1 files changed, 105 insertions, 0 deletions
diff --git a/src/libutil/users.cc b/src/libutil/users.cc
new file mode 100644
index 000000000..a9a8a7353
--- /dev/null
+++ b/src/libutil/users.cc
@@ -0,0 +1,105 @@
+#include "environment-variables.hh"
+#include "file-system.hh"
+#include "logging.hh"
+#include "strings.hh"
+
+#include <pwd.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+namespace nix {
+
+std::string getUserName()
+{
+    auto pw = getpwuid(geteuid());
+    std::string name = pw ? pw->pw_name : getEnv("USER").value_or("");
+    if (name.empty())
+        throw Error("cannot figure out user name");
+    return name;
+}
+
+Path getHomeOf(uid_t userId)
+{
+    std::vector<char> buf(16384);
+    struct passwd pwbuf;
+    struct passwd * pw;
+    if (getpwuid_r(userId, &pwbuf, buf.data(), buf.size(), &pw) != 0
+        || !pw || !pw->pw_dir || !pw->pw_dir[0])
+        throw Error("cannot determine user's home directory");
+    return pw->pw_dir;
+}
+
+Path getHome()
+{
+    static Path homeDir = []()
+    {
+        std::optional<std::string> unownedUserHomeDir = {};
+        auto homeDir = getEnv("HOME");
+        if (homeDir) {
+            // Only use $HOME if doesn't exist or is owned by the current user.
+            struct stat st;
+            int result = stat(homeDir->c_str(), &st);
+            if (result != 0) {
+                if (errno != ENOENT) {
+                    warn("couldn't stat $HOME ('%s') for reason other than not existing ('%d'), falling back to the one defined in the 'passwd' file", *homeDir, errno);
+                    homeDir.reset();
+                }
+            } else if (st.st_uid != geteuid()) {
+                unownedUserHomeDir.swap(homeDir);
+            }
+        }
+        if (!homeDir) {
+            homeDir = getHomeOf(geteuid());
+            if (unownedUserHomeDir.has_value() && unownedUserHomeDir != homeDir) {
+                warn("$HOME ('%s') is not owned by you, falling back to the one defined in the 'passwd' file ('%s')", *unownedUserHomeDir, *homeDir);
+            }
+        }
+        return *homeDir;
+    }();
+    return homeDir;
+}
+
+
+Path getCacheDir()
+{
+    auto cacheDir = getEnv("XDG_CACHE_HOME");
+    return cacheDir ? *cacheDir : getHome() + "/.cache";
+}
+
+
+Path getConfigDir()
+{
+    auto configDir = getEnv("XDG_CONFIG_HOME");
+    return configDir ? *configDir : getHome() + "/.config";
+}
+
+std::vector<Path> getConfigDirs()
+{
+    Path configHome = getConfigDir();
+    auto configDirs = getEnv("XDG_CONFIG_DIRS").value_or("/etc/xdg");
+    std::vector<Path> result = tokenizeString<std::vector<std::string>>(configDirs, ":");
+    result.insert(result.begin(), configHome);
+    return result;
+}
+
+
+Path getDataDir()
+{
+    auto dataDir = getEnv("XDG_DATA_HOME");
+    return dataDir ? *dataDir : getHome() + "/.local/share";
+}
+
+Path getStateDir()
+{
+    auto stateDir = getEnv("XDG_STATE_HOME");
+    return stateDir ? *stateDir : getHome() + "/.local/state";
+}
+
+Path createNixStateDir()
+{
+    Path dir = getStateDir() + "/nix";
+    createDirs(dir);
+    return dir;
+}
+
+}