1 files changed, 132 insertions, 0 deletions
diff --git a/lib/util/getusershell.c b/lib/util/getusershell.c
new file mode 100644
index 0000000..7912816
--- /dev/null
+++ b/lib/util/getusershell.c
@@ -0,0 +1,132 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2019-2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "sudo_compat.h"
+#include "sudo_debug.h"
+#include "sudo_gettext.h"
+#include "sudo_util.h"
+
+static char **allowed_shells, **current_shell;
+static char *default_shells[] = {
+    "/bin/sh",
+    "/bin/ksh",
+    "/bin/ksh93",
+    "/bin/bash",
+    "/bin/dash",
+    "/bin/zsh",
+    "/bin/csh",
+    "/bin/tcsh",
+    NULL
+};
+
+static char **
+read_shells(void)
+{
+    size_t maxshells = 16, nshells = 0;
+    size_t linesize = 0;
+    char *line = NULL;
+    FILE *fp;
+    debug_decl(read_shells, SUDO_DEBUG_UTIL);
+
+    if ((fp = fopen("/etc/shells", "r")) == NULL)
+	goto bad;
+
+    free(allowed_shells);
+    allowed_shells = reallocarray(NULL, maxshells, sizeof(char *));
+    if (allowed_shells == NULL)
+	goto bad;
+
+    while (sudo_parseln(&line, &linesize, NULL, fp, PARSELN_CONT_IGN) != -1) {
+	if (nshells + 1 >= maxshells) {
+	    char **new_shells;
+
+	    new_shells = reallocarray(NULL, maxshells + 16, sizeof(char *));
+	    if (new_shells == NULL)
+		goto bad;
+	    allowed_shells = new_shells;
+	    maxshells += 16;
+	}
+	if ((allowed_shells[nshells] = strdup(line)) == NULL)
+	    goto bad;
+	nshells++;
+    }
+    allowed_shells[nshells] = NULL;
+
+    free(line);
+    fclose(fp);
+    debug_return_ptr(allowed_shells);
+bad:
+    free(line);
+    if (fp != NULL)
+	fclose(fp);
+    while (nshells != 0)
+	free(allowed_shells[--nshells]);
+    free(allowed_shells);
+    allowed_shells = NULL;
+    debug_return_ptr(default_shells);
+}
+
+void
+sudo_setusershell(void)
+{
+    debug_decl(setusershell, SUDO_DEBUG_UTIL);
+
+    current_shell = read_shells();
+
+    debug_return;
+}
+
+void
+sudo_endusershell(void)
+{
+    debug_decl(endusershell, SUDO_DEBUG_UTIL);
+
+    if (allowed_shells != NULL) {
+	char **shell;
+
+	for (shell = allowed_shells; *shell != NULL; shell++)
+	    free(*shell);
+	free(allowed_shells);
+	allowed_shells = NULL;
+    }
+    current_shell = NULL;
+
+    debug_return;
+}
+
+char *
+sudo_getusershell(void)
+{
+    debug_decl(getusershell, SUDO_DEBUG_UTIL);
+
+    if (current_shell == NULL)
+	current_shell = read_shells();
+
+    debug_return_str(*current_shell++);
+}