Implementation for blocking fraudulent 3PID /unbind attempts

docs/threepids/notification/sendgrid-handler.md

@@ -36,4 +36,10 @@ notification:
               body:
                 text: <Path to file containing the raw text part of the email. Do not set to not use one>
                 html: <Path to file containing the HTML part of the email. Do not set to not use one>
+          unbind:
+            fraudulent:
+              subject: <Subject of the email notification sent for potentially fraudulent 3PID unbinds>
+              body:
+                text: <Path to file containing the raw text part of the email. Do not set to not use one>
+                html: <Path to file containing the raw text part of the email. Do not set to not use one>
 ``` 

docs/threepids/notification/template-generator.md

@@ -20,7 +20,9 @@ threepid:
           session:
             validation:
               local: '/path/to/validate-local-template.eml'
-              remote: 'path/to/validate-remote-template.eml'
+              remote: '/path/to/validate-remote-template.eml'
+            unbind:
+              frandulent: '/path/to/unbind-fraudulent-template.eml'
           generic:
             matrixId: '/path/to/mxid-invite-template.eml'
 ```

docs/threepids/session/session.md

@@ -149,6 +149,9 @@ session:
         toRemote:
           enabled: true
           server: 'configExample'  # Not to be included in config! Already present in default config!
+    unbind:
+      fraudulent:
+        sendWarning: true
 # DO NOT COPY/PASTE THIS IN YOUR CONFIGURATION
 # CONFIGURATION EXAMPLE
 ```
@@ -168,6 +171,14 @@ Each scope is divided into three parts:
 If both `toLocal` and `toRemote` are enabled, the user will be offered to initiate a remote session once their 3PID
 locally validated.
 
+---
+
+`unbind.fraudulent` controls warning notifications if an illegal/fraudulent 3PID removal is attempted on the Identity server.  
+This is directly related to synapse disregard for privacy and new GDPR laws in Europe in an attempt to inform users about
+potential privacy leaks.
+
+For more information, see the corresponding [synapse issue](https://github.com/matrix-org/synapse/issues/4540).
+
 ### Web views
 Once a user click on a validation link, it is taken to the Identity Server validation page where the token is submitted.  
 If the session or token is invalid, an error page is displayed.  

src/main/java/io/kamax/mxisd/HttpMxisd.java

@@ -85,7 +85,7 @@ public class HttpMxisd {
                 .post(SessionValidateHandler.Path, sessValidateHandler)
                 .get(SessionTpidGetValidatedHandler.Path, SaneHandler.around(new SessionTpidGetValidatedHandler(m.getSession())))
                 .post(SessionTpidBindHandler.Path, SaneHandler.around(new SessionTpidBindHandler(m.getSession(), m.getInvitationManager())))
-                .post(SessionTpidUnbindHandler.Path, SaneHandler.around(new SessionTpidUnbindHandler()))
+                .post(SessionTpidUnbindHandler.Path, SaneHandler.around(new SessionTpidUnbindHandler(m.getSession())))
                 .get(RemoteIdentityAPIv1.SESSION_REQUEST_TOKEN, SaneHandler.around(new RemoteSessionStartHandler(m.getSession(), m.getConfig().getView())))
                 .get(RemoteIdentityAPIv1.SESSION_CHECK, SaneHandler.around(new RemoteSessionCheckHandler(m.getSession(), m.getConfig().getView())))
 

src/main/java/io/kamax/mxisd/Mxisd.java

@@ -102,7 +102,7 @@ public class Mxisd {
         idStrategy = new RecursivePriorityLookupStrategy(cfg.getLookup(), ThreePidProviders.get(), bridgeFetcher);
         pMgr = new ProfileManager(ProfileProviders.get(), clientDns, httpClient);
         notifMgr = new NotificationManager(cfg.getNotification(), NotificationHandlers.get());
-        sessMgr = new SessionMananger(cfg.getSession(), cfg.getMatrix(), store, notifMgr, httpClient);
+        sessMgr = new SessionMananger(cfg.getSession(), cfg.getMatrix(), store, notifMgr, idStrategy, httpClient);
