My issue was due to the root certificate not being presented to appgw, and resulted in the error: "The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. To troubleshoot this issue, check the Details column on the Backend Health tab. Content Source:<---> Which language's style guidelines should be used when writing code that is supposed to be called from another language? I did not find this error message listed here https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshooting. For more information about how to extract and upload Trusted Root Certificates in Application Gateway, see Export trusted root certificate (for v2 SKU). Quickstart - Configure end-to-end SSL encryption with Azure Application Gateway - Azure portal, articles/application-gateway/end-to-end-ssl-portal.md, https://www.domstamand.com/end-to-end-ssl-solution-using-web-apps-and-azure-application-gateway-multisite-hosting/, https://learn.microsoft.com/en-us/azure/application-gateway/ssl-overview#for-probe-traffic, Version Independent ID: 948878b1-6224-e4c5-e65a-3009c4feda74. Check the document page that's provided in step 3a to learn more about how to create NSG rules. On the App Gateway side, there are 6 public listeners are on the App Gateway with public .pfx certs, and 6 authentication certificates (.cer) within the HTTPsSettings, a single backendpool with both VMs configured, and various rules created. Already on GitHub? craigclouditpro your a lifesaver thanks for posting this friend ! An issue with your configuration needs to be ruled out first. Were you able to reproduce this scenario and check? rev2023.5.1.43405. You signed in with another tab or window. Now Clients will check the Server certificate and confirm if the certificate is issued by Trusted root or not. Ive deployed 2 Virtual Machines in North Europe (Across Zones 1 and 2) both configured with IIS with 6 sites with different URLs (all with Server Name Indication ticked) installed all the certificates to match their names as-well. Adding the certificate ensures that the application gateway communicates only with known back-end instances. Open a command prompt (Win+R -> cmd), enter netstat, and select Enter. But when we have multiple chain certificate and if your backend application/server sends only the leaf the certificate , AppGW will not be able to trust the cert up to the top level domain root. Ensure that you add the correct root certificate to allowlist the backend. You can find this by running openssl from either windows client or Linux client which is present in the same network/subnet of the backend application. Cause: This error occurs when Application Gateway can't verify the validity of the certificate. Message: Time taken by the backend to respond to application gateway's health probe is more than the timeout threshold in the probe setting. Current date is not within the "Valid from" and "Valid to" date range on the certificate. Follow steps 1a and 1b to determine your subnet. Configure that certificate on your backend server. If it's not, the certificate is considered invalid, and that will create a Not the answer you're looking for? Otherwise, register and sign in. "The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway". Configure that certificate on your backend server. Or, if Pick host name from backend address is mentioned in the HTTP settings, where the backend address pool contains a valid FQDN, this setting will be applied. The protocol and destination port are inherited from the HTTP settings. certificate. Passing negative parameters to a wolframscript. If your certificate is working on browser directly hitting the app and not with AppGW then what is the exact problem? i have configured a Azure Application gateway (v2) and there is one backend servers. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If you have properly added the certificate, and the backend pool is pointing to the custom domain (not the azurewebsites.net domain), then your best options are to either try the V2 SKU, or open a support request to troubleshoot further. https://docs.microsoft.com/en-us/azure/application-gateway/application-gateway-end-to-end-ssl-powershell, Azure Cyber Security: Protect & Secure Your Cloud Infrastructure, Send Text & WhatsApp Messages for Azure VM Status with Azure Automation, Migrate SOAR Use Cases from Splunk to Microsoft Sentinel, Azure Defender and Azure Sentinel Alerts Bi-Directional Sync. d. To check the effective routes and rules for a network adapter, you can use the following PowerShell commands: If you don't find any issues with NSG or UDR, check your backend server for application-related issues that are preventing clients from establishing a TCP session on the ports configured. Make sure https probe is configured correctly as well. Microsoft Word Multiple Choice Questions & Answers, Excel Multiple Choice Questions & Answers, Different Ways to Change Power Button Action in Windows 11. Also, please let me know your ticket number so that I can track it internally. I am having the same issue with App GW v1 in front of an API Management. I have some questions in regards to application gateway and need help with the same : 1)Is that application gateway can be configured with multiple backend pools and each pool can serve a request for different applications ? Can you recreate this scenario in your lab using multi-site and custom domain on appservices with SNI bind SSL and cert issued by different CA than Microsoft and not the default azurewebsites.net and you may hit this issue? If Pick hostname from backend address is set in the HTTP settings, the backend address pool must contain a valid FQDN. What was the resolution? 566), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Check whether the backend server requires authentication. You signed in with another tab or window. