184 lines
6.6 KiB
Java
184 lines
6.6 KiB
Java
package org.thoughtcrime.securesms.linkpreview;
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import androidx.annotation.NonNull;
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import androidx.annotation.Nullable;
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import androidx.annotation.VisibleForTesting;
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import android.text.Html;
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import android.text.SpannableString;
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import android.text.TextUtils;
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import android.text.style.URLSpan;
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import android.text.util.Linkify;
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import com.annimon.stream.Stream;
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import com.google.android.collect.Sets;
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import org.thoughtcrime.securesms.stickers.StickerUrl;
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import org.thoughtcrime.securesms.util.Util;
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import org.whispersystems.libsignal.util.guava.Optional;
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import org.whispersystems.signalservice.api.util.OptionalUtil;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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import okhttp3.HttpUrl;
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public final class LinkPreviewUtil {
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private static final Pattern DOMAIN_PATTERN = Pattern.compile("^(https?://)?([^/]+).*$");
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private static final Pattern ALL_ASCII_PATTERN = Pattern.compile("^[\\x00-\\x7F]*$");
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private static final Pattern ALL_NON_ASCII_PATTERN = Pattern.compile("^[^\\x00-\\x7F]*$");
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private static final Pattern OPEN_GRAPH_TAG_PATTERN = Pattern.compile("<\\s*meta[^>]*property\\s*=\\s*\"\\s*og:([^\"]+)\"[^>]*/?\\s*>");
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private static final Pattern OPEN_GRAPH_CONTENT_PATTERN = Pattern.compile("content\\s*=\\s*\"([^\"]*)\"");
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private static final Pattern TITLE_PATTERN = Pattern.compile("<\\s*title[^>]*>(.*)<\\s*/title[^>]*>");
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private static final Pattern FAVICON_PATTERN = Pattern.compile("<\\s*link[^>]*rel\\s*=\\s*\".*icon.*\"[^>]*>");
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private static final Pattern FAVICON_HREF_PATTERN = Pattern.compile("href\\s*=\\s*\"([^\"]*)\"");
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private static final Set<String> INVALID_TOP_LEVEL_DOMAINS = Sets.newHashSet("onion");
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/**
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* @return All whitelisted URLs in the source text.
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*/
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public static @NonNull List<Link> findValidPreviewUrls(@NonNull String text) {
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SpannableString spannable = new SpannableString(text);
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boolean found = Linkify.addLinks(spannable, Linkify.WEB_URLS);
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if (!found) {
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return Collections.emptyList();
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}
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return Stream.of(spannable.getSpans(0, spannable.length(), URLSpan.class))
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.map(span -> new Link(span.getURL(), spannable.getSpanStart(span)))
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.filter(link -> isValidPreviewUrl(link.getUrl()))
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.toList();
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}
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/**
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* @return True if the host is present in the link whitelist.
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*/
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public static boolean isValidPreviewUrl(@Nullable String linkUrl) {
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if (linkUrl == null) return false;
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if (StickerUrl.isValidShareLink(linkUrl)) return true;
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HttpUrl url = HttpUrl.parse(linkUrl);
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return url != null &&
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!TextUtils.isEmpty(url.scheme()) &&
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"https".equals(url.scheme()) &&
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isLegalUrl(linkUrl);
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}
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public static boolean isLegalUrl(@NonNull String url) {
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Matcher matcher = DOMAIN_PATTERN.matcher(url);
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if (matcher.matches()) {
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String domain = matcher.group(2);
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String cleanedDomain = domain.replaceAll("\\.", "");
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String topLevelDomain = parseTopLevelDomain(domain);
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boolean validCharacters = ALL_ASCII_PATTERN.matcher(cleanedDomain).matches() ||
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ALL_NON_ASCII_PATTERN.matcher(cleanedDomain).matches();
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boolean validTopLevelDomain = !INVALID_TOP_LEVEL_DOMAINS.contains(topLevelDomain);
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return validCharacters && validTopLevelDomain;
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} else {
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return false;
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}
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}
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public static @NonNull OpenGraph parseOpenGraphFields(@Nullable String html) {
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return parseOpenGraphFields(html, text -> Html.fromHtml(text).toString());
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}
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@VisibleForTesting
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static @NonNull OpenGraph parseOpenGraphFields(@Nullable String html, @NonNull HtmlDecoder htmlDecoder) {
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if (html == null) {
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return new OpenGraph(Collections.emptyMap(), null, null);
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}
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Map<String, String> openGraphTags = new HashMap<>();
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Matcher openGraphMatcher = OPEN_GRAPH_TAG_PATTERN.matcher(html);
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while (openGraphMatcher.find()) {
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String tag = openGraphMatcher.group();
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String property = openGraphMatcher.groupCount() > 0 ? openGraphMatcher.group(1) : null;
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if (property != null) {
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Matcher contentMatcher = OPEN_GRAPH_CONTENT_PATTERN.matcher(tag);
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if (contentMatcher.find() && contentMatcher.groupCount() > 0) {
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String content = htmlDecoder.fromEncoded(contentMatcher.group(1));
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openGraphTags.put(property, content);
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}
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}
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}
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String htmlTitle = "";
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String faviconUrl = "";
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Matcher titleMatcher = TITLE_PATTERN.matcher(html);
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if (titleMatcher.find() && titleMatcher.groupCount() > 0) {
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htmlTitle = titleMatcher.group(1);
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}
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Matcher faviconMatcher = FAVICON_PATTERN.matcher(html);
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if (faviconMatcher.find()) {
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Matcher faviconHrefMatcher = FAVICON_HREF_PATTERN.matcher(faviconMatcher.group());
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if (faviconHrefMatcher.find() && faviconHrefMatcher.groupCount() > 0) {
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faviconUrl = faviconHrefMatcher.group(1);
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}
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}
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return new OpenGraph(openGraphTags, htmlTitle, faviconUrl);
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}
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private static @Nullable String parseTopLevelDomain(@NonNull String domain) {
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int periodIndex = domain.lastIndexOf(".");
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if (periodIndex >= 0 && periodIndex < domain.length() - 1) {
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return domain.substring(periodIndex + 1);
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} else {
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return null;
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}
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}
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public static final class OpenGraph {
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private final Map<String, String> values;
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private final @Nullable String htmlTitle;
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private final @Nullable String faviconUrl;
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private static final String KEY_TITLE = "title";
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private static final String KEY_DESCRIPTION_URL = "description";
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private static final String KEY_IMAGE_URL = "image";
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public OpenGraph(@NonNull Map<String, String> values, @Nullable String htmlTitle, @Nullable String faviconUrl) {
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this.values = values;
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this.htmlTitle = htmlTitle;
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this.faviconUrl = faviconUrl;
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}
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public @NonNull Optional<String> getTitle() {
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return OptionalUtil.absentIfEmpty(Util.getFirstNonEmpty(values.get(KEY_TITLE), htmlTitle));
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}
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public @NonNull Optional<String> getImageUrl() {
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return OptionalUtil.absentIfEmpty(Util.getFirstNonEmpty(values.get(KEY_IMAGE_URL), faviconUrl));
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}
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public @NonNull Optional<String> getDescription() {
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return OptionalUtil.absentIfEmpty(values.get(KEY_DESCRIPTION_URL));
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}
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}
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public interface HtmlDecoder {
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@NonNull String fromEncoded(@NonNull String html);
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}
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}
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