fix(end-to-encryption): verify metadata

.codacy.yml

@@ -0,0 +1,5 @@
+# SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+exclude_paths:
+  - "app/src/main/cpp/**"

REUSE.toml

@@ -29,6 +29,12 @@ precedence = "aggregate"
 SPDX-FileCopyrightText = "2015-2016 ownCloud Inc."
 SPDX-License-Identifier = "GPL-2.0-only"
 
+[[annotations]]
+path = ["app/libs/local-maven/**/*.aar", "app/libs/local-maven/**/*.pom"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2026 Nextcloud GmbH and Nextcloud contributors"
+SPDX-License-Identifier = "AGPL-3.0-or-later"
+
 [[annotations]]
 path = ["app/src/**/res/mipmap-**dpi/ic_launcher.png", "app/src/**/ic_launcher-web.png", "src/**/fastlane/metadata/en-US/images/*.png",  "src/generic/fastlane/metadata/android/en-US/images/icon.png", "src/versionDev/fastlane/metadata/android/en-US/images/icon.png", "app/src/main/ic_launcher-web-round.png"]
 precedence = "aggregate"

app/build.gradle.kts

@@ -86,6 +86,7 @@ android {
     externalNativeBuild {
         cmake {
             version = "${ndkEnv["CMAKE_VERSION"]}"
+            path = file("src/main/cpp/CMakeLists.txt")
         }
     }
 
@@ -107,7 +108,7 @@ android {
         compileSdk = 36
 
         ndk {
-            abiFilters += listOf("arm64-v8a", "x86_64", "x86")
+            abiFilters += listOf("arm64-v8a", "x86_64")
         }
 
         buildConfigField("boolean", "CI", ciBuild.toString())
@@ -192,6 +193,7 @@ android {
         viewBinding = true
         aidl = true
         compose = true
+        prefab = true
     }
 
     compileOptions {
@@ -444,6 +446,7 @@ dependencies {
 
     // region Crypto
     implementation(libs.conscrypt.android)
+    implementation(libs.openssl)
     // endregion
 
     // region Library

app/libs/local-maven/com/nextcloud/openssl/3.5.6/openssl-3.5.6.pom

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.nextcloud</groupId>
+  <artifactId>openssl</artifactId>
+  <version>3.5.6</version>
+  <packaging>aar</packaging>
+</project>

app/src/androidTest/java/com/owncloud/android/utils/EncryptionUtilsMetadataVerificationTests.kt

