commit c889534dd5ae6620634720a4fa7a771be9858069 Author: teor teor2345@gmail.com Date: Wed May 3 09:47:31 2017 +1000

Add an offline mode to chutney, which disables DNS

Using --offline makes chutney much more reliable, and removes the dependency on an external DNS resolver. Chutney automatically does this when the default /etc/resolv.conf file is missing. To use offline mode by default, set CHUTNEY_DNS_CONF="/dev/null".

This change makes chutney ignore tor's compile-time ServerDNSResolvConfFile default. If you rely on a custom default for this option (which isn't /etc/resolv.conf), use --dns-conf-default or CHUTNEY_DNS_CONF="".

To use a custom DNS file, use --dns-conf PATH or CHUTNEY_DNS_CONF="PATH".

Closes ticket 21903, and other related tickets. --- README | 34 +++++++++++++++++++++++++++++++++- lib/chutney/TorNet.py | 38 ++++++++++++++++++++++++++++++++++++++ resolv.conf | 4 ++++ tools/ignore.warnings | 4 ++++ tools/test-network.sh | 25 +++++++++++++++++++++++++ torrc_templates/relay-non-dir.tmpl | 11 +++++++++++ 6 files changed, 115 insertions(+), 1 deletion(-)

diff --git a/README b/README index 14d521a..cfa41c4 100644 --- a/README +++ b/README @@ -48,9 +48,14 @@ Traffic Options: --rounds CHUTNEY_ROUNDS=N --hs-multi-client CHUTNEY_HS_MULTI_CLIENT=N

-Address Options: +Address/DNS Options: --ipv4 CHUTNEY_LISTEN_ADDRESS --ipv6 CHUTNEY_LISTEN_ADDRESS_V6 + # Chutney uses /etc/resolv.conf if none of these options are set + --dns-conf CHUTNEY_DNS_CONF=PATH + --offline CHUTNEY_DNS_CONF=/dev/null + # Use tor's compile-time default for ServerDNSResolvConfFile + --dns-conf-default CHUTNEY_DNS_CONF=""

Warning Options: --all-warnings CHUTNEY_WARNINGS_IGNORE_EXPECTED=false @@ -149,6 +154,33 @@ Changing the network address: chutney verifies IPv6 client, bridge client (?), hidden service, and exit connections. It does not use IPv6 SOCKSPorts or HiddenServicePorts.

+Using DNS: + + Chutney verify uses IP addresses by default. It does not need to look up + any hostnames. We recommend that chutney users disable DNS using --offline + or CHUTNEY_DNS_CONF=/dev/null , because any DNS failures causes tests to + fail. Chutney's DNS queries also produce external traffic in a predictable + pattern. + + If you want to use a hostname with CHUTNEY_LISTEN_ADDRESS[_V6], or you want + to run tests that use DNS, set CHUTNEY_DNS_CONF to the path to a file in + resolv.conf format. Chutney's default of /etc/resolv.conf should be fine for + most UNIX-based operating systems. If your tor is compiled with a different + default, use --dns-resolv-conf-default or CHUTNEY_DNS_CONF="". + + When the CHUTNEY_DNS_CONF file does not exist, or is a broken symlink, + chutney uses /dev/null instead. This is a workaround for bugs in tor's + use of eventdns. For example, macOS deletes the resolv.conf file when it + thinks the network is down: this can make tor exits reject all traffic, + even if a working DNS server is running on 127.0.0.1:53. + + When tor has no working name servers (including --offline mode), it can + crash on SETCONF. (Chutney does not use SETCONF, but some external tor + controllers do.) To avoid this crash, set CHUTNEY_DNS_CONF to a file + containing a working name server address. For your convenience, chutney + provides a local resolv.conf file containing IPv4, IPv6, and "localhost". + Use --dns-conf resolv.conf (relative paths work). + The configuration files: networks/basic holds the configuration for the network you're configuring above. It refers to some torrc template files in torrc_templates/. diff --git a/lib/chutney/TorNet.py b/lib/chutney/TorNet.py index 9ccf4a5..3ace8a7 100644 --- a/lib/chutney/TorNet.py +++ b/lib/chutney/TorNet.py @@ -756,6 +756,10 @@ DEFAULTS = { 'controlling_pid': (int(os.environ.get('CHUTNEY_CONTROLLING_PID', 0)) if 'CHUTNEY_CONTROLLING_PID' in os.environ else None), + # a DNS config file (for ServerDNSResolvConfFile) + 'dns_conf': (os.environ.get('CHUTNEY_DNS_CONF', '/etc/resolv.conf') + if 'CHUTNEY_DNS_CONF' in os.environ + else None), }

@@ -775,6 +779,10 @@ class TorEnviron(chutney.Templating.Environ): hs_hostname: the hostname of the key generated by a hidden service owning_controller_process: the __OwningControllerProcess torrc line, disabled if tor should continue after the script exits + server_dns_resolv_conf: the ServerDNSResolvConfFile torrc line, + disabled if tor should use the default DNS conf. + If the dns_conf file is missing, this option is also disabled: + otherwise, exits would not work due to tor bug #21900.