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Azure Application Gateway 502 Web Server Backend Certificate not whitelisted. d. If an NSG is configured, search for that NSG resource on the Search tab or under All resources. Check whether your server allows this method. here is what happens in in Multiple chain certificate. Horizontal and vertical centering in xltabular, one or more moons orbitting around a double planet system, Embedded hyperlinks in a thesis or research paper, Proving that Every Quadratic Form With Only Cross Product Terms is Indefinite. Document Details @sajithvasu My apologies for this taking a long time, but there are some strange issues here(as you have already discovered). The following steps help you export the .cer file in Base-64 encoded X.509(.CER) format for your certificate: If you can't find the certificate under Current User\Personal\Certificates, you may have accidentally opened "Certificates - Local Computer", rather than "Certificates - Current User"). Do not edit this section. (LogOut/ From the properties displayed, find the CN of the certificate and enter the same in the host name field of the http settings. We have private key .pfx issued by CA uploaded to app services and its public certificate .cer file uploaded to app gateway backend authentication as mentioned in this document. This causes SSL/TLS negoatiation failure and AppGW marks the backend as unhealthy because it is not able to initiate the probe. Version Independent ID: <---> Because the probe requests don't carry any user credentials, they will fail, and an HTTP 401 status code will be returned by the backend server. @JeromeVigne did you find a solution in your setup? @einarasm read thru the responses from @krish-gh, specifically around leveraging OpenSSL toolkit to query the backend pool for the certificate trust chain, example: %> openssl s_client -connect 10.0.0.4:443 -servername www.example.com -showcerts. If your cert is issued by Internal Root CA , you would have export the root cert and import it the Trust Root Store in the Client. The chain looks ok to me. Solution: To resolve this issue, verify that the certificate on your server was created properly. This happens when an NSG/UDR/Firewall on the application gateway subnet is blocking traffic on ports 65503-65534 in case of v1 SKU, and ports 65200-65535 in case of the v2 SKU or if the FQDN configured in the backend pool could not be resolved to an IP address. Message: Application Gateway could not connect to the backend. Expected:{HTTPStatusCode0} Received:{HTTPStatusCode1}. This causes SSL/TLS negoatiation failure and AppGW marks the backend as unhealthy because it is not able to initiate the probe. This error can also occur if the backend server doesn't exchange the complete chain of the cert, including the Root Intermediate (if applicable) Leaf during the TLS handshake. Find out more about the Microsoft MVP Award Program. In this example, requests using TLS1.2 are routed to backend servers in Pool1 using end to end TLS. During SSL negotiation , Client sends "Client Hello" and Server Responds with "Server Hello" with its Certificate to the Client. Azure Tip #9 Application Gateway Backend Certificate not whitelisted Error, Azure DevOps Fix for Access to path \SourceMapping.json is denied. What are the advantages of running a power tool on 240 V vs 120 V? Message: Backend certificate is invalid. This usually happens when the FQDN of the backend has not been entered correctly.. I will clean-up some of my older comments to keep it generic to all since the issue has been identified. If the output doesn't show the complete chain of the certificate being returned, export the certificate again with the complete chain, including the root certificate. If you can resolve the IP address, there might be something wrong with the DNS configuration in the virtual network. Choose the destination manually as any internet-routable IP address like 1.1.1.1. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? Just FYI. applications. Ive recently faced with the dreaded 502 Web Server error when dealing with the App Gateway, my Backend Health was screaming unhealthy Backend server certificate is not whitelisted with Application Gateway. b. Most of the browsers are thick clients , so it may work in the new browsers but reverse proxies like Application Gateway wont behave like our browsers they only trust the certificates if the backend sends the complete chain. If the output doesnt show the complete chain of the certificate being returned, export the certificate again with the complete chain, including the root certificate. How do I bypass Microsoft account login in Windows11? here is what happens in in Multiple chain certificate. Ensure that you add the correct root certificate to whitelist the backend". If Application Gateway can't establish a TCP session on the port specified, the probe is marked as Unhealthy with this message. Learn more about Application Gateway diagnostics and logging. In this article I am going to talk about one most common issue backend certificate not whitelisted, If you check the backend health of the application gateway you will see the error like this The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. The status retrieved by any of these methods can be any one of the following states: If the backend health status for a server is healthy, it means that Application Gateway will forward the requests to that server. If Internet and private traffic are going through an Azure Firewall hosted in a secured Virtual hub (using Azure Virtual WAN Hub): a. Cause: After the DNS resolution phase, Application Gateway tries to connect to the backend server on the TCP port that's configured in the HTTP settings. Message: The server