ref: 1f5a91b06083d47de0a85f432e1c4213c0a12095
dir: /libc/convM2S.c/
#include <u.h>
#include <libc.h>
#include <fcall.h>
static
uchar*
gstring(uchar *p, uchar *ep, char **s)
{
uint n;
if(p+BIT16SZ > ep)
return nil;
n = GBIT16(p);
p += BIT16SZ - 1;
if(p+n+1 > ep)
return nil;
/* move it down, on top of count, to make room for '\0' */
memmove(p, p + 1, n);
p[n] = '\0';
*s = (char*)p;
p += n+1;
return p;
}
static
uchar*
gqid(uchar *p, uchar *ep, Qid *q)
{
if(p+QIDSZ > ep)
return nil;
q->type = GBIT8(p);
p += BIT8SZ;
q->vers = GBIT32(p);
p += BIT32SZ;
q->path = GBIT64(p);
p += BIT64SZ;
return p;
}
/*
* no syntactic checks.
* three causes for error:
* 1. message size field is incorrect
* 2. input buffer too short for its own data (counts too long, etc.)
* 3. too many names or qids
* gqid() and gstring() return nil if they would reach beyond buffer.
* main switch statement checks range and also can fall through
* to test at end of routine.
*/
uint
convM2S(uchar *ap, uint nap, Fcall *f)
{
uchar *p, *ep;
uint i, size;
p = ap;
ep = p + nap;
if(p+BIT32SZ+BIT8SZ+BIT16SZ > ep)
return 0;
size = GBIT32(p);
p += BIT32SZ;
if(size < BIT32SZ+BIT8SZ+BIT16SZ)
return 0;
f->type = GBIT8(p);
p += BIT8SZ;
f->tag = GBIT16(p);
p += BIT16SZ;
switch(f->type)
{
default:
return 0;
case Tversion:
if(p+BIT32SZ > ep)
return 0;
f->msize = GBIT32(p);
p += BIT32SZ;
p = gstring(p, ep, &f->version);
break;
case Tflush:
if(p+BIT16SZ > ep)
return 0;
f->oldtag = GBIT16(p);
p += BIT16SZ;
break;
case Tauth:
if(p+BIT32SZ > ep)
return 0;
f->afid = GBIT32(p);
p += BIT32SZ;
p = gstring(p, ep, &f->uname);
if(p == nil)
break;
p = gstring(p, ep, &f->aname);
if(p == nil)
break;
break;
case Tattach:
if(p+BIT32SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
if(p+BIT32SZ > ep)
return 0;
f->afid = GBIT32(p);
p += BIT32SZ;
p = gstring(p, ep, &f->uname);
if(p == nil)
break;
p = gstring(p, ep, &f->aname);
if(p == nil)
break;
break;
case Twalk:
if(p+BIT32SZ+BIT32SZ+BIT16SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
f->newfid = GBIT32(p);
p += BIT32SZ;
f->nwname = GBIT16(p);
p += BIT16SZ;
if(f->nwname > MAXWELEM)
return 0;
for(i=0; i<f->nwname; i++){
p = gstring(p, ep, &f->wname[i]);
if(p == nil)
break;
}
break;
case Topen:
if(p+BIT32SZ+BIT8SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
f->mode = GBIT8(p);
p += BIT8SZ;
break;
case Tcreate:
if(p+BIT32SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
p = gstring(p, ep, &f->name);
if(p == nil)
break;
if(p+BIT32SZ+BIT8SZ > ep)
return 0;
f->perm = GBIT32(p);
p += BIT32SZ;
f->mode = GBIT8(p);
p += BIT8SZ;
break;
case Tread:
if(p+BIT32SZ+BIT64SZ+BIT32SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
f->offset = GBIT64(p);
p += BIT64SZ;
f->count = GBIT32(p);
p += BIT32SZ;
break;
case Twrite:
if(p+BIT32SZ+BIT64SZ+BIT32SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
f->offset = GBIT64(p);
p += BIT64SZ;
f->count = GBIT32(p);
p += BIT32SZ;
if(p+f->count > ep)
return 0;
f->data = (char*)p;
p += f->count;
break;
case Tclunk:
case Tremove:
if(p+BIT32SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
break;
case Tstat:
if(p+BIT32SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
break;
case Twstat:
if(p+BIT32SZ+BIT16SZ > ep)
return 0;
f->fid = GBIT32(p);
p += BIT32SZ;
f->nstat = GBIT16(p);
p += BIT16SZ;
if(p+f->nstat > ep)
return 0;
f->stat = p;
p += f->nstat;
break;
/*
*/
case Rversion:
if(p+BIT32SZ > ep)
return 0;
f->msize = GBIT32(p);
p += BIT32SZ;
p = gstring(p, ep, &f->version);
break;
case Rerror:
p = gstring(p, ep, &f->ename);
break;
case Rflush:
break;
case Rauth:
p = gqid(p, ep, &f->aqid);
if(p == nil)
break;
break;
case Rattach:
p = gqid(p, ep, &f->qid);
if(p == nil)
break;
break;
case Rwalk:
if(p+BIT16SZ > ep)
return 0;
f->nwqid = GBIT16(p);
p += BIT16SZ;
if(f->nwqid > MAXWELEM)
return 0;
for(i=0; i<f->nwqid; i++){
p = gqid(p, ep, &f->wqid[i]);
if(p == nil)
break;
}
break;
case Ropen:
case Rcreate:
p = gqid(p, ep, &f->qid);
if(p == nil)
break;
if(p+BIT32SZ > ep)
return 0;
f->iounit = GBIT32(p);
p += BIT32SZ;
break;
case Rread:
if(p+BIT32SZ > ep)
return 0;
f->count = GBIT32(p);
p += BIT32SZ;
if(p+f->count > ep)
return 0;
f->data = (char*)p;
p += f->count;
break;
case Rwrite:
if(p+BIT32SZ > ep)
return 0;
f->count = GBIT32(p);
p += BIT32SZ;
break;
case Rclunk:
case Rremove:
break;
case Rstat:
if(p+BIT16SZ > ep)
return 0;
f->nstat = GBIT16(p);
p += BIT16SZ;
if(p+f->nstat > ep)
return 0;
f->stat = p;
p += f->nstat;
break;
case Rwstat:
break;
}
if(p==nil || p>ep)
return 0;
if(ap+size == p)
return size;
return 0;
}