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chore: fix csrf error message on empty session header #14018

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merged 3 commits into from
Jul 25, 2024
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chore: fix csrf error message on empty session header #14018

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ebdf3ab
chore: fix csrf error message on empty session header
Emyrk Jul 25, 2024
44724f1
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Emyrk Jul 25, 2024
49f16a2
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Emyrk Jul 25, 2024
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4 changes: 3 additions & 1 deletion coderd/httpmw/csrf.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,9 @@ func CSRF(secureCookie bool) func(next http.Handler) http.Handler {
mw.SetBaseCookie(http.Cookie{Path: "/", HttpOnly: true, SameSite: http.SameSiteLaxMode, Secure: secureCookie})
mw.SetFailureHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
sessCookie, err := r.Cookie(codersdk.SessionTokenCookie)
if err == nil && r.Header.Get(codersdk.SessionTokenHeader) != sessCookie.Value {
if err == nil &&
r.Header.Get(codersdk.SessionTokenHeader) != "" &&
r.Header.Get(codersdk.SessionTokenHeader) != sessCookie.Value {
// If a user is using header authentication and cookie auth, but the values
// do not match, the cookie value takes priority.
// At the very least, return a more helpful error to the user.
Expand Down
75 changes: 75 additions & 0 deletions coderd/httpmw/csrf_test.go
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Expand Up @@ -3,6 +3,7 @@ package httpmw_test
import (
"context"
"net/http"
"net/http/httptest"
"testing"

"github.com/justinas/nosurf"
Expand Down Expand Up @@ -69,3 +70,77 @@ func TestCSRFExemptList(t *testing.T) {
})
}
}

// TestCSRFError verifies the error message returned to a user when CSRF
// checks fail.
//
//nolint:bodyclose // Using httptest.Recorders
func TestCSRFError(t *testing.T) {
t.Parallel()

// Hard coded matching CSRF values
const csrfCookieValue = "JXm9hOUdZctWt0ZZGAy9xiS/gxMKYOThdxjjMnMUyn4="
const csrfHeaderValue = "KNKvagCBEHZK7ihe2t7fj6VeJ0UyTDco1yVUJE8N06oNqxLu5Zx1vRxZbgfC0mJJgeGkVjgs08mgPbcWPBkZ1A=="
// Use a url with "/api" as the root, other routes bypass CSRF.
const urlPath = "https://coder.com/api/v2/hello"

var handler http.Handler = http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
writer.WriteHeader(http.StatusOK)
})
handler = httpmw.CSRF(false)(handler)

// Not testing the error case, just providing the example of things working
// to base the failure tests off of.
t.Run("ValidCSRF", func(t *testing.T) {
t.Parallel()

req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, urlPath, nil)
require.NoError(t, err)

req.AddCookie(&http.Cookie{Name: codersdk.SessionTokenCookie, Value: "session_token_value"})
req.AddCookie(&http.Cookie{Name: nosurf.CookieName, Value: csrfCookieValue})
req.Header.Add(nosurf.HeaderName, csrfHeaderValue)

rec := httptest.NewRecorder()
handler.ServeHTTP(rec, req)
resp := rec.Result()
require.Equal(t, http.StatusOK, resp.StatusCode)
})

// The classic CSRF failure returns the generic error.
t.Run("MissingCSRFHeader", func(t *testing.T) {
t.Parallel()

req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, urlPath, nil)
require.NoError(t, err)

req.AddCookie(&http.Cookie{Name: codersdk.SessionTokenCookie, Value: "session_token_value"})
req.AddCookie(&http.Cookie{Name: nosurf.CookieName, Value: csrfCookieValue})

rec := httptest.NewRecorder()
handler.ServeHTTP(rec, req)
resp := rec.Result()
require.Equal(t, http.StatusBadRequest, resp.StatusCode)
require.Contains(t, rec.Body.String(), "Something is wrong with your CSRF token.")
})

// Include the CSRF cookie, but not the CSRF header value.
// Including the 'codersdk.SessionTokenHeader' will bypass CSRF only if
// it matches the cookie. If it does not, we expect a more helpful error.
t.Run("MismatchedHeaderAndCookie", func(t *testing.T) {
t.Parallel()

req, err := http.NewRequestWithContext(context.Background(), http.MethodPost, urlPath, nil)
require.NoError(t, err)

req.AddCookie(&http.Cookie{Name: codersdk.SessionTokenCookie, Value: "session_token_value"})
req.AddCookie(&http.Cookie{Name: nosurf.CookieName, Value: csrfCookieValue})
req.Header.Add(codersdk.SessionTokenHeader, "mismatched_value")

rec := httptest.NewRecorder()
handler.ServeHTTP(rec, req)
resp := rec.Result()
require.Equal(t, http.StatusBadRequest, resp.StatusCode)
require.Contains(t, rec.Body.String(), "CSRF error encountered. Authentication via")
})
}
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