From f5bd6a6a4ee50475ca056fe9cc0246bb424debe1 Mon Sep 17 00:00:00 2001
From: Maxim Goretskyy <maximg@fb.com>
Date: Wed, 29 Jan 2020 13:11:19 -0800
Subject: [PATCH] Cert Hashing

Summary: See D19583338 for context

Reviewed By: jingping2015

Differential Revision: D19584725

fbshipit-source-id: 0d31a7a989a57d717930c37bc7aa54e6c7f537ae
---
 .../appevents/AppEventsConstants.java         |  5 ++
 .../appevents/internal/SessionLogger.java     |  3 ++
 .../internal/security/CertificateUtil.java    | 46 +++++++++++++++++++
 3 files changed, 54 insertions(+)
 create mode 100644 facebook-core/src/main/java/com/facebook/internal/security/CertificateUtil.java

diff --git a/facebook-core/src/main/java/com/facebook/appevents/AppEventsConstants.java b/facebook-core/src/main/java/com/facebook/appevents/AppEventsConstants.java
index c14b3e4db1..d7af3fd354 100644
--- a/facebook-core/src/main/java/com/facebook/appevents/AppEventsConstants.java
+++ b/facebook-core/src/main/java/com/facebook/appevents/AppEventsConstants.java
@@ -269,6 +269,11 @@ public class AppEventsConstants {
      */
     public static final String EVENT_PARAM_PACKAGE_FP = "fb_mobile_pckg_fp";
 
+    /**
+     * Parameter key used to specify hashed cert for signing the apk.
+     */
+    public static final String EVENT_PARAM_APP_CERT_HASH = "fb_mobile_app_cert_hash";
+
     // Parameter values
 
     /** Yes-valued parameter value to be used with parameter keys that need a Yes/No value */
diff --git a/facebook-core/src/main/java/com/facebook/appevents/internal/SessionLogger.java b/facebook-core/src/main/java/com/facebook/appevents/internal/SessionLogger.java
index 033f48d961..9cad03376b 100644
--- a/facebook-core/src/main/java/com/facebook/appevents/internal/SessionLogger.java
+++ b/facebook-core/src/main/java/com/facebook/appevents/internal/SessionLogger.java
@@ -34,6 +34,7 @@
 import com.facebook.appevents.AppEventsLogger;
 import com.facebook.appevents.InternalAppEventsLogger;
 import com.facebook.internal.Logger;
+import com.facebook.internal.security.CertificateUtil;
 
 import java.util.Locale;
 
@@ -81,6 +82,8 @@ public static void logActivateApp(
         eventParams.putString(
                 AppEventsConstants.EVENT_PARAM_PACKAGE_FP,
                 computePackageChecksum(context));
+        eventParams.putString(AppEventsConstants.EVENT_PARAM_APP_CERT_HASH,
+                CertificateUtil.getCertificateHash(context));
         InternalAppEventsLogger logger = new InternalAppEventsLogger(
                 activityName,
                 appId,
diff --git a/facebook-core/src/main/java/com/facebook/internal/security/CertificateUtil.java b/facebook-core/src/main/java/com/facebook/internal/security/CertificateUtil.java
new file mode 100644
index 0000000000..34b860a028
--- /dev/null
+++ b/facebook-core/src/main/java/com/facebook/internal/security/CertificateUtil.java
@@ -0,0 +1,46 @@
+package com.facebook.internal.security;
+
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.content.pm.Signature;
+import android.util.Base64;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+/*
+    This would need to be changed if we change the docs for how to submit the certificate hashes
+    https://developers.facebook.com/docs/android/getting-started/
+ */
+public class CertificateUtil {
+
+    private CertificateUtil() {}
+
+    private static final String DELIMITER = ":"; //not part of valid characters for base64
+
+    /**
+     * @return String of concatenated signatures, since there can be more than one
+     */
+    public static String getCertificateHash(Context ctx) {
+        try {
+            Signature[] signatures = ctx.getPackageManager().getPackageInfo(ctx.getPackageName(), PackageManager.GET_SIGNATURES).signatures;
+            StringBuilder sb = new StringBuilder();
+            MessageDigest md = MessageDigest.getInstance("SHA1");
+            for (Signature signature : signatures) {
+                md.update(signature.toByteArray());
+                sb.append(Base64.encodeToString(md.digest(), Base64.DEFAULT));
+                sb.append(DELIMITER);
+            }
+
+            if (sb.length() > 0) {
+                sb.setLength(sb.length() - 1); //remove last delimiter
+            }
+
+            return sb.toString();
+        } catch (PackageManager.NameNotFoundException e) {
+            //do nothing
+        } catch (NoSuchAlgorithmException e) {
+            //do nothing
+        }
+        return "";
+    }
+}