Message: Status code of the backend's HTTP response did not match the probe setting. (LogOut/ If Application Gateway can't establish a TCP session on the port specified, the probe is marked as Unhealthy with this message. To allow this access, upload trusted root certificates (for v2 SKU) of the back-end servers to the application gateway. 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". To Answer we need to understand what happens in any SSL/TLS negotiation. c. If the next hop is virtual network gateway, there might be a default route advertised over ExpressRoute or VPN. Once the public key has been exported, open the file. How to organize your open apps in windows 11? If the backend server response for the probe request contains the string unauthorized, it will be marked as Healthy. Otherwise please share the message in that scenario without adding root explicitly. d. If an NSG is configured, search for that NSG resource on the Search tab or under All resources. I have created an application gateway with 3 backend nodes, when I set the "Http Listener" with all the 3 nodes certificates, the health probe is green. @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. "Backend server certificate is not whitelisted with Application Gateway." Something that you will see missing is microsft docs is having a default site binding to a SSL certificate without the SNI enabled. Cause: Application Gateway checks whether the host name specified in the backend HTTP settings matches that of the CN presented by the backend servers TLS/SSL certificate. This approach is useful in situations where the backend website needs authentication. here is the sample command you need to run, from the machine that can connect to the backend server/application. I will let you know what I find. If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? It is required for docs.microsoft.com GitHub issue linking. Alternatively, you can do that through PowerShell/CLI. To ensure the application gateway can send traffic directly to the Internet, configure the following user defined route: Address prefix: 0.0.0.0/0 Application Gateway probes can't pass credentials for authentication. 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 , you can check yourself as below, Now lets discuss what exactly is the confusion here if we have multiple Chain Cert, Check this below 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. @TravisCragg-MSFT : Did you find out anything? We should get one Linux machine which is in the same subnet/VNET of the backend application and run the following commands. We are in the same situation as @JeromeVigne: App Gateway v1 as front-end to API Management, the health probe is unhealthy with the "Backend server certificate is not whitelisted with Application Gateway." If you do not have a support plan, please let me know. If the backend server doesn't Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Fast-forward 2022, we are also faced with the same issue and getting the same error "Backend server certificate is not whitelisted with Application Gateway" using Application Gateway v1. Do not edit this section. 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.. We initially faced an issue with the certificate on the backend server which has since been sorted out by MS Support. Cause: If the backend pool is of type IP Address, FQDN or App Service, Application Gateway resolves to the IP address of the FQDN entered through DNS (custom or Azure default). Message: The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. @krish-gh actually it was actually what have i tried firstly but sitouiotion was same. Received response body doesn't contain {string}. 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. By clicking Sign up for GitHub, you agree to our terms of service and So, I created a default site pointed it to wwwroot, and selected one of my already installed certificates (you can probably PowerShell an SSL for this tbh, but I chose to re-use an already existing one) you dont have to supply a hostname, just a dummy site with an authenticated cert on port 443. 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. I have tried to upload root CA instead of using well-known CA and the issue persist. During SSL negotiation , Client sends Client Hello and Server Responds with Server Hello with its Certificate to the Client. In 5e D&D and Grim Hollow, how does the Specter transformation affect a human PC in regards to the 'undead' characteristics and spells? 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. 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. To ensure the application gateway can send traffic to the backend pool via an Azure Firewall in the Virtual WAN hub, configure the following user defined route: Address Prefix: Backend pool subnet Ensure that you add the correct root certificate to whitelist the backend". Azure Application Gateway "502 Web Server" - Backend Certificate not Solution: If you receive this error message, there's a mismatch between the certificate that has been uploaded to Application Gateway and the one that was uploaded to the backend server. If that's not the desired host name for your website, you must get a certificate for that domain or enter the correct host name in the custom probe or HTTP setting configuration. 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. An existing backend certificate is required to generate the authentication certificates or trusted root certificates required for allowing backend instances with Application Gateway. Make sure the UDR isn't directing the traffic away from the backend subnet. Make sure https probe is configured correctly as well. Now use steps 2-9 mentioned in the section Export authentication certificate from a backend certificate (for v1 SKU) above to export the trusted root certificate in the Base-64 encoded X.509(.CER) format. The default probe request is sent in the format of ://127.0.0.1:. 