dnscrypt-proxy v2.1.0 on Debian 10.2 (Buster) responding to DNS lookups from downstream Pi-hole with REFUSED

[jdrch]

I have dnscrypt-proxy v2.1.0 and Pi-hole (Pi-hole v5.3.1 Web Interface v5.5.1 FTL v5.8.1) running on this machine (full specs at link).

Lately dnscrypt-proxy has been responding to some DNS queries from Pi-hole with REFUSED. There appears to be no rhyme or reason to the REFUSE responses; sometimes the same URL for which a query was REFUSEd gets a proper DNS record response. I know the issue lies with dnscrypt-proxy because when I switch to Cloudflare as my direct upstream DNS in Pi-hole's settings I do not have the same problem.

I checked that only dnscrypt-proxy is running on the port on which it is supposed to be listening:

sudo lsof -i :54
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
dnscrypt- 1128 root    6u  IPv4  35146      0t0  UDP localhost:54
dnscrypt- 1128 root    7u  IPv4  35147      0t0  TCP localhost:54 (LISTEN)

Does anyone have any clue as to what is going wrong and how to fix it?

[jedisct1]

REFUSED means that the query was blocked.

You can enable the blocklist log or the IP blocklist log to see what rule is matching.

[jdrch]

Thanks @jedisct1. What confuses me is to my knowledge I don't have any dnscrypt-proxy blocklists enabled at all. Also, the URLs that are being refused are not on any Pi-hole blocklist (if they were, Pi-hole wouldn't forward them in the 1st place, AFAIK.)

Below is my config file, do you see anything in it that would cause the issues I'm having?

##############################################
#                                            #
#        dnscrypt-proxy configuration        #
#                                            #
##############################################

## This is an example configuration file.
## You should adjust it to your needs, and save it as "dnscrypt-proxy.toml"
##
## Online documentation is available here: https://dnscrypt.info/doc



##################################
#         Global settings        #
##################################

## List of servers to use
##
## Servers from the "public-resolvers" source (see down below) can
## be viewed here: https://dnscrypt.info/public-servers
##
## If this line is commented, all registered servers matching the require_* filters
## will be used.
##
## The proxy will automatically pick the fastest, working servers from the list.
## Remove the leading # first to enable this; lines starting with # are ignored.

server_names = ['cloudflare']


## List of local addresses and ports to listen to. Can be IPv4 and/or IPv6.
## Note: When using systemd socket activation, choose an empty set (i.e. [] ).

listen_addresses = ['127.0.0.1:54']


## Maximum number of simultaneous client connections to accept

max_clients = 250


## Switch to a different system user after listening sockets have been created.
## Note (1): this feature is currently unsupported on Windows.
## Note (2): this feature is not compatible with systemd socket activation.
## Note (3): when using -pidfile, the PID file directory must be writable by the new user

# user_name = 'nobody'


## Require servers (from static + remote sources) to satisfy specific properties

# Use servers reachable over IPv4
ipv4_servers = true

# Use servers reachable over IPv6 -- Do not enable if you don't have IPv6 connectivity
ipv6_servers = false

# Use servers implementing the DNSCrypt protocol
dnscrypt_servers = false

# Use servers implementing the DNS-over-HTTPS protocol
doh_servers = true


## Require servers defined by remote sources to satisfy specific properties

# Server must support DNS security extensions (DNSSEC)
require_dnssec = true

# Server must not log user queries (declarative)
require_nolog = true

# Server must not enforce its own blacklist (for parental control, ads blocking...)
require_nofilter = true


## Always use TCP to connect to upstream servers.
## This can be useful if you need to route everything through Tor.
## Otherwise, leave this to `false`, as it doesn't improve security
## (dnscrypt-proxy will always encrypt everything even using UDP), and can
## only increase latency.

force_tcp = false


## SOCKS proxy
## Uncomment the following line to route all TCP connections to a local Tor node
## Tor doesn't support UDP, so set `force_tcp` to `true` as well.

