forward: remove hosts entry feature (#20)

* remove hosts entry feature

* remove host entry feature

Author: JordiSubira

docs/source/forward-proxy.rst

@@ -170,13 +170,8 @@ For more information, see the `Caddy TLS configuration <https://caddyserver.com/
 Running the SCION HTTP Forward Proxy locally
 --------------------------------------------
 End users can run the SCION HTTP Forward Proxy locally by following the installation steps above.
-For smooth running experience, grant DAC capabilities to the binary:
 
-  .. code-block:: bash
-
-    sudo setcap cap_dac_override=+ep scion-caddy
-
-If you do not want to grant those privileges, you can run the binary without them but you will have to manually add the following line to your ``/etc/hosts`` before running the SCION HTTP Forward Proxy:
+Add the following line on ``/etc/hosts`` before running the SCION HTTP Forward Proxy:
 
   .. code-block:: bash
 

forward/forwardproxy.go

@@ -24,7 +24,6 @@ import (
 	"net"
 	"net/http"
 	"net/textproto"
-	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -41,7 +40,6 @@ import (
 )
 
 const (
-	hostsFile    = "/etc/hosts"
 	hostsComment = " # Line added by the SCION HTTP Forward Proxy"
 	hostName     = "forward-proxy.scion"
 	// TODO: make the address injectable via configuration
@@ -99,17 +97,11 @@ func (cp *CoreProxy) Initialize() error {
 	cp.metricsHandler = panpolicy.NewMetricsHandler(cp.policyManager, cp.logger.With(zap.String("component", "metrics-handler")))
 	cp.resolver = resolver.NewPANResolver(cp.logger.With(zap.String("component", "resolver")), cp.resolveTimeout)
 
-	if err := cp.addHostsEntry(); err != nil {
-		cp.logger.Warn("Failed to add entry to /etc/hosts file", zap.Error(err))
-	}
 	return nil
 }
 
 // Cleanup cleans up the core proxy logic.
 func (cp *CoreProxy) Cleanup() error {
-	if err := cp.removeHostsEntry(); err != nil {
-		cp.logger.Warn("Failed to remove entry from /etc/hosts file", zap.Error(err))
-	}
 	return cp.policyManager.Stop()
 }
 
@@ -174,58 +166,6 @@ func (cp *CoreProxy) HandleTunnelRequest(w http.ResponseWriter, r *http.Request)
 	return cp.forwardRequest(w, r, dialer)
 }
 
-func (cp *CoreProxy) addHostsEntry() error {
-	content, err := os.ReadFile(hostsFile)
-	if err != nil {
-		return fmt.Errorf("failed to read hosts file: %w", err)
-	}
-
-	lines := strings.Split(string(content), "\n")
-	for _, line := range lines {
-		if !strings.HasPrefix(strings.TrimSpace(line), "#") && strings.Contains(line, hostName) {
-			cp.logger.Debug("Entry for host name already exists", zap.String("entry", line))
-			return nil
-		}
-	}
-
-	file, err := os.OpenFile(hostsFile, os.O_APPEND|os.O_WRONLY, 0644)
-	if err != nil {
-		return fmt.Errorf("failed to open hosts file for writing: %w", err)
-	}
-	defer file.Close()
-
-	entry := hostsComment + "\n" + hostsEntry + "\n"
-	if _, err := file.WriteString(entry); err != nil {
-		return fmt.Errorf("failed to write to hosts file: %w", err)
-	}
-
-	cp.logger.Info("Added entry to hosts file", zap.String("entry", hostsEntry))
-	return nil
-}
-
-func (cp *CoreProxy) removeHostsEntry() error {
-	content, err := os.ReadFile(hostsFile)
-	if err != nil {
-		return fmt.Errorf("failed to read hosts file: %w", err)
-	}
-
-	var newLines []string
-	lines := strings.Split(string(content), "\n")
-	for _, line := range lines {
-		if !strings.Contains(line, hostsEntry) && !strings.Contains(line, hostsComment) {
-			newLines = append(newLines, line)
-		}
-	}
-
-	err = os.WriteFile(hostsFile, []byte(strings.Join(newLines, "\n")), 0644)
-	if err != nil {
-		return fmt.Errorf("failed to write to hosts file: %w", err)
-	}
-
-	cp.logger.Info("Removed entry from hosts file", zap.String("entry", hostsEntry))
-	return nil
-}
-
 func (cp *CoreProxy) parseCookieFromProxyAuth(w http.ResponseWriter, r *http.Request) error {
 	// the path policy cookie is passed in the proxy-authorization header as the cookie
 	username, cookie, err := proxyBasicAuth(r)