         invMgr = new InvitationManager(cfg.getInvite(), store, idStrategy, signMgr, fedDns, notifMgr);
         authMgr = new AuthManager(cfg, AuthProviders.get(), idStrategy, invMgr, clientDns, httpClient);
         dirMgr = new DirectoryManager(cfg.getDirectory(), clientDns, httpClient, DirectoryProviders.get());

src/main/java/io/kamax/mxisd/config/SessionConfig.java

@@ -125,6 +125,34 @@ public class SessionConfig {
 
         }
 
+        public static class PolicyUnbind {
+
+            public static class PolicyUnbindFraudulent {
+
+                private boolean sendWarning = true;
+
+                public boolean getSendWarning() {
+                    return sendWarning;
+                }
+
+                public void setSendWarning(boolean sendWarning) {
+                    this.sendWarning = sendWarning;
+                }
+            }
+
+
+            private PolicyUnbindFraudulent fraudulent = new PolicyUnbindFraudulent();
+
+            public PolicyUnbindFraudulent getFraudulent() {
+                return fraudulent;
+            }
+
+            public void setFraudulent(PolicyUnbindFraudulent fraudulent) {
+                this.fraudulent = fraudulent;
+            }
+
+        }
+
         public Policy() {
             validation.enabled = true;
             validation.forLocal.enabled = true;
@@ -139,6 +167,7 @@ public class SessionConfig {
         }
 
         private PolicyTemplate validation = new PolicyTemplate();
+        private PolicyUnbind unbind = new PolicyUnbind();
 
         public PolicyTemplate getValidation() {
             return validation;
@@ -148,6 +177,14 @@ public class SessionConfig {
             this.validation = validation;
         }
 
+        public PolicyUnbind getUnbind() {
+            return unbind;
+        }
+
+        public void setUnbind(PolicyUnbind unbind) {
+            this.unbind = unbind;
+        }
+
     }
 
     private Policy policy = new Policy();

src/main/java/io/kamax/mxisd/config/threepid/connector/EmailSendGridConfig.java

@@ -115,7 +115,7 @@ public class EmailSendGridConfig {
 
     public static class Templates {
 
-        public static class TemplateSession {
+        public static class TemplateSessionValidation {
 
             private EmailTemplate local = new EmailTemplate();
             private EmailTemplate remote = new EmailTemplate();
@@ -137,6 +137,43 @@ public class EmailSendGridConfig {
             }
         }
 
+        public static class TemplateSessionUnbind {
+
+            private EmailTemplate fraudulent = new EmailTemplate();
+
+            public EmailTemplate getFraudulent() {
+                return fraudulent;
+            }
+
+            public void setFraudulent(EmailTemplate fraudulent) {
+                this.fraudulent = fraudulent;
+            }
+
+        }
+
+        public static class TemplateSession {
+
+            private TemplateSessionValidation validation = new TemplateSessionValidation();
+            private TemplateSessionUnbind unbind = new TemplateSessionUnbind();
+
+            public TemplateSessionValidation getValidation() {
+                return validation;
+            }
+
+            public void setValidation(TemplateSessionValidation validation) {
+                this.validation = validation;
+            }
+
+            public TemplateSessionUnbind getUnbind() {
+                return unbind;
+            }
+
+            public void setUnbind(TemplateSessionUnbind unbind) {
+                this.unbind = unbind;
+            }
+
+        }
+
         private EmailTemplate invite = new EmailTemplate();
         private TemplateSession session = new TemplateSession();
         private Map<String, EmailTemplate> generic = new HashMap<>();

src/main/java/io/kamax/mxisd/config/threepid/medium/EmailTemplateConfig.java

@@ -32,6 +32,7 @@ public class EmailTemplateConfig extends GenericTemplateConfig {
         getGeneric().put("matrixId", "classpath:/threepids/email/mxid-template.eml");
