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Reported by Christopher Allan Webber <cwebber@dustycloud.org> Co-authored-by: Ludovic Courtès <ludo@gnu.org> This commit adds protection to Guile's REPL servers against HTTP inter-protocol exploitation attacks, a scenario whereby an attacker can, via an HTML page, cause a web browser to send data to TCP servers listening on a loopback interface or private network. See <https://en.wikipedia.org/wiki/Inter-protocol_exploitation> and <https://www.jochentopf.com/hfpa/hfpa.pdf>, The HTML Form Protocol Attack (2001) by Tochen Topf <jochen@remote.org>. Here we add a procedure to 'before-read-hook' that looks for a possible HTTP request-line in the first line of input from the client socket. If present, the socket is drained and closed, and a loud warning is written to stderr (POSIX file descriptor 2). * module/system/repl/server.scm: Add 'maybe-check-for-http-request' to 'before-read-hook' when this module is loaded. (with-temporary-port-encoding, with-saved-port-line+column) (drain-input-and-close, permissive-http-request-line?) (check-for-http-request, guard-against-http-request) (maybe-check-for-http-request): New procedures. (serve-client): Use 'guard-against-http-request'. * module/system/repl/coop-server.scm (start-repl-client): Use 'guard-against-http-request'. * doc/ref/guile-invoke.texi (Command-line Options): In the description of the --listen option, make the security warning more prominent. Mention the new protection added here. Recommend using UNIX domain sockets for REPL servers. "a path to" => "the file name of". |
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| foreign-object.scm | ||
| foreign.scm | ||
| xref.scm | ||