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. 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. Have done s_client -connect backend_ip:443 -servername backend_url -showcerts and found that Root CA is missing. I have created an application gateway with 3 backend nodes, when I set the "Http Listener" with all the 3 nodes certificates, the health probe is green. This article describes the symptoms, cause, and resolution for each of the errors shown. 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. This is the exact thing what we do when import .CER file in the HTTP Settings of the Application Gateway. After the server starts responding or is that all the backend pools has to serve the request for one application ? "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. The issue was on certificate. You can add this to the application gateway to allow your backend servers for end to end TLS encryption. Most of the browsers are thick clients , so it may work in the new browsers but PRODUCTs like Application Gateway will not be able to trust the cert unless the backend sends the complete chain. 10.0.0.4 = IP of backend server (if using DNS ensure it points to backend server and not the public IP of appgw). This doesn't indicate an error. For File to Export, Browse to the location to which you want to export the certificate. backend server, it waits for a response from the backend server for a configured period. OpenSSL s_client -connect 10.0.0.4:443 -servername www.example.com -showcerts. An Azure service that provides a platform-managed, scalable, and highly available application delivery controller as a service. PS : Dont forget to upload the CER file to the HTTP settings in ApplicationGateway before you do the Health Check. Azure Application Gateway health probe error with "Backend server Azure Tip #3 What is Scale up and Scale Out ? https://learn.microsoft.com/en-us/azure/application-gateway/certificates-for-backend-authentication#export-trusted-root-certificate-for-v2-sku, End-to-end TLS with the v2 SKU Otherwise, register and sign in. Also, in this example, you'll use the Windows Certificate Manager tool to export the required certificates. Find centralized, trusted content and collaborate around the technologies you use most. successfully, Application Gateway resumes forwarding the requests. Posted in Azure Tagged 502webserver, Azure, azure502, azureapplicationgateway, azurecertificate, azurewaf, backend certificate not whitelisted Post navigation Azure Cyber Security: Protect & Secure Your Cloud Infrastructure If you can't connect on the port from your local machine as well, then: a. 2)How should we get this issue fixed ? Applicaiton works fine on the backend servers with 443 certificate from Digicert. 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. If thats not a desired value, you should create a custom probe and associate it with the HTTP settings. Backend Health page on the Azure portal. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. If you want Application Gateway to probe on a different protocol, host name, or path and to recognize a different status code as Healthy, configure a custom probe and associate it with the HTTP settings. The default route is advertised by an ExpressRoute/VPN connection to a virtual network over BGP. Sharing best practices for building any app with .NET. Check the backend server's health and whether the services are running. We have not faced any issues with HTTP sites but we are facing issues with end-to-end SSL. f. Select Save and verify that you can view the backend as Healthy. Export trusted root certificate (for v2 SKU): or from external over WAF ? When we check the certificate with the openssl there were following errors: Content: <---> You'll see the Certificate Export Wizard. How to Allow or Prevent Themes to Change Desktop Icons in Desktop Icon Settings in Windows 11? In Azure docs, it is clearly documented that you dont have import Auth certificate in HTTP settings of the backend if your backend application has Global trusted certificate. Thanks in advance. error. 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. Or, you can use Azure PowerShell, CLI, or REST API. Thanks! The intermediate certificate(s) should be bundled with server certificate and installed on the backend server. Only HTTP status codes of 200 through 399 are considered healthy. Solution: If you receive this error, follow these steps: Check whether you can connect to the backend server on the port mentioned in the HTTP settings by using a browser or PowerShell. . You should see the root certificate details. Well occasionally send you account related emails. Service unavailable. 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. Azure Application Gateway: 502 error due to backend certificate not whitelisted in the AppGW, Troubleshoot backend health issues in Azure Application Gateway | Microsoft Docs. Here is a blog post to fix the issue. There is ROOT certificate on httpsettings. Check whether your UDR has a default route (0.0.0.0/0) with the next hop not set as Internet: a. Solution: To resolve this issue, verify that the certificate on your server was created properly. 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. 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. Change). Azure Application Gateway: 502 error due to backend certificate not b. This causes SSL/TLS negoatiation failure and AppGW marks the backend as unhealthy because it is not able to initiate the probe. If you are not familiar with Cloud Shell, it allows you to access bash or powershell from your browser to run commands within your Azure subscription https://docs.microsoft.com/en-us/azure/cloud-shell/overview. The authentication certificate is the public key of backend server certificates in Base-64 encoded X.509 (.CER) format. (LogOut/ with open ssl i should run the command on from local server ? @EmreMARTiN , you mentioned your backend certificate is from "Digicert" which is already a well-known trusted CA. 