         getSession().getValidation().setLocal("classpath:/threepids/email/validate-local-template.eml");
         getSession().getValidation().setRemote("classpath:/threepids/email/validate-remote-template.eml");
+        getSession().getUnbind().setFraudulent("classpath:/threepids/email/unbind-fraudulent.eml");
     }
 
     public EmailTemplateConfig build() {

src/main/java/io/kamax/mxisd/config/threepid/medium/GenericTemplateConfig.java

@@ -62,7 +62,22 @@ public class GenericTemplateConfig {
 
         }
 
+        public static class SessionUnbind {
+
+            private String fraudulent;
+
+            public String getFraudulent() {
+                return fraudulent;
+            }
+
+            public void setFraudulent(String fraudulent) {
+                this.fraudulent = fraudulent;
+            }
+
+        }
+
         private SessionValidation validation = new SessionValidation();
+        private SessionUnbind unbind = new SessionUnbind();
 
         public SessionValidation getValidation() {
             return validation;
@@ -72,6 +87,14 @@ public class GenericTemplateConfig {
             this.validation = validation;
         }
 
+        public SessionUnbind getUnbind() {
+            return unbind;
+        }
+
+        public void setUnbind(SessionUnbind unbind) {
+            this.unbind = unbind;
+        }
+
     }
 
     private String invite;

src/main/java/io/kamax/mxisd/config/threepid/medium/PhoneSmsTemplateConfig.java

@@ -32,6 +32,7 @@ public class PhoneSmsTemplateConfig extends GenericTemplateConfig {
         getGeneric().put("matrixId", "classpath:/threepids/email/mxid-template.eml");
         getSession().getValidation().setLocal("classpath:/threepids/sms/validate-local-template.txt");
         getSession().getValidation().setRemote("classpath:/threepids/sms/validate-remote-template.txt");
+        getSession().getUnbind().setFraudulent("classpath:/threepids/sms/unbind-fraudulent.txt");
     }
 
     public PhoneSmsTemplateConfig build() {

src/main/java/io/kamax/mxisd/http/undertow/handler/identity/v1/SessionTpidUnbindHandler.java

@@ -21,10 +21,9 @@
 package io.kamax.mxisd.http.undertow.handler.identity.v1;
 
 import com.google.gson.JsonObject;
-import io.kamax.mxisd.exception.FeatureNotAvailable;
-import io.kamax.mxisd.exception.NotAllowedException;
 import io.kamax.mxisd.http.IsAPIv1;
 import io.kamax.mxisd.http.undertow.handler.BasicHttpHandler;
+import io.kamax.mxisd.session.SessionMananger;
 import io.undertow.server.HttpServerExchange;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -33,38 +32,19 @@ public class SessionTpidUnbindHandler extends BasicHttpHandler {
 
     public static final String Path = IsAPIv1.Base + "/3pid/unbind";
 
-    private transient final Logger log = LoggerFactory.getLogger(SessionTpidUnbindHandler.class);
+    private static final Logger log = LoggerFactory.getLogger(SessionTpidUnbindHandler.class);
+
+    private final SessionMananger sessMgr;
+
+    public SessionTpidUnbindHandler(SessionMananger sessMgr) {
+        this.sessMgr = sessMgr;
+    }
 
     @Override
     public void handleRequest(HttpServerExchange exchange) {
         JsonObject body = parseJsonObject(exchange);
-
-        // TODO also check for HS header to know which domain attempting the unbind
-        if (body.entrySet().size() == 2 && body.has("mxisd") && body.has("threepid")) {
-            /* This is a HS request to remove a 3PID and is considered:
-             * - An attack on user privacy
-             * - A baffling spec breakage requiring IS and HS 3PID info to be independent [1]
-             * - A baffling spec breakage that 3PID (un)bind is only one way [2]
-             *
-             * Given the lack of response on our extensive feedback on the proposal [3] which has not landed in the spec yet [4],
-             * We'll be denying such unbind requests and will inform users using their 3PID that a fraudulent attempt of
-             * removing their 3PID binding has been attempting but blocked.
