From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTP id 69B785A005E for ; Tue, 29 Nov 2022 14:34:48 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1669728887; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Oh4XAWpZDZbrXOTKvk4CZrBiL1HjubtmO3rGqc/uqgI=; b=NHdozafOXoYVHWRAow+U1Ck3KzYgIwJVLmG7ydvDJKnjWTyDQRkUb3fZP90Lsvah25/cms DV0urOMmvBrbFeOky0I6FyzNDZtdx2MSagQy9HdKz8qp7PTPEfLXmt8yQ1zkATQO2LNpbR EV15fZdqVVQaMYWM5AV2O4MBfhZRuQk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-371-ZMWU8w47PBOJflQGOisALg-1; Tue, 29 Nov 2022 08:34:45 -0500 X-MC-Unique: ZMWU8w47PBOJflQGOisALg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A794929DD985 for ; Tue, 29 Nov 2022 13:34:45 +0000 (UTC) Received: from maya.cloud.tilaa.com (ovpn-208-33.brq.redhat.com [10.40.208.33]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7AB7C40C6EC4; Tue, 29 Nov 2022 13:34:45 +0000 (UTC) Date: Tue, 29 Nov 2022 14:34:42 +0100 From: Stefano Brivio To: "Richard W.M. Jones" Subject: Re: [PATCH passt v2 0/7] Add fuzzing Message-ID: <20221129143442.4ae32a9b@elisabeth> In-Reply-To: <20221125101103.GO7636@redhat.com> References: <20221117184938.2270462-1-rjones@redhat.com> <20221125102354.0540ad95@elisabeth> <20221125101103.GO7636@redhat.com> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: FQQXPNCOACYOO3R2OZ24VCID3A5UW4QF X-Message-ID-Hash: FQQXPNCOACYOO3R2OZ24VCID3A5UW4QF X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.3 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Fri, 25 Nov 2022 10:11:03 +0000 "Richard W.M. Jones" wrote: > On Fri, Nov 25, 2022 at 10:23:54AM +0100, Stefano Brivio wrote: > > and introducing frames with special values, as you hinted on IRC, for > > example one-byte frames with commands such as "go ahead with socket > > processing then come back to 'tap' frames", so that passt has a chance > > to do some meaningful socket-side operations before getting back to > > fuzz input. > > You can improve the chance that the fuzzer will find these frames by > either including them in test cases (we need better test cases, which > is separate issue), or by making the encoding such that they are easy > to find. eg. if you had four possible values, encode them only in the > bottom two bits and ignore the higher bits. Since these frames are > only used for fuzzing you can change the meaning of them later, so > exact encoding isn't an ABI issue. Right, yes, I was thinking we could, under #ifdef FUZZING, accept frames that are shorter than a 802.3 header (up to 13 bytes), and take their length (in network order, but I guess AFL++ can easily get familiar with it) as fuzzing flow commands. About test cases, I'm not sure this should be included in regular test runs, because there's no reasonable definition for a test duration. I'd rather have a separate script which keeps running indefinitely, updating sources as they become available. > > Patch 7/7 is very useful and appreciated anyway as it demystifies the > > whole topic for me, and we can probably recycle most of the > > documentation. I'm not sure yet how/if the wrapper still fits with the > > stuff I'm looking into. > > It would definitely be better to have passt itself be able to > read a file off disk. > > For example when we fuzz nbdkit we do not used or need a wrapper, > because nbdkit has an -s / --single option that reads from stdin and > writes to stdout. This was originally added to inetd support. > > We drive nbdkit from the fuzzer directly like this: > > afl-fuzz -i fuzzing/testcase_dir -o fuzzing/sync_dir -M fuzz01 \ > ./server/nbdkit -s -t 1 ./plugins/memory/.libs/nbdkit-memory-plugin.so 1M > > (https://gitlab.com/nbdkit/nbdkit/-/blob/ef035f7090d8bec2700ef1f941e371d351d647ad/fuzzing/README#L35-36) Ah, I didn't know, interesting. On the other hand, would it really make sense to add support for that (which has probably no use other than fuzzing) instead of a hack with __AFL_FUZZ_TESTCASE_BUF and mmap()? According to AFL++ documentation that should speed things up considerably: https://github.com/AFLplusplus/AFLplusplus/blob/stable/instrumentation/README.persistent_mode.md#5-shared-memory-fuzzing -- Stefano