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tufclient: authenticate repo requests as this machine #82
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02e5dec
funchelpers: split out OnError from CloseOnError
cyphar a754c36
httputils: make VerifiedHTTPGet take http.Client
cyphar 4d95d45
httpsig: implement RFC 9421 HTTP message signing
cyphar 8b65007
tufclient: sign repo requests as this machine when configured
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,196 @@ | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
| // Copyright (C) 2026 Amutable GmbH | ||
|
|
||
| //go:build fixtures | ||
|
|
||
| // acp-sample-gen regenerates the control plane's | ||
| // deploy/cloudflare/quarry-worker/test/fixtures/go-signed-read.json, which | ||
| // pins the Worker's verifier to what Transport puts on the wire: | ||
| // | ||
| // go run -tags fixtures ./internal/fixtures/acp-sample-gen \ | ||
| // <control-plane>/deploy/cloudflare/quarry-worker/test/fixtures/go-signed-read.json | ||
| // | ||
| // Transport gets its WIT from a fake identity agent, which mints one with a | ||
| // throwaway tenant key and binds the key Transport asked for. | ||
| package main | ||
|
|
||
| import ( | ||
| "crypto/ecdsa" | ||
| "crypto/elliptic" | ||
| "crypto/rand" | ||
| "crypto/sha256" | ||
| "encoding/base64" | ||
| "encoding/json" | ||
| "fmt" | ||
| "log" | ||
| "net/http" | ||
| "os" | ||
| "time" | ||
|
|
||
| jose "github.com/go-jose/go-jose/v4" | ||
| "snai.pe/go-varlink" | ||
|
|
||
| "go.amutable.dev/quarry/internal/wimseagent" | ||
| ) | ||
|
|
||
| const ( | ||
| broker = "https://wit-broker.test" | ||
| tenant = "acme" | ||
| stamp = "test.example" | ||
| machine = "0123456789abcdef0123456789abcdef" | ||
| audience = "urn:amutable:quarry-worker" | ||
| kid = "tenant-key" | ||
| // publicURL is the Worker tests' PUBLIC_URL, so the request's default | ||
| // wimse-aud (its target URI) is one the Worker accepts. | ||
| publicURL = "https://customerdata.test" | ||
| ) | ||
|
|
||
| // captureTransport records the headers of the one request sent through it, | ||
| // so the signed request never has to reach a server at publicURL. | ||
| type captureTransport struct { | ||
| header http.Header | ||
| } | ||
|
|
||
| func (c *captureTransport) RoundTrip(req *http.Request) (*http.Response, error) { | ||
| c.header = req.Header.Clone() | ||
| return &http.Response{StatusCode: http.StatusNoContent, Body: http.NoBody, Request: req}, nil | ||
| } | ||
|
|
||
| var b64 = base64.RawURLEncoding.EncodeToString | ||
|
|
||
| func es256JWT(key *ecdsa.PrivateKey, header, claims any) (string, error) { | ||
| h, err := json.Marshal(header) | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| c, err := json.Marshal(claims) | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| signing := b64(h) + "." + b64(c) | ||
| digest := sha256.Sum256([]byte(signing)) | ||
| r, s, err := ecdsa.Sign(rand.Reader, key, digest[:]) | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| sig := make([]byte, 64) | ||
| r.FillBytes(sig[:32]) | ||
| s.FillBytes(sig[32:]) | ||
| return signing + "." + b64(sig), nil | ||
| } | ||
|
|
||
| // p256JWK returns the JWK to bind into the WIT for jwk. Like the real agent, | ||
| // it only accepts P-256 public keys with "alg" ES256, which WIMSE requires. | ||
| func p256JWK(jwk jose.JSONWebKey) (jose.JSONWebKey, error) { | ||
| pub, ok := jwk.Key.(*ecdsa.PublicKey) | ||
| if !ok || pub.Curve != elliptic.P256() || !jwk.Valid() { | ||
| return jose.JSONWebKey{}, fmt.Errorf("not a P-256 public key: %T", jwk.Key) | ||
| } | ||
| if jwk.Algorithm != string(jose.ES256) { | ||
| return jose.JSONWebKey{}, fmt.Errorf("alg %q does not match a P-256 key", jwk.Algorithm) | ||
| } | ||
| return jose.JSONWebKey{Key: pub, Algorithm: string(jose.ES256)}, nil | ||
| } | ||
|
|
||
| // startAgent serves GetWorkloadIdentityToken from a socket in dir, replying | ||
| // with a WIT signed by tenantKey and bound to the requested key. | ||
| func startAgent(dir string, tenantKey *ecdsa.PrivateKey, now time.Time) (string, error) { | ||
| uri := "unix:" + dir + "/agent" | ||
| listener, err := varlink.Listen(uri) | ||
| if err != nil { | ||
| return "", fmt.Errorf("listen on fake agent socket: %w", err) | ||
| } | ||
| var mux varlink.ServeMux | ||
| mux.HandleFunc("com.amutable.IdentityAgent.GetWorkloadIdentityToken", func(w varlink.ReplyWriter, c *varlink.Call) { | ||
| var p struct { | ||