-             *
-             * [1]: https://matrix.org/docs/spec/client_server/r0.4.0.html#adding-account-administrative-contact-information
-             * [2]: https://matrix.org/docs/spec/identity_service/r0.1.0.html#privacy
-             * [3]: https://docs.google.com/document/d/135g2muVxmuml0iUnLoTZxk8M2ZSt3kJzg81chGh51yg/edit
-             * [4]: https://github.com/matrix-org/matrix-doc/issues/1194
-             */
-
-            log.warn("A remote host attempted to unbind without proper authorization. Request was denied");
-
-            // TODO notify the 3PID owner
-
-            throw new NotAllowedException("You have attempted to alter 3PID bindings, which can only be done by the 3PID owner directly. " +
-                    "We have informed the 3PID owner of your fraudulent attempt.");
-        }
-
-        throw new FeatureNotAvailable("Unbind using a 3PID session is not defined in the spec");
+        sessMgr.unbind(body);
+        writeBodyAsUtf8(exchange, "{}");
     }
 
 }

src/main/java/io/kamax/mxisd/notification/NotificationHandler.java

@@ -20,6 +20,7 @@
 
 package io.kamax.mxisd.notification;
 
+import io.kamax.matrix.ThreePid;
 import io.kamax.mxisd.as.IMatrixIdInvite;
 import io.kamax.mxisd.invitation.IThreePidInviteReply;
 import io.kamax.mxisd.threepid.session.IThreePidSession;
@@ -38,4 +39,6 @@ public interface NotificationHandler {
 
     void sendForRemoteValidation(IThreePidSession session);
 
+    void sendForFraudulentUnbind(ThreePid tpid);
+
 }

src/main/java/io/kamax/mxisd/notification/NotificationManager.java

@@ -20,6 +20,7 @@
 
 package io.kamax.mxisd.notification;
 
+import io.kamax.matrix.ThreePid;
 import io.kamax.mxisd.as.IMatrixIdInvite;
 import io.kamax.mxisd.config.threepid.notification.NotificationConfig;
 import io.kamax.mxisd.exception.NotImplementedException;
@@ -81,4 +82,8 @@ public class NotificationManager {
         ensureMedium(session.getThreePid().getMedium()).sendForRemoteValidation(session);
     }
 
+    public void sendForFraudulentUnbind(ThreePid tpid) throws NotImplementedException {
+        ensureMedium(tpid.getMedium()).sendForFraudulentUnbind(tpid);
+    }
+
 }

src/main/java/io/kamax/mxisd/session/SessionMananger.java

@@ -28,12 +28,15 @@ import io.kamax.matrix.MatrixID;
 import io.kamax.matrix.ThreePid;
 import io.kamax.matrix.ThreePidMedium;
 import io.kamax.matrix._MatrixID;
+import io.kamax.matrix.json.GsonUtil;
 import io.kamax.mxisd.config.MatrixConfig;
 import io.kamax.mxisd.config.SessionConfig;
 import io.kamax.mxisd.exception.*;
 import io.kamax.mxisd.http.io.identity.RequestTokenResponse;
 import io.kamax.mxisd.http.undertow.handler.identity.v1.RemoteIdentityAPIv1;
+import io.kamax.mxisd.lookup.SingleLookupReply;
 import io.kamax.mxisd.lookup.ThreePidValidation;
+import io.kamax.mxisd.lookup.strategy.LookupStrategy;
 import io.kamax.mxisd.matrix.IdentityServerUtils;
 import io.kamax.mxisd.notification.NotificationManager;
 import io.kamax.mxisd.storage.IStorage;
@@ -71,6 +74,7 @@ public class SessionMananger {
     private MatrixConfig mxCfg;
     private IStorage storage;
     private NotificationManager notifMgr;
+    private LookupStrategy lookupMgr;
 
     private GsonParser parser = new GsonParser();
     private PhoneNumberUtil phoneUtil = PhoneNumberUtil.getInstance(); // FIXME refactor for sessions handling their own stuff
@@ -78,11 +82,19 @@ public class SessionMananger {
     // FIXME export into central class, set version
     private CloseableHttpClient client;
 
-    public SessionMananger(SessionConfig cfg, MatrixConfig mxCfg, IStorage storage, NotificationManager notifMgr, CloseableHttpClient client) {
+    public SessionMananger(
+            SessionConfig cfg,
+            MatrixConfig mxCfg,
+            IStorage storage,
+            NotificationManager notifMgr,
+            LookupStrategy lookupMgr,
+            CloseableHttpClient client
+    ) {
         this.cfg = cfg;
         this.mxCfg = mxCfg;
         this.storage = storage;
         this.notifMgr = notifMgr;
+        this.lookupMgr = lookupMgr;
         this.client = client;
     }
 
@@ -259,6 +271,54 @@ public class SessionMananger {
         }
     }
 
+    public void unbind(JsonObject reqData) {
+        // TODO also check for HS header to know which domain attempting the unbind
+        if (reqData.entrySet().size() == 2 && reqData.has("mxid") && reqData.has("threepid")) {
+            /* This is a HS request to remove a 3PID and is considered:
+             * - An attack on user privacy
+             * - A baffling spec breakage requiring IS and HS 3PID info to be independent [1]
+             * - A baffling spec breakage that 3PID (un)bind is only one way [2]
+             *
+             * Given the lack of response on our extensive feedback on the proposal [3] which has not landed in the spec yet [4],
+             * We'll be denying such unbind requests and will inform users using their 3PID that a fraudulent attempt of
+             * removing their 3PID binding has been attempted and blocked.
