From: Brian Warner Date: Sat, 3 Nov 2007 05:28:07 +0000 (-0700) Subject: mutable.txt: need offset of EOF too X-Git-Tag: allmydata-tahoe-0.7.0~293 X-Git-Url: https://git.rkrishnan.org/install.html?a=commitdiff_plain;h=70bd92f24dbea1b8eb8e9456160b7f0b5c27962b;p=tahoe-lafs%2Ftahoe-lafs.git mutable.txt: need offset of EOF too --- diff --git a/docs/mutable.txt b/docs/mutable.txt index a71945ea..f1cc6c28 100644 --- a/docs/mutable.txt +++ b/docs/mutable.txt @@ -370,6 +370,10 @@ steps will be implemented in a separate class in allmydata/mutable.py . This SMDF data lives inside a server-side MutableSlot container. The server is oblivious to this format. +This data is tightly packed. In particular, the share data is defined to run +all the way to the beginning of the encrypted private key (the encprivkey +offset is used both to terminate the share data and to begin the encprivkey). + # offset size name 1 0 1 version byte, \x00 for this format 2 1 8 sequence number. 2^64-1 must be handled specially, TBD @@ -378,25 +382,26 @@ is oblivious to this format. 41 1 k 42 1 N 43 8 segment size - 51 8 data length - 5 59 32 offset table: - 91 4 (7) signature - 95 4 (8) share hash chain - 99 4 (9) block hash tree - 103 4 (10) IV - 107 4 (11) share data - 111 8 (12) encrypted private key - TODO: (13) end of file - 6 119 256 verification key (2048 RSA key 'n' value, e=3) - 7 375 256 signature= RSAenc(sig-key, H(version+seqnum+r+encparm)) - 8 631 (a) share hash chain, encoded as: + 51 8 data length (of original plaintext) + 5 59 36 offset table: + 59 4 (7) signature + 63 4 (8) share hash chain + 67 4 (9) block hash tree + 71 4 (10) IV + 75 4 (11) share data + 79 8 (12) encrypted private key + 87 8 (13) EOF + 6 95 256 verification key (2048 RSA key 'n' value, e=3) + 7 361 256 signature= RSAenc(sig-key, H(version+seqnum+r+encparm)) + 8 607 (a) share hash chain, encoded as: "".join([pack(">H32s", shnum, hash) for (shnum,hash) in needed_hashes]) 9 ?? (b) block hash tree, encoded as: "".join([pack(">32s",hash) for hash in block_hash_tree]) 10 ?? 16 IV (share data is AES(H(readkey+IV)) ) -11 ?? LEN share data +11 ?? LEN share data (no gap between this and encprivkey) 12 ?? 256 encrypted private key= AESenc(write-key, RSA 'd' value) +13 ?? -- EOF (a) The share hash chain contains ceil(log(N)) hashes, each 32 bytes long. This is the set of hashes necessary to validate this share's leaf in the