m/n/core: factor out gRPC/TLS into rpc and identity libraries
This is an annoying large change, which started its life as me pulling
the 'let's add tests for authentication' thread, and ended up in
unifying a whole bunch of dispersed logic under two new libraries.
Notable changes:
- m/n/core/identity now contains the NodeCertificate (now called Node)
and NodeCredentials types. These used to exist in the cluster code,
but were factored out to prevent loops between the curator, the
cluster enrolment logic, and other code. They can now be shared by
nearly all of the node code, removing the need for some conversions
between subsystems/packages.
- Alongside Node{,Credentials} types, the identity package contains
code that creates x509 certificate templates and verifies x509
certificates, and has functions specific to nodes and users - not
clients and servers. This allows moving most of the rest of
certificate checking code into a single set of functions, and allows
us to test this logic thoroughly.
- pki.{Client,Server,CA} are not used by the node core code anymore,
and can now be moved to kubernetes-specific code (as that was their
original purpose and that's their only current use).
- m/n/core/rpc has been refactored to deduplicate code between the
local/external gRPC servers and unary/stream interceptors for these
servers, also allowing for more thorough testing and unified
behaviour between all.
- A PeerInfo structure is now injected into all gRPC handlers, and is
unified to contain information both about nodes, users, and possibly
unauthenticated callers.
- The AAA.Escrow implementation now makes use of PeerInfo in order to
retrieve the client's certificate, instead of rolling its own logic.
- The EphemeralClusterCredentials test helper has been moved to the rpc
library, and now returns identity objects, allowing for simplified
test code (less juggling of bare public keys and
{x509,tls}.Certificate objects).
Change-Id: I9284966b4f18c0d7628167ca3168b4b4037808c1
Reviewed-on: https://review.monogon.dev/c/monogon/+/325
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/node/core/identity/identity.go b/metropolis/node/core/identity/identity.go
new file mode 100644
index 0000000..862e794
--- /dev/null
+++ b/metropolis/node/core/identity/identity.go
@@ -0,0 +1,138 @@
+package identity
+
+import (
+ "crypto/ed25519"
+ "crypto/subtle"
+ "crypto/tls"
+ "crypto/x509"
+ "encoding/hex"
+ "fmt"
+
+ "source.monogon.dev/metropolis/node/core/localstorage"
+)
+
+// Node is the public part of the credentials of a node. They are
+// emitted for a node by the cluster CA contained within the curator.
+type Node struct {
+ node *x509.Certificate
+ ca *x509.Certificate
+}
+
+// NewNode wraps a pair CA and node DER-encoded certificates into
+// Node, ensuring the given certificate data is valid and compatible
+// with Metropolis assumptions.
+func NewNode(cert, ca []byte) (*Node, error) {
+ certParsed, err := x509.ParseCertificate(cert)
+ if err != nil {
+ return nil, fmt.Errorf("could not parse node certificate: %w", err)
+ }
+ caCertParsed, err := x509.ParseCertificate(ca)
+ if err != nil {
+ return nil, fmt.Errorf("could not parse ca certificate: %w", err)
+ }
+
+ if _, err := VerifyNodeInCluster(certParsed, caCertParsed); err != nil {
+ return nil, fmt.Errorf("could not node certificate within cluster CA: %w", err)
+ }
+
+ return &Node{
+ node: certParsed,
+ ca: caCertParsed,
+ }, nil
+}
+
+// PublicKey returns the Ed25519 public key corresponding to this node's
+// certificate/credentials.
+func (n *Node) PublicKey() ed25519.PublicKey {
+ // Safe: we have ensured that the given certificate has an Ed25519 public key on
+ // NewNode.
+ return n.node.PublicKey.(ed25519.PublicKey)
+}
+
+// ClusterCA returns the CA certificate of the cluster for which this
+// Node is emitted.
+func (n *Node) ClusterCA() *x509.Certificate {
+ return n.ca
+}
+
+// ID returns the canonical ID/name of the node for which this
+// certificate/credentials were emitted.
+func (n *Node) ID() string {
+ return NodeID(n.PublicKey())
+}
+
+func (n *Node) Certificate() *x509.Certificate {
+ return n.node
+}
+
+// NodeCredentials are the public and private part of the credentials of a node.
+//
+// It represents all the data necessary for a node to authenticate over mTLS to
+// other nodes and the rest of the cluster.
+//
+// It must never be made available to any node other than the node it has been
+// emitted for.
+type NodeCredentials struct {
+ Node
+ private ed25519.PrivateKey
+}
+
+// NewNodeCredentials wraps a pair of CA and node DER-encoded certificates plus
+// a private key into NodeCredentials, ensuring that the given data is valid and
+// compatible with Metropolis assumptions.
+func NewNodeCredentials(priv, cert, ca []byte) (*NodeCredentials, error) {
+ nc, err := NewNode(cert, ca)
+ if err != nil {
+ return nil, err
+ }
+
+ // Ensure that the private key is a valid length.
+ if want, got := ed25519.PrivateKeySize, len(priv); want != got {
+ return nil, fmt.Errorf("private key is not the correct length, wanted %d, got %d", want, got)
+ }
+
+ // Ensure that the given private key matches the given public key.
+ if want, got := ed25519.PrivateKey(priv).Public().(ed25519.PublicKey), nc.PublicKey(); subtle.ConstantTimeCompare(want, got) != 1 {
+ return nil, fmt.Errorf("public key does not match private key")
+ }
+
+ return &NodeCredentials{
+ Node: *nc,
+ private: priv,
+ }, nil
+}
+
+func (n *NodeCredentials) TLSCredentials() tls.Certificate {
+ return tls.Certificate{
+ Leaf: n.node,
+ Certificate: [][]byte{n.node.Raw},
+ PrivateKey: n.private,
+ }
+}
+
+// Save stores the given node credentials in local storage.
+func (n *NodeCredentials) Save(d *localstorage.PKIDirectory) error {
+ if err := d.CACertificate.Write(n.ca.Raw, 0400); err != nil {
+ return fmt.Errorf("when writing CA certificate: %w", err)
+ }
+ if err := d.Certificate.Write(n.node.Raw, 0400); err != nil {
+ return fmt.Errorf("when writing node certificate: %w", err)
+ }
+ if err := d.Key.Write(n.private, 0400); err != nil {
+ return fmt.Errorf("when writing node private key: %w", err)
+ }
+ return nil
+}
+
+// NodeIDBare returns the `{pubkeyHash}` part of the node ID.
+func NodeIDBare(pub []byte) string {
+ return hex.EncodeToString(pub[:16])
+}
+
+// NodeID returns the name of this node, which is `metropolis-{pubkeyHash}`.
+// This name should be the primary way to refer to Metropoils nodes within a
+// cluster, and is guaranteed to be unique by relying on cryptographic
+// randomness.
+func NodeID(pub []byte) string {
+ return fmt.Sprintf("metropolis-%s", NodeIDBare(pub))
+}