From 141289f14b38ee26f52cf8c74cdfd5c9ac488f6b Mon Sep 17 00:00:00 2001
From: Nicolas Williams <nico@twosigma.com>
Date: Wed, 25 Sep 2019 17:49:56 -0500
Subject: [PATCH] roken: add roken_get_loginname()

---
 lib/roken/getuserinfo.c      | 53 +++++++++++++++---------------------
 lib/roken/roken.h.in         |  2 ++
 lib/roken/test-getuserinfo.c |  1 +
 lib/roken/version-script.map |  1 +
 4 files changed, 26 insertions(+), 31 deletions(-)

diff --git a/lib/roken/getuserinfo.c b/lib/roken/getuserinfo.c
index aab9914f5..f59abb4e8 100644
--- a/lib/roken/getuserinfo.c
+++ b/lib/roken/getuserinfo.c
@@ -213,6 +213,10 @@ roken_get_appdatadir(char *appdata, size_t appdatasz)
 /**
  * Return a bare username.  This is used for, e.g., constructing default
  * principal names.
+ *
+ * On POSIX systems, if the caller is not set-uid-like, then this will return
+ * the value of the USER or LOGNAME environment variables (in that order of
+ * preference), else the username found by looking up the effective UID.
  */
 ROKEN_LIB_FUNCTION char * ROKEN_LIB_CALL
 roken_get_username(char *user, size_t usersz)
@@ -253,37 +257,6 @@ roken_get_username(char *user, size_t usersz)
 #else
     size_t buflen = 2048;
 
-    if (issuid())
-        return NULL;
-
-    if (getuid() == 0) {
-        /*
-         * NOTE: When the running process was not the result of executing a
-         * set-uid or set-gid executable, and it is running as root, then the
-         * username will preferentially be taken from the wtmp if at all
-         * possible.  This is depended on by _krb5_get_default_principal_local()
-         * in order to produce <username>/root@DEFAULT_REALM as the default
-         * principal.
-         */
-#ifdef HAVE_GETLOGIN_R
-        if ((errno = getlogin_r(user, usersz)) == 0)
-            return user;
-        if (errno != ENOENT)
-            return NULL;
-#else
-#ifdef HAVE_GETLOGIN
-        if ((p = getlogin()) != NULL && p[0] != '\0') {
-            if strlcpy(user, p, usersz) < usersz)
-                return user;
-            errno = ERANGE;
-            return NULL;
-        }
-        if (errno != ENOENT)
-            return NULL;
-#endif
-#endif
-    }
-
     p = secure_getenv("USER");
     if (p == NULL || p[0] == '\0')
         p = secure_getenv("LOGNAME");
@@ -312,6 +285,24 @@ roken_get_username(char *user, size_t usersz)
         }
     }
 #endif
+#endif
+    errno = 0;
+    return NULL;
+}
+
+/**
+ * Return a bare username.  This is used for, e.g., constructing default
+ * principal names.
+ *
+ * On POSIX systems this returns the name recorded in the system as currently
+ * logged in on the current terminal.
+ */
+ROKEN_LIB_FUNCTION char * ROKEN_LIB_CALL
+roken_get_loginname(char *user, size_t usersz)
+{
+#ifdef WIN32
+    return roken_get_username(user, usersz);
+#else
 #ifdef HAVE_GETLOGIN_R
     if ((errno = getlogin_r(user, usersz)) == 0)
         return user;
diff --git a/lib/roken/roken.h.in b/lib/roken/roken.h.in
index 2ba9dea83..729caabeb 100644
--- a/lib/roken/roken.h.in
+++ b/lib/roken/roken.h.in
@@ -1036,6 +1036,8 @@ roken_get_appdatadir(char *, size_t);
 ROKEN_LIB_FUNCTION char * ROKEN_LIB_CALL
 roken_get_username(char *, size_t);
 ROKEN_LIB_FUNCTION char * ROKEN_LIB_CALL
+roken_get_loginname(char *, size_t);
+ROKEN_LIB_FUNCTION char * ROKEN_LIB_CALL
 roken_get_shell(char *, size_t);
 
 #ifndef HAVE_STRFTIME
diff --git a/lib/roken/test-getuserinfo.c b/lib/roken/test-getuserinfo.c
index 053b24c9f..55a46a095 100644
--- a/lib/roken/test-getuserinfo.c
+++ b/lib/roken/test-getuserinfo.c
@@ -69,6 +69,7 @@ main(void)
     }
 #endif
     printf("Username:\t%s\n", roken_get_username(buf, sizeof(buf)));
+    printf("Loginname:\t%s\n", roken_get_loginname(buf, sizeof(buf)));
     printf("Home:\t\t%s\n", roken_get_homedir(buf, sizeof(buf)));
     printf("Appdatadir:\t%s\n", roken_get_appdatadir(buf, sizeof(buf)));
     printf("Shell:\t\t%s\n", roken_get_shell(buf, sizeof(buf)));
diff --git a/lib/roken/version-script.map b/lib/roken/version-script.map
index 45505d0bf..8f7e57ec2 100644
--- a/lib/roken/version-script.map
+++ b/lib/roken/version-script.map
@@ -182,6 +182,7 @@ HEIMDAL_ROKEN_2.0 {
 		roken_get_homedir;
 		roken_get_shell;
 		roken_get_username;
+		roken_get_loginname;
 		roken_mconcat;
 		roken_vconcat;
 		roken_vmconcat;