+             *
+             * [1]: https://matrix.org/docs/spec/client_server/r0.4.0.html#adding-account-administrative-contact-information
+             * [2]: https://matrix.org/docs/spec/identity_service/r0.1.0.html#privacy
+             * [3]: https://docs.google.com/document/d/135g2muVxmuml0iUnLoTZxk8M2ZSt3kJzg81chGh51yg/edit
+             * [4]: https://github.com/matrix-org/matrix-doc/issues/1194
+             */
+
+            log.warn("A remote host attempted to unbind without proper authorization. Request was denied");
+
+            if (!cfg.getPolicy().getUnbind().getFraudulent().getSendWarning()) {
+                log.info("Not sending notification to 3PID owner as per configuration");
+            } else {
+                log.info("Sending notification to 3PID owner as per configuration");
+
+                ThreePid tpid = GsonUtil.get().fromJson(GsonUtil.getObj(reqData, "threepid"), ThreePid.class);
+                Optional<SingleLookupReply> lookup = lookupMgr.findLocal(tpid.getMedium(), tpid.getAddress());
+                if (!lookup.isPresent()) {
+                    log.info("No 3PID owner found, not sending any notification");
+                } else {
+                    log.info("3PID owner found, sending notification");
+                    try {
+                        notifMgr.sendForFraudulentUnbind(tpid);
+                        log.info("Notification sent");
+                    } catch (NotImplementedException e) {
+                        log.warn("Unable to send notification: {}", e.getMessage());
+                    } catch (RuntimeException e) {
+                        log.warn("Unable to send notification due to unknown error. See stacktrace below", e);
+                    }
+                }
+            }
+        }
+
+        log.info("Denying request");
+        throw new NotAllowedException("You have attempted to alter 3PID bindings, which can only be done by the 3PID owner directly. " +
+                "We have informed the 3PID owner of your fraudulent attempt.");
+    }
+
     public IThreePidSession createRemote(String sid, String secret) {
         ThreePidSession session = getSessionIfValidated(sid, secret);
         log.info("Creating remote 3PID session for {} with local session [{}] to {}", session.getThreePid(), sid);

src/main/java/io/kamax/mxisd/threepid/generator/GenericTemplateNotificationGenerator.java

@@ -20,6 +20,7 @@
 
 package io.kamax.mxisd.threepid.generator;
 
+import io.kamax.matrix.ThreePid;
 import io.kamax.mxisd.as.IMatrixIdInvite;
 import io.kamax.mxisd.config.MatrixConfig;
 import io.kamax.mxisd.config.ServerConfig;
@@ -82,4 +83,10 @@ public abstract class GenericTemplateNotificationGenerator extends PlaceholderNo
         return populateForRemoteValidation(session, getTemplateContent(cfg.getSession().getValidation().getRemote()));
     }
 
+    @Override
+    public String getForFraudulentUnbind(ThreePid tpid) {
+        log.info("Generating notification content for fraudulent unbind");
+        return populateForFraudulentUndind(tpid, getTemplateContent(cfg.getSession().getUnbind().getFraudulent()));
+    }
+
 }

src/main/java/io/kamax/mxisd/threepid/generator/NotificationGenerator.java

@@ -20,6 +20,7 @@
 
 package io.kamax.mxisd.threepid.generator;
 
+import io.kamax.matrix.ThreePid;
 import io.kamax.mxisd.as.IMatrixIdInvite;
 import io.kamax.mxisd.invitation.IThreePidInviteReply;
 import io.kamax.mxisd.threepid.session.IThreePidSession;
@@ -38,4 +39,6 @@ public interface NotificationGenerator {
 
     String getForRemoteValidation(IThreePidSession session);
 
+    String getForFraudulentUnbind(ThreePid tpid);
+
 }

src/main/java/io/kamax/mxisd/threepid/generator/PlaceholderNotificationGenerator.java

@@ -106,4 +106,8 @@ public abstract class PlaceholderNotificationGenerator {
         return populateForValidation(session, input);
     }
 
+    protected String populateForFraudulentUndind(ThreePid tpid, String input) {
