internal/identity: implement github provider support (#582)

Co-authored-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/identity/github.go

@@ -0,0 +1,225 @@
+package identity
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/pomerium/pomerium/internal/httputil"
+	"github.com/pomerium/pomerium/internal/log"
+	"github.com/pomerium/pomerium/internal/sessions"
+	"github.com/pomerium/pomerium/internal/version"
+
+	"golang.org/x/oauth2"
+	"gopkg.in/square/go-jose.v2/jwt"
+)
+
+const (
+	defaultGitHubProviderURL = "https://github.com"
+	githubAuthURL            = "/login/oauth/authorize"
+	githubUserURL            = "https://api.github.com/user"
+	githubUserTeamURL        = "https://api.github.com/user/teams"
+	githubRevokeURL          = "https://github.com/oauth/revoke"
+	githubUserEmailURL       = "https://api.github.com/user/emails"
+
+	// since github doesn't implement oidc, we need this to refresh the user session
+	refreshDeadline = time.Minute * 60
+)
+
+// GitHubProvider is an implementation of the OAuth Provider.
+type GitHubProvider struct {
+	*Provider
+
+	authURL      string
+	tokenURL     string
+	userEndpoint string
+
+	RevokeURL string `json:"revocation_endpoint"`
+}
+
+// NewGitHubProvider returns a new GitHubProvider.
+func NewGitHubProvider(p *Provider) (*GitHubProvider, error) {
+	gp := &GitHubProvider{
+		authURL:      defaultGitHubProviderURL + githubAuthURL,
+		tokenURL:     defaultGitHubProviderURL + "/login/oauth/access_token",
+		userEndpoint: githubUserURL,
+		RevokeURL:    githubRevokeURL,
+	}
+
+	if p.ProviderURL == "" {
+		p.ProviderURL = defaultGitHubProviderURL
+	}
+
+	if len(p.Scopes) == 0 {
+		p.Scopes = []string{"user:email", "read:org"}
+	}
+
+	p.oauth = &oauth2.Config{
+		ClientID:     p.ClientID,
+		ClientSecret: p.ClientSecret,
+		Endpoint: oauth2.Endpoint{
+			AuthURL:  gp.authURL,
+			TokenURL: gp.tokenURL,
+		},
+		RedirectURL: p.RedirectURL.String(),
+		Scopes:      p.Scopes,
+	}
+	gp.Provider = p
+
+	return gp, nil
+}
+
+// Authenticate creates an identity session with github from a authorization code, and follows up
+// call to the user and user group endpoint with the
+func (p *GitHubProvider) Authenticate(ctx context.Context, code string) (*sessions.State, error) {
+	resp, err := p.oauth.Exchange(ctx, code)
+	if err != nil {
+		return nil, fmt.Errorf("identity/github: token exchange failed %v", err)
+	}
+
+	s := &sessions.State{
+		AccessToken: &oauth2.Token{
+			AccessToken: resp.AccessToken,
+			TokenType:   resp.TokenType,
+		},
+		AccessTokenID: resp.AccessToken,
+	}
+
+	err = p.updateSessionState(ctx, s)
+	if err != nil {
+		return nil, err
+	}
+
+	return s, nil
+}
+
+// updateSessionState will get the user information from github and also retrieve the user's team(s)
+//
+// https://developer.github.com/v3/users/#get-the-authenticated-user
+func (p *GitHubProvider) updateSessionState(ctx context.Context, s *sessions.State) error {
+	if s == nil || s.AccessToken == nil {
+		return errors.New("identity/github: user session cannot be empty")
+	}
+	accessToken := s.AccessToken.AccessToken
+
+	err := p.userInfo(ctx, accessToken, s)
+	if err != nil {
+		return fmt.Errorf("identity/github: could not user info %w", err)
+	}
+
+	err = p.userEmail(ctx, accessToken, s)
+	if err != nil {
+		return fmt.Errorf("identity/github: could not retrieve user email %w", err)
+	}
+
+	err = p.userTeams(ctx, accessToken, s)
+	if err != nil {
+		return fmt.Errorf("identity/github: could not retrieve groups %w", err)
+	}
+
+	return nil
+}
+
+// Refresh renews a user's session by making a new userInfo request.
