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+# dnscap
+
+[![Build Status](https://travis-ci.com/DNS-OARC/dnscap.svg?branch=develop)](https://travis-ci.com/DNS-OARC/dnscap) [![Total alerts](https://img.shields.io/lgtm/alerts/g/DNS-OARC/dnscap.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/DNS-OARC/dnscap/alerts/) [![Bugs](https://sonarcloud.io/api/project_badges/measure?project=dns-oarc%3Adnscap&metric=bugs)](https://sonarcloud.io/dashboard?id=dns-oarc%3Adnscap) [![Security Rating](https://sonarcloud.io/api/project_badges/measure?project=dns-oarc%3Adnscap&metric=security_rating)](https://sonarcloud.io/dashboard?id=dns-oarc%3Adnscap)
+
+`dnscap` is a network capture utility designed specifically for DNS traffic.
+It produces binary data in `pcap(3)` and other format. This utility is similar
+to `tcpdump(1)`, but has a number of features tailored to DNS transactions
+and protocol options. DNS-OARC uses `dnscap` for DITL data collections.
+
+Some of its features include:
+- Understands both IPv4 and IPv6
+- Captures UDP, TCP, and IP fragments.
+- Collect only queries, responses, or both (`-s` option)
+- Collect for only certain source/destination addresses (`-a` `-z` `-A` `-Z` options)
+- Periodically creates new pcap files (`-t` option)
+- Spawns an upload script after closing a pcap file (`-k` option)
+- Will start and stop collecting at specific times (`-B` `-E` options)
+
+More information may be found here:
+- https://www.dns-oarc.net/tools/dnscap
+- https://www.dns-oarc.net/oarc/data/ditl
+
+Issues should be reported here:
+- https://github.com/DNS-OARC/dnscap/issues
+
+General support and discussion:
+- Mattermost: https://chat.dns-oarc.net/community/channels/oarc-software
+- mailing-list: https://lists.dns-oarc.net/mailman/listinfo/dnscap-users
+
+## Dependencies
+
+`dnscap` requires a couple of libraries beside a normal C compiling
+environment with autoconf, automake, libtool and pkgconfig.
+
+`dnscap` has a non-optional dependency on the PCAP library and LDNS.
+
+To install the dependencies under Debian/Ubuntu:
+```
+apt-get install -y libpcap-dev libldns-dev zlib1g-dev libyaml-perl libssl-dev
+```
+
+To install the dependencies under CentOS (with EPEL enabled):
+```
+yum install -y libpcap-devel ldns-devel openssl-devel zlib-devel perl-YAML
+```
+
+For the following OS you will need to install some of the dependencies
+from source or Ports, these instructions are not included.
+
+To install some of the dependencies under FreeBSD 10+ using `pkg`:
+```
+pkg install -y libpcap ldns p5-YAML openssl-devel
+```
+
+To install some of the dependencies under OpenBSD 5+ using `pkg_add`:
+```
+pkg_add libldns p5-YAML
+```
+
+NOTE: It is recommended to install the PCAP library from source/ports on
+OpenBSD since the bundled version is an older and modified version.
+
+### Dependencies for `cryptopant.so` plugin
+
+For this plugin a library call `cryptopANT` is required and the original
+can be found here: https://ant.isi.edu/software/cryptopANT/index.html .
+
+For DNS-OARC packages we build our own fork, with slight modifications to
+conform across distributions, of this library which is included in the same
+package repository as `dnscap`. The modifications and packaging files can be
+found here: https://github.com/DNS-OARC/cryptopANT .
+
+## Building from source tarball
+
+The [source tarball from DNS-OARC](https://www.dns-oarc.net/tools/dnscap)
+comes prepared with `configure`:
+
+```
+tar zxvf dnscap-version.tar.gz
+cd dnscap-version
+./configure [options]
+make
+make install
+```
+
+## Building from Git repository
+
+If you are building `dnscap` from it's Git repository you will first need
+to initiate the Git submodules that exists and later create autoconf/automake
+files, this will require a build environment with autoconf, automake, libtool
+and pkg-config to be installed.
+
+```
+git clone https://github.com/DNS-OARC/dnscap.git
+cd dnscap
+git submodule update --init
+./autogen.sh
+./configure [options]
+make
+make install
+```
+
+### 64-bit libraries
+
+If you need to link against 64-bit libraries found in non-standard
+locations, provide the location by setting LDFLAGS before running
+configure:
+
+```
+$ env LDFLAGS=-L/usr/lib64 ./configure
+```
+
+### OpenBSD
+
+For OpenBSD you probably installed libpcap in `/usr/local` so you will need
+to tell `configure` where to find the libraries and header files:
+
+```
+$ env CFLAGS="-I/usr/local/include" LDFLAGS="-L/usr/local/lib" ./configure
+```
+
+## Plugins
+
+`dnscap` comes bundled with a set of plugins, see `-P` option.