| Audience string `json:"aud"` | ||
| PublicKey jose.JSONWebKey `json:"jwk_pub"` | ||
| } | ||
| if err := c.Unmarshal(&p); err != nil { | ||
| _ = w.WriteError(err) | ||
| return | ||
| } | ||
| pub, err := p256JWK(p.PublicKey) | ||
| if err != nil { | ||
| _ = w.WriteError(varlink.NewError("org.varlink.service.InvalidParameter", "parameter", "jwk_pub")) | ||
| return | ||
| } | ||
| wit, err := es256JWT(tenantKey, | ||
| map[string]string{"alg": "ES256", "typ": "wit+jwt", "kid": kid}, | ||
| map[string]any{ | ||
| "iss": broker + "/tenants/" + tenant, | ||
| "sub": "spiffe://" + tenant + "." + stamp + "/machine/" + machine, | ||
| "aud": []string{p.Audience}, | ||
| "iat": now.Unix(), | ||
| "exp": now.Add(time.Hour).Unix(), | ||
| "jti": "fixture", | ||
| "cnf": map[string]any{"jwk": pub}, | ||
| }) | ||
| if err != nil { | ||
| _ = w.WriteError(varlink.NewError("com.amutable.IdentityAgent.Failed", "error", err.Error())) | ||
| return | ||
| } | ||
| _ = w.WriteReply(map[string]any{"wit": wit, "expires_in": int64(time.Hour / time.Second)}) | ||
| }) | ||
| srv := &varlink.Server{Handler: &mux} | ||
| go func() { _ = srv.Serve(listener) }() | ||
| return uri, nil | ||
| } | ||
|
|
||
| func run(out string) error { | ||
| tenantKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| now := time.Now() | ||
|
|
||
| dir, err := os.MkdirTemp("", "quarry-worker-fixture-") //nolint:forbidigo // fresh private directory | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer func() { _ = os.RemoveAll(dir) }() //nolint:forbidigo // our own temporary directory | ||
| agent, err := startAgent(dir, tenantKey, now) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| // The signing transport sends through http.DefaultTransport. | ||
| capture := &captureTransport{} | ||
| http.DefaultTransport = capture | ||
| cred, err := wimseagent.NewCred(wimseagent.ID{WitAudience: audience, Provider: agent}, nil) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| client := &http.Client{Transport: &wimseagent.Transport{WitCred: cred}} | ||
| reqURL := publicURL + "/machine-repos/" + tenant + "/" + machine + "/1.root.json" | ||
| resp, err := client.Get(reqURL) //nolint:noctx // one-shot script | ||
| if err != nil { | ||
| return err | ||
| } | ||
| _ = resp.Body.Close() // empty body from captureTransport | ||
| header := capture.header | ||
|
|
||
| jwk := jose.JSONWebKey{Key: &tenantKey.PublicKey, KeyID: kid, Algorithm: "ES256", Use: "sig"} | ||
| data, err := json.MarshalIndent(map[string]any{ | ||
| "now": now.Unix(), | ||
| "url": reqURL, | ||
| "jwks": map[string]any{"keys": []any{jwk}}, | ||
| "wit": header.Get("Workload-Identity-Token"), | ||
| "signatureInput": header.Get("Signature-Input"), | ||
| "signature": header.Get("Signature"), | ||
| }, "", " ") | ||
| if err != nil { | ||
| return err | ||
| } | ||
| return os.WriteFile(out, append(data, '\n'), 0o644) //nolint:forbidigo // path given by the user | ||
| } | ||
|
|
||
| func main() { | ||
| if len(os.Args) != 2 { | ||
| fmt.Fprintf(os.Stderr, "usage: %s <go-signed-read.json>\n", os.Args[0]) | ||
| os.Exit(2) | ||
| } | ||
| if err := run(os.Args[1]); err != nil { | ||
| log.Fatal(err) | ||
| } | ||
| } |
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This is quite unfortunate, though since only the method and URI are included in the signature I guess we can eventually pre-compute the signed headers and provide them to
sd-pullonce it switches to UAPI.16 (and a UAPI.16 extension is added to support it).@davidstrauss Do we plan to extend the scope of things we would sign for WIMSE/WIT? If we start signing other headers then we would just need to accept that we are going to be proxying data a lot. (Though we could of course choose to proxy based n what headers are needed to be signed...)
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I might need more context, but I wasn't expecting we'd use WIT/WIMSE for repo auth at all. I thought we only wanted to rely on authZ mechanisms that (1) we can delegate to the delivery system itself (mainly for cost, DoS protection, and maybe some basic infrastructure disclosure control) or (2) we can achieve via sealing the data going through Quarry (for load-bearing secret delivery to specific machines).
In short, I assumed our entire model would work fine with publicly readable buckets.
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This is the "front door" access control we discussed in January, BTW.