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-rw-r--r--src/openvpn/run_command.c288
1 files changed, 288 insertions, 0 deletions
diff --git a/src/openvpn/run_command.c b/src/openvpn/run_command.c
new file mode 100644
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--- /dev/null
+++ b/src/openvpn/run_command.c
@@ -0,0 +1,288 @@
+/*
+ * OpenVPN -- An application to securely tunnel IP networks
+ * over a single TCP/UDP port, with support for SSL/TLS-based
+ * session authentication and key exchange,
+ * packet encryption, packet authentication, and
+ * packet compression.
+ *
+ * Copyright (C) 2002-2017 OpenVPN Technologies, Inc. <sales@openvpn.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#elif defined(_MSC_VER)
+#include "config-msvc.h"
+#endif
+
+#include "syshead.h"
+
+#include "buffer.h"
+#include "error.h"
+#include "platform.h"
+#include "win32.h"
+
+#include "memdbg.h"
+
+#include "run_command.h"
+
+/* contains an SSEC_x value defined in platform.h */
+static int script_security_level = SSEC_BUILT_IN; /* GLOBAL */
+
+int
+script_security(void)
+{
+ return script_security_level;
+}
+
+void
+script_security_set(int level)
+{
+ script_security_level = level;
+}
+
+/*
+ * Generate an error message based on the status code returned by openvpn_execve().
+ */
+static const char *
+system_error_message(int stat, struct gc_arena *gc)
+{
+ struct buffer out = alloc_buf_gc(256, gc);
+
+ switch (stat)
+ {
+ case OPENVPN_EXECVE_NOT_ALLOWED:
+ buf_printf(&out, "disallowed by script-security setting");
+ break;
+
+#ifdef _WIN32
+ case OPENVPN_EXECVE_ERROR:
+ buf_printf(&out, "external program did not execute -- ");
+ /* fall through */
+
+ default:
+ buf_printf(&out, "returned error code %d", stat);
+ break;
+#else /* ifdef _WIN32 */
+
+ case OPENVPN_EXECVE_ERROR:
+ buf_printf(&out, "external program fork failed");
+ break;
+
+ default:
+ if (!WIFEXITED(stat))
+ {
+ buf_printf(&out, "external program did not exit normally");
+ }
+ else
+ {
+ const int cmd_ret = WEXITSTATUS(stat);
+ if (!cmd_ret)
+ {
+ buf_printf(&out, "external program exited normally");
+ }
+ else if (cmd_ret == OPENVPN_EXECVE_FAILURE)
+ {
+ buf_printf(&out, "could not execute external program");
+ }
+ else
+ {
+ buf_printf(&out, "external program exited with error status: %d", cmd_ret);
+ }
+ }
+ break;
+#endif /* ifdef _WIN32 */
+ }
+ return (const char *)out.data;
+}
+
+bool
+openvpn_execve_allowed(const unsigned int flags)
+{
+ if (flags & S_SCRIPT)
+ {
+ return script_security() >= SSEC_SCRIPTS;
+ }
+ else
+ {
+ return script_security() >= SSEC_BUILT_IN;
+ }
+}
+
+
+#ifndef _WIN32
+/*
+ * Run execve() inside a fork(). Designed to replicate the semantics of system() but
+ * in a safer way that doesn't require the invocation of a shell or the risks
+ * associated with formatting and parsing a command line.
+ * Returns the exit status of child, OPENVPN_EXECVE_NOT_ALLOWED if openvpn_execve_allowed()
+ * returns false, or OPENVPN_EXECVE_ERROR on other errors.
