427 lines
14 KiB
C++
427 lines
14 KiB
C++
#include "globals.hh"
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#include "current-process.hh"
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#include "archive.hh"
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#include "args.hh"
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#include "users.hh"
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#include "abstract-setting-to-json.hh"
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#include "compute-levels.hh"
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#include <algorithm>
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#include <map>
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#include <mutex>
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#include <thread>
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#include <dlfcn.h>
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#include <sys/utsname.h>
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#include <nlohmann/json.hpp>
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#ifdef __GLIBC__
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# include <gnu/lib-names.h>
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# include <nss.h>
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# include <dlfcn.h>
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#endif
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#if __APPLE__
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# include "processes.hh"
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#endif
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#include "config-impl.hh"
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#ifdef __APPLE__
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#include <sys/sysctl.h>
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#endif
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namespace nix {
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/* The default location of the daemon socket, relative to nixStateDir.
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The socket is in a directory to allow you to control access to the
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Nix daemon by setting the mode/ownership of the directory
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appropriately. (This wouldn't work on the socket itself since it
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must be deleted and recreated on startup.) */
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#define DEFAULT_SOCKET_PATH "/daemon-socket/socket"
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Settings settings;
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static GlobalConfig::Register rSettings(&settings);
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Settings::Settings()
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: nixPrefix(NIX_PREFIX)
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, nixStore(canonPath(getEnvNonEmpty("NIX_STORE_DIR").value_or(getEnvNonEmpty("NIX_STORE").value_or(NIX_STORE_DIR))))
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, nixDataDir(canonPath(getEnvNonEmpty("NIX_DATA_DIR").value_or(NIX_DATA_DIR)))
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, nixLogDir(canonPath(getEnvNonEmpty("NIX_LOG_DIR").value_or(NIX_LOG_DIR)))
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, nixStateDir(canonPath(getEnvNonEmpty("NIX_STATE_DIR").value_or(NIX_STATE_DIR)))
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, nixConfDir(canonPath(getEnvNonEmpty("NIX_CONF_DIR").value_or(NIX_CONF_DIR)))
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, nixUserConfFiles(getUserConfigFiles())
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, nixBinDir(canonPath(getEnvNonEmpty("NIX_BIN_DIR").value_or(NIX_BIN_DIR)))
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, nixManDir(canonPath(NIX_MAN_DIR))
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, nixDaemonSocketFile(canonPath(getEnvNonEmpty("NIX_DAEMON_SOCKET_PATH").value_or(nixStateDir + DEFAULT_SOCKET_PATH)))
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{
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buildUsersGroup = getuid() == 0 ? "nixbld" : "";
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allowSymlinkedStore = getEnv("NIX_IGNORE_SYMLINK_STORE") == "1";
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auto sslOverride = getEnv("NIX_SSL_CERT_FILE").value_or(getEnv("SSL_CERT_FILE").value_or(""));
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if (sslOverride != "")
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caFile = sslOverride;
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/* Backwards compatibility. */
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auto s = getEnv("NIX_REMOTE_SYSTEMS");
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if (s) {
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Strings ss;
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for (auto & p : tokenizeString<Strings>(*s, ":"))
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ss.push_back("@" + p);
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builders = concatStringsSep(" ", ss);
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}
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#if defined(__linux__) && defined(SANDBOX_SHELL)
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sandboxPaths = tokenizeString<StringSet>("/bin/sh=" SANDBOX_SHELL);
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#endif
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/* chroot-like behavior from Apple's sandbox */
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#if __APPLE__
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sandboxPaths = tokenizeString<StringSet>("/System/Library/Frameworks /System/Library/PrivateFrameworks /bin/sh /bin/bash /private/tmp /private/var/tmp /usr/lib");
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allowedImpureHostPrefixes = tokenizeString<StringSet>("/System/Library /usr/lib /dev /bin/sh");
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#endif
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/* Set the build hook location
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For builds we perform a self-invocation, so Nix has to be self-aware.
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That is, it has to know where it is installed. We don't think it's sentient.
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Normally, nix is installed according to `nixBinDir`, which is set at compile time,
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but can be overridden. This makes for a great default that works even if this
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code is linked as a library into some other program whose main is not aware
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that it might need to be a build remote hook.
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However, it may not have been installed at all. For example, if it's a static build,
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there's a good chance that it has been moved out of its installation directory.
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That makes `nixBinDir` useless. Instead, we'll query the OS for the path to the
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current executable, using `getSelfExe()`.
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As a last resort, we resort to `PATH`. Hopefully we find a `nix` there that's compatible.
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If you're porting Nix to a new platform, that might be good enough for a while, but
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you'll want to improve `getSelfExe()` to work on your platform.
