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/*
copyright : GPL
title : fakeroot
description : create a "fake" root shell, by wrapping
functions like chown, stat, etc. Useful for debian
packaging mechanism
author : joost witteveen, joostje@debian.org
*/
/*
upon startup, the fakeroot script (/usr/bin/fakeroot)
forks faked (this program), and the shell or user program that
will run with the libtricks.so.0.0 wrapper.
These tree running programs have the following tasks:
fakeroot scripot
starts the other two processes, waits for the user process to
die, and then send a SIGTERM signal to faked, causing
Faked to clear the ipc message ques.
faked
the ``main'' daemon, creates ipc message ques, and later
recieves ipc messages from the user program, maintains
fake inode<->ownership database (actually just a
lot of struct stat entries). Will clear ipc message ques
upon reciept of a SIGTERM. Will show debug output upon
reciept of a SIGUSR1 (if started with -d debug option)
user program
Any shell or other programme, run with
LD_PRELOAD=libtricks.so.0.0, and FAKEROOTKEY=ipc-key,
thus the executed commands will communicate with
faked. libtricks will wrap all file ownership etc modification
calls, and send the info to faked. Also the stat() function
is wrapped, it will first ask the database kept by faked
and report the `fake' data if available.
The following functions are currently wrapped:
getuid(), geteuid(), getgid(), getegid(),
mknod()
chown(), fchown() lchown()
chmod(), fchmod()
mkdir(),
lstat(), fstat(), stat() (actually, __xlstat, ...)
unlink(), remove(), rmdir(), rename()
comments:
I need to wrap unlink because of the following:
install -o admin foo bar
rm bar
touch bar //bar now may have the same inode:dev as old bar,
//but unless the rm was caught,
//fakeroot still has the old entry.
ls -al bar
Same goes for all other ways to remove inodes form the filesystem,
like rename(existing_file, any_file).
The communication between client (user progamme) and faked happens
with inode/dev information, not filenames. This is
needed, as the client is the only one who knows what cwd is,
so it's much easier to stat in the client. Otherwise, the daemon
needs to keep a list of client pids vs cwd, and I'd have to wrap
fork e.d., as they inherit their parent's cwd. Very compilcated.
*/
/* ipc documentation bugs: msgsnd(2): MSGMAX=4056, not 4080
(def in ./linux/msg.h, couldn't find other def in /usr/include/
*/
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/wait.h>
#include <sys/sem.h>
#include <sys/types.h>
#include <fcntl.h>
#include <ctype.h>
#include <stdio.h>
#include <time.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <set>
#include <string.h>
#include <iostream.h>
#include <signal.h>
#include "libfake.h"
#ifndef HAS_SEMUN_DEF
union semun {
int val;
struct semid_ds *buf;
u_short *array;
};
#endif
void process_chown(struct fake_msg *buf);
void process_chmod(struct fake_msg *buf);
void process_mknod(struct fake_msg *buf);
void process_stat(struct fake_msg *buf);
void process_unlink(struct fake_msg *buf);
bool operator <(const struct fakestat &a, const struct fakestat &b);
typedef void (*process_func)(struct fake_msg *);
process_func func_arr[]={process_chown,
process_chmod,
process_mknod,
process_stat,
process_unlink,
NULL};
key_t msg_key=0;
//int msg_get,msg_send, sem_id;
bool debug=false;
// our main (and only) data base, contains all inodes and other info:
bool operator <(const struct fakestat &a, const struct fakestat &b){
if(a.ino<b.ino)
return true;
else if(a.ino> b.ino)
return false;
else
return a.dev<b.dev;
};
set <struct fakestat, less<struct fakestat> > data;
/*********************************/
/* */
/* data base maintainance */
/* */
/*********************************/
void debug_stat(const struct fakestat *st){
fprintf(stderr,"dev:ino=(%lx:%li), mode=0%lo, own=(%li,%li), nlink=%li, rdev=%li\n",
st->dev,
st->ino,
st->mode,
st->uid,
st->gid,
st->nlink,
st->rdev);
}
int init_get_msg(){
return 1;
}
key_t get_ipc_key(){
return msg_key;
}
void insert_or_overwrite(set <struct fakestat, less<struct fakestat> > &data,
struct fakestat &st){
// just doing a data.insert(stat) would not update data
// of inodes that are already present (if operator compares "equal",
// stat isn't writen).
