下面的程序对 2 个文件进行异或，以使用一次性密码器加密创建一个输出文件。当从外部存储源获取密钥文件时，我尝试使用mlockall以避免在硬盘驱动器上留下任何密钥文件的痕迹。
从 mlockall 手册页：
mlock() and mlockall() respectively lock part or all of the calling process's
virtual address space into RAM, preventing that memory from being paged to the
swap area.
我如何检查它是否正常工作以及我mlockall是否正确使用？
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/mman.h>
int main(int argc, char **argv)
{
struct stat statbuf;
struct stat keybuf;
char buffer [20];
int key;
int data;
int output;
int count;
char ans;
int * buf;
FILE * keyfile;
FILE * sourcefile;
FILE * destfile;
if(geteuid() !=0)
{
printf("Root access is required to run this program\n\n");
exit(0);
}
if(argc<4)
{
printf("OTP-Bunny 1.0\n");
printf("USAGE: OTP <source file> <output file> <keyfile>\n");
return (0);
}
/* Check number of arguments. */
if(argc>4)
{
printf("Too many arguments.\n");
printf("USAGE: OTP <source file> <output file> <keyfile>\n");
exit(1);
}
/* Allocate memory required by processes */
buf = (int*) malloc (sizeof(int));
if (buf == NULL)
{
perror("Error");
exit(1);
}
/* Lock down pages mapped to processes */
printf("Locking down processes\n");
if(mlockall (MCL_CURRENT | MCL_FUTURE) < 0)
{
perror("mlockall");
exit (1);
}
/* Check if sourcefile can be opened. */
if((sourcefile = fopen(argv[1], "rb"))== NULL)
{
printf("Can't open source file\n");
perror("Error");
printf("USAGE: OTP <source file> <output file> <keyfile>\n");
exit (1);
}
/* Get size of sourcefile */
fstat(fileno(sourcefile), &statbuf);
/* Check if keyfile can be opened. */
if((keyfile = fopen(argv[3], "rb"))== NULL)
{
printf("Can't open keyfile.\n");
perror("Error");
printf("USAGE: OTP <source file> <output file> <keyfile>\n");
exit(1);
}
/* Get size of keyfile */
fstat(fileno(keyfile), &keybuf);
/* Check if keyfile is the same size as, or bigger than the sourcefile */
if((keybuf.st_size) < (statbuf.st_size))
{
printf("Source file is larger than keyfile.\n");
printf("This significantly reduces cryptographic strength.\n");
printf("Do you wish to continue? (Y/N)\n");
fgets(buffer, 20, stdin);
sscanf(buffer, "%c", &ans);
if(ans == 'n' || ans == 'N')
{
exit (1);
}
if(ans == 'y' || ans == 'Y')
{
printf("Proceeding with Encryption/Decryption.\n");
}
else
{
printf("No option selected. Exiting...\n");
exit (1);
}
}
/* Check if destfile can be opened. */
if((destfile = fopen(argv[2], "wb"))== NULL)
{
printf("Can't open output file.\n");
perror("Error");
exit(1);
}
/* Encrypt/Decrypt and write to output file. */
while(count < (statbuf.st_size))
{
key=fgetc(keyfile);
data=fgetc(sourcefile);
output=(key^data);
fputc(output,destfile);
count++;
}
/* Close files. */
fclose(keyfile);
fclose(sourcefile);
fclose(destfile);
printf("Encryption/Decryption Complete.\n\n");
/* delete keyfile option. */
printf("Do you wish to delete the keyfile? (Y/N)\n");
fgets(buffer, 20, stdin);
sscanf(buffer, "%c", &ans);
if(ans == 'y' || ans == 'Y')
{
if ( remove(argv[3]) == 0)
{
printf("File deleted successfully.\n");
}
else
{
printf("Unable to delete the file.\n");
perror("Error");
exit(1);
}
}
/* cleanup */
printf("Releasing memory\n");
free (buf);
return(0);
}