[client, management] implement certificate posture check (#7535)

Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>

client/internal/certproof/helper_spawn_test.go

@@ -0,0 +1,56 @@
+//go:build darwin || windows
+
+package certproof
+
+import (
+	"crypto/sha256"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/shared/management/certposture"
+	"github.com/netbirdio/netbird/shared/management/certposture/certtest"
+	"github.com/netbirdio/netbird/shared/management/proto"
+)
+
+func TestMergeProofs_ProvesACertificateHeldByBothStoresOnce(t *testing.T) {
+	ca := certtest.NewCA(t, "corp-root")
+	shared := ca.Issue(t, certtest.ECDSAKey(t), "shared")
+	userOnly := ca.Issue(t, certtest.ECDSAKey(t), "user-only")
+
+	device := []certposture.Proof{{Chain: [][]byte{shared.Raw}}}
+	user := []certposture.Proof{{Chain: [][]byte{shared.Raw}}, {Chain: [][]byte{userOnly.Raw}}, {}}
+
+	merged := mergeProofs(device, user)
+
+	require.Len(t, merged, 2, "the shared leaf is proven once and the empty chain is dropped")
+	assert.Equal(t, shared.Raw, merged[0].Chain[0], "the device proof keeps its place")
+	assert.Equal(t, userOnly.Raw, merged[1].Chain[0], "the user-only certificate is appended")
+}
+
+func TestMergeProofs_KeepsDeviceProofsWhenNoUserSession(t *testing.T) {
+	ca := certtest.NewCA(t, "corp-root")
+	device := []certposture.Proof{{Chain: [][]byte{ca.Issue(t, certtest.ECDSAKey(t), "device").Raw}}}
+
+	merged := mergeProofs(device, nil)
+
+	require.Len(t, merged, 1, "a machine with nobody signed in still sends its device proof")
+	assert.Equal(t, sha256.Sum256(device[0].Chain[0]), sha256.Sum256(merged[0].Chain[0]), "the device proof is unchanged")
+}
+
+func TestHelperRequest_CarriesEveryChallenge(t *testing.T) {
+	ca := certtest.NewCA(t, "corp-root")
+	challenges := []*proto.CertificateChallenge{
+		{Nonce: []byte("first"), CaCertificates: []string{ca.PEM}},
+		{Nonce: []byte("second")},
+	}
+
+	req := helperRequest(challenges, peerKey)
+
+	require.Len(t, req.Challenges, 2, "every challenge must reach the helper")
+	assert.Equal(t, peerKey, req.PeerKey, "the peer key binds the signature to this machine")
+	assert.Equal(t, []byte("first"), req.Challenges[0].Nonce, "the nonce must survive unchanged")
+	assert.Equal(t, []string{ca.PEM}, req.Challenges[0].CACertificates, "the accepted CAs must survive unchanged")
+	assert.Empty(t, req.Challenges[1].CACertificates, "a challenge without CAs stays without CAs")
+}