Patch 120-decrypt from David Mansfield

src/libmdb/file.c

@@ -52,8 +52,69 @@ MdbFormatConstants MdbJet3Constants = {
 	2048, 0x08, 12, 25, 27, 31, 35, 36, 43, 8, 13, 16, 1, 18, 39, 3, 14, 5
 };
 
+typedef struct _RC4_KEY
+{
+	unsigned char state[256];
+	unsigned char x;
+	unsigned char y;
+} RC4_KEY;
+
+#define swap_byte(x,y) t = *(x); *(x) = *(y); *(y) = t
+
 static ssize_t _mdb_read_pg(MdbHandle *mdb, void *pg_buf, unsigned long pg);
 
+static void RC4_set_key(RC4_KEY *key, int key_data_len, unsigned char *key_data_ptr)
+{
+	unsigned char t;
+	unsigned char index1;
+	unsigned char index2;
+	unsigned char* state;
+	short counter;
+
+	state = &key->state[0];
+	for(counter = 0; counter < 256; counter++)
+		state[counter] = counter;
+	key->x = 0;
+	key->y = 0;
+	index1 = 0;
+	index2 = 0;
+	for(counter = 0; counter < 256; counter++) {
+		index2 = (key_data_ptr[index1] + state[counter] + index2) % 256;
+		swap_byte(&state[counter], &state[index2]);
+		index1 = (index1 + 1) % key_data_len;
+	}
+}
+
+/*
+ * this algorithm does 'encrypt in place' instead of inbuff/outbuff
+ * note also: encryption and decryption use same routine
+ * implementation supplied by (Adam Back) at <adam at cypherspace dot org>
+ */
+
+static void RC4(RC4_KEY *key, int buffer_len, unsigned char * buff)
+{
+	unsigned char t;
+	unsigned char x;
+	unsigned char y;
+	unsigned char* state;
+	unsigned char xorIndex;
+	short counter;
+
+	x = key->x;
+	y = key->y;
+	state = &key->state[0];
+	for(counter = 0; counter < buffer_len; counter++) {
+		x = (x + 1) % 256;
+		y = (state[x] + y) % 256;
+		swap_byte(&state[x], &state[y]);
+		xorIndex = (state[x] + state[y]) % 256;
+		buff[counter] ^= state[xorIndex];
+	}
+	key->x = x;
+	key->y = y;
+}
+
+
 /**
  * mdb_find_file:
  * @filename: path to MDB (database) file
@@ -108,6 +169,8 @@ static char *mdb_find_file(const char *file_name)
 MdbHandle *mdb_open(const char *filename, MdbFileFlags flags)
 {
 	MdbHandle *mdb;
+	int key[] = {0x86, 0xfb, 0xec, 0x37, 0x5d, 0x44, 0x9c, 0xfa, 0xc6, 0x5e, 0x28, 0xe6, 0x13, 0xb6};
+	int j, pos;
 	int open_flags;
 
 	mdb = (MdbHandle *) g_malloc0(sizeof(MdbHandle));
@@ -164,6 +227,42 @@ MdbHandle *mdb_open(const char *filename, MdbFileFlags flags)
 		mdb_close(mdb);
 		return NULL; 
 	}
+	mdb->f->db_key = mdb_get_int32(mdb->pg_buf, 0x3e);
+	/* I don't know if this value is valid for some versions?
+	 * it doesn't seem to be valid for the databases I have
+	 *
+	 * f->db_key ^= 0xe15e01b9;
+	 */
+	mdb->f->db_key ^= 0x4ebc8afb;
+	/* fprintf(stderr, "Encrypted file, RC4 key seed= %d\n", mdb->f->db_key); */
+	if (mdb->f->db_key) {
+		/* write is not supported for encrypted files yet */
+		mdb->f->writable = FALSE;
+		/* that should be enought, but reopen the file read only just to be
+		 * sure we don't write invalid data */
+		close(mdb->f->fd);
+		open_flags = O_RDONLY;
+#ifdef _WIN32
+		open_flags |= O_BINARY;
+#endif
+		mdb->f->fd = open(mdb->f->filename, open_flags);
+		if (mdb->f->fd==-1) {
+			fprintf(stderr, "Couldn't ropen file %s in read only\n", mdb->f->filename);
+			mdb_close(mdb);
+			return NULL;
+		}
+	}
+
+	/* get the db password located at 0x42 bytes into the file */
+	for (pos=0;pos<14;pos++) {
+		j = mdb_get_int32(mdb,0x42+pos);
+		j ^= key[pos];
+		if ( j != 0)
+			mdb->f->db_passwd[pos] = j;
+		else
+			mdb->f->db_passwd[pos] = '\0';
+	}
+
 	mdb_iconv_init(mdb);
 
 	return mdb;
@@ -277,6 +376,18 @@ static ssize_t _mdb_read_pg(MdbHandle *mdb, void *pg_buf, unsigned long pg)
 		/* fprintf(stderr,"EOF reached %d bytes returned.\n",len, mdb->fmt->pg_size); */
 		return 0;
 	} 
+	/*
+	 * unencrypt the page if necessary.
+	 * it might make sense to cache the unencrypted data blocks?
+	 */
+	if (pg != 0 && mdb->f->db_key != 0)
+	{
+		RC4_KEY rc4_key;
+		unsigned int tmp_key = mdb->f->db_key ^ pg;
+		RC4_set_key(&rc4_key, 4, (unsigned char *)&tmp_key);
+		RC4(&rc4_key, mdb->fmt->pg_size, pg_buf);
+	}
+
 	return len;
 }
 void mdb_swap_pgbuf(MdbHandle *mdb)

src/libmdb/write.c

@@ -446,6 +446,7 @@ mdb_new_data_pg(MdbCatalogEntry *entry)
 	return new_pg;
 }
 
+/* could be static */
 int
 mdb_update_indexes(MdbTableDef *table, int num_fields, MdbField *fields, guint32 pgnum, guint16 rownum)
 {
@@ -476,6 +477,7 @@ mdb_init_index_chain(MdbTableDef *table, MdbIndex *idx)
 	return 1;
 }
 
+/* could be static */
 int
 mdb_update_index(MdbTableDef *table, MdbIndex *idx, unsigned int num_fields, MdbField *fields, guint32 pgnum, guint16 rownum)
 {