feat: add azure oidc PKI auth instead of client secret

Emyrk · Emyrk · commit 8ba23b1ebcc5 · 2023-08-11T10:38:03.000-05:00
diff --git a/cli/server.go b/cli/server.go
@@ -33,6 +33,8 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/coder/coder/coderd/azureauth"
+
 	"github.com/coreos/go-oidc/v3/oidc"
 	"github.com/coreos/go-systemd/daemon"
 	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
@@ -551,7 +553,7 @@ func (r *RootCmd) Server(newAPI func(context.Context, *coderd.Options) (*coderd.
 				}
 			}
 
-			if cfg.OIDC.ClientSecret != "" {
+			if true || cfg.OIDC.ClientSecret != "" {
 				if cfg.OIDC.ClientID == "" {
 					return xerrors.Errorf("OIDC client ID be set!")
 				}
@@ -578,15 +580,20 @@ func (r *RootCmd) Server(newAPI func(context.Context, *coderd.Options) (*coderd.
 				if slice.Contains(cfg.OIDC.Scopes, "groups") && cfg.OIDC.GroupField == "" {
 					cfg.OIDC.GroupField = "groups"
 				}
+				oauthCfg := &oauth2.Config{
+					ClientID:     cfg.OIDC.ClientID.String(),
+					ClientSecret: cfg.OIDC.ClientSecret.String(),
+					RedirectURL:  redirectURL.String(),
+					Endpoint:     oidcProvider.Endpoint(),
+					Scopes:       cfg.OIDC.Scopes,
+				}
+				jwtCfg, err := azureauth.NewJWTAssertion(oauthCfg)
+				if err != nil {
+					return xerrors.Errorf("configure azure auth: %w", err)
+				}
 				options.OIDCConfig = &coderd.OIDCConfig{
-					OAuth2Config: &oauth2.Config{
-						ClientID:     cfg.OIDC.ClientID.String(),
-						ClientSecret: cfg.OIDC.ClientSecret.String(),
-						RedirectURL:  redirectURL.String(),
-						Endpoint:     oidcProvider.Endpoint(),
-						Scopes:       cfg.OIDC.Scopes,
-					},
-					Provider: oidcProvider,
+					OAuth2Config: jwtCfg,
+					Provider:     oidcProvider,
 					Verifier: oidcProvider.Verifier(&oidc.Config{
 						ClientID: cfg.OIDC.ClientID.String(),
 					}),
diff --git a/coderd/azureauth/oidcpki.go b/coderd/azureauth/oidcpki.go
@@ -0,0 +1,94 @@
+package azureauth
+
+import (
+	"context"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/pem"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/golang-jwt/jwt/v4"
+
+	"golang.org/x/xerrors"
+
+	"golang.org/x/oauth2"
+)
+
+// JWTAssertion is used by Azure AD when doing OIDC with a PKI cert instead of
+// a client secret.
+// https://learn.microsoft.com/en-us/azure/active-directory/develop/certificate-credentials
+type JWTAssertion struct {
+	*oauth2.Config
+
+	// ClientSecret is the private key of the PKI cert.
+	// Azure AD only supports RS256 signing algorithm.
+	clientKey *rsa.PrivateKey
+	// Base64url-encoded SHA-1 thumbprint of the X.509 certificate's DER encoding.
+	x5t string
+}
+
+func NewJWTAssertion(config *oauth2.Config, pemEncodedKey string, pemEncodedCert string) (*JWTAssertion, error) {
+	rsaKey, err := DecodeKeyCertificate([]byte(pemEncodedKey))
+	if err != nil {
+		return nil, err
+	}
+
+	block, _ := pem.Decode([]byte(pemEncodedCert))
+	hashed := sha1.Sum(block.Bytes)
+
+	return &JWTAssertion{
+		Config:    config,
+		clientKey: rsaKey,
+		x5t:       base64.StdEncoding.EncodeToString(hashed[:]),
+	}, nil
+}
+
+// DecodeKeyCertificate decodes a PEM encoded PKI cert.
+func DecodeKeyCertificate(pemEncoded []byte) (*rsa.PrivateKey, error) {
+	block, _ := pem.Decode(pemEncoded)
+	key, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, xerrors.Errorf("failed to parse private key: %w", err)
+	}
+
+	return key, nil
+}
+
+func (ja *JWTAssertion) AuthCodeURL(state string, opts ...oauth2.AuthCodeOption) string {
+	return ja.Config.AuthCodeURL(state, opts...)
+}
+
+func (ja *JWTAssertion) Exchange(ctx context.Context, code string, opts ...oauth2.AuthCodeOption) (*oauth2.Token, error) {
+	now := time.Now()
+	token := jwt.NewWithClaims(jwt.SigningMethodRS256, jwt.MapClaims{
+		"aud": ja.Config.Endpoint.TokenURL,
+		"exp": now.Add(time.Minute * 5).Unix(),
+		"jti": uuid.New().String(),
+		"nbf": now.Unix(),
+		"iat": now.Unix(),
+
+		// TODO: Should be app GUID, not client ID.
+		"iss": ja.Config.ClientID,
+		"sub": ja.Config.ClientID,
+	})
+	token.Header["x5t"] = ja.x5t
+
+	signed, err := token.SignedString(ja.clientKey)
+	if err != nil {
+		return nil, xerrors.Errorf("failed to sign jwt assertion: %w", err)
+	}
+
+	opts = append(opts,
+		oauth2.SetAuthURLParam("client_assertion_type", "urn:ietf:params:oauth:client-assertion-type:jwt-bearer"),
+		oauth2.SetAuthURLParam("client_assertion", signed),
+	)
+	return ja.Config.Exchange(ctx, code, opts...)
+}
+
+func (ja *JWTAssertion) TokenSource(ctx context.Context, token *oauth2.Token) oauth2.TokenSource {
+	return ja.Config.TokenSource(ctx, token)
+}
diff --git a/codersdk/deployment.go b/codersdk/deployment.go
@@ -280,6 +280,17 @@ type OIDCConfig struct {
 	UserRolesDefault    clibase.StringArray                 `json:"user_roles_default" typescript:",notnull"`
 	SignInText          clibase.String                      `json:"sign_in_text" typescript:",notnull"`
 	IconURL             clibase.URL                         `json:"icon_url" typescript:",notnull"`
+	// OIDC Provider Specific Configurations
+	// Ideally all OIDC providers would follow all the same standards, but in practice they
+	// all have unique quirks.
+
+}
+
+// AzureADOIDCConfig is the configuration for Azure AD OIDC IDP.
+// Try at all costs to keep configuration in the generic OIDCConfig struct above.
+// Only use this if you absolutely need to.
+type AzureADOIDCConfig struct {
+	Certificate clibase.String
 }
 
 type TelemetryConfig struct {
diff --git a/site/src/api/typesGenerated.ts b/site/src/api/typesGenerated.ts
