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libexpr/flake: allow automatic rejection of configuration options from flakes

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The `allow-flake-configuration` option allows the user to control whether to
accept configuration options supplied by flakes. Unfortunately, setting this
to false really meant "ask each time" (with an option to remember the choice
for each specific option encountered). Let no mean no, and introduce (and
default to) a separate value for the "ask each time" behaviour.

Co-Authored-By: Jade Lovelace <lix@jade.fyi>
Change-Id: I7ccd67a95bfc92cffc1ebdc972d243f5191cc1b4
This commit is contained in:
alois31 2024-06-29 20:23:17 +02:00
parent 5dc85e8b72
commit a55112898e
Signed by untrusted user: alois31
GPG key ID: E0F59EA5E5216914
6 changed files with 107 additions and 26 deletions
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9
doc/manual/rl-next/reject-flake-config.md Normal file
View file

@ -0,0 +1,9 @@
---
synopsis: Allow automatic rejection of configuration options from flakes
cls: [1541]
credits: [alois31]
category: Improvements
---
Setting `accept-flake-config` to `false` now respects user choice by automatically rejecting configuration options set by flakes.
The old behaviour of asking each time is still available (and default) by setting it to the special value `ask`.

28
src/libexpr/flake/config.cc
View file

@ -51,8 +51,14 @@ void ConfigFile::apply()
else
assert(false);
if (!whitelist.count(baseName) && !nix::fetchSettings.acceptFlakeConfig) {
bool trusted = false;
bool trusted = whitelist.count(baseName);
if (!trusted) {
switch (nix::fetchSettings.acceptFlakeConfig) {
case AcceptFlakeConfig::True: {
trusted = true;
break;
}
case AcceptFlakeConfig::Ask: {
auto trustedList = readTrustedList();
auto tlname = get(trustedList, name);
if (auto saved = tlname ? get(*tlname, valueS) : nullptr) {
@ -60,21 +66,31 @@ void ConfigFile::apply()
printInfo("Using saved setting for '%s = %s' from ~/.local/share/nix/trusted-settings.json.", name, valueS);
} else {
// FIXME: filter ANSI escapes, newlines, \r, etc.
if (std::tolower(logger->ask(fmt("do you want to allow configuration setting '%s' to be set to '" ANSI_RED "%s" ANSI_NORMAL "' (y/N)?", name, valueS)).value_or('n')) == 'y') {
if (std::tolower(logger->ask(fmt("Do you want to allow configuration setting '%s' to be set to '" ANSI_RED "%s" ANSI_NORMAL "' (y/N)? This may allow the flake to gain root, see the nix.conf manual page.", name, valueS)).value_or('n')) == 'y') {
trusted = true;
} else {
warn("you can set '%s' to '%b' to automatically reject configuration options supplied by flakes", "accept-flake-config", false);
}
if (std::tolower(logger->ask(fmt("do you want to permanently mark this value as %s (y/N)?", trusted ? "trusted": "untrusted" )).value_or('n')) == 'y') {
trustedList[name][valueS] = trusted;
writeTrustedList(trustedList);
}
}
if (!trusted) {
warn("ignoring untrusted flake configuration setting '%s'.\nPass '%s' to trust it", name, "--accept-flake-config");
continue;
break;
}
case nix::AcceptFlakeConfig::False: {
trusted = false;
break;
};
}
}
if (trusted) {
debug("accepting trusted flake configuration setting '%s'", name);
globalConfig.set(name, valueS);
} else {
warn("ignoring untrusted flake configuration setting '%s', pass '%s' to trust it (may allow the flake to gain root, see the nix.conf manual page)", name, "--accept-flake-config");
}
}
}

