www.pudn.com > tftp001.rar > TFTPD.C
#include
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#include "tftpdfunc.h"
#define TLMEOUT 4
struct transfer;
static void tftp(struct tftphdr*tp,int size);
static void snderr(int error);
static void sndfile(struct transfer *pf);
static void recvfile(struct transfer*pf);
static int check_file(const char*,int);
static struct sockaddr_in s_in={AF_INET};
static int peer;
static int rexmtval=TLMEOUT;
static int maxtimeout=5*TLMEOUT;
#define PACKSIZE BLOCKSIZE+4
static char buf[PACKSIZE];
static char ackbut[PACKSIZE];
static struct sockaddr_in from;
static size_t fromlen;
#define MAXARG 4
static char dirs[MAXARG+1];/*客户可以访问的目录*/
int main(int argc,char**argv)
{
struct tftphdr*tp;
int n=0;
int on=1;
argc--;argv++;
if(argc= =0)dirs[0]=″/tftpboot″; /*默认可访问的目录*/
while(argc<0 && n0){
n=i;
fromlen=k;
}
}else{/*如fork成功，则跳出for循环*/
break;
}
}/*for*/
if(pif<0){/*循环10次仍无法生成子进程，进程终止*/
syslog(LOG_ERR,″fork :%m/n″);
exit(1);
}else if(pid!=0){
exit(0);
}
if(!getuid()||!geteuid()){
struct passwd *pwd=getpwnam(″nobody″);
if(pwd)setuid(pwd->pw_uid);
else setuid(32765);/*设置一较大的UID*/
}
from.sin_family=AF_INT;
alarm(0);
close(0);
close(1);
Peer=socket(AF_INET.SOCK_DGRAM,0);
if(peer<0){
syslog(LOG_ERR,″socket:%m/n″);
exit(1);
}
if(bind(peer,(struct sockaddr*)&s_in,sizeof(s_in))<0){
syslog(LOG_ERR,″bind:%m/n″);
exit(1);
}
if(connect(peer,(struct sockaddr*)&from,sizef(from))<0) {
syslog(LOG_ERR,″connect:%m/n″);
exit(1);
}
Tp=(struct tftphdr*)buf;
Tp-th_opcode=ntohs(tp-th_opcode);
if(tp-th_opcode= =RRQ||tp->th_opcode= =WRQ) {
tftp(tp,n);
exit(1);
}
struct transfer{
const char*f_mode;/*文件传输格式*/
int(*f_validate)(const char,int);/*验证函数*/
void(*f_send)(struct transfer*);/*发送函数*/
void(*f_recv)(struct transfer*);/*接收函数*/
}transfer[]={
{″netasci″, check_file, sndfile, recvfile,1},
{″octet″, check_file, sndfile, recvfile,0},
{0}
/*最后一个元素值为0，以便于查接*/
}；
/*处理请求数据报*/
static void tftp(struct tftphdr*tp,int size)
{
char*cp;
int first=1,ecode;
struct transfer*pf;
char*filemane,*mode=NULL;
filemane=cp=tp->th_stuff;
again:
while(cpf_mode;pf++)
if(strcmp(pf->f_mode,mode)= =0)
break;
if(pf->f_mode= =0){
snderr(EBADOP);
exit(1);
}
ecode=(*pf->f_validate)(filename,tp->th_opcode);
if(ecode){
snderr(ecode);
exit(1);
}/*ecode等于0，文件允许访问*/
if(tp->th_opcode= =WRQ)
(*pf->f_recv)(pf);
else
(*pf->f_send)(pf);
exit(0);
}
}
FILE*file;
static int check_file(const char*filename,int mode)
{
struct stat stbuf;
int fd;
const char *cp;
char **dirp;
syslog(LOG_ERR,″tftpd:trying to get file:%s|n″,filename);
if(*filename != ′/′){/*文件名不含绝对路径*/
syslog(LOG_ERR,″tftpd:serving file %s\n″,dirs[0]);
chdir(dirs[0]);
}else{
for(dirp=dirs;*dirp;dirp++)
if(strncmp(filename,*dirp,strlen(*dirp))==0)
break;
if(*dirp==0&&dirp!=dirs)
return(EACCESS);
}
/*文件名filename里包含有允许访问的路径*/
if(!strncmp(filename,″../″,3))
return EACCESS;
for(cp=filename+1;*cp;cp++)
if(*cp==′. ′&&strncmp(cp-1,″/../″,4)==0 )
return(EACCESS);
if(stat(filename,&stbuf)<0)
return(errno==ENOENT?ENOTFOUND:EACCESS);
if(mode==RRQ){
if(stbuf.st_mode&(S_IREAD>>6)==0)
return(EACCESS);
}else{
if((stbuf.st_mode&(S_IREAD>>6))==0)
return(EACCESS);
}
fd=open(filename,mode==RRQ?0:1);
if(fd<0)
return(errno+100);
file=fdopen(fd,(mode==RRQ)?″r″:″w″);
if(file==NULL){
return errno++100;
}
return(0);
}
int timeout;
sigjmp_buf timeoutbuf;
static void timer(int signum)
{
(void)signum;
timeout += rexmtval;
if(timeout>=naxtimeout)
exit(1);
siglongjmp(timeoutbuf,1);/*跳到断点处执行*/
