MD4 checksum fix
Eric Whiting
ewhiting at amis.com
Tue Apr 8 06:33:28 EST 2003
This patch does not change PROTOCOL_VERSION in rsync.h. Was I supposed to patch
against a CVS version?
I'll change the value manually and retest.
eric
cbarratt at users.sourceforge.net wrote:
>
> > > I agree, they should be done together. I don't have my original
> > > patch but I can reimplement it with the correct remote_version
> > > dependence and send it in the next couple of days (by Thursday
> > > evening). My intent is the minimal set of changes, rather than
> > > changing the internals.
> >
> > That is a workable timeframe, thanks.
>
> Two days late, but here is the patch against 2.5.6. This implements the
> following changes:
>
> - for protocol version >= 27, mdfour_tail() is called when the block size
> (including checksum_seed) is a multiple of 64. Previously it was not
> called, giving the wrong MD4 checksum.
>
> - for protocol version >= 27, a 64 bit bit counter is used in mdfour.c as
> required by the RFC. Previously only a 32 bit bit counter was used,
> causing incorrect MD4 file checksums for file sizes >= 512MB - 4.
>
> Craig
>
> ###########################################################################
> diff -bur rsync-2.5.6/checksum.c rsync-2.5.6-fixed-md4/checksum.c
> --- rsync-2.5.6/checksum.c 2002-04-08 01:29:04.000000000 -0700
> +++ rsync-2.5.6-fixed-md4/checksum.c 2003-04-05 16:03:15.000000000 -0800
> @@ -74,7 +74,13 @@
> for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
> mdfour_update(&m, (uchar *)(buf1+i), CSUM_CHUNK);
> }
> - if (len - i > 0) {
> + /*
> + * Prior to version 27 an incorrect MD4 checksum was computed
> + * by failing to call mdfour_tail() for block sizes that
> + * are multiples of 64. This is fixed by calling mdfour_update()
> + * even when there are no more bytes.
> + */
> + if (len - i > 0 || (remote_version >= 27 && len - i == 0)) {
> mdfour_update(&m, (uchar *)(buf1+i), (len-i));
> }
>
> @@ -105,8 +111,16 @@
> mdfour_update(&m, (uchar *)tmpchunk, CSUM_CHUNK);
> }
>
> + /*
> + * Prior to version 27 an incorrect MD4 checksum was computed
> + * by failing to call mdfour_tail() for block sizes that
> + * are multiples of 64. This is fixed by calling mdfour_update()
> + * even when there are no more bytes.
> + */
> + if (len - i > 0 || (remote_version >= 27 && len - i == 0)) {
> if (len - i > 0) {
> memcpy(tmpchunk, map_ptr(buf,i,len-i), len-i);
> + }
> mdfour_update(&m, (uchar *)tmpchunk, (len-i));
> }
>
> diff -bur rsync-2.5.6/lib/mdfour.c rsync-2.5.6-fixed-md4/lib/mdfour.c
> --- rsync-2.5.6/lib/mdfour.c 2001-06-27 22:07:15.000000000 -0700
> +++ rsync-2.5.6-fixed-md4/lib/mdfour.c 2003-04-05 16:04:46.000000000 -0800
> @@ -109,29 +109,53 @@
> md->C = 0x98badcfe;
> md->D = 0x10325476;
> md->totalN = 0;
> + md->totalN2 = 0;
> }
>
>
> -static void mdfour_tail(unsigned char *in, int n)
> +static void mdfour_tail(unsigned char *in, uint32 n)
> {
> unsigned char buf[128];
> uint32 M[16];
> - uint32 b;
> + extern int remote_version;
>
> - m->totalN += n;
> -
> - b = m->totalN * 8;
> + /*
> + * Count total number of bits, modulo 2^64
> + */
> + m->totalN += n << 3;
> + if (m->totalN < (n << 3)) {
> + m->totalN2++;
> + }
> + m->totalN2 += n >> 29;
>
> memset(buf, 0, 128);
> if (n) memcpy(buf, in, n);
> buf[n] = 0x80;
>
> if (n <= 55) {
> - copy4(buf+56, b);
> + copy4(buf+56, m->totalN);
> + /*
> + * Prior to protocol version 27 only the number of bits
> + * modulo 2^32 was included. MD4 requires the number
> + * of bits modulo 2^64, which was fixed starting with
> + * protocol version 27.
> + */
> + if (remote_version >= 27) {
> + copy4(buf+60, m->totalN2);
> + }
> copy64(M, buf);
> mdfour64(M);
> } else {
> - copy4(buf+120, b);
> + copy4(buf+120, m->totalN);
> + /*
> + * Prior to protocol version 27 only the number of bits
> + * modulo 2^32 was included. MD4 requires the number
> + * of bits modulo 2^64, which was fixed starting with
> + * protocol version 27.
> + */
> + if (remote_version >= 27) {
> + copy4(buf+124, m->totalN2);
> + }
> copy64(M, buf);
> mdfour64(M);
> copy64(M, buf+64);
> @@ -139,20 +163,23 @@
> }
> }
>
> -void mdfour_update(struct mdfour *md, unsigned char *in, int n)
> +void mdfour_update(struct mdfour *md, unsigned char *in, uint32 n)
> {
> uint32 M[16];
>
> - if (n == 0) mdfour_tail(in, n);
> -
> m = md;
>
> + if (n == 0) mdfour_tail(in, n);
> +
> while (n >= 64) {
> copy64(M, in);
> mdfour64(M);
> in += 64;
> n -= 64;
> - m->totalN += 64;
> + m->totalN += 64 << 3;
> + if (m->totalN < 64 << 3) {
> + m->totalN2++;
> + }
> }
>
> if (n) mdfour_tail(in, n);
> diff -bur rsync-2.5.6/lib/mdfour.h rsync-2.5.6-fixed-md4/lib/mdfour.h
> --- rsync-2.5.6/lib/mdfour.h 1998-10-28 21:01:52.000000000 -0800
> +++ rsync-2.5.6-fixed-md4/lib/mdfour.h 2003-04-04 14:25:50.000000000 -0800
> @@ -21,11 +21,12 @@
>
> struct mdfour {
> uint32 A, B, C, D;
> - uint32 totalN;
> + uint32 totalN; /* bit count, lower 32 bits */
> + uint32 totalN2; /* bit count, upper 32 bits */
> };
>
> void mdfour_begin(struct mdfour *md);
> -void mdfour_update(struct mdfour *md, unsigned char *in, int n);
> +void mdfour_update(struct mdfour *md, unsigned char *in, uint32 n);
> void mdfour_result(struct mdfour *md, unsigned char *out);
> void mdfour(unsigned char *out, unsigned char *in, int n);
>
> --
> To unsubscribe or change options: http://lists.samba.org/mailman/listinfo/rsync
> Before posting, read: http://www.tuxedo.org/~esr/faqs/smart-questions.html
More information about the rsync
mailing list