@@ -0,0 +1,102 @@
+/*
+ * Nextcloud - Android Client
+ *
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+package com.owncloud.android.utils
+
+import com.owncloud.android.datamodel.e2e.v2.encrypted.EncryptedFolderMetadataFile
+import com.owncloud.android.datamodel.e2e.v2.encrypted.EncryptedMetadata
+import com.owncloud.android.datamodel.e2e.v2.encrypted.EncryptedUser
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class EncryptionUtilsMetadataVerificationTests {
+
+    private val sut = EncryptionUtilsV2()
+
+    @Test
+    fun testVerifyMetadataWhenGivenValidInputsShouldReturnTrue() {
+        val metadata = EncryptedFolderMetadataFile(
+            metadata =
+                EncryptedMetadata(
+                    authenticationTag = "xkVxj0NbQEXIEMlulYZJgg==",
+                    nonce = "HzRiseUfoFJ5lqUi",
+                    ciphertext = "EOnzuyVn9R8qDUBY4yeuJbhQdkOHBMy3nyRGwY0y/+oWctV17XvE0RIbOhH7+smKV3orJKatu5fG6iIZN+" +
+                        "HZUQASTCdQ0mdFVPJmdk20UH5nFZ/ilQIyyXAFhLHdYwWA/M7wKYoh5W9fDXNX9cZvHgjWPdT9Pq99PUv37atYxj7Je" +
+                        "25GenbtxkVxj0NbQEXIEMlulYZJgg=="
+                ),
+            users = listOf(
+                EncryptedUser(
+                    userId = "admin",
+                    certificate = "-----BEGIN CERTIFICATE-----\nMIIC7jCCAdagAwIBAgIBADANBgkqhkiG9w0BAQUFADAQMQ4wDAYD" +
+                        "VQQDEwVhZG1p\nbjAeFw0yNjA0MjcwNzI5NDdaFw00NjA0MjIwNzI5NDdaMBAxDjAMBgNVBAMTBWFk\nbWluMIIBIjAN" +
+                        "BgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwE513/kdkIp+Z5pI\n7rq1UKV5LBiB6dl4Wh46nI3mhVacOA1dJJWIU" +
+                        "xRkkrUNWJewe8eJ7QWmhSpeBauA\n06PrAOTd1ZA4gSUWKpsYJqKm5Nxjp+BUMK1nHGQCkNQWjRllhyKTJeG/9PPc0Z" +
+                        "rJ\nh4V27bCXC9iX5l/ve35fp99VR4tQ947HWObe07EdPIEFNYfT/IurPwMySZ1WH1gy\nDTw7IxMXcPVg+GUlfBoSV" +
+                        "gQ1UdCkvgHc9pE1LuFmyBguAzGLbXDfspUuTs85RLGX\nGYdv2vZU/R2kJEs3ePMtaGXw6DVSx82RkPFVaLDCdShX24" +
+                        "yk6gLNEv9oTUXY40i3\nn8njRQIDAQABo1MwUTAdBgNVHQ4EFgQUDE381mprCEvSLaFeOwZRliBSJnwwHwYD\nVR0j" +
+                        "BBgwFoAUDE381mprCEvSLaFeOwZRliBSJnwwDwYDVR0TAQH/BAUwAwEB/zAN\nBgkqhkiG9w0BAQUFAAOCAQEAgU0o8" +
+                        "Qp5wn3vkcQLYao2heWKsbYYl8wqkztRVVKb\n+qMe2m/FOOMK1Rxv/anEVHHN+SnTc481fHd8z3w6II28LxJ5M+Ixzo" +
