[Spike] Changes needed to support GitHub Actions direct authentication to Minder #4317
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,76 @@ | ||
| // | ||
| // Copyright 2024 Stacklok, Inc. | ||
| // | ||
| // 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. | ||
|
|
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| // Package githubactions provides an implementation of the GitHub IdentityProvider. | ||
| package githubactions | ||
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|
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| import ( | ||
| "context" | ||
| "errors" | ||
| "net/url" | ||
| "strings" | ||
|
|
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| "github.com/lestrrat-go/jwx/v2/jwt" | ||
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| "github.com/stacklok/minder/internal/auth" | ||
| ) | ||
|
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| // GitHubActions is an implementation of the auth.IdentityProvider interface. | ||
| type GitHubActions struct { | ||
| } | ||
|
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| var _ auth.IdentityProvider = (*GitHubActions)(nil) | ||
| var _ auth.Resolver = (*GitHubActions)(nil) | ||
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| var ghIssuerUrl = url.URL{ | ||
| Scheme: "https", | ||
| Host: "token.actions.githubusercontent.com", | ||
| } | ||
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|
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| // String implements auth.IdentityProvider. | ||
| func (_ *GitHubActions) String() string { | ||
| return "githubactions" | ||
| } | ||
|
|
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| // URL implements auth.IdentityProvider. | ||
| func (_ *GitHubActions) URL() url.URL { | ||
| return ghIssuerUrl | ||
| } | ||
|
|
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| // Resolve implements auth.IdentityProvider. | ||
| func (gha *GitHubActions) Resolve(_ context.Context, id string) (*auth.Identity, error) { | ||
| // GitHub Actions subjects look like: | ||
| // repo:evankanderson/actions-id-token-testing:ref:refs/heads/main | ||
| // however, OpenFGA does not allow the "#" or ":" characters in the subject: | ||
| // https://github.com/openfga/openfga/blob/main/pkg/tuple/tuple.go#L34 | ||
| return &auth.Identity{ | ||
| UserID: strings.ReplaceAll(id, ":", "+"), | ||
| HumanName: strings.ReplaceAll(id, "+", ":"), | ||
| Provider: gha, | ||
| }, nil | ||
| } | ||
|
|
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| // Validate implements auth.IdentityProvider. | ||
| func (gha *GitHubActions) Validate(_ context.Context, token jwt.Token) (*auth.Identity, error) { | ||
| expectedUrl := gha.URL() | ||
| if token.Issuer() != expectedUrl.String() { | ||
| return nil, errors.New("token issuer is not the expected issuer") | ||
| } | ||
| return &auth.Identity{ | ||
| UserID: strings.ReplaceAll(token.Subject(), ":", "+"), | ||
| HumanName: token.Subject(), | ||
| Provider: gha, | ||
| }, nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,129 @@ | ||
| // | ||
| // Copyright 2024 Stacklok, Inc. | ||
| // | ||
| // 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. | ||
|
|
||
| // Package dynamic provides the logic for reading and validating JWT tokens | ||
| // using a JWKS URL from the token's | ||
| package dynamic | ||
|
|
||
| import ( | ||
| "context" | ||
| "encoding/base64" | ||
| "encoding/json" | ||
| "fmt" | ||
| "io" | ||
| "net/http" | ||
| "time" | ||
|
|
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| "github.com/lestrrat-go/jwx/v2/jwk" | ||
| "github.com/lestrrat-go/jwx/v2/jws" | ||
| "github.com/lestrrat-go/jwx/v2/jwt" | ||
| "github.com/lestrrat-go/jwx/v2/jwt/openid" | ||
|
|
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| stacklok_jwt "github.com/stacklok/minder/internal/auth/jwt" | ||
| ) | ||
|
|
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| // a subset of the openID well-known configuration for JSON parsing | ||
| type openIdConfig struct { | ||
| JwksURI string `json:"jwks_uri"` | ||
| } | ||
|
|
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| // Validator dynamically validates JWTs by fetching the key from the well-known OIDC issuer URL. | ||
| type Validator struct { | ||
| jwks *jwk.Cache | ||
| aud string | ||
| } | ||
|
|
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| var _ stacklok_jwt.Validator = (*Validator)(nil) | ||
|
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| // NewDynamicValidator creates a new instance of the dynamic JWT validator | ||
| func NewDynamicValidator(ctx context.Context, aud string) *Validator { | ||
| return &Validator{ | ||
| jwks: jwk.NewCache(ctx), | ||
| aud: aud, | ||
| } | ||
| } | ||
|
|
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| // ParseAndValidate implements jwt.Validator. | ||
| func (m Validator) ParseAndValidate(tokenString string) (openid.Token, error) { | ||
