Artifact [edb850a0a4]

Artifact edb850a0a436d217e92f175f844c99b3f841c50d90ea40deccd435289ab71f54:

• File internal/xfer/login_cookie.go — part of check-in [6963b0a9dc] at 2026-10-12 23:10:13 on branch main — fix(sync): exchange server-version and gate SHA3 content by peer release (#303) (#358)

  fossil's page_xfer answers a client-version that carries DATE and TIME with pragma server-version, and both sides record the peer's release; send_file, send_compressed_file and send_unversioned_file then append "error Fossil version 2.0 or later required." in place of SHA3-named content for a peer older than 2.0, with a server treating a client that announced no release as one (sections 7.6, 9.1). The server sent no server-version and neither side kept or gated on the peer's release.

  The server gates gimme, clone and uvgimme; the client gates its answer to a gimme. Because a server-version from a current release turns fossil's client to logging in through the x-f-l-c cookie (section 6.5), the HTTP server now reads that cookie: xfer.DecodeRequest puts its login card first with the nonce bound to the whole body, as page_xfer does. Without it a real fossil client's later rounds arrived as nobody. That moves sync.6.5.server-cookie-login, marked for #304, here. (user: [email protected], size: 1850) [annotate] [blame] [check-ins using]

package xfer

import (
	"net/url"
	"strings"

	"github.com/danmestas/go-libfossil/internal/deck"
	"github.com/danmestas/go-libfossil/internal/hash"
)

// LoginCookieName is the HTTP cookie in which a client may carry its login
// card instead of the body, once the server's release accepts it (§6.5).
const LoginCookieName = "x-f-l-c"

// DecodeRequest decodes a sync request as Decode does. When loginCookie, the
// value of the request's LoginCookieName cookie, holds a login card, that card
// is put first, its nonce bound to the whole decompressed body: fossil's
// page_xfer handles a cookie login as a login line ahead of the body, so the
// "rest of the message" its nonce covers is all of it (§6.5, check_tail_hash).
// A cookie that is not a login card is ignored, as page_xfer ignores it.
func DecodeRequest(data []byte, contentType, loginCookie string) (*Message, error) {
	raw := data
	if len(data) > 0 && contentTypeIsCompressed(contentType) {
		var err error
		if raw, err = decompressContainer(data); err != nil {
			return nil, err
		}
	}
	msg, err := DecodeUncompressed(raw)
	if err != nil {
		return nil, err
	}
	if lc := parseLoginCookie(loginCookie); lc != nil {
		lc.tailSHA1 = hash.SHA1(raw)
		msg.Cards = append([]Card{lc}, msg.Cards...)
	}
	return msg, nil
}

// parseLoginCookie reads a login card from a cookie value: URL-encoded, as
// fossil's %T writes it, then "login USER NONCE SIGNATURE" split on white
// space, as page_xfer tokenizes it. It returns nil for anything else.
func parseLoginCookie(v string) *LoginCard {
	if v == "" {
		return nil
	}
	line, err := url.QueryUnescape(v)
	if err != nil {
		return nil
	}
	tokens := strings.Fields(line)
	if len(tokens) != 4 || tokens[0] != "login" {
		return nil
	}
	return &LoginCard{
		User: deck.FossilDecode(tokens[1]), Nonce: tokens[2], Signature: tokens[3],
	}
}