Add option to override CDN Host Header

- This is useful if a proxy sits behind the CDN and an operator needs to route traffic
via the proxy before it reaches the container app.

terraform/README.md

@@ -153,6 +153,7 @@ No resources.
 | <a name="input_cdn_frontdoor_health_probe_path"></a> [cdn\_frontdoor\_health\_probe\_path](#input\_cdn\_frontdoor\_health\_probe\_path) | Specifies the path relative to the origin that is used to determine the health of the origin. | `string` | n/a | yes |
 | <a name="input_cdn_frontdoor_host_add_response_headers"></a> [cdn\_frontdoor\_host\_add\_response\_headers](#input\_cdn\_frontdoor\_host\_add\_response\_headers) | List of response headers to add at the CDN Front Door `[{ "name" = "Strict-Transport-Security", "value" = "max-age=31536000" }]` | `list(map(string))` | n/a | yes |
 | <a name="input_cdn_frontdoor_origin_fqdn_override"></a> [cdn\_frontdoor\_origin\_fqdn\_override](#input\_cdn\_frontdoor\_origin\_fqdn\_override) | Manually specify the hostname that the CDN Front Door should target. Defaults to the Container App FQDN | `string` | `""` | no |
+| <a name="input_cdn_frontdoor_origin_host_header_override"></a> [cdn\_frontdoor\_origin\_host\_header\_override](#input\_cdn\_frontdoor\_origin\_host\_header\_override) | Manually specify the host header that the CDN sends to the target. Defaults to the recieved host header. Set to null to set it to the host\_name (`cdn_frontdoor_origin_fqdn_override`) | `string` | `""` | no |
 | <a name="input_cdn_frontdoor_rate_limiting_duration_in_minutes"></a> [cdn\_frontdoor\_rate\_limiting\_duration\_in\_minutes](#input\_cdn\_frontdoor\_rate\_limiting\_duration\_in\_minutes) | CDN Front Door rate limiting duration in minutes | `number` | n/a | yes |
 | <a name="input_cdn_frontdoor_rate_limiting_threshold"></a> [cdn\_frontdoor\_rate\_limiting\_threshold](#input\_cdn\_frontdoor\_rate\_limiting\_threshold) | CDN Front Door rate limiting duration in minutes | `number` | n/a | yes |
 | <a name="input_container_command"></a> [container\_command](#input\_container\_command) | Container command | `list(any)` | n/a | yes |

terraform/container-apps-hosting.tf

@@ -30,6 +30,7 @@ module "azure_container_apps_hosting" {
   cdn_frontdoor_host_add_response_headers         = local.cdn_frontdoor_host_add_response_headers
   cdn_frontdoor_custom_domains                    = local.cdn_frontdoor_custom_domains
   cdn_frontdoor_origin_fqdn_override              = local.cdn_frontdoor_origin_fqdn_override
+  cdn_frontdoor_origin_host_header_override       = local.cdn_frontdoor_origin_host_header_override
 
   enable_monitoring               = local.enable_monitoring
   monitor_email_receivers         = local.monitor_email_receivers

terraform/locals.tf

@@ -21,6 +21,7 @@ locals {
   cdn_frontdoor_host_add_response_headers         = var.cdn_frontdoor_host_add_response_headers
   cdn_frontdoor_custom_domains                    = var.cdn_frontdoor_custom_domains
   cdn_frontdoor_origin_fqdn_override              = var.cdn_frontdoor_origin_fqdn_override
+  cdn_frontdoor_origin_host_header_override       = var.cdn_frontdoor_origin_host_header_override
   key_vault_access_users                          = toset(var.key_vault_access_users)
   key_vault_access_ipv4                           = var.key_vault_access_ipv4
   tfvars_filename                                 = var.tfvars_filename

terraform/variables.tf

@@ -75,6 +75,13 @@ variable "cdn_frontdoor_origin_fqdn_override" {
   default     = ""
 }
 
+variable "cdn_frontdoor_origin_host_header_override" {
+  description = "Manually specify the host header that the CDN sends to the target. Defaults to the recieved host header. Set to null to set it to the host_name (`cdn_frontdoor_origin_fqdn_override`)"
+  type        = string
+  default     = ""
+  nullable    = true
+}
+
 variable "cdn_frontdoor_enable_rate_limiting" {
   description = "Enable CDN Front Door Rate Limiting. This will create a WAF policy, and CDN security policy. For pricing reasons, there will only be one WAF policy created."
   type        = bool