 26)
+			a &= 95;
+		if ((unsigned)b - 'a' < 26)
+			b &= 95;
+		if (a != b)
+			return false;
+	}
+	return true;
+}
+
+static bool is_valid_key(string_span_t s)
+{
+	if (s.len != 44 || s.s[43] != '=')
+		return false;
+
+	for (size_t i = 0; i < 43; ++i) {
+		if (!is_decimal(s.s[i]) && !is_alphabet(s.s[i]) &&
+		    s.s[i] != '/' && s.s[i] != '+')
+			return false;
+	}
+	return true;
+}
+
+static bool is_valid_hostname(string_span_t s)
+{
+	size_t num_digit = 0, num_entity = s.len;
+
+	if (s.len > 63 || !s.len)
+		return false;
+	if (s.s[0] == '-' || s.s[s.len - 1] == '-')
+		return false;
+	if (s.s[0] == '.' || s.s[s.len - 1] == '.')
+		return false;
+
+	for (size_t i = 0; i < s.len; ++i) {
+		if (is_decimal(s.s[i])) {
+			++num_digit;
+			continue;
+		}
+		if (s.s[i] == '.') {
+			--num_entity;
+			continue;
+		}
+
+		if (!is_alphabet(s.s[i]) && s.s[i] != '-')
+			return false;
+
+		if (i && s.s[i] == '.' && s.s[i - 1] == '.')
+			return false;
+	}
+	return num_digit != num_entity;
+}
+
+static bool is_valid_ipv4(string_span_t s)
+{
+	for (size_t j, i = 0, pos = 0; i < 4 && pos < s.len; ++i) {
+		uint32_t val = 0;
+
+		for (j = 0; j < 3 && pos + j < s.len && is_decimal(s.s[pos + j]); ++j)
+			val = 10 * val + s.s[pos + j] - '0';
+		if (j == 0 || (j > 1 && s.s[pos] == '0') || val > 255)
+			return false;
+		if (pos + j == s.len && i == 3)
+			return true;
+		if (s.s[pos + j] != '.')
+			return false;
+		pos += j + 1;
+	}
+	return false;
+}
+
+static bool is_valid_ipv6(string_span_t s)
+{
+	size_t pos = 0;
+	bool seen_colon = false;
+
+	if (s.len < 2)
+		return false;
+	if (s.s[pos] == ':' && s.s[++pos] != ':')
+		return false;
+	if (s.s[s.len - 1] == ':' && s.s[s.len - 2] != ':')
+		return false;
+
+	for (size_t j, i = 0; pos < s.len; ++i) {
+		if (s.s[pos] == ':' && !seen_colon) {
+			seen_colon = true;
+			if (++pos == s.len)
+				break;
+			if (i == 7)
+				return false;
+			continue;
+		}
+		for (j = 0; j < 4 && pos + j < s.len && is_hexadecimal(s.s[pos + j]); ++j);
+		if (j == 0)
+			return false;
+		if (pos + j == s.len && (seen_colon || i == 7))
+			break;
+		if (i == 7)
+			return false;
+		if (s.s[pos + j] != ':') {
+			if (s.s[pos + j] != '.' || (i < 6 && !seen_colon))
+				return false;
+			return is_valid_ipv4((string_span_t){ s.s + pos, s.len - pos });
+		}
+		pos += j + 1;
+	}
+	return true;
+}
+
+static bool is_valid_uint(string_span_t s, bool support_hex, uint64_t min, uint64_t max)
+{
+	uint64_t val = 0;
+
+	/* Bound this around 32 bits, so that we don't have to write overflow logic. */
+	if (s.len > 10 || !s.len)
+		return false;
+
+	if (support_hex && s.len > 2 && s.s[0] == '0' && s.s[1] == 'x') {
+		for (size_t i = 2; i < s.len; ++i) {
+			if (s.s[i] - '0' < 10)
+				val = 16 * val + (s.s[i] - '0');
+			else if ((s.s[i] | 32) - 'a' < 6)
+				val = 16 * val + (s.s[i] | 32) - 'a' + 10;
+			else
+				return false;
+		}
+	} else {
+		for (size_t i = 0; i < s.len; ++i) {
+			if (!is_decimal(s.s[i]))
+				return false;
+			val = 10 * val + s.s[i] - '0';
+		}
+	}
+	return val <= max && val >= min;
+}
+
+static bool is_valid_port(string_span_t s)
+{
+	return is_valid_uint(s, false, 0, 65535);
+}
+
+static bool is_valid_mtu(string_span_t s)
+{
+	return is_valid_uint(s, false, 576, 65535);
+}
+
