main3.c

DES加密解密源代码

#define DEBUG 1
/* Encrypt/decrypt with triple DES */
#include <stdio.h>
#include "des.h"
#include "md5.h"

void gethex(char *result,char *cp,int cnt);
void memxor(char *,char *,int);
int doencrypt(DES3_KS,int cbc,char iv[8],FILE *in,FILE *out);
int dodecrypt(DES3_KS,int cbc,char iv[8],FILE *in,FILE *out);

main(int argc,char *argv[])
{
	int c,cnt,encrypt,decrypt,hexflag,tripflag,md5flag,keylen,cbc;
	register int i;
	char key[24],tkey1[256],tkey2[256],iv[8],*akey,*getpass();
	MD5_CTX mdcontext;
	DES3_KS ks;
	extern char *optarg;

	keylen = 8;
	tripflag = hexflag = encrypt = decrypt = md5flag = 0;
	cbc = 1;
	akey = NULL;
	while((c = getopt(argc,argv,"53hedk:b")) != EOF){
		switch(c){
		case 'e':
			encrypt++;
			break;
		case 'd':
			decrypt++;
			break;
		case 'k':
			akey = optarg;
			break;
		case 'b':
			cbc = 0;
			break;
		}
	}
	if(encrypt == 0 && decrypt == 0){
		fprintf(stderr,"Usage: des -e|-d [-b] [-k key]\n");
		exit(2);
	}
	if(akey == NULL){
		/* No key on command line, prompt for it */
		memset(tkey1,0,sizeof(tkey1));
		memset(tkey2,0,sizeof(tkey2));
		for(;;){
			akey = getpass("Enter key: ");
			strncpy(tkey1,akey,sizeof(tkey1));
			akey = getpass("Enter key again: ");
			strncpy(tkey2,akey,sizeof(tkey2));
			if(strncmp(tkey1,tkey2,sizeof(tkey1)) != 0){
				fprintf(stderr,"Key mistyped, try again\n");
			} else
				break;
		}
		akey = tkey1;
	}
	MD5Init(&mdcontext);
	MD5Update(&mdcontext,akey,strlen(akey));
	MD5Final(&mdcontext);
	memcpy(key,mdcontext.digest,16);
	memcpy(key+16,mdcontext.digest,8);

	/* Blot out original key */
	memset(akey,0,strlen(akey));

	des3key(ks,key,!encrypt);

	/* Initialize IV to all zeros */
	memset(iv,0,8);

	return ( encrypt ? doencrypt(ks,cbc,iv,stdin,stdout)
	 : dodecrypt(ks,cbc,iv,stdin,stdout) );
}
/* Encrypt standard input to standard output */
int
doencrypt(DES3_KS ks,int cbc,char iv[8],FILE *in,FILE *out)
{
	char work[8];
	int cnt,i;

	for(;;){
		if((cnt = fread(work,1,8,in)) != 8){
			/* Put residual byte count in the last block.
			 * Note that garbage is left in the other bytes,
			 * if any; this is a feature, not a bug, since it'll
			 * be stripped out at decrypt time.
			 */
			work[7] = cnt;
		}
		if(cbc){
			/* CBC mode; chain in last cipher word */
			memxor(work,iv,8);
		}
		des3(ks,work);	/* Encrypt block */
		if(cbc){	/* Save outgoing ciphertext for chain */
			memcpy(iv,work,8);
		}
		fwrite(work,1,8,out);
		if(cnt != 8)
			break;
	}
	return 0;
}
int
dodecrypt(DES3_KS ks,int cbc,char iv[8],FILE *in,FILE *out)
{
	char work[8],nwork[8],ivtmp[8];
	int cnt,i;

	cnt = fread(work,1,8,in);	/* Prime the pump */
	for(;;){
		if(cbc){	/* Save incoming ciphertext for chain */
			memcpy(ivtmp,work,8);
		}
		des3(ks,work);
		if(cbc){	/* Unchain block, save ciphertext for next */
			memxor(work,iv,8);
			memcpy(iv,ivtmp,8);
		}
		/* Save buffer pending next read */
		memcpy(nwork,work,8);
		/* Try to read next block */
		cnt = fread(work,1,8,stdin);
		if(cnt != 8){	/* Can "only" be 0 if not 8 */
			/* Prev block was last one, write appropriate number
			 * of bytes
			 */
			cnt = nwork[7];
			if(cnt < 0 || cnt > 7){
				fprintf(stderr,"Corrupted file or wrong key\n");
			} else if(cnt != 0)
				fwrite(nwork,1,cnt,stdout);
			exit(0);
		} else {
			/* Now okay to write previous buffer */
			fwrite(nwork,1,8,out);
		}
	}
	return 0;
}
/* Convert hex/ascii nybble to binary */
int
htoa(char c)
{
	if(c >= '0' && c <= '9')
		return c - '0';
	if(c >= 'a' && c <= 'f')
		return 10 + c - 'a';
	if(c >= 'A' && c <= 'F')
		return 10 + c - 'A';
	return -1;
}
/* Convert bytes from hex/ascii to binary */
void
gethex(char *result,char *cp,int cnt)
{
	while(cnt-- != 0){
		*result = htoa(*cp++) << 4;
		*result++ |= htoa(*cp++);
	}
}
void
memxor(char *dest,char *src,int cnt)
{
	int i;

	for(i=0;i<cnt;i++)
		dest[i] ^= src[i];
}

#ifdef	DEBUG
put24(cp)
register char *cp;
{
	int i;

	for(i=0;i<24;i++){
		fprintf(stderr,"%02x ",*cp++ & 0xff);
	}
}
#endif