Access the backend server locally or from a client machine on the probe path, and check the response body. Have done s_client -connect backend_ip:443 -servername backend_url -showcerts and found that Root CA is missing. To check the health of your backend pool, you can use the The custom DNS server is configured on a virtual network that can't resolve public domain names. 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. Page not found. 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. @krish-gh actually it was actually what have i tried firstly but sitouiotion was same. By clicking Sign up for GitHub, you agree to our terms of service and If it's not, the certificate is considered invalid, and that will create a This will take some time to track down, fix, and the docs will need to be updated with limitations & best practices. It is required for docs.microsoft.com GitHub issue linking. We are actually trying to simulate the Linux box as AppGW. Otherwise please share the message in that scenario without adding root explicitly. If they aren't, create a new rule to allow the connections. Thank you everyone. Next hop: Internet. What was the resolution? The text was updated successfully, but these errors were encountered: @sajithvasu I am not aware of any changes that have been made on the App Gateway side that would make this not work. 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. I can confirm that it's NOT a general issue or bug of the product. Trusted root certificate mismatch 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. The backend certificate can be the same as the TLS/SSL certificate or different for added security. 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 raised ticket to Microsoft. To learn more visit - https://aka.ms/UnknownBackendHealth. Service: application-gateway; GitHub Login: @vhorne; Microsoft Alias: absha; The text was updated successfully, but these errors were encountered: . . We should get one Linux machine which is in the same subnet/VNET of the backend application and run the following commands. b. Message: Application Gateway could not connect to the backend. 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. You should remove the exported trusted root you added in the App Gateway. When I use v2 SKU with the option to trust the backend certificate from APIM it works. Asking for help, clarification, or responding to other answers. b. 7 19 comments Add a Comment Nillsf 4 yr. ago 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. 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. 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. The protocol and destination port are inherited from the HTTP settings. Were you able to reproduce this scenario and check? 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. Ensure that you add the correct root certificate to allowlist the backend. I will wait for your response. 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. Ensure that you add the correct root certificate to whitelist the backend. If they don't match, change the probe configuration so that it has the correct string value to accept. You must be a registered user to add a comment. From the properties displayed, find the CN of the certificate and enter the same in the host name field of the http settings. @EmreMARTiN you can run openssl from your local machine pointing to your backend, not external over WAF. c. Check to see if there are any default routes (0.0.0.0/0) with the next hop not set as Internet. 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. Thanks for this information. 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. Azure Tip #5 Change Color Theme in Azure Portal, Azure Tip #1 Azure Services offered by Microsoft, Azure Tip #8 Fix Data for certificate is Invalid error, Azure Tip #6 Reset the Microsoft Azure Dashboard. For example, check whether the database has any issues that might trigger a delay in response. Ensure that you add the correct root certificate to whitelist the backend". Or, you can use Azure PowerShell, CLI, or REST API. 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. Just FYI. Note that this .CER file must match the certificate (PFX) deployed at the backend application. Export trusted root certificate (for v2 SKU): We initially faced an issue with the certificate on the backend server which has since been sorted out by MS Support. In the Certificate properties, select the Details tab. 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. Well occasionally send you account related emails. The issue was on certificate. Access the backend server directly and check the time taken for the server to respond on that page. See Configure end to end TLS by using Application Gateway with PowerShell. During SSL negotiation , Client sends "Client Hello" and Server Responds with "Server Hello" with its Certificate to the Client. Client has renewed cert which is issued by GlobalSign and one of the listeners started to fail with same error. 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). In this example, you'll use a TLS/SSL certificate for the backend certificate and export its public key to be used as authentication certification. If thats not a desired value, you should create a custom probe and associate it with the HTTP settings. How did you verify the cert? 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 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. or is that all the backend pools has to serve the request for one application ? Content: <---> The text was updated successfully, but these errors were encountered: @EmreMARTiN, Thanks for the feedback. Ensure that you add the correct root certificate to whitelist the backend". Open the Application Gateway HTTP Settings page in the Azure portal. If you don't mind can you please post the summary of the root here to help people who might face similar issue. I will let you know what I find. to your account. Cause: Application Gateway resolves the DNS entries for the backend pool at time of startup and doesn't update them dynamically while running. If it's a self-signed certificate, you must generate a valid certificate and upload the root certificate to the Application Gateway HTTP settings. (LogOut/ The default route is advertised by an ExpressRoute/VPN connection to a virtual network over BGP. ID: <---> To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. EDIT: Turned out I uploaded wrong pfx compared to the backend server. Only HTTP status codes of 200 through 399 are considered healthy. The reason why I try to use CA cert is that I manage all the resource in terraform, with a single CA cert, it is better to automate the process. In this article I am going to talk about one most common issue "backend certificate not whitelisted" GitHub Login: <---> "The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway". 