+                        "AFTj6gCv8+\nrL1R9kE91401d1+ulAiJR92ykOcB1h8bk5yoCZSRLIXwViCGUrbC3iu2NLWQDYk4\nvjxwqCSJOWUQh" +
+                        "+qaYGCjB6mgkBMAnXGJCN2fV7sAR7N8Hy7Yh5jvuQOgY574FSoS\nuKCMGJZ6ecJlw+rB5pqanlLS9+HNnQ655/gTYg" +
+                        "VBJClFClh4nwdPHtpyTySwgx1V\nr3VDvglfnZM+gD/D2d9nTLIlT3MZqhGOIkxKvpVVkdJKzg" +
+                        "==\n-----END CERTIFICATE-----",
+                    encryptedMetadataKey = "coawvmhMoAl3iL5okD7K4a4au0Jt0SqUXp6pHP8WD1YTOemFVPsz+ts7TD5kB7ha6Ja3tLdG" +
+                        "Mq76LP/d2/pbHUiKBd6rytUo6ioHsNmmlTGHAlk9VTDY9fcvtVgkNzy7qyXvsdsUn0gBQ18l526J/bt1uRlClYNKva" +
+                        "EnIh2l3B8X58pzNZqhAKNI7z7WRDbXOVskr4rnqWr2ExBeaZgFwo5nNi9yiqpckICb1S2qwuZJbItqZ8VR2bOG+WpC" +
+                        "MwrgcE5UJ6ZvaKLREfmR+qoYYB1oyUuy78eA+sDa3rO5bSgs/9I/cli1b3lZ8JFfgHXRiUYUmBcxZOmUE2IfRSHFTA=="
+                )
+            ),
+            version = "2.0",
+            filedrop = mutableMapOf()
+        )
+        val message = EncryptionUtils.serializeJSON(metadata, true)
+
+        val cert = """
+            -----BEGIN CERTIFICATE-----
+            MIIC7jCCAdagAwIBAgIBADANBgkqhkiG9w0BAQUFADAQMQ4wDAYDVQQDEwVhZG1p
+            bjAeFw0yNjA0MjcwNzI5NDdaFw00NjA0MjIwNzI5NDdaMBAxDjAMBgNVBAMTBWFk
+            bWluMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwE513/kdkIp+Z5pI
+            7rq1UKV5LBiB6dl4Wh46nI3mhVacOA1dJJWIUxRkkrUNWJewe8eJ7QWmhSpeBauA
+            06PrAOTd1ZA4gSUWKpsYJqKm5Nxjp+BUMK1nHGQCkNQWjRllhyKTJeG/9PPc0ZrJ
+            h4V27bCXC9iX5l/ve35fp99VR4tQ947HWObe07EdPIEFNYfT/IurPwMySZ1WH1gy
+            DTw7IxMXcPVg+GUlfBoSVgQ1UdCkvgHc9pE1LuFmyBguAzGLbXDfspUuTs85RLGX
+            GYdv2vZU/R2kJEs3ePMtaGXw6DVSx82RkPFVaLDCdShX24yk6gLNEv9oTUXY40i3
+            n8njRQIDAQABo1MwUTAdBgNVHQ4EFgQUDE381mprCEvSLaFeOwZRliBSJnwwHwYD
+            VR0jBBgwFoAUDE381mprCEvSLaFeOwZRliBSJnwwDwYDVR0TAQH/BAUwAwEB/zAN
+            BgkqhkiG9w0BAQUFAAOCAQEAgU0o8Qp5wn3vkcQLYao2heWKsbYYl8wqkztRVVKb
+            +qMe2m/FOOMK1Rxv/anEVHHN+SnTc481fHd8z3w6II28LxJ5M+IxzoAFTj6gCv8+
+            rL1R9kE91401d1+ulAiJR92ykOcB1h8bk5yoCZSRLIXwViCGUrbC3iu2NLWQDYk4
+            vjxwqCSJOWUQh+qaYGCjB6mgkBMAnXGJCN2fV7sAR7N8Hy7Yh5jvuQOgY574FSoS
+            uKCMGJZ6ecJlw+rB5pqanlLS9+HNnQ655/gTYgVBJClFClh4nwdPHtpyTySwgx1V
