devfs: rewrite cryptio()

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.

sys/src/9/port/devfs.c

@@ -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)) {
+			if(mp->start > inlen)
-				mp->size = inlen - (64 * 1024);
+				error("crypt starts after device end");
-			} else {
+			mp->size = (inlen - mp->start) & ~((vlong)Cryptsectsz-1);
-				mp->size = 0;
-			}
 			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->tweak, &key[0], keylen/2, nil);
-		setupAESstate(&k->ecb, &key[16], 16, nil);
+		setupAESstate(&k->ecb, &key[keylen/2], keylen/2, nil);
-		memset(key, 0, 32);
+		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;
+	long l, m, o, nb;
-	uchar *buf;
+	uchar *b;
-	Chan *mc;
-	Inner *in;
-	Key *k;
-	enum {
-		Sectsz = 512,
-		Maxbuf = 32*Sectsz,
-	};
 
-	if(off < 0 || l <= 0 || ((off|l) & (Sectsz-1)))
+	if((((ulong)off|n) & (Cryptsectsz-1)))
 		error(Ebadarg);
-
+	if(isread){
-	k = mp->key;
+		l = io(mp, mp->inner[0], Isread, a, n, off);
-	in = mp->inner[0];
+		if(l > 0){
-	mc = in->idev;
+			l &= ~(Cryptsectsz-1);
-	if(mc == nil)
+			for(o=0; o<l; o+=Cryptsectsz)
-		error(Egone);
+				aes_xts_decrypt(&mp->key->tweak, &mp->key->ecb,
-	off += 64*1024;	// Header
+					off+o, a+o, a+o, Cryptsectsz);
-	wb = l;
+		}
-	if(wb > Maxbuf)
+		return l;
-		wb = Maxbuf;
+	}
-	buf = smalloc(wb);
+	nb = n < SDmaxio ? n : SDmaxio;
+	while((b = sdmalloc(nb)) == nil){
+		if(!waserror()){
+			resrcwait("no memory for cryptio");
+			poperror();
+		}
+	}
 	if(waserror()) {
-		free(buf);
+		sdfree(b);
-		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: ""));
 		nexterror();
 	}
-	for(ws = 0; ws < l; ws += wo){
+	for(l = 0; (m = n - l) > 0; l += m){
-		wo = l - ws;
+		if(m > nb) m = nb;
-		if(wo > wb)
+		for(o=0; o<m; o+=Cryptsectsz)
-			wo = wb;
+			aes_xts_encrypt(&mp->key->tweak, &mp->key->ecb,
-		if (isread) {
+				off+o, a+o, b+o, Cryptsectsz);
-			wo = devtab[mc->type]->read(mc, buf, wo, off);
+		if(io(mp, mp->inner[0], Iswrite, b, m, off) != m)
-			if(wo < Sectsz)
+			error(Eio);
-				break;
+		off += m;
-			wo &= ~(Sectsz-1);
+		a += m;
-			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;
 	}
+	sdfree(b);
 	poperror();
-	free(buf);
+	return l;
-
-	return ws;
 }
 
 /* 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:

sys/src/9/port/lib.h

@@ -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*));