132 lines
3.5 KiB
Go
132 lines
3.5 KiB
Go
// SPDX-License-Identifier: Apache-2.0
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package api
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import (
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"errors"
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"fmt"
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"net/http"
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"slices"
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"strconv"
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"strings"
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"time"
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"github.com/awnumar/memguard"
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"git.omukk.dev/wrenn/sandbox/envd/internal/shared/keys"
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)
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const (
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SigningReadOperation = "read"
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SigningWriteOperation = "write"
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accessTokenHeader = "X-Access-Token"
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)
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// paths that are always allowed without general authentication
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// POST/init is secured via MMDS hash validation instead
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var authExcludedPaths = []string{
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"GET/health",
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"GET/files",
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"POST/files",
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"POST/init",
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}
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func (a *API) WithAuthorization(handler http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
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if a.accessToken.IsSet() {
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authHeader := req.Header.Get(accessTokenHeader)
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// check if this path is allowed without authentication (e.g., health check, endpoints supporting signing)
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allowedPath := slices.Contains(authExcludedPaths, req.Method+req.URL.Path)
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if !a.accessToken.Equals(authHeader) && !allowedPath {
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a.logger.Error().Msg("Trying to access secured envd without correct access token")
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err := fmt.Errorf("unauthorized access, please provide a valid access token or method signing if supported")
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jsonError(w, http.StatusUnauthorized, err)
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return
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}
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}
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handler.ServeHTTP(w, req)
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})
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}
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func (a *API) generateSignature(path string, username string, operation string, signatureExpiration *int64) (string, error) {
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tokenBytes, err := a.accessToken.Bytes()
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if err != nil {
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return "", fmt.Errorf("access token is not set: %w", err)
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}
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defer memguard.WipeBytes(tokenBytes)
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var signature string
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hasher := keys.NewSHA256Hashing()
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if signatureExpiration == nil {
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signature = strings.Join([]string{path, operation, username, string(tokenBytes)}, ":")
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} else {
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signature = strings.Join([]string{path, operation, username, string(tokenBytes), strconv.FormatInt(*signatureExpiration, 10)}, ":")
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}
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return fmt.Sprintf("v1_%s", hasher.HashWithoutPrefix([]byte(signature))), nil
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}
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func (a *API) validateSigning(r *http.Request, signature *string, signatureExpiration *int, username *string, path string, operation string) (err error) {
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var expectedSignature string
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// no need to validate signing key if access token is not set
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if !a.accessToken.IsSet() {
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return nil
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}
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// check if access token is sent in the header
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tokenFromHeader := r.Header.Get(accessTokenHeader)
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if tokenFromHeader != "" {
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if !a.accessToken.Equals(tokenFromHeader) {
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return fmt.Errorf("access token present in header but does not match")
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}
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return nil
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}
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if signature == nil {
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return fmt.Errorf("missing signature query parameter")
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}
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// Empty string is used when no username is provided and the default user should be used
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signatureUsername := ""
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if username != nil {
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signatureUsername = *username
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}
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if signatureExpiration == nil {
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expectedSignature, err = a.generateSignature(path, signatureUsername, operation, nil)
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} else {
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exp := int64(*signatureExpiration)
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expectedSignature, err = a.generateSignature(path, signatureUsername, operation, &exp)
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}
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if err != nil {
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a.logger.Error().Err(err).Msg("error generating signing key")
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return errors.New("invalid signature")
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}
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// signature validation
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if expectedSignature != *signature {
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return fmt.Errorf("invalid signature")
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}
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// signature expiration
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if signatureExpiration != nil {
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exp := int64(*signatureExpiration)
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if exp < time.Now().Unix() {
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return fmt.Errorf("signature is already expired")
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}
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}
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return nil
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}
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