| // This is based on https://github.com/lestrrat-go/jwx/blob/v2/examples/jwt_parse_with_key_provider_example_test.go | ||
|
|
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| _, b64payload, _, err := jws.SplitCompact([]byte(tokenString)) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to split compact JWT: %w", err) | ||
| } | ||
|
|
||
| jwtPayload := make([]byte, base64.RawStdEncoding.DecodedLen(len(b64payload))) | ||
| if _, err := base64.RawStdEncoding.Decode(jwtPayload, b64payload); err != nil { | ||
| return nil, fmt.Errorf("failed to decode JWT payload: %w", err) | ||
| } | ||
|
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| parsed, err := jwt.Parse(jwtPayload, jwt.WithVerify(false), jwt.WithToken(openid.New())) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to parse JWT payload: %w", err) | ||
| } | ||
| openIdToken, ok := parsed.(openid.Token) | ||
| if !ok { | ||
| return nil, fmt.Errorf("failed to cast JWT payload to openid.Token") | ||
| } | ||
|
|
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| // Now that we've got the issuer, we can validate the token | ||
| keySet, err := m.getKeySet(parsed.Issuer()) | ||
|
There was a problem hiding this comment. There's a possible resource exhaustion attack here if you got a lot of OAuth issuers. We can probably narrow this down with an allow-list, e.g. from IdentityProvider API (get all the allowed issuers, drop the others early). |
||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to get JWK set: %w", err) | ||
| } | ||
| if _, err := jws.Verify([]byte(tokenString), jws.WithKeySet(keySet)); err != nil { | ||
| return nil, fmt.Errorf("failed to verify JWT: %w", err) | ||
| } | ||
|
|
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| return openIdToken, nil | ||
| } | ||
|
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| func (m Validator) getKeySet(issuer string) (jwk.Set, error) { | ||
| jwksUrl, err := getJWKSUrlForOpenId(issuer) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to fetch JWKS URL from openid: %w", err) | ||
| } | ||
| if err := m.jwks.Register(jwksUrl, jwk.WithMinRefreshInterval(15*time.Minute)); err != nil { | ||
| return nil, fmt.Errorf("failed to register JWKS URL: %w", err) | ||
| } | ||
|
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| return m.jwks.Get(context.Background(), jwksUrl) | ||
| } | ||
|
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| func getJWKSUrlForOpenId(issuer string) (string, error) { | ||
|
There was a problem hiding this comment. You would think this function existed in |
||
| wellKnownUrl := fmt.Sprintf("%s/.well-known/openid-configuration", issuer) | ||
|
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| resp, err := http.Get(wellKnownUrl) // #nosec: G107 | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| defer resp.Body.Close() | ||
|
|
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| if resp.StatusCode != http.StatusOK { | ||
| return "", fmt.Errorf("unexpected status code: %d", resp.StatusCode) | ||
| } | ||
|
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| body, err := io.ReadAll(resp.Body) | ||
| if err != nil { | ||
| return "", fmt.Errorf("Failed to read respons body: %w", err) | ||
| } | ||
|
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| config := openIdConfig{} | ||
| if err := json.Unmarshal(body, &config); err != nil { | ||
| return "", fmt.Errorf("failed to unmarshal JSON: %w", err) | ||
| } | ||
|
|
||
| return config.JwksURI, nil | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| // | ||
| // Copyright 2024 Stacklok, Inc. | ||
| // | ||
| // 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. | ||
|
|
||
| // Package merged provides the logic for reading and validating JWT tokens | ||
| package merged | ||
|
|
||
| import ( | ||
| "fmt" | ||
|
|
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| "github.com/lestrrat-go/jwx/v2/jwt/openid" | ||
|
|
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| stacklok_jwt "github.com/stacklok/minder/internal/auth/jwt" | ||
| ) | ||
|
|
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| // Validator is a struct that combines multiple JWT validators. | ||
| type Validator struct { | ||
| Validators []stacklok_jwt.Validator | ||
| } | ||
|
|
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| var _ stacklok_jwt.Validator = (*Validator)(nil) | ||
|
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| // ParseAndValidate implements jwt.Validator. | ||
| func (m Validator) ParseAndValidate(tokenString string) (openid.Token, error) { | ||
| for _, v := range m.Validators { | ||
| t, err := v.ParseAndValidate(tokenString) | ||
| if err == nil { | ||
| return t, nil | ||
| } | ||
| } | ||
| return nil, fmt.Errorf("no validator could parse and validate the token") | ||
| } |
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Oop, this doesn't check audience, and should.