Added the initial file (the gznbd.c example) which I will start hacking on. Also
a Makefile.
This commit is contained in:
Adam Cozzette
commit
eee7d112bf
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@ -0,0 +1,18 @@
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TARGET := abuse
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OBJS := $(TARGET:=.o)
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CC := /usr/bin/gcc
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CFLAGS := -g -pedantic -Wall -Wextra -I$(HOME)/local/include -I$(HOME)/src/nbd
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LDFLAGS := -lz
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.PHONY: all clean
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all: $(TARGET)
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$(TARGET): %: %.o
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$(CC) $(LDFLAGS) -o $@ $<
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$(OBJS): %.o: %.c
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$(CC) $(CFLAGS) -o $@ -c $<
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clean:
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rm -f $(TARGET) $(OBJS)
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@ -0,0 +1,241 @@
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/*
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(c) Marc Welz 2000, released under GPL, tested under Linux 2.2.17
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Most of the stuff cribbed from the nbd package written by Pavel Machek
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Unfortunately quite slow since zlib has to decompress all the stuff between
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seeks, so only suited to smaller files
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Could be a neat way to do userland encryption/steganography if you have
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a crypto library which has a stdiolike interface to replace zlib
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Usage
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dd if=/dev/zero of=/tmp/image bs=1024 count=1024
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mke2fs -f /tmp/image
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mount -o loop /tmp/image /mnt/
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cp /bin/ls /mnt/
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umount /mnt
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sync
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gzip -9 /tmp/image
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gznbd /dev/nbd0 /tmp/image.gz
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gznbd does not background, from another terminal type
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mount -o ro,nocheck /dev/nbd0 /mnt/
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cd /mnt
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ls
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df
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ro is important, since writes will fail horribly and nochecks
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speeds the mount up nicely
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <zlib.h>
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#include <errno.h>
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#include <string.h>
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#include <fcntl.h>
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#include <syslog.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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/* asm/types defines __u??, at least on my system */
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#include <asm/types.h>
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#define MY_NAME "gznbd"
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/* these headers take care of endianness */
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#include "config.h"
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#include "cliserv.h"
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#define BLOCK 1024
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/* don't ask me why this value, I only copied it */
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#define CHUNK BLOCK*20
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int main(int argc, char **argv)
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{
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int pr[2];
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int sk;
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int nbd;
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gzFile *gz;
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int gzerr;
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char chunk[CHUNK];
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struct nbd_request request;
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struct nbd_reply reply;
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u64 size;
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u64 from;
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u32 len;
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if(argc<3){
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printf("Usage: %s nbdevice gzfile [size]\n",argv[0]);
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exit(1);
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}
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gz=gzopen(argv[2], "rb");
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if(gz==NULL){
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fprintf(stderr,"%s: unable open compressed file %s\n",argv[0],argv[2]);
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exit(1);
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}
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if(argc>3){
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size=atol(argv[3]);
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if((size==0)||(size%BLOCK)){
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fprintf(stderr,"%s: %s does not appear to be a valid size\n",argv[0],argv[3]);
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exit(1);
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}
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printf("%s: file=%s, size=%Ld\n",argv[0],argv[2],size);
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} else {
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char buffer[BLOCK];
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int result;
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size=0;
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printf("%s: file=%s, seeking, ",argv[0],argv[2]);
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fflush(stdout);
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/* expensive seek to get file size */
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while(BLOCK==(result=gzread(gz,buffer,BLOCK))){
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size+=BLOCK;
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}
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if(result==0){
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printf("size=%Ld\n",size);
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} else {
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printf("failed\n");
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if(result<0){
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fprintf(stderr,"%s: read failed: %s\n",argv[0],gzerror(gz,&gzerr));
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} else {
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fprintf(stderr,"%s: incomplete last read, file has to be a multiple of %d\n",argv[0],BLOCK);
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}
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exit(1);
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}
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if(gzrewind(gz)!=0){
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fprintf(stderr,"%s: unable to rewind gzfile\n",argv[0]);
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exit(1);
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}
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}
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if(socketpair(AF_UNIX, SOCK_STREAM, 0, pr)){
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fprintf(stderr,"%s: unable to create socketpair: %s\n",argv[0],strerror(errno));
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exit(1);
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}
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switch(fork()){
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case -1 :
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fprintf(stderr,"%s: unable to fork: %s\n",argv[0],strerror(errno));
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exit(1);
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break;
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case 0 : /* child */
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gzclose(gz);
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close(pr[0]);
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sk=pr[1];
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nbd=open(argv[1], O_RDWR);
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if(nbd<0){
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fprintf(stderr,"%s: unable to open %s: %s\n",argv[0],argv[1],strerror(errno));
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exit(1);
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}
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if(ioctl(nbd,NBD_SET_SIZE,size)<0){
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fprintf(stderr,"%s: failed to set size for %s: %s\n",argv[0],argv[1],strerror(errno));
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exit(1);
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}
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ioctl(nbd, NBD_CLEAR_SOCK);
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if(ioctl(nbd,NBD_SET_SOCK,sk)<0){
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fprintf(stderr,"%s: failed to set socket for %s: %s\n",argv[0],argv[1],strerror(errno));
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exit(1);
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}
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if(ioctl(nbd,NBD_DO_IT)<0){
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fprintf(stderr,"%s: block device %s terminated: %s\n",argv[0],argv[1],strerror(errno));
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}
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ioctl(nbd, NBD_CLEAR_QUE);
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ioctl(nbd, NBD_CLEAR_SOCK);
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exit(0);
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break;
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}
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/* only parent here, child always exits */
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close(pr[1]);
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sk=pr[0];
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reply.magic=htonl(NBD_REPLY_MAGIC);
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reply.error=htonl(0);
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while(1){
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if(read(sk,&request,sizeof(request))!=sizeof(request)){
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fprintf(stderr,"%s: incomplete request\n",argv[0]);
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}
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memcpy(reply.handle,request.handle,sizeof(reply.handle));
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len=ntohl(request.len);
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from=ntohll(request.from);
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#ifdef TRACE
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fprintf(stderr,"%s: len=%d, from=%Ld\n",argv[0],len,from);
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#endif
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if(request.magic!=htonl(NBD_REQUEST_MAGIC)){
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fprintf(stderr,"%s: bad magic\n",argv[0]);
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reply.error=htonl(EIO); /* is that the right way of doing things ? */
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}
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if(ntohl(request.type)){
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fprintf(stderr,"%s: unsupported write request\n",argv[0]);
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reply.error=htonl(EROFS);
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}
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if(len+sizeof(struct nbd_reply)>CHUNK){
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fprintf(stderr,"%s: request too long\n",argv[0]);
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reply.error=htonl(EIO);
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}
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if(len+from>size){
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fprintf(stderr,"%s: request outside range\n",argv[0]);
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reply.error=htonl(EIO);
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}
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if(reply.error==htonl(0)){
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gzseek(gz,from,0);
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if(gzread(gz,chunk+sizeof(struct nbd_reply),len)!=len){
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fprintf(stderr,"%s: unable to read\n",argv[0]);
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reply.error=htonl(EIO);
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len=0;
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}
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} else {
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len=0;
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}
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memcpy(chunk,&reply,sizeof(struct nbd_reply));
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if(write(sk,chunk,len+sizeof(struct nbd_reply))!=(len+sizeof(struct nbd_reply))){
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fprintf(stderr,"%s: write failed: %s\n",argv[0],strerror(errno));
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}
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}
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gzclose(gz);
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return 0;
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}
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