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devfs: rewrite cryptio()

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adjust to new aes_xts routines.

allow optional offset in the 4th argument where the encrypted
sectors start instead of hardcoding the 64K header area for
cryptsetup.

avoid allocating temporary buffer for cryptio() reads, we can
just decrypt in place there.

use sdmalloc() to allocate the temporary buffer for cryptio()
writes so that devsd wont need to allocate and copy in case
it didnt like our alignment.

do not duplicate the error reporting code, just use io()
that is what it is for.

allow 2*256 bit keys in addition to 2*128 bit keys.
This commit is contained in:
cinap_lenrek 2017-10-29 22:01:58 +01:00
parent c021390e21
commit 93117262c2
2 changed files with 60 additions and 62 deletions
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121
sys/src/9/port/devfs.c
View file

@ -21,10 +21,9 @@
#include "io.h"
#include "ureg.h"
#include "../port/error.h"
#include "../port/sd.h"
#include <libsec.h>
int dec16(uchar *out, int lim, char *in, int n);
enum
{
Fnone,
@ -39,6 +38,7 @@ enum
Sectorsz = 1,
Blksize = 8*1024, /* for Finter only */
Cryptsectsz = 512, /* for Fcrypt only */
Incr = 5, /* Increments for the dev array */
@ -447,11 +447,9 @@ setdsize(Fsdev* mp, vlong *ilen)
}
break;
case Fcrypt:
if(inlen > (64*1024)) {
mp->size = inlen - (64 * 1024);
} else {
mp->size = 0;
}
if(mp->start > inlen)
error("crypt starts after device end");
mp->size = (inlen - mp->start) & ~((vlong)Cryptsectsz-1);
break;
}
}
@ -552,7 +550,8 @@ mconfig(char* a, long n)
vlong size, start;
vlong *ilen;
char *tname, *dname, *fakef[4];
uchar key[32];
uchar key[2*256/8];
int keylen;
Chan **idev;
Cmdbuf *cb;
Cmdtab *ct;
@ -571,6 +570,7 @@ mconfig(char* a, long n)
cb = nil;
idev = nil;
ilen = nil;
keylen = 0;
if(waserror()){
free(cb);
@ -600,8 +600,19 @@ mconfig(char* a, long n)
mdelctl("*", "*"); /* del everything */
return;
case Fcrypt:
if(dec16(key, 32, cb->f[2], strlen(cb->f[2])) != 32)
if(cb->nf >= 4) {
start = strtoul(cb->f[3], 0, 0);
cb->nf = 3;
} else
start = 64*1024; /* cryptsetup header */
keylen = dec16(key, sizeof(key), cb->f[2], strlen(cb->f[2]));
switch(keylen){
default:
error("bad hexkey");
case 2*128/8:
case 2*256/8:
break;
}
cb->nf -= 1;
break;
case Fpart:
@ -694,10 +705,11 @@ Fail:
}
if(mp->type == Fcrypt) {
Key *k = secalloc(sizeof(Key));
setupAESstate(&k->tweak, &key[0], 16, nil);
setupAESstate(&k->ecb, &key[16], 16, nil);
memset(key, 0, 32);
setupAESstate(&k->tweak, &key[0], keylen/2, nil);
setupAESstate(&k->ecb, &key[keylen/2], keylen/2, nil);
memset(key, 0, sizeof(key));
mp->key = k;
mp->start = start;
}
for(i = 1; i < cb->nf; i++){
inprv = mp->inner[i-1] = mallocz(sizeof(Inner), 1);
@ -1014,62 +1026,47 @@ io(Fsdev *mp, Inner *in, int isread, void *a, long l, vlong off)
}
static long
cryptio(Fsdev *mp, int isread, uchar *a, long l, vlong off)
cryptio(Fsdev *mp, int isread, uchar *a, long n, vlong off)
{
long wl, ws, wo, wb;
uchar *buf;
Chan *mc;
Inner *in;
Key *k;
enum {
Sectsz = 512,
Maxbuf = 32*Sectsz,
};
long l, m, o, nb;
uchar *b;
if(off < 0 || l <= 0 || ((off|l) & (Sectsz-1)))
if((((ulong)off|n) & (Cryptsectsz-1)))
error(Ebadarg);
k = mp->key;
in = mp->inner[0];
mc = in->idev;
if(mc == nil)
error(Egone);
off += 64*1024; // Header
wb = l;
if(wb > Maxbuf)
wb = Maxbuf;
buf = smalloc(wb);
if(isread){
l = io(mp, mp->inner[0], Isread, a, n, off);
if(l > 0){
l &= ~(Cryptsectsz-1);
for(o=0; o<l; o+=Cryptsectsz)
aes_xts_decrypt(&mp->key->tweak, &mp->key->ecb,
off+o, a+o, a+o, Cryptsectsz);
}
return l;
}
nb = n < SDmaxio ? n : SDmaxio;
while((b = sdmalloc(nb)) == nil){
if(!waserror()){
resrcwait("no memory for cryptio");
poperror();
}
}
if(waserror()) {
free(buf);
print("#k: %s: byte %,lld count %ld (of #k/%s): %s error: %s\n",
in->iname, off, l, mp->name, (isread? "read": "write"),
(up && up->errstr? up->errstr: ""));
sdfree(b);
nexterror();
}
for(ws = 0; ws < l; ws += wo){
wo = l - ws;
if(wo > wb)
wo = wb;
if (isread) {
wo = devtab[mc->type]->read(mc, buf, wo, off);
if(wo < Sectsz)
break;
wo &= ~(Sectsz-1);
for(wl=0; wl<wo; wl+=Sectsz)
aes_xts_decrypt(k->tweak.ekey, k->ecb.dkey, off+wl, buf+wl, a+wl, Sectsz);
} else {
for(wl=0; wl<wo; wl+=Sectsz)
aes_xts_encrypt(k->tweak.ekey, k->ecb.ekey, off+wl, a+wl, buf+wl, Sectsz);
if(devtab[mc->type]->write(mc, buf, wo, off) != wo)
error(Eio);
}
off += wo;
a += wo;
for(l = 0; (m = n - l) > 0; l += m){
if(m > nb) m = nb;
for(o=0; o<m; o+=Cryptsectsz)
aes_xts_encrypt(&mp->key->tweak, &mp->key->ecb,
off+o, a+o, b+o, Cryptsectsz);
if(io(mp, mp->inner[0], Iswrite, b, m, off) != m)
error(Eio);
off += m;
a += m;
}
sdfree(b);
poperror();
free(buf);
return ws;
return l;
}
/* NB: a transfer could span multiple inner devices */
@ -1243,7 +1240,7 @@ mread(Chan *c, void *a, long n, vlong off)
(up && up->errstr? up->errstr: ""));
break;
case Fcrypt:
res = cryptio(mp, Isread, a, n, off);
res = cryptio(mp, Isread, a, n, mp->start + off);
break;
}
Done:
@ -1341,7 +1338,7 @@ mwrite(Chan *c, void *a, long n, vlong off)
break;
case Fcrypt:
res = cryptio(mp, Iswrite, a, n, off);
res = cryptio(mp, Iswrite, a, n, mp->start + off);
break;
}
Done:

1
sys/src/9/port/lib.h
View file

@ -155,6 +155,7 @@ extern char end[];
extern int getfields(char*, char**, int, int, char*);
extern int tokenize(char*, char**, int);
extern int dec64(uchar*, int, char*, int);
extern int dec16(uchar*, int, char*, int);
extern int encodefmt(Fmt*);
extern void qsort(void*, long, long, int (*)(void*, void*));