# proxy = "socks5://127.0.0.1:9050"


## HTTP/HTTPS proxy
## Only for DoH servers

# http_proxy = "http://127.0.0.1:8888"


## How long a DNS query will wait for a response, in milliseconds

timeout = 2500


## Keepalive for HTTP (HTTPS, HTTP/2) queries, in seconds

keepalive = 30


## Load-balancing strategy: 'p2' (default), 'ph', 'fastest' or 'random'

# lb_strategy = 'p2'


## Log level (0-6, default: 2 - 0 is very verbose, 6 only contains fatal errors)

# log_level = 2


## log file for the application

# log_file = 'dnscrypt-proxy.log'


## Use the system logger (syslog on Unix, Event Log on Windows)

# use_syslog = true


## Delay, in minutes, after which certificates are reloaded

cert_refresh_delay = 240


## DNSCrypt: Create a new, unique key for every single DNS query
## This may improve privacy but can also have a significant impact on CPU usage
## Only enable if you don't have a lot of network load

# dnscrypt_ephemeral_keys = false


## DoH: Disable TLS session tickets - increases privacy but also latency

tls_disable_session_tickets = false


## DoH: Use a specific cipher suite instead of the server preference
## 49199 = TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
## 49195 = TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
## 52392 = TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305
## 52393 = TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305
##
## On non-Intel CPUs such as MIPS routers and ARM systems (Android, Raspberry Pi...),
## the following suite improves performance.
## This may also help on Intel CPUs running 32-bit operating systems.
##
## Keep tls_cipher_suite empty if you have issues fetching sources or
## connecting to some DoH servers. Google and Cloudflare are fine with it.

tls_cipher_suite = [52392, 49199]


## Fallback resolver
## This is a normal, non-encrypted DNS resolver, that will be only used
## for one-shot queries when retrieving the initial resolvers list, and
## only if the system DNS configuration doesn't work.
## No user application queries will ever be leaked through this resolver,
## and it will not be used after IP addresses of resolvers URLs have been found.
## It will never be used if lists have already been cached, and if stamps
## don't include host names without IP addresses.
## It will not be used if the configured system DNS works.
## A resolver supporting DNSSEC is recommended. This may become mandatory.
##
## People in China may need to use 114.114.114.114:53 here.
## Other popular options include 8.8.8.8 and 1.1.1.1.

bootstrap_resolvers = ['1.1.1.1:53']


## Never let dnscrypt-proxy try to use the system DNS settings;
## unconditionally use the fallback resolver.

ignore_system_dns = true


## Maximum time (in seconds) to wait for network connectivity before
## initializing the proxy.
## Useful if the proxy is automatically started at boot, and network
## connectivity is not guaranteed to be immediately available.
## Use 0 to disable.

netprobe_timeout = 30


## Offline mode - Do not use any remote encrypted servers.
## The proxy will remain fully functional to respond to queries that
## plugins can handle directly (forwarding, cloaking, ...)

# offline_mode = false


## Automatic log files rotation

# Maximum log files size in MB
log_files_max_size = 10

# How long to keep backup files, in days
log_files_max_age = 7

# Maximum log files backups to keep (or 0 to keep all backups)
log_files_max_backups = 1



#########################
#        Filters        #
#########################

## Immediately respond to IPv6-related queries with an empty response
## This makes things faster when there is no IPv6 connectivity, but can
## also cause reliability issues with some stub resolvers.
## Do not enable if you added a validating resolver such as dnsmasq in front
## of the proxy.

block_ipv6 = false



##################################################################################
#        Route queries for specific domains to a dedicated set of servers        #
##################################################################################

## Example map entries (one entry per line):
## example.com 9.9.9.9
## example.net 9.9.9.9,8.8.8.8,1.1.1.1

# forwarding_rules = 'forwarding-rules.txt'



###############################
#        Cloaking rules       #
###############################

## Cloaking returns a predefined address for a specific name.
## In addition to acting as a HOSTS file, it can also return the IP address
## of a different name. It will also do CNAME flattening.
##
## Example map entries (one entry per line)
## example.com     10.1.1.1
## www.google.com  forcesafesearch.google.com

# cloaking_rules = 'cloaking-rules.txt'



###########################
#        DNS cache        #
###########################

## Enable a DNS cache to reduce latency and outgoing traffic

cache = true


## Cache size

cache_size = 512


## Minimum TTL for cached entries

cache_min_ttl = 600


## Maximum TTL for cached entries

cache_max_ttl = 86400


## Minimum TTL for negatively cached entries

cache_neg_min_ttl = 60


## Maximum TTL for negatively cached entries

cache_neg_max_ttl = 600



###############################
#        Query logging        #
###############################

