Add (podman {image,manifest} push --sign-by-sigstore=param-file.yaml)

(podman push) and (podman manifest push) now support --sign-by-sigstore=param-file,
using the containers-sigstore-signing-params.yaml(5) file format.

That notably adds support for Fulcio and Rekor signing.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/hashicorp/go-cleanhttp/handlers.go

@@ -0,0 +1,48 @@
+package cleanhttp
+
+import (
+	"net/http"
+	"strings"
+	"unicode"
+)
+
+// HandlerInput provides input options to cleanhttp's handlers
+type HandlerInput struct {
+	ErrStatus int
+}
+
+// PrintablePathCheckHandler is a middleware that ensures the request path
+// contains only printable runes.
+func PrintablePathCheckHandler(next http.Handler, input *HandlerInput) http.Handler {
+	// Nil-check on input to make it optional
+	if input == nil {
+		input = &HandlerInput{
+			ErrStatus: http.StatusBadRequest,
+		}
+	}
+
+	// Default to http.StatusBadRequest on error
+	if input.ErrStatus == 0 {
+		input.ErrStatus = http.StatusBadRequest
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r != nil {
+			// Check URL path for non-printable characters
+			idx := strings.IndexFunc(r.URL.Path, func(c rune) bool {
+				return !unicode.IsPrint(c)
+			})
+
+			if idx != -1 {
+				w.WriteHeader(input.ErrStatus)
+				return
+			}
+
+			if next != nil {
+				next.ServeHTTP(w, r)
+			}
+		}
+
+		return
+	})
+}