+        return populateForCommon(tpid, input);
+    }
+
 }

src/main/java/io/kamax/mxisd/threepid/notification/GenericNotificationHandler.java

@@ -20,6 +20,7 @@
 
 package io.kamax.mxisd.threepid.notification;
 
+import io.kamax.matrix.ThreePid;
 import io.kamax.mxisd.as.IMatrixIdInvite;
 import io.kamax.mxisd.exception.ConfigurationException;
 import io.kamax.mxisd.invitation.IThreePidInviteReply;
@@ -76,4 +77,9 @@ public abstract class GenericNotificationHandler<A extends ThreePidConnector, B
         send(connector, session.getThreePid().getAddress(), generator.getForRemoteValidation(session));
     }
 
+    @Override
+    public void sendForFraudulentUnbind(ThreePid tpid) {
+        send(connector, tpid.getAddress(), generator.getForFraudulentUnbind(tpid));
+    }
+
 }

src/main/java/io/kamax/mxisd/threepid/notification/email/EmailSendGridNotificationHandler.java

@@ -22,6 +22,7 @@ package io.kamax.mxisd.threepid.notification.email;
 
 import com.sendgrid.SendGrid;
 import com.sendgrid.SendGridException;
+import io.kamax.matrix.ThreePid;
 import io.kamax.matrix.ThreePidMedium;
 import io.kamax.mxisd.as.IMatrixIdInvite;
 import io.kamax.mxisd.config.MxisdConfig;
@@ -107,7 +108,7 @@ public class EmailSendGridNotificationHandler extends PlaceholderNotificationGen
 
     @Override
     public void sendForValidation(IThreePidSession session) {
-        EmailTemplate template = cfg.getTemplates().getSession().getLocal();
+        EmailTemplate template = cfg.getTemplates().getSession().getValidation().getLocal();
         Email email = getEmail();
         email.setSubject(populateForValidation(session, template.getSubject()));
         email.setText(populateForValidation(session, getFromFile(template.getBody().getText())));
@@ -118,7 +119,7 @@ public class EmailSendGridNotificationHandler extends PlaceholderNotificationGen
 
     @Override
     public void sendForRemoteValidation(IThreePidSession session) {
-        EmailTemplate template = cfg.getTemplates().getSession().getLocal();
+        EmailTemplate template = cfg.getTemplates().getSession().getValidation().getRemote();
         Email email = getEmail();
         email.setSubject(populateForRemoteValidation(session, template.getSubject()));
         email.setText(populateForRemoteValidation(session, getFromFile(template.getBody().getText())));
@@ -127,6 +128,17 @@ public class EmailSendGridNotificationHandler extends PlaceholderNotificationGen
         send(session.getThreePid().getAddress(), email);
     }
 
+    @Override
+    public void sendForFraudulentUnbind(ThreePid tpid) {
+        EmailTemplate template = cfg.getTemplates().getSession().getUnbind().getFraudulent();
+        Email email = getEmail();
+        email.setSubject(populateForCommon(tpid, template.getSubject()));
+        email.setText(populateForCommon(tpid, getFromFile(template.getBody().getText())));
+        email.setHtml(populateForCommon(tpid, getFromFile(template.getBody().getHtml())));
+
+        send(tpid.getAddress(), email);
+    }
+
     private void send(String recipient, Email email) {
         if (StringUtils.isBlank(cfg.getIdentity().getFrom())) {
             throw new FeatureNotAvailable("3PID Email identity: sender address is empty - " +

src/main/resources/threepids/email/unbind-fraudulent.eml

@@ -0,0 +1,125 @@
+Subject: IMPORTANT - %DOMAIN% Matrix Identity Server - Unauthorized 3PID unbind blocked
+MIME-Version: 1.0
+Content-Type: multipart/alternative;
+	boundary="7REaIwWQCioQ6NaBlAQlg8ztbUQj6PKJ"
+
+--7REaIwWQCioQ6NaBlAQlg8ztbUQj6PKJ
+Content-Type: text/plain; charset=UTF-8
+Content-Disposition: inline
+
+Hi,
+
+**THIS IS IMPORTANT, PLEASE READ CAREFULLY**.
+If you are the system administrator of the Matrix installation, read the second section.
+
+This is a notification email that a possibly unauthorized entity has attempted to alter your
+3PIDs (email, phone numbers, etc.) settings. The request was denied and no change has been made.