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*/
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std::string nixExePath = nixBinDir + "/nix";
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if (!pathExists(nixExePath)) {
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nixExePath = getSelfExe().value_or("nix");
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}
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buildHook = {
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nixExePath,
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"__build-remote",
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};
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}
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void loadConfFile()
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{
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auto applyConfigFile = [&](const Path & path) {
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try {
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std::string contents = readFile(path);
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globalConfig.applyConfig(contents, path);
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} catch (SysError &) { }
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};
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applyConfigFile(settings.nixConfDir + "/nix.conf");
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/* We only want to send overrides to the daemon, i.e. stuff from
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~/.nix/nix.conf or the command line. */
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globalConfig.resetOverridden();
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auto files = settings.nixUserConfFiles;
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for (auto file = files.rbegin(); file != files.rend(); file++) {
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applyConfigFile(*file);
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}
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auto nixConfEnv = getEnv("NIX_CONFIG");
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if (nixConfEnv.has_value()) {
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globalConfig.applyConfig(nixConfEnv.value(), "NIX_CONFIG");
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}
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}
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std::vector<Path> getUserConfigFiles()
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{
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// Use the paths specified in NIX_USER_CONF_FILES if it has been defined
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auto nixConfFiles = getEnv("NIX_USER_CONF_FILES");
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if (nixConfFiles.has_value()) {
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return tokenizeString<std::vector<std::string>>(nixConfFiles.value(), ":");
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}
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// Use the paths specified by the XDG spec
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std::vector<Path> files;
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auto dirs = getConfigDirs();
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for (auto & dir : dirs) {
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files.insert(files.end(), dir + "/nix/nix.conf");
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}
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return files;
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}
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unsigned int Settings::getDefaultCores()
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{
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const unsigned int concurrency = std::max(1U, std::thread::hardware_concurrency());
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const unsigned int maxCPU = getMaxCPU();
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if (maxCPU > 0)
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return maxCPU;
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else
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return concurrency;
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}
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#if __APPLE__
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static bool hasVirt() {
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int hasVMM;
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int hvSupport;
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size_t size;
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size = sizeof(hasVMM);
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if (sysctlbyname("kern.hv_vmm_present", &hasVMM, &size, NULL, 0) == 0) {
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if (hasVMM)
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return false;
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}
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// whether the kernel and hardware supports virt
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size = sizeof(hvSupport);
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if (sysctlbyname("kern.hv_support", &hvSupport, &size, NULL, 0) == 0) {
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return hvSupport == 1;
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} else {
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return false;
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}
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}
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#endif
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StringSet Settings::getDefaultSystemFeatures()
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{
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/* For backwards compatibility, accept some "features" that are
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used in Nixpkgs to route builds to certain machines but don't
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actually require anything special on the machines. */
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StringSet features{"nixos-test", "benchmark", "big-parallel"};
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#if __linux__
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features.insert("uid-range");
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#endif
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#if __linux__
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if (access("/dev/kvm", R_OK | W_OK) == 0)
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features.insert("kvm");
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#endif
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#if __APPLE__
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if (hasVirt())
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features.insert("apple-virt");
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#endif
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return features;
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}
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StringSet Settings::getDefaultExtraPlatforms()
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{
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StringSet extraPlatforms;
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if (std::string{SYSTEM} == "x86_64-linux" && !isWSL1())
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extraPlatforms.insert("i686-linux");
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#if __linux__
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StringSet levels = computeLevels();
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for (auto iter = levels.begin(); iter != levels.end(); ++iter)
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extraPlatforms.insert(*iter + "-linux");
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#elif __APPLE__
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// Rosetta 2 emulation layer can run x86_64 binaries on aarch64
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// machines. Note that we can’t force processes from executing
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// x86_64 in aarch64 environments or vice versa since they can
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// always exec with their own binary preferences.
