authorize: use jwt insead of state struct (#514)

authenticate: unmarshal and verify state from jwt, instead of middleware
authorize: embed opa policy using statik
authorize: have IsAuthorized handle authorization for all routes
authorize: if no signing key is provided, one is generated
authorize: remove IsAdmin grpc endpoint
authorize/client: return authorize decision struct
cmd/pomerium: main logger no longer contains email and group
cryptutil: add ECDSA signing methods
dashboard: have impersonate form show up for all users, but have api gated by authz
docs: fix typo in signed jwt header
encoding/jws: remove unused es256 signer
frontend: namespace static web assets
internal/sessions: remove leeway to match authz policy
proxy:  move signing functionality to authz
proxy: remove jwt attestation from proxy (authZ does now)
proxy: remove non-signed headers from headers
proxy: remove special handling of x-forwarded-host
sessions: do not verify state in middleware
sessions: remove leeway from state to match authz
sessions/{all}: store jwt directly instead of state

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/cryptutil/sign_test.go

@@ -0,0 +1,60 @@
+package cryptutil
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"testing"
+)
+
+func TestSign(t *testing.T) {
+	message := []byte("Hello, world!")
+
+	key, err := NewSigningKey()
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	signature, err := Sign(message, key)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	if !Verify(message, signature, &key.PublicKey) {
+		t.Error("signature was not correct")
+		return
+	}
+
+	message[0] ^= 0xff
+	if Verify(message, signature, &key.PublicKey) {
+		t.Error("signature was good for altered message")
+	}
+}
+
+func TestSignWithP384(t *testing.T) {
+	message := []byte("Hello, world!")
+
+	key, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	signature, err := Sign(message, key)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	if !Verify(message, signature, &key.PublicKey) {
+		t.Error("signature was not correct")
+		return
+	}
+
+	message[0] ^= 0xff
+	if Verify(message, signature, &key.PublicKey) {
+		t.Error("signature was good for altered message")
+	}
+}