+static bool is_valid_persistentkeepalive(string_span_t s)
+{
+	if (is_same(s, "off"))
+		return true;
+	return is_valid_uint(s, false, 0, 65535);
+}
+
+#ifndef MOBILE_WGQUICK_SUBSET
+
+static bool is_valid_fwmark(string_span_t s)
+{
+	if (is_same(s, "off"))
+		return true;
+	return is_valid_uint(s, true, 0, 4294967295);
+}
+
+static bool is_valid_table(string_span_t s)
+{
+	if (is_same(s, "auto"))
+		return true;
+	if (is_same(s, "off"))
+		return true;
+	/* This pretty much invalidates the other checks, but rt_names.c's
+	 * fread_id_name does no validation aside from this. */
+	if (s.len < 512)
+		return true;
+	return is_valid_uint(s, false, 0, 4294967295);
+}
+
+static bool is_valid_saveconfig(string_span_t s)
+{
+	return is_same(s, "true") || is_same(s, "false");
+}
+
+static bool is_valid_prepostupdown(string_span_t s)
+{
+	/* It's probably not worthwhile to try to validate a bash expression.
+	 * So instead we just demand non-zero length. */
+	return s.len;
+}
+#endif
+
+static bool is_valid_scope(string_span_t s)
+{
+	if (s.len > 64 || !s.len)
+		return false;
+	for (size_t i = 0; i < s.len; ++i) {
+		if (!is_alphabet(s.s[i]) && !is_decimal(s.s[i]) &&
+		    s.s[i] != '_' && s.s[i] != '=' && s.s[i] != '+' &&
+		    s.s[i] != '.' && s.s[i] != '-')
+			return false;
+	}
+	return true;
+}
+
+static bool is_valid_endpoint(string_span_t s)
+{
+
+	if (!s.len)
+		return false;
+
+	if (s.s[0] == '[') {
+		bool seen_scope = false;
+		string_span_t hostspan = { s.s + 1, 0 };
+
+		for (size_t i = 1; i < s.len; ++i) {
+			if (s.s[i] == '%') {
+				if (seen_scope)
+					return false;
+				seen_scope = true;
+				if (!is_valid_ipv6(hostspan))
+					return false;
+				hostspan = (string_span_t){ s.s + i + 1, 0 };
+			} else if (s.s[i] == ']') {
+				if (seen_scope) {
+					if (!is_valid_scope(hostspan))
+						return false;
+				} else if (!is_valid_ipv6(hostspan)) {
+					return false;
+				}
+				if (i == s.len - 1 || s.s[i + 1] != ':')
+					return false;
+				return is_valid_port((string_span_t){ s.s + i + 2, s.len - i - 2 });
+			} else {
+				++hostspan.len;
+			}
+		}
+		return false;
+	}
+	for (size_t i = 0; i < s.len; ++i) {
+		if (s.s[i] == ':') {
+			string_span_t host = { s.s, i }, port = { s.s + i + 1, s.len - i - 1};
+			return is_valid_port(port) && (is_valid_ipv4(host) || is_valid_hostname(host));
+		}
+	}
+	return false;
+}
+
+static bool is_valid_network(string_span_t s)
+{
+	for (size_t i = 0; i < s.len; ++i) {
+		if (s.s[i] == '/') {
+			string_span_t ip = { s.s, i }, cidr = { s.s + i + 1, s.len - i - 1};
+			uint16_t cidrval = 0;
+
+			if (cidr.len > 3 || !cidr.len)
+				return false;
+
+			for (size_t j = 0; j < cidr.len; ++j) {
+				if (!is_decimal(cidr.s[j]))
+					return false;
+				cidrval = 10 * cidrval + cidr.s[j] - '0';
+			}
+			if (is_valid_ipv4(ip))
+				return cidrval <= 32;
+			else if (is_valid_ipv6(ip))
+				return cidrval <= 128;
+			return false;
+		}
+	}
+	return is_valid_ipv4(s) || is_valid_ipv6(s);
+}
+
+static bool is_valid_dns(string_span_t s)
+{
+	return is_valid_ipv4(s) || is_valid_ipv6(s);
+}
+
+enum field {
+	InterfaceSection,
+	PrivateKey,
+	ListenPort,
+	Address,
+	DNS,
+	MTU,
+#ifndef MOBILE_WGQUICK_SUBSET
+	FwMark,
+	Table,
+	PreUp, PostUp, PreDown, PostDown,
+	SaveConfig,
+#endif
+
