diff options
Diffstat (limited to 'lib/kernel/internal_doc/distribution_handshake.txt')
| -rw-r--r-- | lib/kernel/internal_doc/distribution_handshake.txt | 40 |
1 files changed, 20 insertions, 20 deletions
diff --git a/lib/kernel/internal_doc/distribution_handshake.txt b/lib/kernel/internal_doc/distribution_handshake.txt index f64ebe0302..6a3ee22ed3 100644 --- a/lib/kernel/internal_doc/distribution_handshake.txt +++ b/lib/kernel/internal_doc/distribution_handshake.txt @@ -11,7 +11,7 @@ The TCP/IP distribution uses a handshake which expects a connection based protocol, i.e. the protocol does not include any authentication after the handshake procedure. -This is not entirelly safe, as it is vulnerable against takeover +This is not entirely safe, as it is vulnerable against takeover attacks, but it is a tradeoff between fair safety and performance. The cookies are never sent in cleartext and the handshake procedure @@ -23,7 +23,7 @@ random numbers. DEFINITIONS ----------- -A challenge is a 32 bit integer number in big endian. Below the function +A challenge is a 32 bit integer number in big endian order. Below the function gen_challenge() returns a random 32 bit integer used as a challenge. A digest is a (16 bytes) MD5 hash of [the Challenge (as text) concatenated @@ -46,19 +46,19 @@ The cookies are text strings that can be viewed as passwords. Every message in the handshake starts with a 16 bit big endian integer which contains the length of the message (not counting the two initial bytes). In erlang this corresponds to the gen_tcp option {packet, 2}. Note that after -the handshake, the distribution switches to 4 byte backet headers. +the handshake, the distribution switches to 4 byte packet headers. THE HANDSHAKE IN DETAIL ----------------------- -Imagine two nodes, node A, which initiates the handshake and node B, whitch +Imagine two nodes, node A, which initiates the handshake and node B, which accepts the connection. 1) connect/accept: A connects to B via TCP/IP and B accepts the connection. 2) send_name/receive_name: A sends an initial identification to B. B receives the message. The message looks -like this (every "square" beeing one byte and the packet header removed): +like this (every "square" being one byte and the packet header removed): +---+--------+--------+-----+-----+-----+-----+-----+-----+-...-+-----+ |'n'|Version0|Version1|Flag0|Flag1|Flag2|Flag3|Name0|Name1| ... |NameN| @@ -67,7 +67,7 @@ like this (every "square" beeing one byte and the packet header removed): The 'n' is just a message tag, Version0 & Version1 is the distribution version selected by node A, based on information from EPMD. (16 bit big endian) -Flag0 ... Flag3 is capability flags, the capabilities defined in dist.hrl. +Flag0 ... Flag3 are capability flags, the capabilities defined in dist.hrl. (32 bit big endian) Name0 ... NameN is the full nodename of A, as a string of bytes (the packet length denotes how long it is). @@ -91,9 +91,9 @@ alive: A connection to the node is already active, which either means This is the format of the status message: -+---+-------+-------+ ... +-------+ ++---+-------+-------+-...-+-------+ |'s'|Status0|Status1| ... |StatusN| -+---+-------+-------+ ... +-------+ ++---+-------+-------+-...-+-------+ 's' is the message tag Status0 ... StatusN is the status as a string (not terminated) @@ -111,35 +111,35 @@ initially sent from A to B, with the addition of a 32 bit challenge: +---+--------+--------+-----+-----+-----+-----+-----+-----+-----+-----+--- |'n'|Version0|Version1|Flag0|Flag1|Flag2|Flag3|Chal0|Chal1|Chal2|Chal3| -+---+--------+--------+-----+-----+-----+-----+-----+-----+---- +-----+--- ++---+--------+--------+-----+-----+-----+-----+-----+-----+-----+-----+--- ------+-----+-...-+-----+ Name0|Name1| ... |NameN| ------+-----+-... +-----+ -Where Chal0 ... Chal3 is the challenge as a 32 bit biog endian integer +Where Chal0 ... Chal3 is the challenge as a 32 bit big endian integer and the other fields are B's version, flags and full nodename. 5) send_challenge_reply/recv_challenge_reply: Now A has generated -a digest and it's own challenge. Those are sent together in a package +a digest and its own challenge. Those are sent together in a package to B: -+---+-----+-----+-----+-----+-----+-----+-----+-----+ -|'r'|Chal0|Chal1|Chal2|Chal3|Dige0|Dige1|Dige2|Dige3| -+---+-----+-----+-----+-----+-----+-----+---- +-----+ ++---+-----+-----+-----+-----+-----+-----+-----+-----+-...-+------+ +|'r'|Chal0|Chal1|Chal2|Chal3|Dige0|Dige1|Dige2|Dige3| ... |Dige15| ++---+-----+-----+-----+-----+-----+-----+-----+-----+-...-+------+ Where 'r' is the tag, Chal0 ... Chal3 is A's challenge for B to handle and -Dige0 ... Dige3 is the digest that A constructed from the challenge B sent +Dige0 ... Dige15 is the digest that A constructed from the challenge B sent in the previous step. 6) recv_challenge_ack/send_challenge_ack: B checks that the digest received from A is correct and generates a digest from the challenge received from A. The digest is then sent to A. The message looks like this: -+---+-----+-----+-----+-----+ -|'a'|Dige0|Dige1|Dige2|Dige3| -+---+-----+-----+---- +-----+ ++---+-----+-----+-----+-----+-...-+------+ +|'a'|Dige0|Dige1|Dige2|Dige3| ... |Dige15| ++---+-----+-----+-----+-----+-...-+------+ -Where 'a' is the tag and Dige0 ... Dige3 is the digest calculated by B +Where 'a' is the tag and Dige0 ... Dige15 is the digest calculated by B for A's challenge. 7) A checks the digest from B and the connection is up. @@ -206,7 +206,7 @@ Currently the following capability flags are defined: %% The node implements distributed process monitoring. -define(DFLAG_DIST_MONITOR,8). -%% The node uses separate tag for fun's (labmdas) in the distribution protocol. +%% The node uses separate tag for fun's (lambdas) in the distribution protocol. -define(DFLAG_FUN_TAGS,16). An R6 erlang node implements all of the above, while a C or Java node only |