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. Would you like to involve with it ? Connect and share knowledge within a single location that is structured and easy to search. If the backend health is shown as Unknown, the portal view will resemble the following screenshot: This behavior can occur for one or more of the following reasons: Check whether your NSG is blocking access to the ports 65503-65534 (v1 SKU) or 65200-65535 (v2 SKU) from Internet: a. You should remove the exported trusted root you added in the App Gateway. It is required for docs.microsoft.com GitHub issue linking. If they don't match, change the probe configuration so that it has the correct string value to accept. c. Check to see if there are any default routes (0.0.0.0/0) with the next hop not set as Internet. to your account. The root certificate is a Base-64 encoded X.509(.CER) format root certificate from the backend server certificates. If you create the issue from there, the required details will be auto-populated. Service:<---> 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. During SSL negotiation , Client sends "Client Hello" and Server Responds with "Server Hello" with its Certificate to the Client. One pool has 2 servers listed as unhealthy and the error message we see is below: "backend server certificate is not whitelisted with application gateway .Make sure that the certificate uploaded to the application gateway matches with the certificate configured in the backend servers. Failing endpoint is missing root CA as working one has it. Move to the Certification Path view to view the certification authority. During SSL negotiation , Client sends "Client Hello" and Server Responds with "Server Hello" with its Certificate to the Client. Let me know here if you face any issue reaching Azure support or if you do not have any support plan for your subscription. 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. Sub-service: <---> To increase the timeout value, follow these steps: Message: Application Gateway could not create a probe for this backend. I will wait for your response. Our configuration is similar to this article but we are using WAF V1 sku - https://www.domstamand.com/end-to-end-ssl-solution-using-web-apps-and-azure-application-gateway-multisite-hosting/ Azure Tip #11 Get Reports of ARM Deployments in Your Subscription. To automate the approach above, within my template I extracted the .cer and .pfx into base64 string using the below PowerShell command: This gave me the ability to upload this into Key Vault, and reference the Secret within my template parameter file, so no credentials or keys are stored in templates, theyre all in Key Vault (all kinds of secure). Your email address will not be published. Azure Tip #7 What are the Storage Tiers in Azure ? Users can also create custom probes to mention the host name, the path to be probed, and the status codes to be accepted as Healthy. For testing purposes, you can create a self-signed certificate but you shouldn't use it for production workloads. The exported certificate looks similar to this: If you open the exported certificate using Notepad, you see something similar to this example. privacy statement. More info about Internet Explorer and Microsoft Edge, https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-backend-health-troubleshooting, https://learn.microsoft.com/en-us/azure/application-gateway/certificates-for-backend-authentication#export-trusted-root-certificate-for-v2-sku, https://learn.microsoft.com/en-us/azure/application-gateway/ssl-overview#end-to-end-tls-with-the-v2-sku. 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. Enter any timeout value that's greater than the application response time, in seconds. If your certificate is working on browser directly hitting the app and not with AppGW then what is the exact problem? Did the drapes in old theatres actually say "ASBESTOS" on them? As described earlier, the default probe will be to ://127.0.0.1:/, and it considers response status codes in the range 200 through 399 as Healthy. Is "I didn't think it was serious" usually a good defence against "duty to rescue"? i.e. If there's a custom probe associated with the HTTP settings, SNI will be set from the host name mentioned in the custom probe configuration. -No client certificate CA names sent Backend Nginx works just fine with https, but the application gateway https health probes fail with the message "Backend server certificate is not whitelisted with Application Gateway." What is the deal here? The custom DNS server is configured on a virtual network that can't resolve public domain names. Is that we have to follow the below step for resolution ? Which was the first Sci-Fi story to predict obnoxious "robo calls"? Application Gateway must be restarted after any modification to the backend server DNS entries to begin to use the new IP addresses. Ensure that you add the correct root certificate to whitelist the backend". If you open your certificate with Notepad and it doesn't look similar to this, typically this means you didn't export it using the Base-64 encoded X.509(.CER) format. If the domain is private or internal, try to resolve it from a VM in the same virtual network. The protocol and destination port are inherited from the HTTP settings. Well occasionally send you account related emails. The current data must be within the valid from and valid to range. If you have an ExpressRoute/VPN connection to the virtual network over BGP, and if you're advertising a default route, you must make sure that the packet is routed back to the internet destination without modifying it. An issue with your configuration needs to be ruled out first. If the certificate wasn't issued by a trusted CA (for example, if a self-signed certificate was used), users should upload the issuer's certificate to 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. @TravisCragg-MSFT: Any luck? Do not edit this section. Have a question about this project? here is what happens in in Multiple chain certificate. We should get one Linux machine which is in the same subnet/VNET of the backend application and run the following commands. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Save the custom probe settings and check whether the backend health shows as Healthy now. 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 ? But if the backend health for all the servers in a backend pool is unhealthy or unknown, you might encounter problems when you try to access New blog articles in Microsoft Tech Community, Troubleshoot backend health issues in Azure Application Gateway | Microsoft Docs, Set up Granular Delegated Admin Privileges in Microsoft 365 Lighthouse, Data Mapper Patterns: Conditional Mapping, Windows Server Summit 2022: Modernize your Apps with Windows Containers and AKS, Kubernetes External DNS for Azure DNS & AKS, Update: Addressing Karis Law and Ray Baums Act with Microsoft Teams phone system, SSIS Always on AG (Availability Group) and Error Please Create a Master Key, Azure Marketplace new offers January 4, 2023. Now you may ask why it works when you browse the backend directly through browser. Note that this .CER file must match the certificate (PFX) deployed at the backend application. 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. c. Check the user-defined routes (UDR) settings of Application Gateway and the backend server's subnet for any routing anomalies. To do end to end TLS, Application Gateway requires the backend instances to be allowed by uploading authentication/trusted root certificates. The chain looks ok to me. Allow the backend on the Application Gateway by uploading the root certificate of the server certificate used by the backend. @sajithvasu This lab takes quite a long time to set up! The authentication certificate is the public key of backend server certificates in Base-64 encoded X.509(.CER) format. Message: Body of the backend's HTTP response did not match the I have two listeners and my issue has started on one of them when SSL certificate has been renewed. This causes SSL/TLS negoatiation failure and AppGW marks the backend as unhealthy because it is not able to initiate the probe. Server will send its Certificate and because AppGW will already have its Root Cert, it verifies the backend server certificate and finds that it was issued by the Root cert which it is Trusting and they it starts connecting on HTTPs further for probing. This will take some time to track down, fix, and the docs will need to be updated with limitations & best practices. The following steps help you export the .cer file for your certificate: Use the steps 1 - 8 mentioned in the previous section Export authentication certificate (for v1 SKU) to export the public key from your backend certificate. Also, please let me know your ticket number so that I can track it internally. You signed in with another tab or window. Trusted root certificate mismatch applications. Below is what happens during SSL negotiation when you have single chain cert and root in the AppGW. If Internet and private traffic are going through an Azure Firewall hosted in a secured Virtual hub (using Azure Virtual WAN Hub): a. Sign in @TravisCragg-MSFT: Thanks for checking this. Ensure that you add the correct root certificate to whitelist the backend. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Design a site like this with WordPress.com, Troubleshoot backend health issues in Azure Application Gateway | Microsoft Docs. Currently we are seeing issues with app gateway backend going unhealthy due to backend auth cert. b. If your certificate is working on browser directly hitting the app and not with AppGW then what is the exact problem? 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. Now you may ask why it works when you browse the backend directly through browser. 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. On the Subnets tab of your virtual network, select the subnet where Application Gateway has been deployed. Check that the backend responds on the port used for the probe. This configuration further secures end-to-end communication. If it is, check the DNS server about why it can't resolve to the IP address of the specified FQDN. To resolve the issue, follow these steps. 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. 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. A few things to check: a. Check whetheraccess to the path is allowed on the backend server. 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. In this example, you'll use a TLS/SSL certificate for the backend certificate and export its public key to be used as . 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. If you see an Unhealthy or Degraded state, contact support. The certificate that has been uploaded to Application Gateway HTTP settings must match the root certificate of the backend server certificate. We should get one Linux machine which is in the same subnet/VNET of the backend application and run the following commands. Azure Applicaiton Gateway V2 Certification Issue #62578 - Github On the Application Gateway Overview tab, select the Virtual Network/Subnet link. Which language's style guidelines should be used when writing code that is supposed to be called from another language?
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