resource "aws_security_group" "app-prod" { vpc_id = aws_vpc.main.id name = "application - production" description = "security group for my app" egress { from_port = 0 to_port = 0 protocol = "-1" cidr_blocks = ["0.0.0.0/0"] } ingress { from_port = 22 to_port = 22 protocol = "tcp" cidr_blocks = ["0.0.0.0/0"] } tags = { Name = "myinstance" } } resource "aws_security_group" "allow-mariadb" { vpc_id = aws_vpc.main.id name = "allow-mariadb" description = "allow-mariadb" ingress { from_port = 3306 to_port = 3306 protocol = "tcp" security_groups = [aws_security_group.app-prod.id] # allowing access from our example instance } egress { from_port = 0 to_port = 0 protocol = "-1" cidr_blocks = ["0.0.0.0/0"] self = true } tags = { Name = "allow-mariadb" } }