certificate used by the backend is not signed by a well-known Certificate Authority (CA). For all TLS related error messages, to learn more about SNI behavior and differences between the v1 and v2 SKU, check the TLS overview page. Otherwise please share the message in that scenario without adding root explicitly. Configure that certificate on your backend server. To do that, follow these steps: Message: The validity of the backend certificate could not be verified. Set the destination port as anything, and verify the connectivity. At the time of writing the Application Gateway doesnt support uploading the Certificates directly into Key Vault, hence extracting the string into .txt and dumping it in Key Vault Secrets. To check the health of your backend pool, you can use the Required fields are marked *. If the backend health status is Unhealthy, the portal view will resemble the following screenshot: Or if you're using an Azure PowerShell, CLI, or Azure REST API query, you'll get a response that resembles the following example: After you receive an unhealthy backend server status for all the servers in a backend pool, requests aren't forwarded to the servers, and Application Gateway returns a "502 Bad Gateway" error to the requesting client. In the v2 SKU, if there's a default probe (no custom probe has been configured and associated), SNI will be set from the host name mentioned in the HTTP settings. I have two listeners and my issue has started on one of them when SSL certificate has been renewed. Now how can find if my application sending the complete chain , the easy way to find is running openssl from either windows client or Linux client which is present in the same network/subnet of the backend application. Cause: End-to-end SSL with Application Gateway v2 requires the backend server's certificate to be verified in order to deem the server Healthy. To Answer we need to understand what happens in any SSL/TLS negotiation. When i check health probe details are following: For a TLS/SSL certificate to be trusted, the backend server certificate must be issued by a CA that's included in the trusted store of Application Gateway. The section in blue contains the information that is uploaded to application gateway. The Standard and WAF SKU (v1) Server Name Indication (SNI) is set as the FQDN in the backend pool address. We are actually trying to simulate the Linux box as AppGW. For details on this Openssl command you can refer toTroubleshoot backend health issues in Azure Application Gateway | Microsoft Docs , Look for the sub topic "Trusted root certificate mismatch". Now you may ask why it works when you browse the backend directly through browser. Cause: When you create a custom probe, you can mark a backend server as Healthy by matching a string from the response body. Most of the best practice documentation involves the V2 SKU and not the V1. For the server certificate to be trusted we need the Root certificate in Trusted Root Cert Store , usually if you are having certs issued by Godaddy,Digicert,Vergion like Third party Vendors you dont have to do anything because they are automatically trusted by your client/browser. To restart Application Gateway, you need to. If they don't match, change the probe configuration so that it has the correct string value to accept. To find out the reason, check OpenSSL diagnostics for the message associated with error code {errorCode}. If you create the issue from there, the required details will be auto-populated. The certificate added to Backend HTTP Setting to authenticate the backend servers can be the same as the certificate added to the listener for TLS termination at application gateway or different for enhanced security. In this article I am going to talk about one most common issue "backend certificate not whitelisted", If you check the backend health of the application gateway you will see the error like this "The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. The backend certificate can be the same as the TLS/SSL certificate or different for added security. Trusted root certificate is required to allow backend instances in application gateway v2 SKU. Note that this .CER file must match the certificate (PFX) deployed at the backend application. But when we have multiple chain certificate and your backend application is sending the Application Gateway only the leaf the certificate , AppGW will not be able to trust the cert up to the top level domain root. what we are doing is actually trying to simulate the Linux box as AppGW as if that machine is trying probe to the backend server as AppGW. Cause: Application Gateway resolves the DNS entries for the backend pool at time of startup and doesn't update them dynamically while running. From your TLS/SSL certificate, export the public key .cer file (not the private key). Azure Tip #10 Load Balancer vs Traffic Manager, Azure Tip #2 Azure Free Subscription without CreditCard for Learning Sandbox, Azure Charts All about Azure news, stats, and Changes, 100 Multiple Choice Questions & Answers on Microsoft Outlook, 100 Multiple Choice Questions & Answers on PowerPoint. In this article I am going to talk about one most common issue "backend certificate not whitelisted" . For File name, name the certificate file. 2)How should we get this issue fixed ? Thanks. I am currently experimenting with different ways to add the backend pools and heath probes to find a working configuration. Access forbidden. to your account. GitHub Login: <---> Solution: To resolve this issue, follow these steps: Learn more about Application Gateway probe matching. AppGW is a PaaS instance , by default you wont get access to the Applicaiton Gateway. For a TLS/SSL certificate to be trusted, the backend server certificate must be issued by a CA that's included