97 lines
4.0 KiB
Go
97 lines
4.0 KiB
Go
package middleware
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import (
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"context"
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"fmt"
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"net/http"
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"net/url"
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"github.com/superseriousbusiness/gotosocial/internal/ap"
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"github.com/superseriousbusiness/gotosocial/internal/db"
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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/go-fed/httpsig"
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)
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var (
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// this mimics an untyped error returned by httpsig when no signature is present;
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// define it here so that we can use it to decide what to log without hitting
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// performance too hard
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noSignatureError = fmt.Sprintf("neither %q nor %q have signature parameters", httpsig.Signature, httpsig.Authorization)
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signatureHeader = string(httpsig.Signature)
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authorizationHeader = string(httpsig.Authorization)
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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 http-signed with a well-formed signature.
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//
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// If so, it will check if the domain that signed the request is permitted to access the server, using the provided isURIBlocked function.
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//
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// If it is permitted, the handler will set the key verifier and the signature in the gin context for use down the line.
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//
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// If the domain is blocked, the middleware will abort the request chain instead with http code 403 forbidden.
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//
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// In case of an error, the request will be aborted with http code 500 internal server error.
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func SignatureCheck(isURIBlocked func(context.Context, *url.URL) (bool, db.Error)) func(*gin.Context) {
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return func(c *gin.Context) {
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// Acquire ctx from gin request.
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ctx := c.Request.Context()
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// create the verifier from the request, 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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// Something went wrong, so we need to return regardless, but only actually
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// *abort* the request with 401 if a signature was present but malformed
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if err.Error() != noSignatureError {
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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!
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// The key ID should be given in the signature so that we know where to fetch it from the remote server.
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// This will be something like https://example.org/users/whatever_requesting_user#main-key
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requestingPublicKeyIDString := verifier.KeyId()
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requestingPublicKeyID, err := url.Parse(requestingPublicKeyIDString)
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if err != nil {
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log.Debugf(ctx, "http signature requesting public key id %s could not be parsed as a url: %s", requestingPublicKeyIDString, err)
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c.AbortWithStatus(http.StatusUnauthorized)
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return
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} else if requestingPublicKeyID == nil {
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// Key can sometimes be nil, according to url parse function:
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// 'Trying to parse a hostname and path without a scheme is invalid but may not necessarily return an error, due to parsing ambiguities'
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log.Debugf(ctx, "http signature requesting public key id %s was nil after parsing as a url", requestingPublicKeyIDString)
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c.AbortWithStatus(http.StatusUnauthorized)
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return
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}
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// we managed to parse the url!
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// if the domain is blocked we want to bail as early as possible
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if blocked, err := isURIBlocked(c.Request.Context(), requestingPublicKeyID); err != nil {
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log.Errorf(ctx, "could not tell if domain %s was blocked or not: %s", requestingPublicKeyID.Host, err)
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c.AbortWithStatus(http.StatusInternalServerError)
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return
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} else if blocked {
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log.Infof(ctx, "domain %s is blocked", requestingPublicKeyID.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 (most common behavior),
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// but fall back to Authorization header if necessary
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var signature string
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if s := c.GetHeader(signatureHeader); s != "" {
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signature = s
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} else {
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signature = c.GetHeader(authorizationHeader)
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}
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// set the verifier and signature on the context here to save some work further down the line
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c.Set(string(ap.ContextRequestingPublicKeyVerifier), verifier)
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c.Set(string(ap.ContextRequestingPublicKeySignature), signature)
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}
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}
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