120 lines
4.3 KiB
Go
120 lines
4.3 KiB
Go
// GoToSocial
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// Copyright (C) GoToSocial Authors admin@gotosocial.org
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// SPDX-License-Identifier: AGPL-3.0-or-later
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package middleware
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import (
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"context"
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"net/http"
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"net/url"
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"github.com/superseriousbusiness/gotosocial/internal/gtscontext"
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"github.com/superseriousbusiness/gotosocial/internal/log"
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"github.com/gin-gonic/gin"
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"github.com/superseriousbusiness/httpsig"
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)
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const (
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sigHeader = string(httpsig.Signature)
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authHeader = string(httpsig.Authorization)
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// untyped error returned by httpsig when no signature is present
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noSigError = "neither \"" + sigHeader + "\" nor \"" + authHeader + "\" have signature parameters"
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)
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// SignatureCheck returns a gin middleware for checking http signatures.
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//
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// The middleware first checks whether an incoming http request has been
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// http-signed with a well-formed signature. If so, it will check if the
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// domain that signed the request is permitted to access the server, using
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// the provided uriBlocked function. If the domain is blocked, the middleware
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// will abort the request chain with http code 403 forbidden. If it is not
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// blocked, the handler will set the key verifier and the signature in the
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// context for use down the line.
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//
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// In case of an error, the request will be aborted with http code 500.
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func SignatureCheck(uriBlocked func(context.Context, *url.URL) (bool, error)) func(*gin.Context) {
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return func(c *gin.Context) {
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ctx := c.Request.Context()
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// Create the signature verifier from the request;
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// this will error if the request wasn't signed.
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verifier, err := httpsig.NewVerifier(c.Request)
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if err != nil {
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// Only actually *abort* the request with 401
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// if a signature was present but malformed.
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// Otherwise proceed with an unsigned request;
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// it's up to other functions to reject this.
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if err.Error() != noSigError {
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log.Debugf(ctx, "http signature was present but invalid: %s", err)
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c.AbortWithStatus(http.StatusUnauthorized)
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}
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return
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}
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// The request was signed! The key ID should be given
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// in the signature so that we know where to fetch it
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// from the remote server. This will be something like:
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// https://example.org/users/some_remote_user#main-key
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pubKeyIDStr := verifier.KeyId()
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// Key can sometimes be nil, according to url parse
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// func: 'Trying to parse a hostname and path without
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// a scheme is invalid but may not necessarily return
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// an error, due to parsing ambiguities'. Catch this.
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pubKeyID, err := url.Parse(pubKeyIDStr)
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if err != nil || pubKeyID == nil {
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log.Warnf(ctx, "pubkey id %s could not be parsed as a url", pubKeyIDStr)
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c.AbortWithStatus(http.StatusUnauthorized)
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return
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}
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// If the domain is blocked we want to bail as fast as
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// possible without the request proceeding further.
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blocked, err := uriBlocked(ctx, pubKeyID)
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if err != nil {
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log.Errorf(ctx, "error checking block for domain %s: %s", pubKeyID.Host, err)
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c.AbortWithStatus(http.StatusInternalServerError)
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return
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}
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if blocked {
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log.Infof(ctx, "domain %s is blocked", pubKeyID.Host)
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c.AbortWithStatus(http.StatusForbidden)
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return
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}
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// Assume signature was set on Signature header,
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// but fall back to Authorization header if necessary.
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signature := c.GetHeader(sigHeader)
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if signature == "" {
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signature = c.GetHeader(authHeader)
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}
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// Set relevant values on the request context
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// to save some work further down the line.
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ctx = gtscontext.SetHTTPSignatureVerifier(ctx, verifier)
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ctx = gtscontext.SetHTTPSignature(ctx, signature)
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ctx = gtscontext.SetHTTPSignaturePubKeyID(ctx, pubKeyID)
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// Replace request with a shallow
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// copy with the new context.
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c.Request = c.Request.WithContext(ctx)
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}
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}
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