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[83.35.24.93]) by smtp.gmail.com with ESMTPSA id u15sm2193759wmq.48.2021.06.22.05.27.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jun 2021 05:27:10 -0700 (PDT) Subject: Re: [PATCH] block/ssh: add support for sha256 host key fingerprints To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , qemu-devel@nongnu.org, Pino Toscano References: <20210622115156.138458-1-berrange@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <7df266d5-8df4-c063-4bbf-dbf9edf4df92@redhat.com> Date: Tue, 22 Jun 2021 14:27:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210622115156.138458-1-berrange@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.223, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-block@nongnu.org, Markus Armbruster , "Richard W.M. Jones" , Max Reitz , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/22/21 1:51 PM, Daniel P. Berrangé wrote: > Currently the SSH block driver supports MD5 and SHA1 for host key > fingerprints. This is a cryptographically sensitive operation and > so these hash algorithms are inadequate by modern standards. This > adds support for SHA256 which has been supported in libssh since > the 0.8.1 release. > > Signed-off-by: Daniel P. Berrangé > --- > > Note I can't actually get iotest '207' to fully pass. It always > complains that it can't validate the "known_hosts" file > > qemu-img: Could not open 'TEST_IMG': no host key was found in known_hosts > > it seems to rely on some specific developer host setup that my > laptop doesn't satisfy. It would be useful if any pre-requisite > could be documented in the iotest. > > At least the sha256 verification step I added to 207 does pass > though. +Pino > block/ssh.c | 3 +++ > qapi/block-core.json | 3 ++- > tests/qemu-iotests/207 | 54 ++++++++++++++++++++++++++++++++++++++ > tests/qemu-iotests/207.out | 25 ++++++++++++++++++ > 4 files changed, 84 insertions(+), 1 deletion(-) > > diff --git a/block/ssh.c b/block/ssh.c > index b51a031620..d008caf059 100644 > --- a/block/ssh.c > +++ b/block/ssh.c > @@ -442,6 +442,9 @@ static int check_host_key(BDRVSSHState *s, SshHostKeyCheck *hkc, Error **errp) > } else if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_SHA1) { > return check_host_key_hash(s, hkc->u.hash.hash, > SSH_PUBLICKEY_HASH_SHA1, errp); > + } else if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_SHA256) { > + return check_host_key_hash(s, hkc->u.hash.hash, > + SSH_PUBLICKEY_HASH_SHA256, errp); Easier to read as a switch() :) Reviewed-by: Philippe Mathieu-Daudé > } > g_assert_not_reached(); > break; > diff --git a/qapi/block-core.json b/qapi/block-core.json > index 2ea294129e..4247dc46a5 100644 > --- a/qapi/block-core.json > +++ b/qapi/block-core.json > @@ -3186,11 +3186,12 @@ > # > # @md5: The given hash is an md5 hash > # @sha1: The given hash is an sha1 hash > +# @sha256: The given hash is an sha256 hash > # > # Since: 2.12 > ## > { 'enum': 'SshHostKeyCheckHashType', > - 'data': [ 'md5', 'sha1' ] } > + 'data': [ 'md5', 'sha1', 'sha256' ] } > > ## > # @SshHostKeyHash: > diff --git a/tests/qemu-iotests/207 b/tests/qemu-iotests/207 > index f9f3fd7131..0f5c4bc8a0 100755 > --- a/tests/qemu-iotests/207 > +++ b/tests/qemu-iotests/207 > @@ -73,6 +73,9 @@ with iotests.FilePath('t.img') as disk_path, \ > iotests.log("=== Test host-key-check options ===") > iotests.log("") > > + iotests.log("--- no host key checking --") > + iotests.log("") > + > vm.launch() > blockdev_create(vm, { 'driver': 'ssh', > 'location': { > @@ -90,6 +93,9 @@ with iotests.FilePath('t.img') as disk_path, \ > > iotests.img_info_log(remote_path) > > + iotests.log("--- known_hosts key checking --") > + iotests.log("") > + > vm.launch() > blockdev_create(vm, { 'driver': 'ssh', > 'location': { > @@ -115,6 +121,7 @@ with iotests.FilePath('t.img') as disk_path, \ > # Mappings of base64 representations to digests > md5_keys = {} > sha1_keys = {} > + sha256_keys = {} > > for key in keys: > md5_keys[key] = subprocess.check_output( > @@ -125,6 +132,10 @@ with iotests.FilePath('t.img') as disk_path, \ > 'echo %s | base64 -d | sha1sum -b | cut -d" " -f1' % key, > shell=True).rstrip().decode('ascii') > > + sha256_keys[key] = subprocess.check_output( > + 'echo %s | base64 -d | sha256sum -b | cut -d" " -f1' % key, > + shell=True).rstrip().decode('ascii') > + > vm.launch() > > # Find