mrcharles
05ec1a4142
Signature verification (gitea hex HMAC-SHA256 over the raw body via constant-time hmac.Equal; redmine/discourse constant-time shared-secret headers) with one generic ErrUnverified so rejects give attackers no oracle. Tolerant normalization of the known Redmine/Discourse/Gitea payload variants into one Event record (canonical subject ids, actor, title, repo, sha256 payload digest) plus the DESIGN action mapping (dispatch_turn / respond_turn / pipeline_step / ignore). Store: JSONL under state dir, 0600, dedup keyed on provider event id (delivery header, payload-digest fallback), index rebuilt at startup so replays across restarts still dedup; torn tail lines skipped, not fatal.
66 lines
2.2 KiB
Go
66 lines
2.2 KiB
Go
package events
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import (
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"crypto/hmac"
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"crypto/sha256"
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"crypto/subtle"
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"encoding/hex"
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"errors"
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"fmt"
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)
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// giteaSignatureHeader carries the hex HMAC-SHA256 of the raw body.
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const giteaSignatureHeader = "X-Gitea-Signature"
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// Default shared-secret header names (overridable per source in config;
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// gitea is always HMAC and ignores the override).
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const (
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DefaultRedmineSecretHeader = "X-Redmine-Webhook-Secret"
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DefaultDiscourseSecretHeader = "X-Discourse-Webhook-Secret"
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)
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// ErrUnverified marks every verification failure so callers reject with 401
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// without distinguishing WHY (no oracle for attackers poking the receiver).
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var ErrUnverified = errors.New("webhook not verified")
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// VerifyGiteaHMAC checks the X-Gitea-Signature header (hex HMAC-SHA256 of
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// the raw request body) against the shared secret. Comparison is
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// constant-time; error text never echoes header values.
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func VerifyGiteaHMAC(body []byte, headerValue, secret string) error {
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if headerValue == "" {
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return fmt.Errorf("%w: missing %s header", ErrUnverified, giteaSignatureHeader)
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}
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got, err := hex.DecodeString(headerValue)
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if err != nil {
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return fmt.Errorf("%w: %s header is not valid hex", ErrUnverified, giteaSignatureHeader)
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}
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mac := hmac.New(sha256.New, []byte(secret))
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mac.Write(body)
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if !hmac.Equal(got, mac.Sum(nil)) {
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return fmt.Errorf("%w: %s does not match body", ErrUnverified, giteaSignatureHeader)
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}
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return nil
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}
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// VerifySharedSecret constant-time compares the value of the provider's
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// secret header against the configured secret.
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func VerifySharedSecret(headerName, headerValue, secret string) error {
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if headerValue == "" {
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return fmt.Errorf("%w: missing %s header", ErrUnverified, headerName)
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}
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if subtle.ConstantTimeCompare([]byte(headerValue), []byte(secret)) != 1 {
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return fmt.Errorf("%w: %s does not verify", ErrUnverified, headerName)
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}
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return nil
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}
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// GiteaSignatureHeader exposes the fixed HMAC header name (config/docs).
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func GiteaSignatureHeader() string { return giteaSignatureHeader }
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// SignGitea computes the expected HMAC for a body+secret (tests, smoke).
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func SignGitea(body []byte, secret string) string {
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mac := hmac.New(sha256.New, []byte(secret))
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mac.Write(body)
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return hex.EncodeToString(mac.Sum(nil))
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}
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