+func (p *GitHubProvider) Refresh(ctx context.Context, s *sessions.State) (*sessions.State, error) {
+	if s.AccessToken == nil {
+		return nil, errors.New("identity/github: missing oauth2 access token")
+	}
+	if err := p.updateSessionState(ctx, s); err != nil {
+		return nil, err
+	}
+	return s, nil
+}
+
+// userTeams returns a slice of teams the user belongs by making a request
+// to github API
+//
+// https://developer.github.com/v3/teams/#list-user-teams
+// https://developer.github.com/v3/auth/
+func (p *GitHubProvider) userTeams(ctx context.Context, at string, s *sessions.State) error {
+
+	var response []struct {
+		ID          json.Number `json:"id"`
+		Name        string      `json:"name,omitempty"`
+		URL         string      `json:"url,omitempty"`
+		Slug        string      `json:"slug"`
+		Description string      `json:"description,omitempty"`
+		ReposURL    string      `json:"repos_url,omitempty"`
+		Privacy     string      `json:"privacy,omitempty"`
+	}
+
+	headers := map[string]string{"Authorization": fmt.Sprintf("token %s", at)}
+	err := httputil.Client(ctx, http.MethodGet, githubUserTeamURL, version.UserAgent(), headers, nil, &response)
+	if err != nil {
+		return err
+	}
+
+	log.Debug().Interface("teams", response).Msg("identity/github: user teams")
+
+	s.Groups = nil
+	for _, org := range response {
+		s.Groups = append(s.Groups, org.ID.String())
+	}
+
+	return nil
+}
+
+// userEmail returns the primary email of the user by making
+// a query to github API.
+//
+// https://developer.github.com/v3/users/emails/#list-email-addresses-for-a-user
+// https://developer.github.com/v3/auth/
+func (p *GitHubProvider) userEmail(ctx context.Context, at string, s *sessions.State) error {
+	// response represents the github user email
+	// https://developer.github.com/v3/users/emails/#response
+	var response []struct {
+		Email      string `json:"email"`
+		Verified   bool   `json:"verified"`
+		Primary    bool   `json:"primary"`
+		Visibility string `json:"visibility"`
+	}
+	headers := map[string]string{"Authorization": fmt.Sprintf("token %s", at)}
+	err := httputil.Client(ctx, http.MethodGet, githubUserEmailURL, version.UserAgent(), headers, nil, &response)
+	if err != nil {
+		return err
+	}
+
+	log.Debug().Interface("emails", response).Msg("identity/github: user emails")
+	for _, email := range response {
+		if email.Primary && email.Verified {
+			s.Email = email.Email
+			s.EmailVerified = true
+			return nil
+		}
+	}
+	return nil
+}
+
+func (p *GitHubProvider) userInfo(ctx context.Context, at string, s *sessions.State) error {
+	var response struct {
+		ID        int    `json:"id"`
+		Login     string `json:"login"`
+		Name      string `json:"name"`
+		Email     string `json:"email"`
+		AvatarURL string `json:"avatar_url,omitempty"`
+	}
+
+	headers := map[string]string{
+		"Authorization": fmt.Sprintf("token %s", at),
+		"Accept":        "application/vnd.github.v3+json",
+	}
+	err := httputil.Client(ctx, http.MethodGet, p.userEndpoint, version.UserAgent(), headers, nil, &response)
+	if err != nil {
+		return err
+	}
+
+	s.User = response.Login
+	s.Name = response.Name
+	s.Picture = response.AvatarURL
+	// set the session expiry
+	s.Expiry = jwt.NewNumericDate(time.Now().Add(refreshDeadline))
+	return nil
+}