set <struct fakestat, less<struct fakestat> >::iterator i;
i=data.find(st);
if(i==data.end()){
if(debug){
fprintf(stderr,"FAKEROOT: insert_or_overwrite unknown stat:\n");
debug_stat(&st);
}
data.insert(st);
}
else
memcpy(((struct fakestat *)&(*i)),&st,sizeof(st));
}
/*void copy_stat(struct fakestat *dest, const struct stat *source){
//copy only the things we fake (i.e. "know better"), and leave
//the other info (like file size etc).
dest->st_dev =source->st_dev;
dest->st_rdev=source->st_rdev;
dest->st_ino =source->st_ino;
dest->st_uid =source->st_uid;
dest->st_gid =source->st_gid;
dest->st_mode=source->st_mode;
}
*/
/*******************************************/
/* */
/* process requests from wrapper functions */
/* */
/*******************************************/
void process_chown(struct fake_msg *buf){
struct fakestat *st;
set <struct fakestat, less<struct fakestat> >::iterator i;
if(debug){
fprintf(stderr,"FAKEROOT: chown ");
debug_stat(&buf->st);
}
i=data.find(buf->st);
if(i!=data.end()){
st=(struct fakestat *)&(*i);
/* From chown(2): If the owner or group is specified as -1,
then that ID is not changed.
Cannot put that test in libtricks, as at that point it isn't
known what the fake user/group is (so cannot specify `unchanged')
*/
if (buf->st.uid != -1)
st->uid=buf->st.uid;
if (buf->st.gid != -1)
st->gid=buf->st.gid;
}
else
st=&buf->st;
insert_or_overwrite(data,(buf->st));
}
void process_chmod(struct fake_msg *buf){
struct fakestat *st;
set <struct fakestat, less<struct fakestat> >::iterator i;
if(debug)
fprintf(stderr,"FAKEROOT: chmod, mode=%lo\n",
buf->st.mode);
i=data.find(buf->st);
if(i!=data.end()){
st=(struct fakestat *)&(*i);
st->mode = (buf->st.mode&~S_IFMT) | (st->mode&S_IFMT);
}
else{
st=&buf->st;
st->uid=0;
st->gid=0;
}
insert_or_overwrite(data,*st);
}
void process_mknod(struct fake_msg *buf){
struct fakestat *st;
set <struct fakestat, less<struct fakestat> >::iterator i;
if(debug)
fprintf(stderr,"FAKEROOT: chmod, mode=%lo\n",
buf->st.mode);
i=data.find(buf->st);
if(i!=data.end()){
st=(struct fakestat *)&(*i);
st->mode = buf->st.mode;
st->rdev = buf->st.rdev;
}
else{
st=&buf->st;
st->uid=0;
st->gid=0;
}
insert_or_overwrite(data,*st);
}
void process_stat(struct fake_msg *buf){
set <struct fakestat, less<struct fakestat> >::iterator i;
i=data.find(buf->st);
if(debug){
fprintf(stderr,"FAKEROOT: process stat oldstate=");
debug_stat(&buf->st);
}
if(i==data.end()){
if (debug)
fprintf(stderr,"FAKEROOT: (previously unknown)\n");
buf->st.uid=0;
buf->st.gid=0;
}
else{
cpyfakefake(&buf->st,&(*i));
if(debug){
fprintf(stderr,"FAKEROOT: (previously known): fake=");
debug_stat(&buf->st);
}
}
send_fakem(buf);
}
//void process_fstat(struct fake_msg *buf){
// process_stat(buf);
//}
void process_unlink(struct fake_msg *buf){
if((buf->st.nlink==1)||
(S_ISDIR(buf->st.mode)&&(buf->st.nlink==2))){
set <struct fakestat, less<struct fakestat> >::iterator i;
i=data.find(buf->st);
if(i!=data.end()){
if(debug){
fprintf(stderr,"FAKEROOT: unlink known file, old stat=");
debug_stat(&(*i));
}
data.erase(i);
}
if(data.find(buf->st)!=data.end()){
fprintf(stderr,"FAKEROOT************************************************* cannot remove stat (a \"cannot happen\")\n");
}
}
}
void debugdata(int){
set <struct fakestat, less<struct fakestat> >::iterator i;
