For mozilla-mobile#9338 - Introduce SafeUrl to strip unwanted uri sch…

…emes

Interested clients can overwrite "mozac_url_schemes_blocklist" with a custom
list of uri schemes that will be recursively removed from the front of the uri.

components/support/utils/src/main/java/mozilla/components/support/utils/SafeUrl.kt

@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.support.utils
+
+import android.content.Context
+
+/**
+ * Collection of methods used for ensuring the validity and security of URLs.
+ */
+object SafeUrl {
+    /**
+     * Remove recursively the schemes declared in [R.array.mozac_url_schemes_blocklist]
+     * from the front of [unsafeText].
+     */
+    fun stripUnsafeUrlSchemes(context: Context, unsafeText: CharSequence?): String? {
+        val urlSchemesBlocklist = context.resources.getStringArray(R.array.mozac_url_schemes_blocklist)
+        var safeUrl = unsafeText.toString()
+        if (safeUrl.isEmpty()) {
+            return safeUrl
+        }
+
+        @Suppress("ControlFlowWithEmptyBody", "EmptyWhileBlock")
+        while (urlSchemesBlocklist.find {
+                if (safeUrl.startsWith(it, true)) {
+                    safeUrl = safeUrl.replaceFirst(Regex(it, RegexOption.IGNORE_CASE), "")
+                    true
+                } else {
+                    false
+                }
+            } != null) {
+        }
+
+        return safeUrl
+    }
+}

components/support/utils/src/main/res/values/arrays.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8" standalone="yes"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<resources>
+    <!--
+    List of url schemes used by methods of SafeUrl.
+    -->
+    <string-array name="mozac_url_schemes_blocklist" />
+</resources>

components/support/utils/src/test/java/mozilla/components/support/utils/SafeUrlTest.kt

@@ -0,0 +1,55 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.support.utils
+
+import android.content.Context
+import android.content.res.Resources
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import mozilla.components.support.test.mock
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.Mockito.doReturn
+
+@RunWith(AndroidJUnit4::class)
+class SafeUrlTest {
+    @Test
+    fun `WHEN schemes blocklist is empty THEN stripUnsafeUrlSchemes should return the initial String`() {
+        val resources = mock<Resources>()
+        val context = mock<Context>()
+        doReturn(resources).`when`(context).resources
+        doReturn(emptyArray<String>()).`when`(resources).getStringArray(R.array.mozac_url_schemes_blocklist)
+
+        val result = SafeUrl.stripUnsafeUrlSchemes(context, "unsafeText")
+
+        assertEquals("unsafeText", result)
+    }
+
+    @Test
+    fun `WHEN schemes blocklist contains items not found in the argument THEN stripUnsafeUrlSchemes should return the initial String`() {
+        val resources = mock<Resources>()
+        val context = mock<Context>()
+        doReturn(resources).`when`(context).resources
+        doReturn(arrayOf("alien")).`when`(resources).getStringArray(R.array.mozac_url_schemes_blocklist)
+
+        val result = SafeUrl.stripUnsafeUrlSchemes(context, "thisIsAnOkText")
+
+        assertEquals("thisIsAnOkText", result)
+    }
+
+    @Test
+    fun `WHEN schemes blocklist contains items found in the argument THEN stripUnsafeUrlSchemes should recursively remove them from the front`() {
+        val resources = mock<Resources>()
+        val context = mock<Context>()
+        doReturn(resources).`when`(context).resources
+        doReturn(arrayOf("one", "two")).`when`(resources).getStringArray(R.array.mozac_url_schemes_blocklist)
+
+        val result = SafeUrl.stripUnsafeUrlSchemes(context, "two" + "one" + "one" + "two" + "safeText")
+        assertEquals("safeText", result)
+
+        val result2 = SafeUrl.stripUnsafeUrlSchemes(context, "one" + "two" + "one" + "two" + "safeText" + "one")
+        assertEquals("safeText" + "one", result2)
+    }
+}

docs/changelog.md

@@ -12,6 +12,9 @@ permalink: /changelog/
 * [Gecko](https://github.com/mozilla-mobile/android-components/blob/master/buildSrc/src/main/java/Gecko.kt)
 * [Configuration](https://github.com/mozilla-mobile/android-components/blob/master/.config.yml)
 
+* **support-utils**:
+  * 🌟 Added SafeUrl#stripUnsafeUrlSchemes that can cleanup unwanted uri schemes. Interested clients can specify what these are by overwriting "mozac_url_schemes_blocklist".
+
 * **feature-prompts**:
   * 🚒 Bug fixed [issue #9229](https://github.com/mozilla-mobile/android-components/issues/9229) - Dismiss SelectLoginPrompt from the current tab when opening a new one ensuring the new one can show it's own. When returning to the previous tab users should focus a login field to see the SelectLoginPrompt again.