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if (std::string{SYSTEM} == "aarch64-darwin" &&
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runProgram(RunOptions {.program = "arch", .args = {"-arch", "x86_64", "/usr/bin/true"}, .mergeStderrToStdout = true}).first == 0)
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extraPlatforms.insert("x86_64-darwin");
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#endif
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return extraPlatforms;
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}
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bool Settings::isWSL1()
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{
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struct utsname utsbuf;
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uname(&utsbuf);
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// WSL1 uses -Microsoft suffix
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// WSL2 uses -microsoft-standard suffix
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return hasSuffix(utsbuf.release, "-Microsoft");
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}
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Path Settings::getDefaultSSLCertFile()
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{
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for (auto & fn : {"/etc/ssl/certs/ca-certificates.crt", "/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt"})
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if (pathAccessible(fn)) return fn;
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return "";
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}
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const std::string nixVersion = PACKAGE_VERSION;
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NLOHMANN_JSON_SERIALIZE_ENUM(SandboxMode, {
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{SandboxMode::smEnabled, true},
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{SandboxMode::smRelaxed, "relaxed"},
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{SandboxMode::smDisabled, false},
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});
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template<> SandboxMode BaseSetting<SandboxMode>::parse(const std::string & str) const
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{
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if (str == "true") return smEnabled;
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else if (str == "relaxed") return smRelaxed;
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else if (str == "false") return smDisabled;
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else throw UsageError("option '%s' has invalid value '%s'", name, str);
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}
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template<> struct BaseSetting<SandboxMode>::trait
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{
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static constexpr bool appendable = false;
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};
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template<> std::string BaseSetting<SandboxMode>::to_string() const
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{
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if (value == smEnabled) return "true";
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else if (value == smRelaxed) return "relaxed";
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else if (value == smDisabled) return "false";
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else abort();
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}
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template<> void BaseSetting<SandboxMode>::convertToArg(Args & args, const std::string & category)
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{
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args.addFlag({
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.longName = name,
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.description = "Enable sandboxing.",
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.category = category,
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.handler = {[this]() { override(smEnabled); }}
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});
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args.addFlag({
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.longName = "no-" + name,
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.description = "Disable sandboxing.",
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.category = category,
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.handler = {[this]() { override(smDisabled); }}
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});
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args.addFlag({
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.longName = "relaxed-" + name,
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.description = "Enable sandboxing, but allow builds to disable it.",
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.category = category,
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.handler = {[this]() { override(smRelaxed); }}
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});
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}
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unsigned int MaxBuildJobsSetting::parse(const std::string & str) const
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{
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if (str == "auto") return std::max(1U, std::thread::hardware_concurrency());
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else {
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if (auto n = string2Int<decltype(value)>(str))
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return *n;
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else
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throw UsageError("configuration setting '%s' should be 'auto' or an integer", name);
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}
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}
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Paths PluginFilesSetting::parse(const std::string & str) const
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{
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if (pluginsLoaded)
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throw UsageError("plugin-files set after plugins were loaded, you may need to move the flag before the subcommand");
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return BaseSetting<Paths>::parse(str);
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}
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void initPlugins()
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{
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assert(!settings.pluginFiles.pluginsLoaded);
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for (const auto & pluginFile : settings.pluginFiles.get()) {
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Paths pluginFiles;
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try {
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auto ents = readDirectory(pluginFile);
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for (const auto & ent : ents)
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pluginFiles.emplace_back(pluginFile + "/" + ent.name);
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} catch (SysError & e) {
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if (e.errNo != ENOTDIR)
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throw;
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pluginFiles.emplace_back(pluginFile);
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}
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for (const auto & file : pluginFiles) {
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/* handle is purposefully leaked as there may be state in the
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DSO needed by the action of the plugin. */
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void *handle =
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dlopen(file.c_str(), RTLD_LAZY | RTLD_LOCAL);
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if (!handle)
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throw Error("could not dynamically open plugin file '%s': %s", file, dlerror());
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}
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}
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/* Since plugins can add settings, try to re-apply previously
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unknown settings. */
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globalConfig.reapplyUnknownSettings();
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globalConfig.warnUnknownSettings();
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/* Tell the user if they try to set plugin-files after we've already loaded */
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settings.pluginFiles.pluginsLoaded = true;
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}
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static void preloadNSS()
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{
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/* builtin:fetchurl can trigger a DNS lookup, which with glibc can trigger a dynamic library load of
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one of the glibc NSS libraries in a sandboxed child, which will fail unless the library's already
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been loaded in the parent. So we force a lookup of an invalid domain to force the NSS machinery to
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load its lookup libraries in the parent before any child gets a chance to. */
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static std::once_flag dns_resolve_flag;
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std::call_once(dns_resolve_flag, []() {
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#ifdef __GLIBC__
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/* On linux, glibc will run every lookup through the nss layer.
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* That means every lookup goes, by default, through nscd, which acts as a local
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* cache.
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* Because we run builds in a sandbox, we also remove access to nscd otherwise
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* lookups would leak into the sandbox.
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*
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* But now we have a new problem, we need to make sure the nss_dns backend that
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* does the dns lookups when nscd is not available is loaded or available.
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*
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* We can't make it available without leaking nix's environment, so instead we'll
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* load the backend, and configure nss so it does not try to run dns lookups
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* through nscd.
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*
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* This is technically only used for builtins:fetch* functions so we only care
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* about dns.
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*
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* All other platforms are unaffected.
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*/
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if (!dlopen(LIBNSS_DNS_SO, RTLD_NOW))
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warn("unable to load nss_dns backend");
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// FIXME: get hosts entry from nsswitch.conf.
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__nss_configure_lookup("hosts", "files dns");
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#endif
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});
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}
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static bool initLibStoreDone = false;
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void assertLibStoreInitialized() {
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if (!initLibStoreDone) {
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printError("The program must call nix::initNix() before calling any libstore library functions.");
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abort();
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};
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}
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void initLibStore() {
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initLibUtil();
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loadConfFile();
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preloadNSS();
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/* On macOS, don't use the per-session TMPDIR (as set e.g. by
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sshd). This breaks build users because they don't have access
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to the TMPDIR, in particular in ‘nix-store --serve’. */
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#if __APPLE__
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if (hasPrefix(getEnv("TMPDIR").value_or("/tmp"), "/var/folders/"))
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unsetenv("TMPDIR");
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#endif
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initLibStoreDone = true;
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}
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}
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