## Log client queries to a file

[query_log]

  ## Path to the query log file (absolute, or relative to the same directory as the executable file)

  # file = 'query.log'


  ## Query log format (currently supported: tsv and ltsv)

  format = 'tsv'


  ## Do not log these query types, to reduce verbosity. Keep empty to log everything.

  # ignored_qtypes = ['DNSKEY', 'NS']



############################################
#        Suspicious queries logging        #
############################################

## Log queries for nonexistent zones
## These queries can reveal the presence of malware, broken/obsolete applications,
## and devices signaling their presence to 3rd parties.

[nx_log]

  ## Path to the query log file (absolute, or relative to the same directory as the executable file)

  # file = 'nx.log'


  ## Query log format (currently supported: tsv and ltsv)

  format = 'tsv'



######################################################
#        Pattern-based blocking (blacklists)        #
######################################################

## Blacklists are made of one pattern per line. Example of valid patterns:
##
##   example.com
##   =example.com
##   *sex*
##   ads.*
##   ads*.example.*
##   ads*.example[0-9]*.com
##
## Example blacklist files can be found at https://download.dnscrypt.info/blacklists/
## A script to build blacklists from public feeds can be found in the
## `utils/generate-domains-blacklists` directory of the dnscrypt-proxy source code.

[blacklist]

  ## Path to the file of blocking rules (absolute, or relative to the same directory as the executable file)

  # blacklist_file = 'blacklist.txt'


  ## Optional path to a file logging blocked queries

  # log_file = 'blocked.log'


  ## Optional log format: tsv or ltsv (default: tsv)

  # log_format = 'tsv'



###########################################################
#        Pattern-based IP blocking (IP blacklists)        #
###########################################################

## IP blacklists are made of one pattern per line. Example of valid patterns:
##
##   127.*
##   fe80:abcd:*
##   192.168.1.4

[ip_blacklist]

  ## Path to the file of blocking rules (absolute, or relative to the same directory as the executable file)

  # blacklist_file = 'ip-blacklist.txt'


  ## Optional path to a file logging blocked queries

  # log_file = 'ip-blocked.log'


  ## Optional log format: tsv or ltsv (default: tsv)

  # log_format = 'tsv'



######################################################
#   Pattern-based whitelisting (blacklists bypass)   #
######################################################

## Whitelists support the same patterns as blacklists
## If a name matches a whitelist entry, the corresponding session
## will bypass names and IP filters.
##
## Time-based rules are also supported to make some websites only accessible at specific times of the day.

[whitelist]

  ## Path to the file of whitelisting rules (absolute, or relative to the same directory as the executable file)

  # whitelist_file = 'whitelist.txt'


  ## Optional path to a file logging whitelisted queries

  # log_file = 'whitelisted.log'


  ## Optional log format: tsv or ltsv (default: tsv)

  # log_format = 'tsv'



##########################################
#        Time access restrictions        #
##########################################

## One or more weekly schedules can be defined here.
## Patterns in the name-based blocklist can optionally be followed with @schedule_name
## to apply the pattern 'schedule_name' only when it matches a time range of that schedule.
##
## For example, the following rule in a blacklist file:
## *.youtube.* @time-to-sleep
## would block access to YouTube only during the days, and period of the days
## define by the 'time-to-sleep' schedule.
##
## {after='21:00', before= '7:00'} matches 0:00-7:00 and 21:00-0:00
## {after= '9:00', before='18:00'} matches 9:00-18:00

[schedules]

  # [schedules.'time-to-sleep']
  # mon = [{after='21:00', before='7:00'}]
  # tue = [{after='21:00', before='7:00'}]
  # wed = [{after='21:00', before='7:00'}]
  # thu = [{after='21:00', before='7:00'}]
  # fri = [{after='23:00', before='7:00'}]
  # sat = [{after='23:00', before='7:00'}]
  # sun = [{after='21:00', before='7:00'}]

  # [schedules.'work']
  # mon = [{after='9:00', before='18:00'}]
  # tue = [{after='9:00', before='18:00'}]
  # wed = [{after='9:00', before='18:00'}]
  # thu = [{after='9:00', before='18:00'}]
  # fri = [{after='9:00', before='17:00'}]



#########################
#        Servers        #
#########################

## Remote lists of available servers
## Multiple sources can be used simultaneously, but every source
## requires a dedicated cache file.
##
## Refer to the documentation for URLs of public sources.
##
## A prefix can be prepended to server names in order to
## avoid collisions if different sources share the same for
## different servers. In that case, names listed in `server_names`
## must include the prefixes.
##
## If the `urls` property is missing, cache files and valid signatures
## must be already present; This doesn't prevent these cache files from
## expiring after `refresh_delay` hours.