correct key first > @@ -150,6 +161,9 @@ with iotests.FilePath('t.img') as disk_path, \ > vm.shutdown() > iotests.notrun('Did not find a key that fits 127.0.0.1') > > + iotests.log("--- explicit md5 key checking --") > + iotests.log("") > + > blockdev_create(vm, { 'driver': 'ssh', > 'location': { > 'path': disk_path, > @@ -164,6 +178,7 @@ with iotests.FilePath('t.img') as disk_path, \ > } > }, > 'size': 2097152 }) > + > blockdev_create(vm, { 'driver': 'ssh', > 'location': { > 'path': disk_path, > @@ -182,6 +197,9 @@ with iotests.FilePath('t.img') as disk_path, \ > > iotests.img_info_log(remote_path) > > + iotests.log("--- explicit sha1 key checking --") > + iotests.log("") > + > vm.launch() > blockdev_create(vm, { 'driver': 'ssh', > 'location': { > @@ -215,6 +233,42 @@ with iotests.FilePath('t.img') as disk_path, \ > > iotests.img_info_log(remote_path) > > + iotests.log("--- explicit sha256 key checking --") > + iotests.log("") > + > + vm.launch() > + blockdev_create(vm, { 'driver': 'ssh', > + 'location': { > + 'path': disk_path, > + 'server': { > + 'host': '127.0.0.1', > + 'port': '22' > + }, > + 'host-key-check': { > + 'mode': 'hash', > + 'type': 'sha256', > + 'hash': 'wrong', > + } > + }, > + 'size': 2097152 }) > + blockdev_create(vm, { 'driver': 'ssh', > + 'location': { > + 'path': disk_path, > + 'server': { > + 'host': '127.0.0.1', > + 'port': '22' > + }, > + 'host-key-check': { > + 'mode': 'hash', > + 'type': 'sha256', > + 'hash': sha256_keys[matching_key], > + } > + }, > + 'size': 4194304 }) > + vm.shutdown() > + > + iotests.img_info_log(remote_path) > + > # > # Invalid path and user > # > diff --git a/tests/qemu-iotests/207.out b/tests/qemu-iotests/207.out > index 1239d9d648..aeb8569d77 100644 > --- a/tests/qemu-iotests/207.out > +++ b/tests/qemu-iotests/207.out > @@ -16,6 +16,8 @@ virtual size: 4 MiB (4194304 bytes) > > === Test host-key-check options === > > +--- no host key checking -- > + > {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"mode": "none"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 8388608}}} > {"return": {}} > {"execute": "job-dismiss", "arguments": {"id": "job0"}} > @@ -25,6 +27,8 @@ image: TEST_IMG > file format: IMGFMT > virtual size: 8 MiB (8388608 bytes) > > +--- known_hosts key checking -- > + > {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"mode": "known_hosts"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 4194304}}} > {"return": {}} > {"execute": "job-dismiss", "arguments": {"id": "job0"}} > @@ -34,6 +38,8 @@ image: TEST_IMG > file format: IMGFMT > virtual size: 4 MiB (4194304 bytes) > > +--- explicit md5 key checking -- > + > {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "wrong", "mode": "hash", "type": "md5"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 2097152}}} > {"return": {}} > Job failed: remote host key does not match host_key_check 'wrong' > @@ -49,6 +55,8 @@ image: TEST_IMG > file format: IMGFMT > virtual size: 8 MiB (8388608 bytes) > > +--- explicit sha1 key checking -- > + > {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "wrong", "mode": "hash", "type": "sha1"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 2097152}}} > {"return": {}} > Job failed: remote host key does not match host_key_check 'wrong' > @@ -64,6 +72,23 @@ image: TEST_IMG > file format: IMGFMT > virtual size: 4 MiB (4194304 bytes) > > +--- explicit sha256 key checking -- > + > +{"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "wrong", "mode": "hash", "type": "sha256"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 2097152}}} > +{"return": {}} > +Job failed: remote host key does not match host_key_check 'wrong' > +{"execute": "job-dismiss", "arguments": {"id": "job0"}} > +{"return": {}} > + > +{"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "HASH", "mode": "hash", "type": "sha256"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 4194304}}} > +{"return": {}} > +{"execute": "job-dismiss", "arguments": {"id": "job0"}} > +{"return": {}} > + > +image: TEST_IMG > +file format: IMGFMT > +virtual size: 4 MiB (4194304 bytes) > + > === Invalid path and user === > > {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"mode": "none"}, "path": "/this/is/not/an/existing/path", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 4194304}}} >