+
+- `anonaes128.so`: Anonymize IP addresses using AES128
+- `anonmask.so`: Pseudo-anonymize IP addresses by masking them
+- `cryptopan.so`: Anonymize IP addresses using an extension to Crypto-PAn (College of Computing, Georgia Tech) made by David Stott (Lucent)
+- `cryptopant.so`: Anonymize IP addresses using cryptopANT, a different implementation of Crypto-PAn made by the ANT project at USC/ISI
+- `ipcrypt.so`: Anonymize IP addresses using ipcrypt create by Jean-Philippe Aumasson
+- `pcapdump.so`: Dump DNS into a PCAP with some filtering options
+- `royparse.so`: Splits a PCAP into two streams; queries in PCAP format and responses in ASCII format
+- `rssm.so`: Root Server Scaling Measurement plugin, see it's [README.md](plugins/rssm/README.md) for more information
+- `rzkeychange.so`: RFC8145 key tag signal collection and reporting plugin
+- `txtout.so`: Dump DNS as one-line text
+- `eventlog.so`: Syslog style output for easy parsing, use with a SIEM, etc.
+
+There is also a `template` plugin in the source repository to help others
+develop new plugins.
+
+## CBOR DNS Stream Format
+
+This is an experimental format for representing DNS information in CBOR
+with the goals to:
+- Be able to stream the information
+- Support incomplete, broken and/or invalid DNS
+- Have close to no data quality and signature degradation
+- Support additional non-DNS meta data (such as ICMP/TCP attributes)
+
+Read [CBOR_DNS_STREAM.md](https://github.com/DNS-OARC/dnscap/blob/develop/CBOR_DNS_STREAM.md) for more information.
+
+To enable this output please follow the instructions below for Enabling
+CBOR Output, note that this only requires Tinycbor.
+
+### Outputting to CBOR DNS Stream (CDS)
+
+To output to the CDS format you tell `dnscap` to write to a file and set
+the format to CDS. CDS is a stream of CBOR objects and you can control how
+many objects are kept in memory until flushed to the file by setting
+`cds_cbor_size`, note that this is bytes of memory and not number of objects.
+When it reaches this limit it will write the output and start on a new file.
+Read `dnscap`'s man page for all CDS extended options.
+
+```
+src/dnscap [...] -w <file> -F cds [ -o cds_cbor_size=<bytes> ]
+```
+
+## CBOR
+
+There is experimental support for CBOR output using LDNS and Tinycbor with
+a data structure described in the DNS-in-JSON draft.
+
+https://datatracker.ietf.org/doc/draft-hoffman-dns-in-json/
+
+### Enabling CBOR Output
+
+To enable the CBOR output support you will need to install it's dependencies
+before running `configure`, LDNS exists for most distributions but Tinycbor
+is new so you need to download and compile it, you do not necessary need to
+install it as shown in the example below.
+
+```sh
+git clone https://github.com/DNS-OARC/dnscap.git
+cd dnscap
+git submodule update --init
+git clone https://github.com/01org/tinycbor.git
+cd tinycbor
+git checkout v0.4.2
+make
+cd ..
+sh autogen.sh
+CFLAGS="-I$PWD/tinycbor/src" LDFLAGS="-L$PWD/tinycbor/lib" LIBS="-ltinycbor" ./configure
+make
+```
+
+**NOTE**: Paths in `CFLAGS` and `LDFLAGS` must be absolute.
+
+### CBOR to JSON
+
+Tinycbor comes with a tool to convert CBOR to JSON, check `bin/cbordump -h`
+in the Tinycbor directory after having compiled it.
+
+### Outputting to CBOR
+
+To output to the CBOR format you tell `dnscap` to write to a file and set
+the format to CBOR. Since Tinycbor constructs everything in memory there
+is a limit and when it is reached it will write the output and start on a
+new file. You can control the number of bytes with the extended option
+`cbor_chunk_size`.
+
+```
+src/dnscap [...] -w <file> -F cbor [ -o cbor_chunk_size=<bytes> ]
+```
+
+### Additional attributes
+
+There is currently an additional attribute added to the CBOR object which
+contains the IP information as following:
+
+```
+"ip": [
+ <proto>,
+ "<source ip address>",
+ <source port>
+ "<destination ip address>",
+ <destination port>
+]
+```
+
+Example:
+
+```json
+"ip": [
+ 17,
+ "127.0.0.1",
+ 34856,
+ "127.0.0.1",
+ 53
+]
+```
+
+### Limitations, deviations and issues
+
+Since this is still experimental there are of course some issues:
+- RDATA is in binary format
+- DNS packet are parsed by LDNS which can fail if malformed packets
+- `dateSeconds` is added as a C `double` which might loose some of the time precision