176 lines
7.1 KiB
Go
176 lines
7.1 KiB
Go
package iptables
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import (
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"errors"
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"strconv"
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)
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const (
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// ProxyInboundChain is the chain to intercept inbound traffic.
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ProxyInboundChain = "CONSUL_PROXY_INBOUND"
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// ProxyInboundRedirectChain is the chain to redirect inbound traffic to the proxy.
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ProxyInboundRedirectChain = "CONSUL_PROXY_IN_REDIRECT"
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// ProxyOutputChain is the chain to intercept outbound traffic.
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ProxyOutputChain = "CONSUL_PROXY_OUTPUT"
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// ProxyOutputRedirectChain is the chain to redirect outbound traffic to the proxy
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ProxyOutputRedirectChain = "CONSUL_PROXY_REDIRECT"
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// DNSChain is the chain to redirect outbound DNS traffic to Consul DNS.
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DNSChain = "CONSUL_DNS_REDIRECT"
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DefaultTProxyOutboundPort = 15001
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)
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// Config is used to configure which traffic interception and redirection
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// rules should be applied with the iptables commands.
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type Config struct {
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// ConsulDNSIP is the IP for Consul DNS to direct DNS queries to.
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ConsulDNSIP string
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// ProxyUserID is the user ID of the proxy process.
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ProxyUserID string
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// ProxyInboundPort is the port of the proxy's inbound listener.
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ProxyInboundPort int
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// ProxyInboundPort is the port of the proxy's outbound listener.
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ProxyOutboundPort int
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// ExcludeInboundPorts is the list of ports that should be excluded
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// from inbound traffic redirection.
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ExcludeInboundPorts []string
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// ExcludeOutboundPorts is the list of ports that should be excluded
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// from outbound traffic redirection.
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ExcludeOutboundPorts []string
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// ExcludeOutboundCIDRs is the list of IP CIDRs that should be excluded
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// from outbound traffic redirection.
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ExcludeOutboundCIDRs []string
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// ExcludeUIDs is the list of additional user IDs to exclude
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// from traffic redirection.
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ExcludeUIDs []string
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// NetNS is the network namespace where the traffic redirection rules
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// should be applied. This must be a path to the network namespace,
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// e.g. /var/run/netns/foo.
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NetNS string
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// IptablesProvider is the Provider that will apply iptables rules.
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IptablesProvider Provider
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}
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// Provider is an interface for executing iptables rules.
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type Provider interface {
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// AddRule adds a rule without executing it.
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AddRule(name string, args ...string)
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// ApplyRules executes rules that have been added via AddRule.
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// This operation is currently not atomic, and if there's an error applying rules,
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// you may be left in a state where partial rules were applied.
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ApplyRules() error
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// Rules returns the list of rules that have been added but not applied yet.
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Rules() []string
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}
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// Setup will set up iptables interception and redirection rules
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// based on the configuration provided in cfg.
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// This implementation was inspired by
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// https://github.com/openservicemesh/osm/blob/650a1a1dcf081ae90825f3b5dba6f30a0e532725/pkg/injector/iptables.go
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func Setup(cfg Config) error {
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if cfg.IptablesProvider == nil {
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cfg.IptablesProvider = &iptablesExecutor{cfg: cfg}
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}
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err := validateConfig(cfg)
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if err != nil {
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return err
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}
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// Set the default outbound port if it's not already set.
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if cfg.ProxyOutboundPort == 0 {
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cfg.ProxyOutboundPort = DefaultTProxyOutboundPort
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}
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// Create chains we will use for redirection.
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chains := []string{ProxyInboundChain, ProxyInboundRedirectChain, ProxyOutputChain, ProxyOutputRedirectChain, DNSChain}
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for _, chain := range chains {
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-N", chain)
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}
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// Configure outbound rules.
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{
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// Redirects outbound TCP traffic hitting PROXY_REDIRECT chain to Envoy's outbound listener port.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", ProxyOutputRedirectChain, "-p", "tcp", "-j", "REDIRECT", "--to-port", strconv.Itoa(cfg.ProxyOutboundPort))
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// The DNS rules are applied before the rules that directs all TCP traffic, so that the traffic going to port 53 goes through this rule first.
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if cfg.ConsulDNSIP != "" {
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// Traffic in the DNSChain is directed to the Consul DNS Service IP.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", DNSChain, "-p", "udp", "--dport", "53", "-j", "DNAT", "--to-destination", cfg.ConsulDNSIP)
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", DNSChain, "-p", "tcp", "--dport", "53", "-j", "DNAT", "--to-destination", cfg.ConsulDNSIP)
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// For outbound TCP and UDP traffic going to port 53 (DNS), jump to the DNSChain.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", "OUTPUT", "-p", "udp", "--dport", "53", "-j", DNSChain)
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", "OUTPUT", "-p", "tcp", "--dport", "53", "-j", DNSChain)
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}
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// For outbound TCP traffic jump from OUTPUT chain to PROXY_OUTPUT chain.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", "OUTPUT", "-p", "tcp", "-j", ProxyOutputChain)
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// Don't redirect proxy traffic back to itself, return it to the next chain for processing.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", ProxyOutputChain, "-m", "owner", "--uid-owner", cfg.ProxyUserID, "-j", "RETURN")
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// Skip localhost traffic, doesn't need to be routed via the proxy.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", ProxyOutputChain, "-d", "127.0.0.1/32", "-j", "RETURN")
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// Redirect remaining outbound traffic to Envoy.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", ProxyOutputChain, "-j", ProxyOutputRedirectChain)
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// We are using "insert" (-I) instead of "append" (-A) so the the provided rules take precedence over default ones.
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for _, outboundPort := range cfg.ExcludeOutboundPorts {
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-I", ProxyOutputChain, "-p", "tcp", "--dport", outboundPort, "-j", "RETURN")
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}
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for _, outboundIP := range cfg.ExcludeOutboundCIDRs {
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-I", ProxyOutputChain, "-d", outboundIP, "-j", "RETURN")
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}
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for _, uid := range cfg.ExcludeUIDs {
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-I", ProxyOutputChain, "-m", "owner", "--uid-owner", uid, "-j", "RETURN")
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}
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}
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// Configure inbound rules.
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{
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// Redirects inbound TCP traffic hitting the PROXY_IN_REDIRECT chain to Envoy's inbound listener port.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", ProxyInboundRedirectChain, "-p", "tcp", "-j", "REDIRECT", "--to-port", strconv.Itoa(cfg.ProxyInboundPort))
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// For inbound traffic jump from PREROUTING chain to PROXY_INBOUND chain.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", "PREROUTING", "-p", "tcp", "-j", ProxyInboundChain)
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// Redirect remaining inbound traffic to Envoy.
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-A", ProxyInboundChain, "-p", "tcp", "-j", ProxyInboundRedirectChain)
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for _, inboundPort := range cfg.ExcludeInboundPorts {
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cfg.IptablesProvider.AddRule("iptables", "-t", "nat", "-I", ProxyInboundChain, "-p", "tcp", "--dport", inboundPort, "-j", "RETURN")
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}
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}
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return cfg.IptablesProvider.ApplyRules()
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}
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func validateConfig(cfg Config) error {
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if cfg.ProxyUserID == "" {
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return errors.New("ProxyUserID is required to set up traffic redirection")
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}
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if cfg.ProxyInboundPort == 0 {
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return errors.New("ProxyInboundPort is required to set up traffic redirection")
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}
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return nil
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}
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