fix: apply shared limiters before email / sms is sent (supabase#1748)

## What kind of change does this PR introduce?
* Fixes supabase#1236
* Reduces the number of false positives arising from validation errors
when counting rate limits for emails / sms sent
* This change applies the shared rate limiter for email and phone
functions before the actual email / sms is being sent out rather than at
the start of the request
* The `limitEmailOrPhoneSentHandler()` now initialises the rate limiters
and sets it in the request context so we can subsequently retrieve it
right before the email / sms is sent

## What is the current behavior?

Please link any relevant issues here.

## What is the new behavior?

Feel free to include screenshots if it includes visual changes.

## Additional context

Add any other context or screenshots.

internal/api/context.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"net/url"
 
+	"github.com/didip/tollbooth/v5/limiter"
 	jwt "github.com/golang-jwt/jwt/v5"
 	"github.com/supabase/auth/internal/models"
 )
@@ -31,6 +32,7 @@ const (
 	ssoProviderKey          = contextKey("sso_provider")
 	externalHostKey         = contextKey("external_host")
 	flowStateKey            = contextKey("flow_state_id")
+	sharedLimiterKey        = contextKey("shared_limiter")
 )
 
 // withToken adds the JWT token to the context.
@@ -241,3 +243,20 @@ func getExternalHost(ctx context.Context) *url.URL {
 	}
 	return obj.(*url.URL)
 }
+
+type SharedLimiter struct {
+	EmailLimiter *limiter.Limiter
+	PhoneLimiter *limiter.Limiter
+}
+
+func withLimiter(ctx context.Context, limiter *SharedLimiter) context.Context {
+	return context.WithValue(ctx, sharedLimiterKey, limiter)
+}
+
+func getLimiter(ctx context.Context) *SharedLimiter {
+	obj := ctx.Value(sharedLimiterKey)
+	if obj == nil {
+		return nil
+	}
+	return obj.(*SharedLimiter)
+}

internal/api/external.go

@@ -2,7 +2,6 @@ package api
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -383,10 +382,7 @@ func (a *API) createAccountFromExternalIdentity(tx *storage.Connection, r *http.
 			emailConfirmationSent := false
 			if decision.CandidateEmail.Email != "" {
 				if terr = a.sendConfirmation(r, tx, user, models.ImplicitFlow); terr != nil {
-					if errors.Is(terr, MaxFrequencyLimitError) {
-						return nil, tooManyRequestsError(ErrorCodeOverEmailSendRateLimit, "For security purposes, you can only request this once every minute")
-					}
-					return nil, internalServerError("Error sending confirmation mail").WithInternalError(terr)
+					return nil, terr
 				}
 				emailConfirmationSent = true
 			}

internal/api/identity.go

@@ -7,7 +7,6 @@ import (
 	"github.com/fatih/structs"
 	"github.com/go-chi/chi/v5"
 	"github.com/gofrs/uuid"
-	"github.com/pkg/errors"
 	"github.com/supabase/auth/internal/api/provider"
 	"github.com/supabase/auth/internal/models"
 	"github.com/supabase/auth/internal/storage"
@@ -133,9 +132,7 @@ func (a *API) linkIdentityToUser(r *http.Request, ctx context.Context, tx *stora
 		}
 		if !userData.Metadata.EmailVerified {
 			if terr := a.sendConfirmation(r, tx, targetUser, models.ImplicitFlow); terr != nil {
-				if errors.Is(terr, MaxFrequencyLimitError) {
-					return nil, tooManyRequestsError(ErrorCodeOverSMSSendRateLimit, "For security purposes, you can only request this once every minute")
-				}
+				return nil, terr
 			}
 			return nil, storage.NewCommitWithError(unprocessableEntityError(ErrorCodeEmailNotConfirmed, "Unverified email with %v. A confirmation email has been sent to your %v email", providerType, providerType))
 		}

internal/api/invite.go

@@ -80,7 +80,7 @@ func (a *API) Invite(w http.ResponseWriter, r *http.Request) error {
 		}
 
 		if err := a.sendInvite(r, tx, user); err != nil {
-			return internalServerError("Error inviting user").WithInternalError(err)
+			return err
 		}
 		return nil
 	})

internal/api/magic_link.go

@@ -3,7 +3,6 @@ package api
 import (
 	"bytes"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -141,10 +140,7 @@ func (a *API) MagicLink(w http.ResponseWriter, r *http.Request) error {
 		return a.sendMagicLink(r, tx, user, flowType)
 	})
 	if err != nil {
-		if errors.Is(err, MaxFrequencyLimitError) {
-			return tooManyRequestsError(ErrorCodeOverEmailSendRateLimit, generateFrequencyLimitErrorMessage(user.RecoverySentAt, config.SMTP.MaxFrequency))
-		}
-		return internalServerError("Error sending magic link").WithInternalError(err)
+		return err
 	}
 
 	return sendJSON(w, http.StatusOK, make(map[string]string))