+	PeerSection,
+	PublicKey,
+	PresharedKey,
+	AllowedIPs,
+	Endpoint,
+	PersistentKeepalive,
+
+	Invalid
+};
+
+static enum field section_for_field(enum field t)
+{
+	if (t > InterfaceSection && t < PeerSection)
+		return InterfaceSection;
+	if (t > PeerSection && t < Invalid)
+		return PeerSection;
+	return Invalid;
+}
+
+static enum field get_field(string_span_t s)
+{
+#define check_enum(t) do { if (is_caseless_same(s, #t)) return t; } while (0)
+	check_enum(PrivateKey);
+	check_enum(ListenPort);
+	check_enum(Address);
+	check_enum(DNS);
+	check_enum(MTU);
+	check_enum(PublicKey);
+	check_enum(PresharedKey);
+	check_enum(AllowedIPs);
+	check_enum(Endpoint);
+	check_enum(PersistentKeepalive);
+#ifndef MOBILE_WGQUICK_SUBSET
+	check_enum(FwMark);
+	check_enum(Table);
+	check_enum(PreUp);
+	check_enum(PostUp);
+	check_enum(PreDown);
+	check_enum(PostDown);
+	check_enum(SaveConfig);
+#endif
+	return Invalid;
+#undef check_enum
+}
+
+static enum field get_sectiontype(string_span_t s)
+{
+	if (is_caseless_same(s, "[Peer]"))
+		return PeerSection;
+	if (is_caseless_same(s, "[Interface]"))
+		return InterfaceSection;
+	return Invalid;
+}
+
+struct highlight_span_array {
+	size_t len, capacity;
+	struct highlight_span *spans;
+};
+
+/* A useful OpenBSD-ism. */
+static void *realloc_array(void *optr, size_t nmemb, size_t size)
+{
+	if ((nmemb >= (size_t)1 << (sizeof(size_t) * 4) ||
+	     size >= (size_t)1 << (sizeof(size_t) * 4)) &&
+	    nmemb > 0 && SIZE_MAX / nmemb < size) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	return realloc(optr, size * nmemb);
+}
+
+static bool append_highlight_span(struct highlight_span_array *a, const char *o, string_span_t s, enum highlight_type t)
+{
+	if (!s.len)
+		return true;
+	if (a->len >= a->capacity) {
+		struct highlight_span *resized;
+
+		a->capacity = a->capacity ? a->capacity * 2 : 64;
+		resized = realloc_array(a->spans, a->capacity, sizeof(*resized));
+		if (!resized) {
+			free(a->spans);
+			memset(a, 0, sizeof(*a));
+			return false;
+		}
+		a->spans = resized;
+	}
+	a->spans[a->len++] = (struct highlight_span){ t, s.s - o, s.len };
+	return true;
+}
+
+static void highlight_multivalue_value(struct highlight_span_array *ret, const string_span_t parent, const string_span_t s, enum field section)
+{
+	switch (section) {
+	case DNS:
+		append_highlight_span(ret, parent.s, s, is_valid_dns(s) ? HighlightIP : HighlightError);
+		break;
+	case Address:
+	case AllowedIPs: {
+		size_t slash;
+
+		if (!is_valid_network(s)) {
+			append_highlight_span(ret, parent.s, s, HighlightError);
+			break;
+		}
+		for (slash = 0; slash < s.len; ++slash) {
+			if (s.s[slash] == '/')
+				break;
+		}
+		if (slash == s.len) {
+			append_highlight_span(ret, parent.s, s, HighlightIP);
+		} else {
+			append_highlight_span(ret, parent.s, (string_span_t){ s.s, slash }, HighlightIP);
+			append_highlight_span(ret, parent.s, (string_span_t){ s.s + slash, 1 }, HighlightDelimiter);
+			append_highlight_span(ret, parent.s, (string_span_t){ s.s + slash + 1, s.len - slash - 1 }, HighlightCidr);
+		}
+		break;
+	}
+	default:
+		append_highlight_span(ret, parent.s, s, HighlightError);
+	}
+}
+
+static void highlight_multivalue(struct highlight_span_array *ret, const string_span_t parent, const string_span_t s, enum field section)
