Recording commandline for shell sessions.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <fcntl.h>

static void encode(char *buffer, const char *string)
{
	while (1) {
		const unsigned char c = *(const unsigned char *) string++;
		if (!c)
			break;
		else if (c == '\\') {
			*buffer++ = '\\';
			*buffer++ = '\\';
		} else if (c > 32 && c < 127)
			*buffer++ = c;
		else {
			*buffer++ = '\\';
			*buffer++ = '0' + (c >> 6);
			*buffer++ = '0' + ((c >> 3) & 7);
			*buffer++ = '0' + (c & 7);
		}
	}
}

int main(int raw_argc, char *raw_argv[])
{
	int i;
	int argc;
	int envc;
	char *filename;
	char **argv;
	char **envp;
	{ /* Check that I'm an execute handler process.  */
		int fd = open("/proc/ccs/.execute_handler", O_RDONLY);
		close(fd);
		if (fd == EOF) {
			fprintf(stderr, "FATAL: I'm not execute_handler.\n");
			return 1;
		}
	}
	if (raw_argc < 7)
		return 1;
	filename = raw_argv[4];
	argc = atoi(raw_argv[5]);
	envc = atoi(raw_argv[6]);
	if (raw_argc != argc + envc + 7)
		return 1;
	for (i = 5; i < argc + 5; i++)
		raw_argv[i] = raw_argv[i + 2];
	raw_argv[argc + 5] = NULL;
	for (i = argc + 6; i < argc + envc + 6; i++)
		raw_argv[i] = raw_argv[i + 1];
	raw_argv[argc + envc + 6] = NULL;
	argv = raw_argv + 5;
	envp = raw_argv + argc + 6;

	{ /* Record parameters including argv[] and envp[]. */
		/* Get exlusive lock for serializing syslog(). */
		const int fd = open("/proc/self/exe", O_RDONLY);
		if (fd == EOF || flock(fd, LOCK_EX) == EOF)
			return 1;
		openlog(raw_argv[0], LOG_NDELAY, LOG_USER);
                syslog(LOG_INFO, "Domain = %s\n", raw_argv[1]);
                syslog(LOG_INFO, "Caller Program = %s\n", raw_argv[2]);
                syslog(LOG_INFO, "Process Status = %s\n", raw_argv[3]);
                syslog(LOG_INFO, "Requested Program = %s\n", filename);
                syslog(LOG_INFO, "argc=%d\n", argc);
                syslog(LOG_INFO, "envc=%d\n", envc);
		for (i = 0; i < argc; i++) {
			int max_len = strlen(argv[i]) * 4 + 128;
			int len;
			char *buffer = calloc(max_len, 1);
			if (!buffer)
				return 1;
			len = snprintf(buffer, 100, "argv[%d] = \"", i);
			encode(buffer + len, argv[i]);
			len = strlen(buffer);
			snprintf(buffer + len, max_len - len - 1, "\"");
			syslog(LOG_INFO, "%s\n", buffer);
			free(buffer);
		}
		for (i = 0; i < envc; i++) {
			int max_len = strlen(envp[i]) * 4 + 128;
			int len;
			char *buffer = calloc(max_len, 1);
			if (!buffer)
				return 1;
			len = snprintf(buffer, 100, "envp[%d] = \"", i);
			encode(buffer + len, envp[i]);
			len = strlen(buffer);
			snprintf(buffer + len, max_len - len - 1, "\"");
			syslog(LOG_INFO, "%s\n", buffer);
			free(buffer);
		}
		closelog();
		/* Release exclusive lock. */
		close(fd);
	}

	/* Execute requested program. */
	execve(filename, argv, envp);
	fprintf(stderr, "ERROR: Can't execute %s .\n", filename);
	return 1;
}