mirror of
https://gitlab.torproject.org/tpo/core/tor.git
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469051f650
I started this repository a while ago to work on documentation for Tor's internals. It needs substantial revision, but first, let's get it copied into Tor's repository. These files are copied, "warts and all", from the tor-guts.git repo, commit de1e34259178b09861c0dea319c760fa80d0099a. Part of 31819.
248 lines
6.9 KiB
Markdown
248 lines
6.9 KiB
Markdown
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## Tor's modules ##
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### Generic modules ###
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`buffers.c`
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: Implements the `buf_t` buffered data type for connections, and several
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low-level data handling functions to handle network protocols on it.
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`channel.c`
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: Generic channel implementation. Channels handle sending and receiving cells
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among tor nodes.
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`channeltls.c`
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: Channel implementation for TLS-based OR connections. Uses `connection_or.c`.
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`circuitbuild.c`
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: Code for constructing circuits and choosing their paths. (*Note*:
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this module could plausibly be split into handling the client side,
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the server side, and the path generation aspects of circuit building.)
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`circuitlist.c`
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: Code for maintaining and navigating the global list of circuits.
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`circuitmux.c`
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: Generic circuitmux implementation. A circuitmux handles deciding, for a
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particular channel, which circuit should write next.
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`circuitmux_ewma.c`
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: A circuitmux implementation based on the EWMA (exponentially
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weighted moving average) algorithm.
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`circuituse.c`
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: Code to actually send and receive data on circuits.
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`command.c`
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: Handles incoming cells on channels.
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`config.c`
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: Parses options from torrc, and uses them to configure the rest of Tor.
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`confparse.c`
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: Generic torrc-style parser. Used to parse torrc and state files.
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`connection.c`
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: Generic and common connection tools, and implementation for the simpler
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connection types.
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`connection_edge.c`
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: Implementation for entry and exit connections.
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`connection_or.c`
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: Implementation for OR connections (the ones that send cells over TLS).
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`main.c`
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: Principal entry point, main loops, scheduled events, and network
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management for Tor.
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`ntmain.c`
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: Implements Tor as a Windows service. (Not very well.)
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`onion.c`
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: Generic code for generating and responding to CREATE and CREATED
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cells, and performing the appropriate onion handshakes. Also contains
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code to manage the server-side onion queue.
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`onion_fast.c`
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: Implements the old SHA1-based CREATE_FAST/CREATED_FAST circuit
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creation handshake. (Now deprecated.)
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`onion_ntor.c`
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: Implements the Curve25519-based NTOR circuit creation handshake.
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`onion_tap.c`
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: Implements the old RSA1024/DH1024-based TAP circuit creation handshake. (Now
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deprecated.)
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`relay.c`
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: Handles particular types of relay cells, and provides code to receive,
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encrypt, route, and interpret relay cells.
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`scheduler.c`
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: Decides which channel/circuit pair is ready to receive the next cell.
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`statefile.c`
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: Handles loading and storing Tor's state file.
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`tor_main.c`
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: Contains the actual `main()` function. (This is placed in a separate
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file so that the unit tests can have their own `main()`.)
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### Node-status modules ###
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`directory.c`
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: Implements the HTTP-based directory protocol, including sending,
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receiving, and handling most request types. (*Note*: The client parts
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of this, and the generic-HTTP parts of this, could plausibly be split
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off.)
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`microdesc.c`
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: Implements the compact "microdescriptor" format for keeping track of
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what we know about a router.
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`networkstatus.c`
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: Code for fetching, storing, and interpreting consensus vote documents.
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`nodelist.c`
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: Higher-level view of our knowledge of which Tor servers exist. Each
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`node_t` corresponds to a router we know about.
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`routerlist.c`
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: Code for storing and retrieving router descriptors and extrainfo
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documents.
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`routerparse.c`
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: Generic and specific code for parsing all Tor directory information
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types.
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`routerset.c`
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: Parses and interprets a specification for a set of routers (by IP
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range, fingerprint, nickname (deprecated), or country).
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### Client modules ###
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`addressmap.c`
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: Handles client-side associations between one address and another.
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These are used to implement client-side DNS caching (NOT RECOMMENDED),
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MapAddress directives, Automapping, and more.
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`circpathbias.c`
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: Path bias attack detection for circuits: tracks whether
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connections made through a particular guard have an unusually high failure rate.
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`circuitstats.c`
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: Code to track circuit performance statistics in order to adapt our behavior.
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Notably includes an algorithm to track circuit build times.
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`dnsserv.c`
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: Implements DNSPort for clients. (Note that in spite of the word
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"server" in this module's name, it is used for Tor clients. It
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implements a DNS server, not DNS for servers.)
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`entrynodes.c`
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: Chooses, monitors, and remembers guard nodes. Also contains some
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bridge-related code.
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`torcert.c`
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: Code to interpret and generate Ed25519-based certificates.
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### Server modules ###
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`dns.c`
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: Server-side DNS code. Handles sending and receiving DNS requests on
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exit nodes, and implements the server-side DNS cache.
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`dirserv.c`
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: Implements part of directory caches that handles responding to
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client requests.
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`ext_orport.c`
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: Implements the extended ORPort protocol for communication between
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server-side pluggable transports and Tor servers.
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`hibernate.c`
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: Performs bandwidth accounting, and puts Tor relays into hibernation
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when their bandwidth is exhausted.
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`router.c`
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: Management code for running a Tor server. In charge of RSA key
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maintenance, descriptor generation and uploading.
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`routerkeys.c`
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: Key handling code for a Tor server. (Currently handles only the
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Ed25519 keys, but the RSA keys could be moved here too.)
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### Onion service modules ###
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`rendcache.c`
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: Stores onion service descriptors.
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`rendclient.c`
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: Client-side implementation of the onion service protocol.
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`rendcommon.c`
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: Parts of the onion service protocol that are shared by clients,
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services, and/or Tor servers.
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`rendmid.c`
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: Tor-server-side implementation of the onion service protocol. (Handles
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acting as an introduction point or a rendezvous point.)
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`rendservice.c`
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: Service-side implementation of the onion service protocol.
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`replaycache.c`
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: Backend to check introduce2 requests for replay attempts.
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### Authority modules ###
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`dircollate.c`
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: Helper for `dirvote.c`: Given a set of votes, each containing a list
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of Tor nodes, determines which entries across all the votes correspond
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to the same nodes, and yields them in a useful order.
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`dirvote.c`
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: Implements the directory voting algorithms that authorities use.
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`keypin.c`
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: Implements a persistent key-pinning mechanism to tie RSA1024
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identities to ed25519 identities.
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### Miscellaneous modules ###
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`control.c`
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: Implements the Tor controller protocol.
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`cpuworker.c`
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: Implements the inner work queue function. We use this to move the
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work of circuit creation (on server-side) to other CPUs.
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`fp_pair.c`
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: Types for handling 2-tuples of 20-byte fingerprints.
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`geoip.c`
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: Parses geoip files (which map IP addresses to country codes), and
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performs lookups on the internal geoip table. Also stores some
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geoip-related statistics.
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`policies.c`
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: Parses and implements Tor exit policies.
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`reasons.c`
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: Maps internal reason-codes to human-readable strings.
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`rephist.c`
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: Tracks Tor servers' performance over time.
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`status.c`
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: Writes periodic "heartbeat" status messages about the state of the Tor
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process.
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`transports.c`
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: Implements management for the pluggable transports subsystem.
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