+{
+	string_span_t current_span = { s.s, 0 };
+	size_t len_at_last_space = 0;
+
+	for (size_t i = 0; i < s.len; ++i) {
+		if (s.s[i] == ',') {
+			current_span.len = len_at_last_space;
+			highlight_multivalue_value(ret, parent, current_span, section);
+			append_highlight_span(ret, parent.s, (string_span_t){ s.s + i, 1 }, HighlightDelimiter);
+			len_at_last_space = 0;
+			current_span = (string_span_t){ s.s + i + 1, 0 };
+		} else if (s.s[i] == ' ' || s.s[i] == '\t') {
+			if (&s.s[i] == current_span.s && !current_span.len)
+				++current_span.s;
+			else
+				++current_span.len;
+		} else {
+			len_at_last_space = ++current_span.len;
+		}
+	}
+	current_span.len = len_at_last_space;
+	if (current_span.len)
+		highlight_multivalue_value(ret, parent, current_span, section);
+	else if (ret->spans[ret->len - 1].type == HighlightDelimiter)
+		ret->spans[ret->len - 1].type = HighlightError;
+}
+
+static void highlight_value(struct highlight_span_array *ret, const string_span_t parent, const string_span_t s, enum field section)
+{
+	switch (section) {
+	case PrivateKey:
+		append_highlight_span(ret, parent.s, s, is_valid_key(s) ? HighlightPrivateKey : HighlightError);
+		break;
+	case PublicKey:
+		append_highlight_span(ret, parent.s, s, is_valid_key(s) ? HighlightPublicKey : HighlightError);
+		break;
+	case PresharedKey:
+		append_highlight_span(ret, parent.s, s, is_valid_key(s) ? HighlightPresharedKey : HighlightError);
+		break;
+	case MTU:
+		append_highlight_span(ret, parent.s, s, is_valid_mtu(s) ? HighlightMTU : HighlightError);
+		break;
+#ifndef MOBILE_WGQUICK_SUBSET
+	case SaveConfig:
+		append_highlight_span(ret, parent.s, s, is_valid_saveconfig(s) ? HighlightSaveConfig : HighlightError);
+		break;
+	case FwMark:
+		append_highlight_span(ret, parent.s, s, is_valid_fwmark(s) ? HighlightFwMark : HighlightError);
+		break;
+	case Table:
+		append_highlight_span(ret, parent.s, s, is_valid_table(s) ? HighlightTable : HighlightError);
+		break;
+	case PreUp:
+	case PostUp:
+	case PreDown:
+	case PostDown:
+		append_highlight_span(ret, parent.s, s, is_valid_prepostupdown(s) ? HighlightCmd : HighlightError);
+		break;
+#endif
+	case ListenPort:
+		append_highlight_span(ret, parent.s, s, is_valid_port(s) ? HighlightPort : HighlightError);
+		break;
+	case PersistentKeepalive:
+		append_highlight_span(ret, parent.s, s, is_valid_persistentkeepalive(s) ? HighlightKeepalive : HighlightError);
+		break;
+	case Endpoint: {
+		size_t colon;
+
+		if (!is_valid_endpoint(s)) {
+			append_highlight_span(ret, parent.s, s, HighlightError);
+			break;
+		}
+		for (colon = s.len; colon --> 0;) {
+			if (s.s[colon] == ':')
+				break;
+		}
+		append_highlight_span(ret, parent.s, (string_span_t){ s.s, colon }, HighlightHost);
+		append_highlight_span(ret, parent.s, (string_span_t){ s.s + colon, 1 }, HighlightDelimiter);
+		append_highlight_span(ret, parent.s, (string_span_t){ s.s + colon + 1, s.len - colon - 1 }, HighlightPort);
+		break;
+	}
+	case Address:
+	case DNS:
+	case AllowedIPs:
+		highlight_multivalue(ret, parent, s, section);
+		break;
+	default:
+		append_highlight_span(ret, parent.s, s, HighlightError);
+	}
+}
+
+struct highlight_span *highlight_config(const char *config)
+{
+	struct highlight_span_array ret = { 0 };