+            r3VDvglfnZM+gD/D2d9nTLIlT3MZqhGOIkxKvpVVkdJKzg==
+            -----END CERTIFICATE-----
+        """.trimIndent()
+        val certs = listOf(EncryptionUtils.convertCertFromString(cert))
+        val signature = """
+            MIIE1wYJKoZIhvcNAQcCoIIEyDCCBMQCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGgggLyMIIC7jCCAdagAwIBAgIB
+            ADANBgkqhkiG9w0BAQUFADAQMQ4wDAYDVQQDEwVhZG1pbjAeFw0yNjA0MjcwNzI5NDdaFw00NjA0MjIwNzI5NDdaMBAxDjAMBgNV
+            BAMTBWFkbWluMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwE513/kdkIp+Z5pI7rq1UKV5LBiB6dl4Wh46nI3mhVa
+            cOA1dJJWIUxRkkrUNWJewe8eJ7QWmhSpeBauA06PrAOTd1ZA4gSUWKpsYJqKm5Nxjp+BUMK1nHGQCkNQWjRllhyKTJeG/9PPc0Zr
+            Jh4V27bCXC9iX5l/ve35fp99VR4tQ947HWObe07EdPIEFNYfT/IurPwMySZ1WH1gyDTw7IxMXcPVg+GUlfBoSVgQ1UdCkvgHc9p
+            E1LuFmyBguAzGLbXDfspUuTs85RLGXGYdv2vZU/R2kJEs3ePMtaGXw6DVSx82RkPFVaLDCdShX24yk6gLNEv9oTUXY40i3n8nj
+            RQIDAQABo1MwUTAdBgNVHQ4EFgQUDE381mprCEvSLaFeOwZRliBSJnwwHwYDVR0jBBgwFoAUDE381mprCEvSLaFeOwZRliBSJnww
+            DwYDVR0TAQH/BAUwAwEB/zANBgkqhkiG9w0BAQUFAAOCAQEAgU0o8Qp5wn3vkcQLYao2heWKsbYYl8wqkztRVVKb+qMe2m/FOOMK
+            1Rxv/anEVHHN+SnTc481fHd8z3w6II28LxJ5M+IxzoAFTj6gCv8+rL1R9kE91401d1+ulAiJR92ykOcB1h8bk5yoCZSRLIXwViCG
+            UrbC3iu2NLWQDYk4vjxwqCSJOWUQh+qaYGCjB6mgkBMAnXGJCN2fV7sAR7N8Hy7Yh5jvuQOgY574FSoSuKCMGJZ6ecJlw+rB5pqa
+            nlLS9+HNnQ655/gTYgVBJClFClh4nwdPHtpyTySwgx1Vr3VDvglfnZM+gD/D2d9nTLIlT3MZqhGOIkxKvpVVkdJKzjGCAakwggGl
+            AgEAMBUwEDEOMAwGA1UEAxMFYWRtaW4CAQAwDQYJYIZIAWUDBAIBBQCgaTAYBgkqhkiG9w0BCQMxCwYJKoZIhvcNAQcBMC8GCSqG
+            SIb3DQEJBDEiBCDJDYSA3+VA0KfGQbP7BQsnL/s24W/WIb99zb+4uQ8KLjAcBgkqhkiG9w0BCQUxDxcNMjYwNDI3MDczMDAyWjAL
+            BgkqhkiG9w0BAQsEggEAYgDB02/z+KaLvieL1hMMA9IZN8KKc4igvilBoS5W7isiArP8D/GIxghMZkrC0Tzqs+/VRlfFREUgf4aBd
+            9GVzd86Qfrhcrzrdd8hoDQvOw/X3UGftqbgJQmOjZUDpI3TiupyQvOU/zqlIjOq5BiZN6RNti2BTcbNyjaTeVh6u1tcqVVSp/Z0ke
+            Ub+CnJFtIk6WhFepJMWI0vN84OyegNsjzIMSU2WjiN3i0jmYc62MpxUN0ZzmNgdZ7y6exe1Sb8EYUYL83BehQUPKO5EwEjEwX+ScYz
+            iWK0atXZioZYI2XLejVbQm1/czPTlA3frywKyM1dnkiufzmRpB49QN4o3g==
+        """.trimIndent()
+        val signedData = sut.getSignedData(signature, message)
+        val result = sut.verifySignedData(signedData, certs)
+        assertTrue(result)
+    }
+}

