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// Copyright 2024 OpenPubkey
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
package providers
import (
"context"
"encoding/json"
"fmt"
"net/http"
"net/url"
"github.com/awnumar/memguard"
"github.com/openpubkey/openpubkey/discover"
simpleoidc "github.com/openpubkey/openpubkey/oidc"
"github.com/openpubkey/openpubkey/pktoken/clientinstance"
)
const githubIssuer = "https://token.actions.githubusercontent.com"
type GithubOp struct {
issuer string // Change issuer to point this to a test issuer
rawTokenRequestURL string
tokenRequestAuthToken string
publicKeyFinder discover.PublicKeyFinder
requestTokensOverrideFunc func(string) (*simpleoidc.Tokens, error)
}
var _ OpenIdProvider = (*GithubOp)(nil)
func NewGithubOpFromEnvironment() (*GithubOp, error) {
tokenURL, err := getEnvVar("ACTIONS_ID_TOKEN_REQUEST_URL")
if err != nil {
return nil, err
}
token, err := getEnvVar("ACTIONS_ID_TOKEN_REQUEST_TOKEN")
if err != nil {
return nil, err
}
return NewGithubOp(tokenURL, token), nil
}
func NewGithubOp(tokenURL string, token string) *GithubOp {
op := &GithubOp{
issuer: githubIssuer,
rawTokenRequestURL: tokenURL,
tokenRequestAuthToken: token,
publicKeyFinder: *discover.DefaultPubkeyFinder(),
requestTokensOverrideFunc: nil,
}
return op
}
func buildTokenURL(rawTokenURL, audience string) (string, error) {
parsedURL, err := url.Parse(rawTokenURL)
if err != nil {
return "", fmt.Errorf("failed to parse URL: %w", err)
}
if audience == "" {
return "", fmt.Errorf("audience is required")
}
query := parsedURL.Query()
query.Set("audience", audience)
parsedURL.RawQuery = query.Encode()
return parsedURL.String(), nil
}
func (g *GithubOp) PublicKeyByToken(ctx context.Context, token []byte) (*discover.PublicKeyRecord, error) {
return g.publicKeyFinder.ByToken(ctx, g.issuer, token)
}
func (g *GithubOp) PublicKeyByKeyId(ctx context.Context, keyID string) (*discover.PublicKeyRecord, error) {
return g.publicKeyFinder.ByKeyID(ctx, g.issuer, keyID)
}
func (g *GithubOp) requestTokens(ctx context.Context, cicHash string) (*memguard.LockedBuffer, error) {
if g.requestTokensOverrideFunc != nil {
tokens, err := g.requestTokensOverrideFunc(cicHash)
if err != nil {
return nil, fmt.Errorf("error requesting ID Token: %w", err)
}
return memguard.NewBufferFromBytes(tokens.IDToken), nil
}
tokenURL, err := buildTokenURL(g.rawTokenRequestURL, cicHash)
if err != nil {
return nil, err
}
request, err := http.NewRequestWithContext(ctx, "GET", tokenURL, nil)
if err != nil {
return nil, err
}
request.Header.Set("Authorization", "Bearer "+g.tokenRequestAuthToken)
var httpClient http.Client
response, err := httpClient.Do(request)
if err != nil {
return nil, err
}
defer response.Body.Close()
if response.StatusCode != http.StatusOK {
return nil, fmt.Errorf("received non-200 from jwt api: %s", http.StatusText(response.StatusCode))
}
rawBody, err := memguard.NewBufferFromEntireReader(response.Body)
if err != nil {
return nil, err
}
defer rawBody.Destroy()
var jwt struct {
Value json.RawMessage
}
err = json.Unmarshal(rawBody.Bytes(), &jwt)
if err != nil {
return nil, err
}
defer memguard.WipeBytes([]byte(jwt.Value))
// json.RawMessage leaves the " (quotes) on the string. We need to remove the quotes
return memguard.NewBufferFromBytes(jwt.Value[1 : len(jwt.Value)-1]), nil
}
func (g *GithubOp) RequestTokens(ctx context.Context, cic *clientinstance.Claims) (*simpleoidc.Tokens, error) {
// Define our commitment as the hash of the client instance claims
commitment, err := cic.Hash()
if err != nil {
return nil, fmt.Errorf("error calculating client instance claim commitment: %w", err)
}
// Use the commitment nonce to complete the OIDC flow and get an ID token from the provider
idTokenLB, err := g.requestTokens(ctx, string(commitment))
// idTokenLB is the ID Token in a memguard LockedBuffer, this is done
// because the ID Token contains the OPs RSA signature which is a secret
// in GQ signatures. For non-GQ signatures OPs RSA signature is considered
// a public value.
if err != nil {
return nil, fmt.Errorf("error requesting ID Token: %w", err)
}
defer idTokenLB.Destroy()
gqToken, err := CreateGQToken(ctx, idTokenLB.Bytes(), g)
return &simpleoidc.Tokens{IDToken: gqToken}, err
}
func (g *GithubOp) Issuer() string {
return g.issuer
}
func (g *GithubOp) VerifyIDToken(ctx context.Context, idt []byte, cic *clientinstance.Claims) error {
vp := NewProviderVerifier(g.issuer, ProviderVerifierOpts{CommitType: CommitTypesEnum.AUD_CLAIM, GQOnly: true, SkipClientIDCheck: true})
return vp.VerifyIDToken(ctx, idt, cic)
}
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