}
/*用于发送文件的函数*/
static void sndfile(struct transfer*pf)
{
struct tftphdr*dp;
struct tftphdr*ap; /*ACK数据报报头*/
int block=1;
int size, n;
signal(SIGALRM,timer); /*设置定时器*/
dp=read_init(); /*取得一块缓冲区用于存放读出的文件块*/
ap=(struct tftphdr*)ackbuf;
do{
size=my_read(file,*dp,pf->f_convert);/*读文件块到缓冲区里*/
if(size<0){
snderr(errno+100);
goto abort;
}
dp->th_opcode=htons((u_short)DATA);
dp->th_block=htons((u_short)block);
timeout=-;
(void)sigsetjmp(timeoutbuf,1); /*设置断点*/
send_data:
if(send(peer,dp,size+4,0)!=size+4){
syslog(LOG_ERR,″tftpd:write:%m\n″);
goto abort;
}
read_block(file,pf->f_convert);
for(;;){
alarm(rexmtval); /*启动定时器*/
n=recv(peer,ackbuf,sizeof(ackbuf),0);
alarm(0); /*收到数据报，关闭定时器*/
if(n<0){
syslog(LOG_ERR,″tftpd:read:%m\n″);
goto abort;
}
ap->th_opcode=ntohs(u_short)ap->th_opcode;
ap->th_block=ntohs((u_short)ap->th_bolck);
if(ap->th_opcode==ERROR)
goto abort;
if(ap->th_opcode==ACK){
if(ap->th_block==block){
break;
}
/*同步*/
(void)synch(peer);
if(ap->th_block==(block-1)){
goto send_data; /*返回重发*/
}
}
}/*for*/
block++;
}while (size==BLOCKSIZE);
abort;
(void )fclose(file);
}
Static void justquit(int signum)
{
(void)signum;
eixt(0);
}
/*接收文件*/
static void recvfile(struct transfer *pf)
{
struct tftphdr *dp;
struct tftphdr ap; /*ACK缓冲区*/
int block=0;
int n, size;
signal(SIGALRM,timer);
dp=write_init(); /*取得一块缓冲区用于存放接收到的文件块*/
ap=(struct tftphdr *)adkbuf;
do{
timeout=0;
ap->th_opcode=htons(u_short)ACK;
ap->th_block=htons((u_short)block);
block++;
(void)sigsetjmp(timeoutbuf,1);
send_ack;
if(send(peer,ackbuf,4,0)!=4){
syslog(LOG_ERR,″tftpd:write:%m\n″);
goto abort;
}
write_block(file,pf->f_convert);
for(;;){
alarm(rexmtval);
n=recv(peer,dp,PACKSIZE,0); /*接收文件块*/
alarm(0);
if(n<0)
syslog(LOG_ERR,″tftpd:read:%m\n″);
goto abort;
}
dp->th_opcode=ntohs(u_shot)dp->th_opcode;
dp->th_block=ntohs(u_short)dp->th_block;
if(dp->th_opcode==ERROR)
goto abort;
if(dp->th_opcode==DATA){
if(dp->th_block==block){
break; /*normal*/
}
/*同步*/
(void)synch(peer);
if(dp->th_block==(block-1){
goto send_ack; /*重发*/
}
size =my+write(file,&dp,n-4,pf->f_convert);
if(size!=(n-4))
if(size<0)
snderr(errno+100);
else snderr(ENOSPACE);
goto abort;
}
}while(size==BLOCKSIZE);
write_block(file,pf->f_convert);
(void)fclose(file); /*关闭文件*/
ap->th_opcode=htons(u_short)ACK);
ap->th_block=htons(u_short)(block);
(void)send(peer,ackbuf,4,0);
/*发送最后一个文件块的ACK*/
signal(SIGALRM,justquit); /*设置定时器*/
alarm(rexmtval);
n=recv(peer,buf ,sizeof(buf),0); /*超时将退出*/
alarm(0);
if(n>=4 &&dp->th_block){
/*客户端重发了最后一文件块，南非要发ACK*/
（void）send(peer,ackbuf,4,0);
}
abort;
return;
}
struct errmsg{
int e_code;
const char*e_msg;
}errmsgs[]={
{EUNDEF, ″Undefined error code″},
{ENOTFOUND, ″File not found″},
{EACCESS, ″Access violation″},
{ENOSPACE , ″Disk full or allocation exceeded″},
{EBADOP, ″Illegal TFTP operation″},
{EBADID, ″Unknown transfer ID″},
{EEXISTS, ″File already exists″},
{ENOUSER, ″No such user″},
{-1, 0},
};
/*此函数用于发送一个ERROR数据报*/
static void snderr(int error)
{
struct tftphdr*tp;
int length;
struct errmsg *pe;
tp=(struct tftphdr*)buf;
tp->th_opcode=htons(u_short)ERROR;
tp->th_code=htons(u_short)error;
for(pe=errmsgs;pe->e_code>=0;pe++)
if(pe->e_code==error)/*该错误号已定义*/
break;
if(pe->e_code<0){
pe->e_msg=strerror(error-100);
tp->th_code=EUNDEF; /*置错误号为"UNDEF"*/
}
strcpy(tp->th_msg,pe-e_msg);
length=strlen(pe->e_msg);
tp->th_msg[length]= ′\0′;
length +=5;
if(send(peer,buf,length,0)!=length)
syslog(LOG_ERR,″snderr:%m\n″);
}