librpc: Add autogenerated checksum calculation for Cabinet files

Guenther

Signed-off-by: Guenther Deschner <gd@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>

3 files changed, 51 insertions, 1 deletions

diff --git a/librpc/idl/cab.idl b/librpc/idl/cab.idl
index af8dad24404..2174bce7334 100644
--- a/librpc/idl/cab.idl
+++ b/librpc/idl/cab.idl
@@ -111,7 +111,7 @@ import "misc.idl";
 	} CFFILE;
 
 	typedef [public,flag(NDR_PAHEX|NDR_LITTLE_ENDIAN|NDR_NOALIGN)] struct {
-		uint32 csum;		/* checksum of this CFDATA entry */
+		[value(ndr_cab_generate_checksum(r))] uint32 csum;		/* checksum of this CFDATA entry */
 		uint16 cbData;		/* number of compressed bytes in this block */
 		uint16 cbUncomp;	/* number of uncompressed bytes in this block */
 #if 0
diff --git a/librpc/ndr/ndr_cab.c b/librpc/ndr/ndr_cab.c
index 87c103a4901..611e378cb34 100644
--- a/librpc/ndr/ndr_cab.c
+++ b/librpc/ndr/ndr_cab.c
@@ -63,6 +63,55 @@ uint32_t ndr_count_cfdata(const struct cab_file *r)
 	return count;
 }
 
+static uint32_t ndr_cab_compute_checksum(uint8_t *data, uint32_t length, uint32_t seed)
+{
+	int num_ulong;
+	uint32_t checksum;
+	uint8_t *pb;
+	uint32_t ul;
+
+	num_ulong = length / 4;
+	checksum = seed;
+	pb = data;
+
+	while (num_ulong-- > 0) {
+		ul = *pb++;
+		ul |= (((uint32_t)(*pb++)) <<  8);
+		ul |= (((uint32_t)(*pb++)) << 16);
+		ul |= (((uint32_t)(*pb++)) << 24);
+
+		checksum ^= ul;
+	}
+
+	ul = 0;
+
+	switch (length % 4) {
+	case 3:
+		ul |= (((uint32_t)(*pb++)) << 16);
+	case 2:
+		ul |= (((uint32_t)(*pb++)) <<  8);
+	case 1:
+		ul |= *pb++;
+	default:
+		break;
+	}
+
+	checksum ^= ul;
+
+	return checksum;
+}
+
+uint32_t ndr_cab_generate_checksum(const struct CFDATA *r)
+{
+	uint32_t csumPartial;
+
+	csumPartial = ndr_cab_compute_checksum(&r->ab[0], r->cbData, 0);
+
+	return ndr_cab_compute_checksum((uint8_t *)discard_const(&r->cbData),
+					sizeof(r->cbData) + sizeof(r->cbUncomp),
+					csumPartial);
+}
+
 _PUBLIC_ enum ndr_err_code ndr_push_cab_file(struct ndr_push *ndr, int ndr_flags, const struct cab_file *r)
 {
 	uint32_t cntr_cffolders_0;
diff --git a/librpc/ndr/ndr_cab.h b/librpc/ndr/ndr_cab.h
index 39b6bc9b483..59dbc991442 100644
--- a/librpc/ndr/ndr_cab.h
+++ b/librpc/ndr/ndr_cab.h
@@ -20,3 +20,4 @@
 */
 
 uint32_t ndr_count_cfdata(const struct cab_file *r);
+uint32_t ndr_cab_generate_checksum(const struct CFDATA *r);