Detect HTTPS interception

CONTRIBUTING.md

@@ -99,7 +99,9 @@ one collaborator who did not open the pull request before merging. This will
 help ensure high code quality as new collaborators are added to the project.
 
 Read [CodeReviewComments](https://github.com/golang/go/wiki/CodeReviewComments)
-on the Go wiki for an idea of what we look for in good, clean Go code.
+on the Go wiki for an idea of what we look for in good, clean Go code, and
+check out [what Linus suggests](https://gist.github.com/matthewhudson/1475276)
+for good commit messages.
 
 
 

caddy.go

@@ -5,6 +5,8 @@
 //   1. Set the AppName and AppVersion variables.
 //   2. Call LoadCaddyfile() to get the Caddyfile.
 //      Pass in the name of the server type (like "http").
+//      Make sure the server type's package is imported
+//      (import _ "github.com/mholt/caddy/caddyhttp").
 //   3. Call caddy.Start() to start Caddy. You get back
 //      an Instance, on which you can call Restart() to
 //      restart it or Stop() to stop it.

caddyhttp/httpserver/context.go

@@ -321,3 +321,14 @@ func (c Context) Files(name string) ([]string, error) {
 
 	return names, nil
 }
+
+// IsMITM returns true if it seems likely that the TLS connection
+// is being intercepted.
+func (c Context) IsMITM() bool {
+	if val, ok := c.Req.Context().Value(CtxKey("mitm")).(bool); ok {
+		return val
+	}
+	return false
+}
+
+type CtxKey string