[sources]

  ## An example of a remote source from https://github.com/DNSCrypt/dnscrypt-resolvers

  [sources.'public-resolvers']
  urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v2/public-resolvers.md', 'https://download.dnscrypt.info/resolvers-list/v2/public-resolvers.md']
  cache_file = 'public-resolvers.md'
  minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'
  refresh_delay = 72
  prefix = ''

  ## Quad9 over DNSCrypt - https://quad9.net/

  # [sources.quad9-resolvers]
  # urls = ["https://www.quad9.net/quad9-resolvers.md"]
  # minisign_key = "RWQBphd2+f6eiAqBsvDZEBXBGHQBJfeG6G+wJPPKxCZMoEQYpmoysKUN"
  # cache_file = "quad9-resolvers.md"
  # refresh_delay = 72
  # prefix = "quad9-"

  ## Another example source, with resolvers censoring some websites not appropriate for children
  ## This is a subset of the `public-resolvers` list, so enabling both is useless

  #  [sources.'parental-control']
  #  urls = ['https://raw.githubusercontent.com/DNSCrypt/dnscrypt-resolvers/master/v2/parental-control.md', 'https://download.dnscrypt.info/resolvers-list/v2/parental-control.md']
  #  cache_file = 'parental-control.md'
  #  minisign_key = 'RWQf6LRCGA9i53mlYecO4IzT51TGPpvWucNSCh1CBM0QTaLn73Y7GFO3'



## Optional, local, static list of additional servers
## Mostly useful for testing your own servers.

[static]

  # [static.'google']
  # stamp = 'sdns://AgUAAAAAAAAAAAAOZG5zLmdvb2dsZS5jb20NL2V4cGVyaW1lbnRhbA'

[jedisct1]

What status are you seeing for these queries in the dnscrypt-proxy query log?

[jdrch]

What status are you seeing for these queries in the dnscrypt-proxy query log?

Looks like I'm getting RESPONSE_ERROR:

[2021-09-29 10:35:37]	127.0.0.1	dl.google.com	A	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	dl.google.com	AAAA	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	dl.cloudsmith.io	A	RESPONSE_ERROR	19ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	repository.veeam.com	A	RESPONSE_ERROR	26ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	dl.cloudsmith.io	AAAA	RESPONSE_ERROR	20ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	A	RESPONSE_ERROR	20ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	repository.spotify.com	A	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	security.debian.org	AAAA	RESPONSE_ERROR	23ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	linux-packages.resilio.com	AAAA	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	linux-packages.resilio.com	A	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	AAAA	RESPONSE_ERROR	24ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	repository.spotify.com	AAAA	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	updates.signal.org	A	RESPONSE_ERROR	20ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	updates.signal.org	AAAA	RESPONSE_ERROR	20ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	download.sublimetext.com	A	RESPONSE_ERROR	20ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	repo.skype.com	A	RESPONSE_ERROR	25ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	security.debian.org	A	RESPONSE_ERROR	31ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	linux.teamviewer.com	A	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	download.sublimetext.com	AAAA	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	linux.teamviewer.com	AAAA	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	repo.skype.com	AAAA	RESPONSE_ERROR	30ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	_https._tcp.dl.cloudsmith.io	SRV	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	A	RESPONSE_ERROR	20ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	AAAA	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	_https._tcp.dl.cloudsmith.io	SRV	RESPONSE_ERROR	22ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	AAAA	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	A	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	A	RESPONSE_ERROR	21ms	cloudflare
[2021-09-29 10:35:37]	127.0.0.1	deb.debian.org	AAAA	RESPONSE_ERROR	29ms	cloudflare

Any ideas?

[jdrch]

UPDATE: Please continue the discussion of this problem here.