+
+This is so you are aware of a possible failure in case you just tried to remove a 3PID from your account.
+
+If you do not understand this email, please forward it to your System administrator.
+
+-----------
+
+As the system administrator:
+
+If you are using synapse as a Homeserver, this is a known issue and abuse of separation of concerns. As a privacy-centric
+product and given that it is not possible to remove 3PIDs using mxisd as those only exists in your Identity stores, the
+request was actively blocked.
+
+We have open an issue on the synapse repos to reflect the related privacy concerns and GDPR violation(s) and would
+appreciate if you could comment on it or simply adds a thumbs up so the concerns are finally dealt with by the synapse dev team.
+Issue: https://github.com/matrix-org/synapse/issues/4540
+
+If you are using another Homeserver or this came following no action from your own users, then you have been the target
+of an unbind attack from a rogue entity which was blocked. You may want to check your logs to see the exact source of
+the attack and take relevant actions following your policy.
+
+If you would like to disable these notifications, please see the 3PID sessions configuration documentation.
+
+Thanks,
+
+%DOMAIN_PRETTY% Admins
+
+--7REaIwWQCioQ6NaBlAQlg8ztbUQj6PKJ
+Content-Type: multipart/related;
+	boundary="M3yzHl5YZehm9v4bAM8sKEdcOoVnRnKR";
+	type="text/html"
+
+--M3yzHl5YZehm9v4bAM8sKEdcOoVnRnKR
+Content-Type: text/html; charset=UTF-8
+Content-Disposition: inline
+
+<!doctype html>
+<html lang="en">
+    <head>
+        <style type="text/css">
+body {
+    margin: 0px;
+}
+
+pre, code {
+    word-break: break-word;
+    white-space: pre-wrap;
+}
+
+#page {
+    font-family: 'Open Sans', Helvetica, Arial, Sans-Serif;
+    font-color: #454545;
+    font-size: 12pt;
+    width: 100%%;
+    padding: 20px;
+}
+
+#inner {
+    width: 640px;
+}
+        </style>
+    </head>
+    <body>
+        <table id="page">
+            <tr>
+                <td> </td>
+                <td id="inner">
+<p>Hi,</p>
+
+<p><b>THIS IS IMPORTANT, PLEASE READ CAREFULLY</b>.<br/>
+If you are the system administrator of the Matrix installation, read the second section.</p>
+
+<p>This is a notification email that a possibly unauthorized entity has attempted to alter your
+   3PIDs (email, phone numbers, etc.) settings. The request was denied and no change has been made.</p>
+
+<p>This is so you are aware of a possible failure in case you just tried to remove a 3PID from your account.</p>
+
+<p>If you do not understand this email, please forward it to your System administrator.</p>
+
+<hr>
+
+<p>As the system administrator:</p>
+
+<p>If you are using synapse as a Homeserver, this is a known issue and abuse of separation of concerns. As a privacy-centric
+   product and given that it is not possible to remove 3PIDs using mxisd as those only exists in your Identity stores, the
+   request was actively blocked.</p>
+
+<p>We have open an issue on the synapse repos to reflect the related privacy concerns and GDPR violation(s) and would
+   appreciate if you could comment on it or simply adds a thumbs up so the concerns are finally dealt with by the synapse dev team.<br/>
+   Issue: <a href="https://github.com/matrix-org/synapse/issues/4540">https://github.com/matrix-org/synapse/issues/4540</a></p>
+
+<p>If you are using another Homeserver or this came following no action from your own users, then you have been the target
+   of an unbind attack from a rogue entity which was blocked. You may want to check your logs to see the exact source of
+   the attack and take relevant actions following your policy.</p>
+
+<p>If you would like to disable these notifications, please see the 3PID sessions configuration documentation.</p>
+
+<p>Thanks,</p>
+
+<p>%DOMAIN_PRETTY% Admins</p>
+                </td>
+                <td> </td>
+            </tr>
+        </table>
+    </body>
+</html>
+--M3yzHl5YZehm9v4bAM8sKEdcOoVnRnKR--
+
+--7REaIwWQCioQ6NaBlAQlg8ztbUQj6PKJ--

src/main/resources/threepids/sms/unbind-fraudulent.txt

@@ -0,0 +1 @@
+INFORMATIONAL ONLY - Someone attempted to change your Matrix 3PIDs, with a potential data leak. Please contact your system administrator.