app/src/main/cpp/CMakeLists.txt

@@ -0,0 +1,24 @@
+# Nextcloud - Android Client
+#
+# SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+cmake_minimum_required(VERSION 3.10.2)
+
+project(cms_verifier VERSION 1.0)
+
+find_package(openssl REQUIRED CONFIG)
+
+add_library(
+    cms_verifier
+    SHARED
+    cms_verifier.cpp
+)
+
+target_link_libraries(
+    cms_verifier
+    openssl::ssl
+    openssl::crypto
+    android
+    log
+)

app/src/main/cpp/cms_verifier.cpp

@@ -0,0 +1,100 @@
+/*
+ * Nextcloud - Android Client
+ *
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <jni.h>
+#include <android/log.h>
+#include <openssl/bio.h>
+#include <openssl/cms.h>
+#include <openssl/pem.h>
+#include <openssl/x509.h>
+#include <cstring>
+
+#define LOG_TAG "CmsVerifier"
+#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
+
+extern "C" JNIEXPORT jboolean JNICALL
+Java_com_nextcloud_utils_CmsSignatureVerifier_verifySignedData(
+    JNIEnv* env,
+    jobject /* thiz */,
+    jbyteArray cmsDataArray,
+    jbyteArray messageDataArray,
+    jobjectArray certPemArray
+) {
+    jsize cmsLen = env->GetArrayLength(cmsDataArray);
+    jbyte* cmsBytes = env->GetByteArrayElements(cmsDataArray, nullptr);
+    BIO* cmsBio = BIO_new_mem_buf(cmsBytes, static_cast<int>(cmsLen));
+
+    jsize msgLen = env->GetArrayLength(messageDataArray);
+    jbyte* msgBytes = env->GetByteArrayElements(messageDataArray, nullptr);
+    BIO* dataBio = BIO_new_mem_buf(msgBytes, static_cast<int>(msgLen));
+
+    CMS_ContentInfo* contentInfo = d2i_CMS_bio(cmsBio, nullptr);
+
+    BIO_free(cmsBio);
+    env->ReleaseByteArrayElements(cmsDataArray, cmsBytes, JNI_ABORT);
+
+    if (contentInfo == nullptr) {
+        LOGE("Failed to parse CMS content info");
+        BIO_free(dataBio);
+        env->ReleaseByteArrayElements(messageDataArray, msgBytes, JNI_ABORT);
+        return JNI_FALSE;
+    }
+
+    int verifyResult = CMS_verify(
+        contentInfo,
+        nullptr,
+        nullptr,
+        dataBio,
+        nullptr,
+        CMS_DETACHED | CMS_NO_SIGNER_CERT_VERIFY
+    );
+
+    BIO_free(dataBio);
+    env->ReleaseByteArrayElements(messageDataArray, msgBytes, JNI_ABORT);
+
+    if (verifyResult != 1) {
+        LOGE("CMS_verify failed");
+        CMS_ContentInfo_free(contentInfo);
+        return JNI_FALSE;
+    }
+
+    STACK_OF(CMS_SignerInfo)* signerInfos = CMS_get0_SignerInfos(contentInfo);
+    int numSigners = sk_CMS_SignerInfo_num(signerInfos);
+    jsize numCerts = env->GetArrayLength(certPemArray);
+    jboolean matched = JNI_FALSE;
+
+    for (jsize i = 0; i < numCerts && !matched; ++i) {
+        auto certPem = reinterpret_cast<jstring>(env->GetObjectArrayElement(certPemArray, i));
+        const char* pemChars = env->GetStringUTFChars(certPem, nullptr);
+
+        BIO* certBio = BIO_new(BIO_s_mem());
+        BIO_write(certBio, pemChars, static_cast<int>(strlen(pemChars)));
+        X509* certX509 = PEM_read_bio_X509(certBio, nullptr, nullptr, nullptr);
+
+        BIO_free(certBio);
+        env->ReleaseStringUTFChars(certPem, pemChars);
+        env->DeleteLocalRef(certPem);
+
+        if (certX509 == nullptr) {
+            LOGE("Failed to parse PEM certificate at index %d", i);
+            continue;
+        }
+
+        for (int j = 0; j < numSigners; ++j) {
+            CMS_SignerInfo* signerInfo = sk_CMS_SignerInfo_value(signerInfos, j);
+            if (CMS_SignerInfo_cert_cmp(signerInfo, certX509) == 0) {
+                matched = JNI_TRUE;
+                break;
+            }
+        }
+
+        X509_free(certX509);
+    }
+
+    CMS_ContentInfo_free(contentInfo);
+    return matched;
+}

app/src/main/java/com/nextcloud/utils/CmsSignatureVerifier.kt

@@ -0,0 +1,18 @@
+/*
+ * Nextcloud - Android Client
+ *
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+package com.nextcloud.utils
+
+class CmsSignatureVerifier {
+    external fun verifySignedData(cmsData: ByteArray, messageData: ByteArray, certificates: Array<String>): Boolean
+
+    companion object {
+        init {
+            System.loadLibrary("cms_verifier")
+        }
+    }
+}