in the trusted store of Application Gateway. To do the whitlisting, you will need to export APIM SSL certificate into a Base-64 encoded (CER) format, and apply the exported certificate in (Backend authentication certificates) under the Application Gateway's HTTP settings configured for the APIM. There is certificate with private key as PFX on listenner settings. Public domain name resolution might be required in scenarios where Application Gateway must reach out to external domains like OCSP servers or to check the certificates revocation status. Our backend web server is running Apache with multiple HTTPS sites on the same server and the issue we face is regardless of the HTTPS . Ensure that you create a default website in the IIS with-in the VM without the SNI enabled and you should not see this error. You should remove the exported trusted root you added in the App Gateway. It seems like something changed on the app gateway starting this month. In that case, I suggest you to create an Azure Support ticket to take a closer look at internal diagnostics of your app gateway instance considering it's still occurring after troubleshooting. I am opening a PR to update the End-to-End Howto guide with a description of the error and a link to the SSL overview. I am 3 backend pools . Open your Application Gateway HTTP settings in the portal. Only HTTP status codes of 200 through 399 are considered healthy. Select the root certificate and then select View Certificate. Currently we are seeing issues with app gateway backend going unhealthy due to backend auth cert. The default route is advertised by an ExpressRoute/VPN connection to a virtual network over BGP. when the backend server cert hits AppGW after Server Hello , AppGW tries to check who issued the certificate and it finds that it was issued by Intermediate certificate but then it does not have information about Intermediate cert, like who issued the cert and what is the root certificate of that intermediate certificate. Let me set the scene. Or, if Pick hostname from backend HTTP settings is selected in the custom probe, SNI will be set from the host name mentioned in the HTTP settings. If there's a custom DNS server configured on the virtual network, verify that the servers can resolve public domains. Azure Nwtworking> Azure Application Gateway: 502 error due to backend certificate not whitelisted in the AppGW, https://techcommunity.microsoft.com/t5/azure-networking-blog/azure-application-gateway-502-error-due-to-backend-certificate/ba-p/3271805, If you are using Azure Application Gateway as Layer 7 WAF for End to End SSL connectivity , you might have come across Certificate related issues most of the times. This can create problems when uploaded the text from this certificate to Azure. #please-close. ", The UDR on the Application Gateway subnet is set to the default route (0.0.0.0/0) and the next hop is not specified as "Internet.". This is the exact thing what we do when import .CER file in the HTTP Settings of the Application Gateway. Now you have the authentication certificate/trusted root certificate in Base-64 encoded X.509(.CER) format. i raised ticket to Microsoft. Below is what happens during SSL negotiation when you have single chain cert and root in the AppGW. To learn more visit https://aka.ms/authcertificatemismatch" I have some questions in regards to application gateway and need help with the same : Unfortunately I have to use the v1 for this set-up. Follow steps 1-11 in the preceding method to upload the correct trusted root certificate to Application Gateway. We have not faced any issues with HTTP sites but we are facing issues with end-to-end SSL. It is required for docs.microsoft.com GitHub issue linking. e. In the Inbound Rules section, add an inbound rule to allow destination port range 65503-65534 for v1 SKU or 65200-65535 v2 SKU with the Source set as GatewayManager service tag. I guess you need a Default SITE binding to a certificate, without SNI ticked. of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. For more information about how to extract and upload Trusted Root Certificates in Application Gateway, see Export trusted root certificate (for v2 SKU). If it's a self-signed certificate, you must generate a valid certificate and upload the root certificate to the Application Gateway HTTP settings. Sorry my bad, this is actually now working - I just needed to have the CN in the certificate match with what was set in backend pool. For testing purposes, you can create a self-signed certificate but you shouldn't use it for production workloads. Solution: Follow these steps to export and upload the trusted root certificate to Application Gateway. After CA autohority re-created the certificate problem was gone. When I use v2 SKU with the option to trust the backend certificate from APIM it works. You should do this only if the backend has cert which is issued by internal CA, I hope we are clear till now on why we import Authenticate cert in the HTTP settings of the AppGW and when we use the option Use Well Known CA, But the actual problem arises if you are using a Third party Cert or Internal CA Cert which has Intermediate CA and then Leaf certificate, Most of the orgs for security reasons use Root Cert-> Intermediate Cert > Leaf Cert , even Microsoft follows the same for bing , check the screenshot below, Now lets discuss what exactly is the confusion here if we have multiple Chain Cert, When you have single chain certificate , then there will be no confusion with appgw , if your root CA is Global trusted just select Use Trusted Root CA option in HTTPsettings, If you root CA is Internal CA , then import that Top root cert in .cer format and upload it in the HTTP settings. If the port mentioned is not the desired port, enter the correct port