+ */
+int
+openvpn_execve(const struct argv *a, const struct env_set *es, const unsigned int flags)
+{
+ struct gc_arena gc = gc_new();
+ int ret = OPENVPN_EXECVE_ERROR;
+ static bool warn_shown = false;
+
+ if (a && a->argv[0])
+ {
+#if defined(ENABLE_FEATURE_EXECVE)
+ if (openvpn_execve_allowed(flags))
+ {
+ const char *cmd = a->argv[0];
+ char *const *argv = a->argv;
+ char *const *envp = (char *const *)make_env_array(es, true, &gc);
+ pid_t pid;
+
+ pid = fork();
+ if (pid == (pid_t)0) /* child side */
+ {
+ execve(cmd, argv, envp);
+ exit(OPENVPN_EXECVE_FAILURE);
+ }
+ else if (pid < (pid_t)0) /* fork failed */
+ {
+ msg(M_ERR, "openvpn_execve: unable to fork");
+ }
+ else /* parent side */
+ {
+ if (waitpid(pid, &ret, 0) != pid)
+ {
+ ret = OPENVPN_EXECVE_ERROR;
+ }
+ }
+ }
+ else
+ {
+ ret = OPENVPN_EXECVE_NOT_ALLOWED;
+ if (!warn_shown && (script_security() < SSEC_SCRIPTS))
+ {
+ msg(M_WARN, SCRIPT_SECURITY_WARNING);
+ warn_shown = true;
+ }
+ }
+#else /* if defined(ENABLE_FEATURE_EXECVE) */
+ msg(M_WARN, "openvpn_execve: execve function not available");
+#endif /* if defined(ENABLE_FEATURE_EXECVE) */
+ }
+ else
+ {
+ msg(M_FATAL, "openvpn_execve: called with empty argv");
+ }
+
+ gc_free(&gc);
+ return ret;
+}
+#endif /* ifndef _WIN32 */
+
+/*
+ * Wrapper around openvpn_execve
+ */
+bool
+openvpn_execve_check(const struct argv *a, const struct env_set *es, const unsigned int flags, const char *error_message)
+{
+ struct gc_arena gc = gc_new();
+ const int stat = openvpn_execve(a, es, flags);
+ int ret = false;
+
+ if (platform_system_ok(stat))
+ {
+ ret = true;
+ }
+ else
+ {
+ if (error_message)
+ {
+ msg(((flags & S_FATAL) ? M_FATAL : M_WARN), "%s: %s",
+ error_message,
+ system_error_message(stat, &gc));
+ }
+ }
+ gc_free(&gc);
+ return ret;
+}
+
+/*
+ * Run execve() inside a fork(), duping stdout. Designed to replicate the semantics of popen() but
+ * in a safer way that doesn't require the invocation of a shell or the risks
+ * associated with formatting and parsing a command line.
+ */
+int
+openvpn_popen(const struct argv *a, const struct env_set *es)
+{
+ struct gc_arena gc = gc_new();
+ int ret = -1;
+ static bool warn_shown = false;
+
+ if (a && a->argv[0])
+ {
+#if defined(ENABLE_FEATURE_EXECVE)
+ if (script_security() >= SSEC_BUILT_IN)
+ {
+ const char *cmd = a->argv[0];
+ char *const *argv = a->argv;
+ char *const *envp = (char *const *)make_env_array(es, true, &gc);
+ pid_t pid;
+ int pipe_stdout[2];
+
+ if (pipe(pipe_stdout) == 0)
+ {
+ pid = fork();
+ if (pid == (pid_t)0) /* child side */
+ {
+ close(pipe_stdout[0]); /* Close read end */
+ dup2(pipe_stdout[1],1);
+ execve(cmd, argv, envp);
+ exit(OPENVPN_EXECVE_FAILURE);
+ }
+ else if (pid > (pid_t)0) /* parent side */
+ {
+ int status = 0;
+
+ close(pipe_stdout[1]); /* Close write end */
+ waitpid(pid, &status, 0);
+ ret = pipe_stdout[0];
+ }
+ else /* fork failed */
+ {
+ close(pipe_stdout[0]);
+ close(pipe_stdout[1]);
+ msg(M_ERR, "openvpn_popen: unable to fork %s", cmd);
+ }
+ }
+ else
+ {
+ msg(M_WARN, "openvpn_popen: unable to create stdout pipe for %s", cmd);
+ ret = -1;
+ }
+ }
+ else if (!warn_shown && (script_security() < SSEC_SCRIPTS))
+ {
+ msg(M_WARN, SCRIPT_SECURITY_WARNING);
+ warn_shown = true;
+ }
+#else /* if defined(ENABLE_FEATURE_EXECVE) */
+ msg(M_WARN, "openvpn_popen: execve function not available");
+#endif /* if defined(ENABLE_FEATURE_EXECVE) */
+ }
+ else
+ {
+ msg(M_FATAL, "openvpn_popen: called with empty argv");
+ }
+
+ gc_free(&gc);
+ return ret;
+}
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