Environment fields used: nodenum: chutney's internal node number for the node @@ -792,6 +800,8 @@ class TorEnviron(chutney.Templating.Environ): hs-hostname (note hyphen): cached hidden service hostname value controlling_pid: the PID of the controlling process. After this process exits, the child tor processes will exit + dns_conf: the path to a DNS config file for Tor Exits. If this file + is empty or unreadable, Tor will try 127.0.0.1:53. """

def __init__(self, parent=None, **kwargs): @@ -867,6 +877,34 @@ class TorEnviron(chutney.Templating.Environ): else: return ocp_line

+ # the default resolv.conf path is set at compile time + # there's no easy way to get it out of tor, so we use the typical value + DEFAULT_DNS_RESOLV_CONF = "/etc/resolv.conf" + # if we can't find the specified file, use this one as a substitute + OFFLINE_DNS_RESOLV_CONF = "/dev/null" + + def _get_server_dns_resolv_conf(self, my): + if my['dns_conf'] == "": + # if the user asked for tor's default + return "#ServerDNSResolvConfFile using tor's compile-time default" + elif my['dns_conf'] is None: + # if there is no DNS conf file set + print("CHUTNEY_DNS_CONF not specified, using '%s'." + % (DEFAULT_DNS_RESOLV_CONF)) + dns_conf = DEFAULT_DNS_RESOLV_CONF + else: + dns_conf = my['dns_conf'] + dns_conf = os.path.abspath(my['dns_conf']) + # work around Tor bug #21900, where exits fail when the DNS conf + # file does not exist, or is a broken symlink + # (os.path.exists returns False for broken symbolic links) + if not os.path.exists(dns_conf): + # Issue a warning so the user notices + print("CHUTNEY_DNS_CONF '%s' does not exist, using '%s'." + % (dns_conf, OFFLINE_DNS_RESOLV_CONF)) + dns_conf = OFFLINE_DNS_RESOLV_CONF + return "ServerDNSResolvConfFile %s" % (dns_conf) +

class Network(object):

diff --git a/resolv.conf b/resolv.conf new file mode 100644 index 0000000..98944a1 --- /dev/null +++ b/resolv.conf @@ -0,0 +1,4 @@ +# Use localhost as the resolver +127.0.0.1 +::1 +localhost diff --git a/tools/ignore.warnings b/tools/ignore.warnings index 8384066..5429533 100644 --- a/tools/ignore.warnings +++ b/tools/ignore.warnings @@ -19,6 +19,8 @@ Consensus with empty bandwidth Could not add queued signature to new consensus: Mismatched digest Could not add queued signature to new consensus: Valid-After times do not match Could not open.*sr-state.*No such file or directory +# Chutney does not use DNS by default +Couldn't set up any working nameservers. Network not up yet Currently, sandboxing is only implemented on Linux # We ignore consensus failure warnings Error publishing .* consensus @@ -50,6 +52,8 @@ TestingTorNetwork is set # Older versions might need them, we should remove them at some point in 0.3.* The DirAuthority options 'hs' and 'no-hs' are obsolete This copy of Tor was compiled.*to run in a non-anonymous mode +# Chutney does not use DNS by default +Unable to parse '.*', or no nameservers in '.*' # Tor Bug 21525? Unable to store signatures posted by .* Mismatched digest Unable to store signatures posted by .* Valid-After times do not match diff --git a/tools/test-network.sh b/tools/test-network.sh index 2be5558..e893e80 100755 --- a/tools/test-network.sh +++ b/tools/test-network.sh @@ -15,6 +15,10 @@ export CHUTNEY_WARNINGS_SUMMARY=${CHUTNEY_WARNINGS_SUMMARY:-true} # default to exiting when this script exits export CHUTNEY_CONTROLLING_PID=${CHUTNEY_CONTROLLING_PID:-$$}

+# default to no DNS: this is a safe, working default for most users +# If a custom test expects DNS, it needs to set CHUTNEY_DNS_CONF +export CHUTNEY_DNS_CONF=${CHUTNEY_DNS_CONF:-/dev/null} + # what we say when we fail UPDATE_YOUR_CHUTNEY="Please update your chutney using 'git pull'."

@@ -111,6 +115,21 @@ do export CHUTNEY_LISTEN_ADDRESS_V6="$2" shift ;; + # The DNS server config for Tor Exits. Chutney's default is + # /etc/resolv.conf, even if tor's compile time default is different. + --dns-conf) + export CHUTNEY_DNS_CONF="$2" + shift + ;; + # Do not make any DNS queries. This is incompatible with external + # controllers that use SETCONF. + --offline) + export CHUTNEY_DNS_CONF="/dev/null" + ;; + # Use tor's compile-time default for ServerDNSResolvConfFile. + --dns-conf-default) + export CHUTNEY_DNS_CONF="" + ;; # Warning Options # we summarise unexpected warnings by default # this shows all warnings per-node @@ -158,6 +177,12 @@ do shift done

+# If the DNS server doesn't work, tor exits may reject all exit traffic, and +# chutney may fail +if [ "$CHUTNEY_WARNINGS_ONLY" != true ]; then + $ECHO "$myname: using CHUTNEY_DNS_CONF '$CHUTNEY_DNS_CONF'" +fi + # optional: $TOR_DIR is the tor build directory # it's used to find the location of tor binaries # if it's not set: diff --git a/torrc_templates/relay-non-dir.tmpl b/torrc_templates/relay-non-dir.tmpl index b2899f7..560ebdf 100644 --- a/torrc_templates/relay-non-dir.tmpl +++ b/torrc_templates/relay-non-dir.tmpl @@ -15,3 +15,14 @@ ExitRelay 0 # then half the minimum testing consensus interval TestingServerDownloadSchedule 0, 5 TestingServerConsensusDownloadSchedule 0, 5 + +# These options are set here so they apply to IPv4 and IPv6 Exits +# +# Tell Exits to avoid using DNS: otherwise, chutney will fail if DNS fails +# (Chutney only accesses 127.0.0.1 and ::1, so it doesn't need DNS) +ServerDNSDetectHijacking 0 +ServerDNSTestAddresses +# If this option is /dev/null, or any other empty or unreadable file, tor exits +# will not use DNS. Otherwise, DNS is enabled with this config. +# (If the following line is commented out, tor uses /etc/resolv.conf.) +${server_dns_resolv_conf}