Handle SAML enforcement challenge from the server (#5054)

Whenever a SSO challenge gets issued by the server by means of a URL in
the `X-GitHub-SSO` response header, gh now additionally prints that URL
on the standard error stream.

This is achieved by installing a middleware to all HTTP requests and
storing the server challenge to a value accessible by `factory.SSOURL()`.
Such approach was made necessary mainly because of the
`shurcool-graphql` client which doesn't give access to response headers
when a GraphQL error case is encountered.

api/client.go

@@ -98,6 +98,22 @@ func ReplaceTripper(tr http.RoundTripper) ClientOption {
 	}
 }
 
+// ExtractHeader extracts a named header from any response received by this client and, if non-blank, saves
+// it to dest.
+func ExtractHeader(name string, dest *string) ClientOption {
+	return func(tr http.RoundTripper) http.RoundTripper {
+		return &funcTripper{roundTrip: func(req *http.Request) (*http.Response, error) {
+			res, err := tr.RoundTrip(req)
+			if err == nil {
+				if value := res.Header.Get(name); value != "" {
+					*dest = value
+				}
+			}
+			return res, err
+		}}
+	}
+}
+
 type funcTripper struct {
 	roundTrip func(*http.Request) (*http.Response, error)
 }

cmd/gh/main.go

@@ -224,8 +224,9 @@ func mainRun() exitCode {
 		var httpErr api.HTTPError
 		if errors.As(err, &httpErr) && httpErr.StatusCode == 401 {
 			fmt.Fprintln(stderr, "Try authenticating with:  gh auth login")
-		} else if strings.Contains(err.Error(), "Resource protected by organization SAML enforcement") {
-			fmt.Fprintln(stderr, "Try re-authenticating with:  gh auth refresh")
+		} else if u := factory.SSOURL(); u != "" {
+			// handles organization SAML enforcement error
+			fmt.Fprintf(stderr, "Authorize in your web browser:  %s\n", u)
 		} else if msg := httpErr.ScopesSuggestion(); msg != "" {
 			fmt.Fprintln(stderr, msg)
 		}

pkg/cmd/api/api.go

@@ -21,6 +21,7 @@ import (
 	"github.com/cli/cli/v2/internal/config"
 	"github.com/cli/cli/v2/internal/ghinstance"
 	"github.com/cli/cli/v2/internal/ghrepo"
+	"github.com/cli/cli/v2/pkg/cmd/factory"
 	"github.com/cli/cli/v2/pkg/cmdutil"
 	"github.com/cli/cli/v2/pkg/export"
 	"github.com/cli/cli/v2/pkg/iostreams"
@@ -393,6 +394,9 @@ func processResponse(resp *http.Response, opts *ApiOptions, headersOutputStream
 		if msg := api.ScopesSuggestion(resp); msg != "" {
 			fmt.Fprintf(opts.IO.ErrOut, "gh: %s\n", msg)
 		}
+		if u := factory.SSOURL(); u != "" {
+			fmt.Fprintf(opts.IO.ErrOut, "Authorize in your web browser: %s\n", u)
+		}
 		err = cmdutil.SilentError
 		return
 	}

pkg/cmd/factory/http.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"regexp"
 	"strings"
 	"time"
 
@@ -54,7 +55,6 @@ var timezoneNames = map[int]string{
 }
 
 type configGetter interface {
-	GetOrDefault(string, string) (string, error)
 	Get(string, string) (string, error)
 }
 
@@ -108,6 +108,7 @@ func NewHTTPClient(io *iostreams.IOStreams, cfg configGetter, appVersion string,
 			}
 			return "", nil
 		}),
+		api.ExtractHeader("X-GitHub-SSO", &ssoHeader),
 	)
 
 	if setAccept {
@@ -127,6 +128,22 @@ func NewHTTPClient(io *iostreams.IOStreams, cfg configGetter, appVersion string,
 	return api.NewHTTPClient(opts...), nil
 }
 
+var ssoHeader string
+var ssoURLRE = regexp.MustCompile(`\burl=([^;]+)`)
+
+// SSOURL returns the URL of a SAML SSO challenge received by the server for clients that use ExtractHeader
+// to extract the value of the "X-GitHub-SSO" response header.
+func SSOURL() string {
+	if ssoHeader == "" {
+		return ""
+	}
+	m := ssoURLRE.FindStringSubmatch(ssoHeader)
+	if m == nil {
+		return ""
+	}
+	return m[1]
+}
+
 func getHost(r *http.Request) string {
 	if r.Host != "" {
 		return r.Host

pkg/cmd/factory/http_test.go

@@ -25,8 +25,10 @@ func TestNewHTTPClient(t *testing.T) {
 		args       args
 		envDebug   string
 		host       string
+		sso        string
 		wantHeader map[string]string
 		wantStderr string
+		wantSSO    string
 	}{
 		{
 			name: "github.com with Accept header",
@@ -117,11 +119,25 @@ func TestNewHTTPClient(t *testing.T) {
 			},
 			wantStderr: "",
 		},
+		{
+			name: "SSO challenge in response header",
+			args: args{
+				config:     tinyConfig{},
+				appVersion: "v1.2.3",
+			},
+			host:       "github.com",
+			sso:        "required; url=https://github.com/login/sso?return_to=xyz&param=123abc; another",
+			wantStderr: "",
+			wantSSO:    "https://github.com/login/sso?return_to=xyz&param=123abc",
+		},
 	}
 
 	var gotReq *http.Request
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		gotReq = r
+		if sso := r.URL.Query().Get("sso"); sso != "" {
+			w.Header().Set("X-GitHub-SSO", sso)
+		}
 		w.WriteHeader(http.StatusNoContent)
 	}))
 	defer ts.Close()
@@ -139,6 +155,11 @@ func TestNewHTTPClient(t *testing.T) {
 			require.NoError(t, err)
 
 			req, err := http.NewRequest("GET", ts.URL, nil)
+			if tt.sso != "" {
+				q := req.URL.Query()
+				q.Set("sso", tt.sso)
+				req.URL.RawQuery = q.Encode()
+			}
 			req.Host = tt.host
 			require.NoError(t, err)
 
@@ -151,16 +172,13 @@ func TestNewHTTPClient(t *testing.T) {
 
 			assert.Equal(t, 204, res.StatusCode)
 			assert.Equal(t, tt.wantStderr, normalizeVerboseLog(stderr.String()))
+			assert.Equal(t, tt.wantSSO, SSOURL())
 		})
 	}
 }
 
 type tinyConfig map[string]string
 
-func (c tinyConfig) GetOrDefault(host, key string) (string, error) {
-	return c[fmt.Sprintf("%s:%s", host, key)], nil
-}
-
 func (c tinyConfig) Get(host, key string) (string, error) {
 	return c[fmt.Sprintf("%s:%s", host, key)], nil
 }