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SSH access should not be accessible from the Internet, should be blocked on port 22

Explanation

SSH access can be configured on either the network security group or in the network security group rule.

SSH access should not be permitted from the internet (*, 0.0.0.0, /0, internet, any)

Insecure Example

The following example will fail the AZU017 check.

resource "azurerm_network_security_rule" "bad_example" {
     name                        = "bad_example_security_rule"
     direction                   = "Inbound"
     access                      = "Allow"
     protocol                    = "TCP"
     source_port_range           = "*"
     destination_port_range      = ["22"]
     source_address_prefix       = "*"
     destination_address_prefix  = "*"
}

resource "azurerm_network_security_group" "example" {
  name                = "tf-appsecuritygroup"
  location            = azurerm_resource_group.example.location
  resource_group_name = azurerm_resource_group.example.name
  
  security_rule {
	 source_port_range           = "any"
     destination_port_range      = ["22"]
     source_address_prefix       = "*"
     destination_address_prefix  = "*"
  }
}

Secure Example

The following example will pass the AZU017 check.

resource "azurerm_network_security_rule" "good_example" {
     name                        = "good_example_security_rule"
     direction                   = "Inbound"
     access                      = "Allow"
     protocol                    = "TCP"
     source_port_range           = "*"
     destination_port_range      = ["22"]
     source_address_prefix       = "82.102.23.23"
     destination_address_prefix  = "*"
}

resource "azurerm_network_security_group" "example" {
  name                = "tf-appsecuritygroup"
  location            = azurerm_resource_group.example.location
  resource_group_name = azurerm_resource_group.example.name
  
  security_rule {
	 source_port_range           = "any"
     destination_port_range      = ["22"]
     source_address_prefix       = "82.102.23.23"
     destination_address_prefix  = "*"
  }
}