1 files changed, 138 insertions, 0 deletions
diff --git a/src/lib/fs/userdb.c b/src/lib/fs/userdb.c
new file mode 100644
index 0000000000..95205c670e
--- /dev/null
+++ b/src/lib/fs/userdb.c
@@ -0,0 +1,138 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file userdb.c
+ *
+ * \brief Access the POSIX user database.
+ **/
+
+#include "lib/fs/userdb.h"
+
+#ifndef _WIN32
+#include "lib/malloc/malloc.h"
+#include "lib/log/log.h"
+#include "lib/log/util_bug.h"
+
+#include <pwd.h>
+#include <stddef.h>
+#include <string.h>
+
+/** Cached struct from the last getpwname() call we did successfully. */
+static struct passwd *passwd_cached = NULL;
+
+/** Helper: copy a struct passwd object.
+ *
+ * We only copy the fields pw_uid, pw_gid, pw_name, pw_dir.  Tor doesn't use
+ * any others, and I don't want to run into incompatibilities.
+ */
+static struct passwd *
+tor_passwd_dup(const struct passwd *pw)
+{
+  struct passwd *new_pw = tor_malloc_zero(sizeof(struct passwd));
+  if (pw->pw_name)
+    new_pw->pw_name = tor_strdup(pw->pw_name);
+  if (pw->pw_dir)
+    new_pw->pw_dir = tor_strdup(pw->pw_dir);
+  new_pw->pw_uid = pw->pw_uid;
+  new_pw->pw_gid = pw->pw_gid;
+
+  return new_pw;
+}
+
+#define tor_passwd_free(pw) \
+  FREE_AND_NULL(struct passwd, tor_passwd_free_, (pw))
+
+/** Helper: free one of our cached 'struct passwd' values. */
+static void
+tor_passwd_free_(struct passwd *pw)
+{
+  if (!pw)
+    return;
+
+  tor_free(pw->pw_name);
+  tor_free(pw->pw_dir);
+  tor_free(pw);
+}
+
+/** Wrapper around getpwnam() that caches result. Used so that we don't need
+ * to give the sandbox access to /etc/passwd.
+ *
+ * The following fields alone will definitely be copied in the output: pw_uid,
+ * pw_gid, pw_name, pw_dir.  Other fields are not present in cached values.
+ *
+ * When called with a NULL argument, this function clears storage associated
+ * with static variables it uses.
+ **/
+const struct passwd *
+tor_getpwnam(const char *username)
+{
+  struct passwd *pw;
+
+  if (username == NULL) {
+    tor_passwd_free(passwd_cached);
+    passwd_cached = NULL;
+    return NULL;
+  }
+
+  if ((pw = getpwnam(username))) {
+    tor_passwd_free(passwd_cached);
+    passwd_cached = tor_passwd_dup(pw);
+    log_info(LD_GENERAL, "Caching new entry %s for %s",
+             passwd_cached->pw_name, username);
+    return pw;
+  }
+
+  /* Lookup failed */
+  if (! passwd_cached || ! passwd_cached->pw_name)
+    return NULL;
+
+  if (! strcmp(username, passwd_cached->pw_name))
+    return passwd_cached; // LCOV_EXCL_LINE - would need to make getpwnam flaky
+
+  return NULL;
+}
+
+/** Wrapper around getpwnam() that can use cached result from
+ * tor_getpwnam(). Used so that we don't need to give the sandbox access to
+ * /etc/passwd.
+ *
+ * The following fields alone will definitely be copied in the output: pw_uid,
+ * pw_gid, pw_name, pw_dir.  Other fields are not present in cached values.
+ */
+const struct passwd *
+tor_getpwuid(uid_t uid)
+{
+  struct passwd *pw;
+
+  if ((pw = getpwuid(uid))) {
+    return pw;
+  }
+
+  /* Lookup failed */
+  if (! passwd_cached)
+    return NULL;
+
+  if (uid == passwd_cached->pw_uid)
+    return passwd_cached; // LCOV_EXCL_LINE - would need to make getpwnam flaky
+
+  return NULL;
+}
+
+/** Allocate and return a string containing the home directory for the
+ * user <b>username</b>. Only works on posix-like systems. */
+char *
+get_user_homedir(const char *username)
+{
+  const struct passwd *pw;
+  tor_assert(username);
+
+  if (!(pw = tor_getpwnam(username))) {
+    log_err(LD_CONFIG,"User \"%s\" not found.", username);
+    return NULL;
+  }
+  return tor_strdup(pw->pw_dir);
+}
+#endif /* !defined(_WIN32) */