feat: deliver Sense audits to Bell (T-016)

Sense/internal/auditrelay/client.go

@@ -0,0 +1,131 @@
+package auditrelay
+
+import (
+	"bytes"
+	"context"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const (
+	HeaderKeyID     = "X-YoVision-Key-Id"
+	HeaderTimestamp = "X-YoVision-Timestamp"
+	HeaderNonce     = "X-YoVision-Nonce"
+	HeaderSignature = "X-YoVision-Signature"
+	RelayPath       = "/internal/v1/audit-events:batch"
+)
+
+type Client struct {
+	endpoint   *url.URL
+	keyID      string
+	secret     []byte
+	httpClient *http.Client
+	now        func() time.Time
+	nonce      func() (string, error)
+}
+
+func NewClient(rawURL, keyID string, secret []byte, client *http.Client) (*Client, error) {
+	endpoint, err := ValidateEndpoint(rawURL)
+	if err != nil {
+		return nil, err
+	}
+	if keyID == "" || len(secret) < 32 {
+		return nil, errors.New("audit relay key ID and 32-byte secret are required")
+	}
+	if client == nil {
+		client = &http.Client{Timeout: 10 * time.Second}
+	}
+	return &Client{endpoint: endpoint, keyID: keyID, secret: append([]byte(nil), secret...), httpClient: client, now: time.Now, nonce: randomNonce}, nil
+}
+
+func ValidateEndpoint(rawURL string) (*url.URL, error) {
+	parsed, err := url.Parse(rawURL)
+	if err != nil || parsed.Host == "" || parsed.Path != RelayPath || parsed.RawQuery != "" || parsed.Fragment != "" || parsed.User != nil {
+		return nil, errors.New("invalid Bell audit relay URL")
+	}
+	host := parsed.Hostname()
+	ip := net.ParseIP(host)
+	loopback := strings.EqualFold(host, "localhost") || (ip != nil && ip.IsLoopback())
+	if parsed.Scheme != "https" && !(parsed.Scheme == "http" && loopback) {
+		return nil, errors.New("Bell audit relay URL requires HTTPS outside loopback")
+	}
+	return parsed, nil
+}
+
+func CanonicalString(method, path, timestamp, nonce string, body []byte) string {
+	digest := sha256.Sum256(body)
+	return strings.Join([]string{method, path, timestamp, nonce, hex.EncodeToString(digest[:])}, "\n")
+}
+
+func Signature(secret []byte, canonical string) string {
+	mac := hmac.New(sha256.New, secret)
+	_, _ = mac.Write([]byte(canonical))
+	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
+}
+
+func randomNonce() (string, error) {
+	value := make([]byte, 16)
+	if _, err := rand.Read(value); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(value), nil
+}
+
+func (c *Client) Send(ctx context.Context, events []Envelope) ([]Result, error) {
+	if len(events) < 1 || len(events) > MaxBatchSize {
+		return nil, errors.New("audit relay batch must contain 1 to 100 events")
+	}
+	body, err := json.Marshal(BatchRequest{Events: events})
+	if err != nil || len(body) > MaxBodyBytes {
+		return nil, errors.New("encode audit relay batch")
+	}
+	requestContext, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+	timestamp := strconv.FormatInt(c.now().UTC().Unix(), 10)
+	nonce, err := c.nonce()
+	if err != nil {
+		return nil, errors.New("generate audit relay nonce")
+	}
+	request, err := http.NewRequestWithContext(requestContext, http.MethodPost, c.endpoint.String(), bytes.NewReader(body))
+	if err != nil {
+		return nil, errors.New("create audit relay request")
+	}
+	request.Header.Set("Content-Type", "application/json")
+	request.Header.Set(HeaderKeyID, c.keyID)
+	request.Header.Set(HeaderTimestamp, timestamp)
+	request.Header.Set(HeaderNonce, nonce)
+	request.Header.Set(HeaderSignature, Signature(c.secret, CanonicalString(http.MethodPost, RelayPath, timestamp, nonce, body)))
+	response, err := c.httpClient.Do(request)
+	if err != nil {
+		return nil, errors.New("send audit relay request")
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		_, _ = io.Copy(io.Discard, io.LimitReader(response.Body, 4096))
+		return nil, fmt.Errorf("Bell audit relay returned HTTP %d", response.StatusCode)
+	}
+	decoder := json.NewDecoder(io.LimitReader(response.Body, MaxBodyBytes+1))
+	decoder.DisallowUnknownFields()
+	var decoded BatchResponse
+	if err := decoder.Decode(&decoded); err != nil {
+		return nil, errors.New("decode audit relay response")
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
+		return nil, errors.New("audit relay response contains trailing data")
+	}
+	return decoded.Results, nil
+}