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Merge pull request #177273 from dali99/escape-systemd

Make escapeSystemdPath implement the correct systemd escaping algorithm
This commit is contained in:
Guillaume Girol 2022-10-20 19:15:31 +00:00 committed by GitHub
commit 91a3819bad
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4 changed files with 162 additions and 5 deletions

96
lib/ascii-table.nix Normal file
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@ -0,0 +1,96 @@
{ " " = 32;
"!" = 33;
"\"" = 34;
"#" = 35;
"$" = 36;
"%" = 37;
"&" = 38;
"'" = 39;
"(" = 40;
")" = 41;
"*" = 42;
"+" = 43;
"," = 44;
"-" = 45;
"." = 46;
"/" = 47;
"0" = 48;
"1" = 49;
"2" = 50;
"3" = 51;
"4" = 52;
"5" = 53;
"6" = 54;
"7" = 55;
"8" = 56;
"9" = 57;
":" = 58;
";" = 59;
"<" = 60;
"=" = 61;
">" = 62;
"?" = 63;
"@" = 64;
"A" = 65;
"B" = 66;
"C" = 67;
"D" = 68;
"E" = 69;
"F" = 70;
"G" = 71;
"H" = 72;
"I" = 73;
"J" = 74;
"K" = 75;
"L" = 76;
"M" = 77;
"N" = 78;
"O" = 79;
"P" = 80;
"Q" = 81;
"R" = 82;
"S" = 83;
"T" = 84;
"U" = 85;
"V" = 86;
"W" = 87;
"X" = 88;
"Y" = 89;
"Z" = 90;
"[" = 91;
"\\" = 92;
"]" = 93;
"^" = 94;
"_" = 95;
"`" = 96;
"a" = 97;
"b" = 98;
"c" = 99;
"d" = 100;
"e" = 101;
"f" = 102;
"g" = 103;
"h" = 104;
"i" = 105;
"j" = 106;
"k" = 107;
"l" = 108;
"m" = 109;
"n" = 110;
"o" = 111;
"p" = 112;
"q" = 113;
"r" = 114;
"s" = 115;
"t" = 116;
"u" = 117;
"v" = 118;
"w" = 119;
"x" = 120;
"y" = 121;
"z" = 122;
"{" = 123;
"|" = 124;
"}" = 125;
"~" = 126;
}

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@ -185,6 +185,16 @@ rec {
*/
makeBinPath = makeSearchPathOutput "bin" "bin";
/* Normalize path, removing extranous /s
Type: normalizePath :: string -> string
Example:
normalizePath "/a//b///c/"
=> "/a/b/c/"
*/
normalizePath = s: (builtins.foldl' (x: y: if y == "/" && hasSuffix "/" x then x else x+y) "" (splitString "" s));
/* Depending on the boolean `cond', return either the given string
or the empty string. Useful to concatenate against a bigger string.
@ -294,6 +304,21 @@ rec {
map f (stringToCharacters s)
);
/* Convert char to ascii value, must be in printable range
Type: charToInt :: string -> int
Example:
charToInt "A"
=> 65
charToInt "("
=> 40
*/
charToInt = let
table = import ./ascii-table.nix;
in c: builtins.getAttr c table;
/* Escape occurrence of the elements of `list` in `string` by
prefixing it with a backslash.
@ -305,6 +330,19 @@ rec {
*/
escape = list: replaceChars list (map (c: "\\${c}") list);
/* Escape occurence of the element of `list` in `string` by
converting to its ASCII value and prefixing it with \\x.
Only works for printable ascii characters.
Type: escapeC = [string] -> string -> string
Example:
escapeC [" "] "foo bar"
=> "foo\\x20bar"
*/
escapeC = list: replaceChars list (map (c: "\\x${ toLower (lib.toHexString (charToInt c))}") list);
/* Quote string to be used safely within the Bourne shell.
Type: escapeShellArg :: string -> string

View file

@ -312,6 +312,21 @@ runTests {
expected = true;
};
testNormalizePath = {
expr = strings.normalizePath "//a/b//c////d/";
expected = "/a/b/c/d/";
};
testCharToInt = {
expr = strings.charToInt "A";
expected = 65;
};
testEscapeC = {
expr = strings.escapeC [ " " ] "Hello World";
expected = "Hello\\x20World";
};
# LISTS
testFilter = {

View file

@ -39,11 +39,19 @@ rec {
|| hasPrefix a'.mountPoint b'.mountPoint
|| any (hasPrefix a'.mountPoint) b'.depends;
# Escape a path according to the systemd rules, e.g. /dev/xyzzy
# becomes dev-xyzzy. FIXME: slow.
escapeSystemdPath = s:
replaceChars ["/" "-" " "] ["-" "\\x2d" "\\x20"]
(removePrefix "/" s);
# Escape a path according to the systemd rules. FIXME: slow
# The rules are described in systemd.unit(5) as follows:
# The escaping algorithm operates as follows: given a string, any "/" character is replaced by "-", and all other characters which are not ASCII alphanumerics, ":", "_" or "." are replaced by C-style "\x2d" escapes. In addition, "." is replaced with such a C-style escape when it would appear as the first character in the escaped string.
# When the input qualifies as absolute file system path, this algorithm is extended slightly: the path to the root directory "/" is encoded as single dash "-". In addition, any leading, trailing or duplicate "/" characters are removed from the string before transformation. Example: /foo//bar/baz/ becomes "foo-bar-baz".
escapeSystemdPath = s: let
replacePrefix = p: r: s: (if (hasPrefix p s) then r + (removePrefix p s) else s);
trim = s: removeSuffix "/" (removePrefix "/" s);
normalizedPath = strings.normalizePath s;
in
replaceChars ["/"] ["-"]
(replacePrefix "." (strings.escapeC ["."] ".")
(strings.escapeC (stringToCharacters " !\"#$%&'()*+,;<=>=@[\\]^`{|}~-")
(if normalizedPath == "/" then normalizedPath else trim normalizedPath)));
# Quotes an argument for use in Exec* service lines.
# systemd accepts "-quoted strings with escape sequences, toJSON produces