process: Provide an abstraction to spawn child processes with redirected I/O

src/libstrongswan/utils/process.c

@@ -0,0 +1,232 @@
+/*
+ * Copyright (C) 2014 Martin Willi
+ * Copyright (C) 2014 revosec AG
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ */
+
+#include "process.h"
+
+#include <utils/debug.h>
+
+#include <fcntl.h>
+
+typedef struct private_process_t private_process_t;
+
+/**
+ * Ends of a pipe()
+ */
+enum {
+	PIPE_READ = 0,
+	PIPE_WRITE = 1,
+	PIPE_ENDS,
+};
+
+#ifndef WIN32
+
+#include <unistd.h>
+#include <errno.h>
+#include <sys/wait.h>
+
+/**
+ * Private data of an process_t object.
+ */
+struct private_process_t {
+
+	/**
+	 * Public process_t interface.
+	 */
+	process_t public;
+
+	/**
+	 * child stdin pipe
+	 */
+	int in[PIPE_ENDS];
+
+	/**
+	 * child stdout pipe
+	 */
+	int out[PIPE_ENDS];
+
+	/**
+	 * child stderr pipe
+	 */
+	int err[PIPE_ENDS];
+
+	/**
+	 * child process
+	 */
+	int pid;
+};
+
+/**
+ * Close a file descriptor if it is not -1
+ */
+static void close_if(int *fd)
+{
+	if (*fd != -1)
+	{
+		close(*fd);
+		*fd = -1;
+	}
+}
+
+/**
+ * Destroy a process structure, close all pipes
+ */
+static void process_destroy(private_process_t *this)
+{
+	close_if(&this->in[PIPE_READ]);
+	close_if(&this->in[PIPE_WRITE]);
+	close_if(&this->out[PIPE_READ]);
+	close_if(&this->out[PIPE_WRITE]);
+	close_if(&this->err[PIPE_READ]);
+	close_if(&this->err[PIPE_WRITE]);
+	free(this);
+}
+
+METHOD(process_t, wait_, bool,
+	private_process_t *this, int *code)
+{
+	int status, ret;
+
+	ret = waitpid(this->pid, &status, 0);
+	process_destroy(this);
+	if (ret == -1)
+	{
+		return FALSE;
+	}
+	if (!WIFEXITED(status))
+	{
+		return FALSE;
+	}
+	if (code)
+	{
+		*code = WEXITSTATUS(status);
+	}
+	return TRUE;
+}
+
+/**
+ * See header
+ */
+process_t* process_start(char *const argv[], char *const envp[],
+						 int *in, int *out, int *err, bool close_all)
+{
+	private_process_t *this;
+	char *empty[] = { NULL };
+
+	INIT(this,
+		.public = {
+			.wait = _wait_,
+		},
+		.in = { -1, -1 },
+		.out = { -1, -1 },
+		.err = { -1, -1 },
+	);
+
+	if (in && pipe(this->in) != 0)
+	{
+		DBG1(DBG_LIB, "creating stdin pipe failed: %s", strerror(errno));
+		process_destroy(this);
+		return NULL;
+	}
+	if (out && pipe(this->out) != 0)
+	{
+		DBG1(DBG_LIB, "creating stdout pipe failed: %s", strerror(errno));
+		process_destroy(this);
+		return NULL;
+	}
+	if (err && pipe(this->err) != 0)
+	{
+		DBG1(DBG_LIB, "creating stderr pipe failed: %s", strerror(errno));
+		process_destroy(this);
+		return NULL;
+	}
+
+	this->pid = fork();
+	switch (this->pid)
+	{
+		case -1:
+			DBG1(DBG_LIB, "forking process failed: %s", strerror(errno));
+			process_destroy(this);
+			return NULL;
+		case 0:
+			/* child */
+			close_if(&this->in[PIPE_WRITE]);
+			close_if(&this->out[PIPE_READ]);
+			close_if(&this->err[PIPE_READ]);
+			if (this->in[PIPE_READ] != -1)
+			{
+				if (dup2(this->in[PIPE_READ], 0) == -1)
+				{
+					raise(SIGKILL);
+				}
+			}
+			if (this->out[PIPE_WRITE] != -1)
+			{
+				if (dup2(this->out[PIPE_WRITE], 1) == -1)
+				{
+					raise(SIGKILL);
+				}
+			}
+			if (this->err[PIPE_WRITE] != -1)
+			{
+				if (dup2(this->err[PIPE_WRITE], 2) == -1)
+				{
+					raise(SIGKILL);
+				}
+			}
+			if (close_all)
+			{
+				closefrom(3);
+			}
+			if (execve(argv[0], argv, envp ?: empty) == -1)
+			{
+				raise(SIGKILL);
+			}
+			/* not reached */
+		default:
+			/* parent */
+			close_if(&this->in[PIPE_READ]);
+			close_if(&this->out[PIPE_WRITE]);
+			close_if(&this->err[PIPE_WRITE]);
+			if (in)
+			{
+				*in = this->in[PIPE_WRITE];
+				this->in[PIPE_WRITE] = -1;
+			}
+			if (out)
+			{
+				*out = this->out[PIPE_READ];
+				this->out[PIPE_READ] = -1;
+			}
+			if (err)
+			{
+				*err = this->err[PIPE_READ];
+				this->err[PIPE_READ] = -1;
+			}
+			return &this->public;
+	}
+}
+
+#else /* WIN32 */
+
+/**
+ * See header
+ */
+process_t* process_start(char *const argv[], char *const envp[],
+						 int *in, int *out, int *err, bool close_all)
+{
+	return NULL;
+}
+
+#endif /* WIN32 */