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gpg-agent: rewrite hash algo in Nix to avoid IFD

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oxalica 2021-11-26 03:47:45 +08:00 committed by Robert Helgesson
parent 78ff6b851c
commit 736581f113
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1 changed files with 30 additions and 9 deletions
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39
modules/services/gpg-agent.nix
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@ -21,18 +21,39 @@ let
# state, but we need the values at build time. original:
# https://github.com/gpg/gnupg/blob/c6702d77d936b3e9d91b34d8fdee9599ab94ee1b/common/homedir.c#L672-L681
gpgconf = dir:
if homedir == options.programs.gpg.homedir.default then
let
hash = substring 0 24 (hexStringToBase32 (builtins.hashString "sha1" homedir));
in if homedir == options.programs.gpg.homedir.default then
"%t/gnupg/${dir}"
else
builtins.readFile (pkgs.runCommand dir {} ''
PATH=${pkgs.xxd}/bin:$PATH
"%t/gnupg/d.${hash}/${dir}";
hash=$(echo -n ${homedir} | sha1sum -b | xxd -r -p | base32 | \
cut -c -24 | tr '[:upper:]' '[:lower:]' | \
tr abcdefghijklmnopqrstuvwxyz234567 \
ybndrfg8ejkmcpqxot1uwisza345h769)
echo -n "%t/gnupg/d.$hash/${dir}" > "$out"
'');
# Act like `xxd -r -p | base32` but with z-base-32 alphabet and no trailing padding.
# Written in Nix for purity.
hexStringToBase32 = let
mod = a: b: a - a / b * b;
pow2 = elemAt [ 1 2 4 8 16 32 64 128 256 ];
splitChars = s: init (tail (splitString "" s));
base32Alphabet = splitChars "ybndrfg8ejkmcpqxot1uwisza345h769";
hexToIntTable = listToAttrs (genList (x: { name = toLower (toHexString x); value = x; }) 16);
initState = { ret = ""; buf = 0; bufBits = 0; };
go = { ret, buf, bufBits }: hex:
let
buf' = buf * pow2 4 + hexToIntTable.${hex};
bufBits' = bufBits + 4;
extraBits = bufBits' - 5;
in if bufBits >= 5 then {
ret = ret + elemAt base32Alphabet (buf' / pow2 extraBits);
buf = mod buf' (pow2 extraBits);
bufBits = bufBits' - 5;
} else {
ret = ret;
buf = buf';
bufBits = bufBits';
};
in hexString: (foldl' go initState (splitChars hexString)).ret;
in