43
src/libfetchers/fetch-settings.cc
View file

@ -1,7 +1,50 @@
#include "abstract-setting-to-json.hh"
#include "args.hh"
#include "config-impl.hh"
#include "fetch-settings.hh"
#include <nlohmann/json.hpp>
namespace nix {
template<> AcceptFlakeConfig BaseSetting<AcceptFlakeConfig>::parse(const std::string & str) const
{
if (str == "true") return AcceptFlakeConfig::True;
else if (str == "ask") return AcceptFlakeConfig::Ask;
else if (str == "false") return AcceptFlakeConfig::False;
else throw UsageError("option '%s' has invalid value '%s'", name, str);
}
template<> std::string BaseSetting<AcceptFlakeConfig>::to_string() const
{
if (value == AcceptFlakeConfig::True) return "true";
else if (value == AcceptFlakeConfig::Ask) return "ask";
else if (value == AcceptFlakeConfig::False) return "false";
else abort();
}
template<> void BaseSetting<AcceptFlakeConfig>::convertToArg(Args & args, const std::string & category)
{
args.addFlag({
.longName = name,
.description = "Accept Lix configuration options from flakes without confirmation. This allows flakes to gain root access to your machine if you are a trusted user; see the nix.conf manual page for more details.",
.category = category,
.handler = {[this]() { override(AcceptFlakeConfig::True); }}
});
args.addFlag({
.longName = "ask-" + name,
.description = "Ask whether to accept Lix configuration options from flakes.",
.category = category,
.handler = {[this]() { override(AcceptFlakeConfig::Ask); }}
});
args.addFlag({
.longName = "no-" + name,
.description = "Reject Lix configuration options from flakes.",
.category = category,
.handler = {[this]() { override(AcceptFlakeConfig::False); }}
});
}
FetchSettings::FetchSettings()
{
}

16
src/libfetchers/fetch-settings.hh
View file

@ -11,6 +11,8 @@
namespace nix {
enum class AcceptFlakeConfig { False, Ask, True };
struct FetchSettings : public Config
{
FetchSettings();
@ -86,15 +88,21 @@ struct FetchSettings : public Config
"Whether to use flake registries to resolve flake references.",
{}, true, Xp::Flakes};
Setting<bool> acceptFlakeConfig{this, false, "accept-flake-config",
Setting<AcceptFlakeConfig> acceptFlakeConfig{
this, AcceptFlakeConfig::Ask, "accept-flake-config",
R"(
Whether to accept Lix configuration from the `nixConfig` attribute of
a flake without prompting. This is almost always a very bad idea.
Setting this setting as a trusted user allows Nix flakes to gain root
a flake. Doing so as a trusted user allows Nix flakes to gain root
access on your machine if they set one of the several
trusted-user-only settings that execute commands as root.
If set to `true`, such configuration will be accepted without asking;
this is almost always a very bad idea. Setting this to `ask` will
prompt the user each time whether to allow a certain configuration
option set this way, and offer to optionally remember their choice.
When set to `false`, the configuration will be automatically
declined.
See [multi-user installations](@docroot@/installation/multi-user.md)
for more details on the Lix security model.
)",

4
tests/functional/experimental-features.sh
View file

@ -32,7 +32,7 @@ NIX_CONFIG='
experimental-features = nix-command
accept-flake-config = true
' nix config show accept-flake-config 1>$TEST_ROOT/stdout 2>$TEST_ROOT/stderr
grepQuiet "false" $TEST_ROOT/stdout
grepQuiet "ask" $TEST_ROOT/stdout
grepQuiet "Ignoring setting 'accept-flake-config' because experimental feature 'flakes' is not enabled" $TEST_ROOT/stderr
# 'flakes' experimental-feature is disabled after, ignore and warn
@ -40,7 +40,7 @@ NIX_CONFIG='
accept-flake-config = true
experimental-features = nix-command
' nix config show accept-flake-config 1>$TEST_ROOT/stdout 2>$TEST_ROOT/stderr
grepQuiet "false" $TEST_ROOT/stdout
grepQuiet "ask" $TEST_ROOT/stdout
grepQuiet "Ignoring setting 'accept-flake-config' because experimental feature 'flakes' is not enabled" $TEST_ROOT/stderr
# 'flakes' experimental-feature is enabled before, process

5
tests/functional/flakes/config.sh
View file

@ -28,6 +28,11 @@ nix build < /dev/null
(! [[ -f post-hook-ran ]])
clearStore
# likewise with no-accept-flake-config
nix build --no-accept-flake-config
(! [[ -f post-hook-ran ]])
clearStore
nix build --accept-flake-config
test -f post-hook-ran || fail "The post hook should have ran"