fprintf(stderr," FAKED keeps data of %i inodes:\n",data.size());
for(i=data.begin(); i!=data.end(); i++)
debug_stat(&(*i));
}
void process_msg(struct fake_msg *buf){
func_id f;
f= buf->id;
func_arr[f]((struct fake_msg*)buf);
}
void get_msg(){
struct fake_msg buf;
int r=0;
if(debug)
fprintf(stderr,"FAKEROOT: msg=%i, key=%i\n",msg_get,msg_key);
do{
r=msgrcv(msg_get,&buf,sizeof(fake_msg),0,0);
if(debug)
fprintf(stderr,"FAKEROOT: r=%i, recieved message type=%li, message=%i\n",r,buf.mtype,buf.id);
if(r!=-1)
process_msg(&buf);
}while ((r!=-1)||(errno==EINTR));
if(debug){
perror("FAKEROOT, get_msg");
fprintf(stderr,"r=%i, EINTR=%i\n",errno,EINTR);
}
}
/***********/
/* */
/* misc */
/* */
/***********/
void cleanup(int g){
union semun sem_union;
if(debug)
fprintf(stderr, "fakeroot: clearing up message ques and semaphores,"
" signal=%i\n", g);
msgctl (msg_get, IPC_RMID,NULL);
msgctl (msg_snd, IPC_RMID,NULL);
semctl (sem_id,0,IPC_RMID,sem_union);
if(g!=-1)
exit(0);
}
/*************/
/* */
/* main */
/* */
/*************/
static long int read_intarg(char **argv){
if(!*argv){
fprintf(stderr,"%s needs numeric argument\n",*(argv-1));
exit(1);
} else{
return atoi(*argv);
}
}
int main(int /*argc*/, char **argv){
union semun sem_union;
struct sigaction sa,sa_debug;
int i;
bool justcleanup=false;
bool foreground=false;
int pid;
if(getenv(FAKEROOTKEY_ENV)){
//(I'm not sure -- maybe this can work?)
fprintf(stderr,"Please, don't run fakeroot from within fakeroot!\n");
exit(1);
}
while(*(++argv)){
if(!strcmp(*argv,"--key"))
msg_key=read_intarg(++argv);
else if(!strcmp(*argv,"--cleanup")){
msg_key=read_intarg(++argv);
justcleanup=true;
}
else if(!strcmp(*argv,"--foreground"))
foreground=true;
else if(!strcmp(*argv,"--debug"))
debug=true;
}
if(!msg_key){
srandom(time(NULL)+getpid()*33151);
while(!msg_key && (msg_key!=-1)) /* values 0 and -1 are treated
specially by libfake */
msg_key=random();
}
if(debug)
fprintf(stderr,"using %i as msg key\n",msg_key);
msg_get=msgget(msg_key,IPC_CREAT|0600);
msg_snd=msgget(msg_key+1,IPC_CREAT|0600);
sem_id=semget(msg_key+2,1,IPC_CREAT|0600);
sem_union.val=1;
semctl (sem_id,0,SETVAL,sem_union);
if((msg_get==-1)||(msg_snd==-1)||(sem_id==-1)){
perror("fakeroot, while creating message channels");
cleanup(-1);
exit(1);
}
if(debug)
fprintf(stderr,"msg_key=%i\n",msg_key);
if(justcleanup)
cleanup(0);
sa.sa_handler=cleanup;
sigemptyset(&sa.sa_mask);
sa.sa_flags=0;
// sa.sa_restorer=0;
sa_debug.sa_handler=debugdata;
sigemptyset(&sa_debug.sa_mask);
sa_debug.sa_flags=0;
// sa_debug.sa_restorer=0;
for(i=1; i< NSIG; i++){
switch (i){
case SIGKILL:
case SIGTSTP:
case SIGCONT:
break;
case SIGUSR1:
case SIGUSR2:
sigaction(i,&sa_debug,NULL);
break;
default:
sigaction(i,&sa,NULL);
break;
}
}
if(!foreground){
/* literally copied from the linux klogd code, go to background */
if ((pid=fork()) == 0){
int fl;
int num_fds = getdtablesize();
fflush(stdout);
/* This is the child closing its file descriptors. */
for (fl= 0; fl <= num_fds; ++fl)
close(fl);
setsid();
} else{
printf("%i:%i\n",msg_key,pid);
exit(0);
}
} else{
printf("%i:%i\n",msg_key,getpid());
fflush(stdout);
}
get_msg(); /* we shouldn't return from this function */
cleanup(-1); /* if we do return, try to clean up and exit with a nonzero
return status */
return 1;
}
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