+	const string_span_t s = { config, strlen(config) };
+	string_span_t current_span = { s.s, 0 };
+	enum field current_section = Invalid, current_field = Invalid;
+	enum { OnNone, OnKey, OnValue, OnComment, OnSection } state = OnNone;
+	size_t len_at_last_space = 0, equals_location = 0;
+
+	for (size_t i = 0; i <= s.len; ++i) {
+		if (i == s.len || s.s[i] == '\n' || (state != OnComment && s.s[i] == '#')) {
+			if (state == OnKey) {
+				current_span.len = len_at_last_space;
+				append_highlight_span(&ret, s.s, current_span, HighlightError);
+			} else if (state == OnValue) {
+				if (current_span.len) {
+					append_highlight_span(&ret, s.s, (string_span_t){ s.s + equals_location, 1 }, HighlightDelimiter);
+					current_span.len = len_at_last_space;
+					highlight_value(&ret, s, current_span, current_field);
+				} else {
+					append_highlight_span(&ret, s.s, (string_span_t){ s.s + equals_location, 1 }, HighlightError);
+				}
+			} else if (state == OnSection) {
+				current_span.len = len_at_last_space;
+				current_section = get_sectiontype(current_span);
+				append_highlight_span(&ret, s.s, current_span, current_section == Invalid ? HighlightError : HighlightSection);
+			} else if (state == OnComment) {
+				append_highlight_span(&ret, s.s, current_span, HighlightComment);
+			}
+			if (i == s.len)
+				break;
+			len_at_last_space = 0;
+			current_field = Invalid;
+			if (s.s[i] == '#') {
+				current_span = (string_span_t){ s.s + i, 1 };
+				state = OnComment;
+			} else {
+				current_span = (string_span_t){ s.s + i + 1, 0 };
+				state = OnNone;
+			}
+		} else if (state == OnComment) {
+			++current_span.len;
+		} else if (s.s[i] == ' ' || s.s[i] == '\t') {
+			if (&s.s[i] == current_span.s && !current_span.len)
+				++current_span.s;
+			else
+				++current_span.len;
+		} else if (s.s[i] == '=' && state == OnKey) {
+			current_span.len = len_at_last_space;
+			current_field = get_field(current_span);
+			enum field section = section_for_field(current_field);
+			if (section == Invalid || current_field == Invalid || section != current_section)
+				append_highlight_span(&ret, s.s, current_span, HighlightError);
+			else
+				append_highlight_span(&ret, s.s, current_span, HighlightField);
+			equals_location = i;
+			current_span = (string_span_t){ s.s + i + 1, 0 };
+			state = OnValue;
+		} else {
+			if (state == OnNone)
+				state = s.s[i] == '[' ? OnSection : OnKey;
+			len_at_last_space = ++current_span.len;
+		}
+	}
+
+	append_highlight_span(&ret, s.s, (string_span_t){ s.s, -1 }, HighlightEnd);
+	return ret.spans;
+}

contrib/highlighter/highlighter.h

@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <sys/types.h>
+
+enum highlight_type {
+	HighlightSection,
+	HighlightField,
+	HighlightPrivateKey,
+	HighlightPublicKey,
+	HighlightPresharedKey,
+	HighlightIP,
+	HighlightCidr,
+	HighlightHost,
+	HighlightPort,
+	HighlightMTU,
+	HighlightKeepalive,
+	HighlightComment,
+	HighlightDelimiter,
+#ifndef MOBILE_WGQUICK_SUBSET
+	HighlightTable,
+	HighlightFwMark,
+	HighlightSaveConfig,
+	HighlightCmd,
+#endif
+	HighlightError,
+	HighlightEnd
+};
+
+struct highlight_span {
+	enum highlight_type type;
+	size_t start, len;
+};
+
+struct highlight_span *highlight_config(const char *config);