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. Message: The root certificate of the server certificate used by the backend does not match the trusted root certificate added to the application gateway. certificate. The section in blue contains the information that is uploaded to application gateway. craigclouditpro your a lifesaver thanks for posting this friend ! Nice article mate! Check whether the host name path is accessible on the backend server. 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. Learn how your comment data is processed. Let me know here if you face any issue reaching Azure support or if you do not have any support plan for your subscription. Failing endpoint is missing root CA as working one has it. Posted in Azure Tagged 502webserver, Azure, azure502, azureapplicationgateway, azurecertificate, azurewaf, backend certificate not whitelisted Post navigation Azure Cyber Security: Protect & Secure Your Cloud Infrastructure 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.. Have raise case with Microsoft as unable to resolve that myself. 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. 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. On the Export File Format page, select Base-64 encoded X.509 (.CER)., and then click Next. We should get one Linux machine which is in the same subnet/VNET of the backend application and run the following commands. Enter any timeout value that's greater than the application response time, in seconds. If the domain is private or internal, try to resolve it from a VM in the same virtual network. c. Check the user-defined routes (UDR) settings of Application Gateway and the backend server's subnet for any routing anomalies. 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. 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. Sure I would be glad to get involved if needed. Check the document page that's provided in step 3a to learn more about how to create NSG rules. here is the sample command you need to run, from the linux box that can connect to the backend application. In Azure docs, it is clearly documented that you dont have to import Auth certificate in HTTP settings of the backend if your backend application has Global trusted certificate. I will post the root cause summary once there is an outcome from your open support case. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Azure Application Gateway health probe error with "Backend server certificate is not whitelisted with Application Gateway", When AI meets IP: Can artists sue AI imitators? To increase the timeout value, follow these steps: Message: Application Gateway could not create a probe for this backend. Allow the backend on the Application Gateway by uploading the root certificate of the server certificate used by the backend. For example, http://127.0.0.1:80 for an HTTP probe on port 80. The authentication certificate is the public key of backend server certificates in Base-64 encoded X.509 (.CER) format. privacy statement. If the backend server response for the probe request contains the string unauthorized, it will be marked as Healthy. backend server, it waits for a response from the backend server for a configured period. 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/ Most of the best practice documentation involves the V2 SKU and not the V1. Your email address will not be published. Our current setup includes app gateway v1 SKU integrated with app services having custom domain enabled. 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. 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. Select the root certificate and then select View Certificate. here is the sample command you need to run, from the machine that can connect to the backend server/application. PS : Dont forget to upload the CER file to the HTTP settings in ApplicationGateway before you do the Health Check. 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. Application Gateway is in an Unhealthy state. Make sure https probe is configured correctly as well. You must have a custom probe to change the timeout value. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, Azure Application Gateway Probe Configuration, Azure App Gateway gives Error 404 but backend probe is healthy, Azure Application Gateway Health Probe Error, Azure Application Gateway : Backend server certificate expired. successfully, Application Gateway resumes forwarding the requests. Sub-service: <---> Check whether the backend server requires authentication. i had this issue for client and split multiple vms ! To Answer we need to understand what happens in any SSL/TLS negotiation. Sign in Something that you will see missing is microsft docs is having a default site binding to a SSL certificate without the SNI enabled. @TravisCragg-MSFT: Thanks for checking this. This causes SSL/TLS negoatiation failure and AppGW marks the backend as unhealthy because it is not able to initiate the probe. I am currently experimenting with different ways to add the backend pools and heath probes to find a working configuration. Check whether the server is listening on the port that's configured. (These steps are for Windows clients.). 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 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. If you can resolve the IP address, there might be something wrong with the DNS configuration in the virtual network. Azure Tip #3 What is Scale up and Scale Out ? error. Now how do we find if my application/backendserver is sending the complete chain to AppGW? multiple chain certificate and if your backend application/server sends only the leaf the certificate , AppGW . Check whether your server allows this method. I guess you need a Default SITE binding to a certificate, without SNI ticked. 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. However, we need few details. probe setting. An existing backend certificate is required to generate the authentication certificates or trusted root certificates required for allowing backend instances with Application Gateway. Configure that certificate on your backend server. 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. Hi @TravisCragg-MSFT : Were you able to check this? 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. 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. If there is, search for the resource on the search bar or under All resources. OpenSSL> s_client -connect 10.0.0.4:443 -servername www.example.com -showcerts
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