number for Application Gateway to connect to the backend server. This error can also occur if the backend server doesn't exchange the complete chain of the cert, including the Root > Intermediate (if applicable) > Leaf during the TLS handshake. For a TLS/SSL certificate to be trusted, that certificate of the backend server must be issued by a CA that's included in the trusted store of Application Gateway. The -servername switch is used in shared hosting environments. To increase the timeout value, follow these steps: Message: Application Gateway could not create a probe for this backend. Few days back , I had to update the Azure backend certificate for authentication in the Application Gateway and i started noticing this error, Backend server certificate is not whitelisted with Application Gateway.. More info about Internet Explorer and Microsoft Edge, Export trusted root certificate (for v2 SKU), Overview of TLS termination and end to end TLS with Application Gateway, Application Gateway diagnostics and logging. d. Otherwise, change the next hop to Internet, select Save, and verify the backend health. Create a free website or blog at WordPress.com. Please log in using one of these methods to post your comment: You are commenting using your WordPress.com account. For File to Export, Browse to the location to which you want to export the certificate. If you receive this error message, the CN of the backend certificate doesn't match the host name configured in the custom probe, or the HTTP settings if Pick hostname from backend HTTP settings is selected. Below is what happens during SSL negotiation when you have single chain cert and root in the AppGW. To learn more visit https://aka.ms/authcertificatemismatch". https://docs.microsoft.com/en-us/azure/application-gateway/ssl-overview#end-to-end-tls-with-the-v2-sku. AppGW is a PaaS instance , by default you wont get access to the Applicaiton Gateway. An authentication certificate is required to allow backend instances in Application Gateway v1 SKU. You must be a registered user to add a comment. How did you verify the cert? Message: The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. In this article I am going to talk about one most common issue "backend certificate not whitelisted" Is there a generic term for these trajectories? In the Certificate properties, select the Details tab. https://learn.microsoft.com/en-us/azure/application-gateway/ssl-overview#end-to-end-tls-with-the-v2-sku. I will now proceed to close this github issue here since this repo is for MS Docs specifically. Cause: After the TCP connection has been established and a TLS handshake is done (if TLS is enabled), Application Gateway will send the probe as an HTTP GET request to the backend server. Azure Application Gateway: 502 error due to backend certificate not whitelisted in the AppGW, Troubleshoot backend health issues in Azure Application Gateway | Microsoft Docs. More info about Internet Explorer and Microsoft Edge, Export authentication certificate (for v1 SKU), Configure end to end TLS by using Application Gateway with PowerShell, Export authentication certificate from a backend certificate (for v1 SKU), Export trusted root certificate from a backend certificate (for v2 SKU), To obtain a .cer file from the certificate, open. Either allow "HTTP 401" in a probe status code match or probe to a path where the serverdoesn't require authentication. @TravisCragg-MSFT : Thank you! It worked fine for me with the new setup in the month of September with V1 SKU. Azure Tip #3 What is Scale up and Scale Out ? Backend protocol: HTTPS Backend port: 443 Use well known CA certificate: Yes Cookie-based affinity*: Disable Connection draining*: Disable Request time-out*: 20 seconds Override backend path*: Blank Override with new host name: Yes Host name override: Override with a specific domain name (webappX.hugelab.net) Use custom probe: Yes If the output doesn't show the complete chain of the certificate being returned, export the certificate again with the complete chain, including the root certificate. here is the IP is your backend Application IP , it changes as per your backend pool you can use even use the hostname directly here. when the backend server cert hits AppGW after Server Hello , AppGW tries to check who issued the certificate and it finds that it was issued by Intermediate certificate but then it does not have information about Intermediate cert, like who issued the cert and what is the root certificate of that intermediate certificate. Check the network security group (NSG) settings of the backend server's network adapter and subnet and whether inbound connections to the configured port are allowed. Certificates signed by well known CA authorities whose CN matches the host name in the HTTP backend settings do not require any additional step for end to end TLS to work. The error says that Root cert is not whitelisted on the AppGW , but you might have a valid Third party certificate on the backend , and more over if you try to access the backend directly bypassing the Application Gateway you will not see any issues related to certificate in the browser. Check the backend server's health and whether the services are running. OpenSSL s_client -connect 10.0.0.4:443 -servername www.example.com -showcerts. backend server, it waits for a response from the backend server for a configured period. Have a question about this project? Would you like to involve with it ? Making sure your App Gateway has the authenticated cert installed on the HTTPs backend settings, with the appropriate Rules & Probe setup and bobs your uncle, I got full Health back, and all my sites were live and kicking. Do not edit this section. . Sub-service: <---> Ensure that you add the correct root certificate to whitelist the backend.