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Disallow store path names that are . or .. (plus opt. -)

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As discussed in the maintainer meeting on 2024-01-29.

Mainly this is to avoid a situation where the name is parsed and
treated as a file name, mostly to protect users.
.-* and ..-* are also considered invalid because they might strip
on that separator to remove versions. Doesn't really work, but that's
what we decided, and I won't argue with it, because .-* probably
doesn't seem to have a real world application anyway.
We do still permit a 1-character name that's just "-", which still
poses a similar risk in such a situation. We can't start disallowing
trailing -, because a non-zero number of users will need it and we've
seen how annoying and painful such a change is.

What matters most is preventing a situation where . or .. can be
injected, and to just get this done.
This commit is contained in:
Robert Hensing 2024-01-30 18:37:23 +01:00
parent 8406da2877
commit f1b4663805
4 changed files with 88 additions and 2 deletions
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2
doc/manual/rl-next/leading-period.md
View File

@ -5,6 +5,6 @@ prs: 9867 9091 9095 9120 9121 9122 9130 9219 9224
---
Leading periods were allowed by accident in Nix 2.4. The Nix team has considered this to be a bug, but this behavior has since been relied on by users, leading to unnecessary difficulties.
From now on, leading periods are officially, definitively supported.
From now on, leading periods are officially, definitively supported. The names `.` and `..` are disallowed, as well as those starting with `.-` or `..-`.
Nix versions that denied leading periods are documented [in the issue](https://github.com/NixOS/nix/issues/912#issuecomment-1919583286).

7
src/libstore/path-regex.hh
View File

@ -3,6 +3,11 @@
namespace nix {
static constexpr std::string_view nameRegexStr = R"([0-9a-zA-Z\+\-\._\?=]+)";
static constexpr std::string_view nameRegexStr =
// This uses a negative lookahead: (?!\.\.?(-|$))
// - deny ".", "..", or those strings followed by '-'
// - when it's not those, start again at the start of the input and apply the next regex, which is [0-9a-zA-Z\+\-\._\?=]+
R"((?!\.\.?(-|$))[0-9a-zA-Z\+\-\._\?=]+)";
}

13
src/libstore/path.cc
View File

@ -10,6 +10,19 @@ static void checkName(std::string_view path, std::string_view name)
throw BadStorePath("store path '%s' has a name longer than %d characters",
path, StorePath::MaxPathLen);
// See nameRegexStr for the definition
if (name[0] == '.') {
// check against "." and "..", followed by end or dash
if (name.size() == 1)
throw BadStorePath("store path '%s' has invalid name '%s'", path, name);
if (name[1] == '-')
throw BadStorePath("store path '%s' has invalid name '%s': first dash-separated component must not be '%s'", path, name, ".");
if (name[1] == '.') {
if (name.size() == 2)
throw BadStorePath("store path '%s' has invalid name '%s'", path, name);
if (name[2] == '-')
throw BadStorePath("store path '%s' has invalid name '%s': first dash-separated component must not be '%s'", path, name, "..");
}
}
for (auto c : name)
if (!((c >= '0' && c <= '9')
|| (c >= 'a' && c <= 'z')

68
tests/unit/libstore/path.cc
View File

@ -39,6 +39,12 @@ TEST_DONT_PARSE(double_star, "**")
TEST_DONT_PARSE(star_first, "*,foo")
TEST_DONT_PARSE(star_second, "foo,*")
TEST_DONT_PARSE(bang, "foo!o")
TEST_DONT_PARSE(dot, ".")
TEST_DONT_PARSE(dot_dot, "..")
TEST_DONT_PARSE(dot_dot_dash, "..-1")
TEST_DONT_PARSE(dot_dash, ".-1")
TEST_DONT_PARSE(dot_dot_dash_a, "..-a")
TEST_DONT_PARSE(dot_dash_a, ".-a")
#undef TEST_DONT_PARSE
@ -63,6 +69,10 @@ TEST_DO_PARSE(period, "foo.txt")
TEST_DO_PARSE(question_mark, "foo?why")
TEST_DO_PARSE(equals_sign, "foo=foo")
TEST_DO_PARSE(dotfile, ".gitignore")
TEST_DO_PARSE(triple_dot_a, "...a")
TEST_DO_PARSE(triple_dot_1, "...1")
TEST_DO_PARSE(triple_dot_dash, "...-")
TEST_DO_PARSE(triple_dot, "...")
#undef TEST_DO_PARSE
@ -84,6 +94,64 @@ RC_GTEST_FIXTURE_PROP(
RC_ASSERT(p == store->parseStorePath(store->printStorePath(p)));
}
RC_GTEST_FIXTURE_PROP(
StorePathTest,
prop_check_regex_eq_parse,
())
{
static auto nameFuzzer =
rc::gen::container<std::string>(
rc::gen::oneOf(
// alphanum, repeated to weigh heavier
rc::gen::oneOf(
rc::gen::inRange('0', '9'),
rc::gen::inRange('a', 'z'),
rc::gen::inRange('A', 'Z')
),
// valid symbols
rc::gen::oneOf(
rc::gen::just('+'),
rc::gen::just('-'),
rc::gen::just('.'),
rc::gen::just('_'),
rc::gen::just('?'),
rc::gen::just('=')
),
// symbols for scary .- and ..- cases, repeated for weight
rc::gen::just('.'), rc::gen::just('.'),
rc::gen::just('.'), rc::gen::just('.'),
rc::gen::just('-'), rc::gen::just('-'),
// ascii symbol ranges
rc::gen::oneOf(
rc::gen::inRange(' ', '/'),
rc::gen::inRange(':', '@'),
rc::gen::inRange('[', '`'),
rc::gen::inRange('{', '~')
),
// typical whitespace
rc::gen::oneOf(
rc::gen::just(' '),
rc::gen::just('\t'),
rc::gen::just('\n'),
rc::gen::just('\r')
),
// some chance of control codes, non-ascii or other garbage we missed
rc::gen::inRange('\0', '\xff')
));
auto name = *nameFuzzer;
std::string path = store->storeDir + "/575s52sh487i0ylmbs9pvi606ljdszr0-" + name;
bool parsed = false;
try {
store->parseStorePath(path);
parsed = true;
} catch (const BadStorePath &) {
}
RC_ASSERT(parsed == std::regex_match(std::string { name }, nameRegex));
}
#endif
}