vfs_fruit: detect empty resource forks in ad_convert()

For some reason the macOS client often writes AppleDouble files with a
non-zero sized resource fork, but the resource fork data is just
boilerplate data with the following string close to the start

  This resource fork intentionally left blank

A dump with apple_dump looks like this:

Entry ID   : 00000002 : Resource Fork
Offset     : 00000052 : 82
Length     : 0000011E : 286

-RAW DUMP--:  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F : (ASCII)
00000000   : 00 00 01 00 00 00 01 00 00 00 00 00 00 00 00 1E : ................
00000010   : 54 68 69 73 20 72 65 73 6F 75 72 63 65 20 66 6F : This resource fo
00000020   : 72 6B 20 69 6E 74 65 6E 74 69 6F 6E 61 6C 6C 79 : rk intentionally
00000030   : 20 6C 65 66 74 20 62 6C 61 6E 6B 20 20 20 00 00 :  left blank   ..
00000040   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
00000050   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
00000060   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
00000070   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
00000080   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
00000090   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
000000A0   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
000000B0   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
000000C0   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
000000D0   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
000000E0   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
000000F0   : 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 : ................
00000100   : 00 00 01 00 00 00 01 00 00 00 00 00 00 00 00 1E : ................
00000110   : 00 00 00 00 00 00 00 00 00 1C 00 1E FF FF       : ..............

We can safely discard this Resource Fork data.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13642

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit 7be979f958295474f0c0df6a4db0b5bca9a6676d)

1 files changed, 110 insertions, 1 deletions

diff --git a/source3/modules/vfs_fruit.c b/source3/modules/vfs_fruit.c
index c9028a93d62..e38d48bea02 100644
--- a/source3/modules/vfs_fruit.c
+++ b/source3/modules/vfs_fruit.c
@@ -468,6 +468,45 @@ static const uint32_t set_eid[] = {
 	AD_DEV, AD_INO, AD_SYN, AD_ID
 };
 
+static char empty_resourcefork[] = {
+	0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1E,
+	0x54, 0x68, 0x69, 0x73, 0x20, 0x72, 0x65, 0x73,
+	0x6F, 0x75, 0x72, 0x63, 0x65, 0x20, 0x66, 0x6F,
+	0x72, 0x6B, 0x20, 0x69, 0x6E, 0x74, 0x65, 0x6E,
+	0x74, 0x69, 0x6F, 0x6E, 0x61, 0x6C, 0x6C, 0x79,
+	0x20, 0x6C, 0x65, 0x66, 0x74, 0x20, 0x62, 0x6C,
+	0x61, 0x6E, 0x6B, 0x20, 0x20, 0x20, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1E,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x1C, 0x00, 0x1E, 0xFF, 0xFF
+};
+
 struct fio {
 	/* tcon config handle */
 	struct fruit_config_data *config;
@@ -1282,6 +1321,70 @@ static bool ad_convert_truncate(struct adouble *ad,
 	return true;
 }
 
+static bool ad_convert_blank_rfork(struct adouble *ad,
+				   bool *blank)
+{
+	struct fruit_config_data *config = NULL;
+	uint8_t *map = MAP_FAILED;
+	size_t maplen;
+	int cmp;
+	ssize_t len;
+	int rc;
+	bool ok;
+
+	*blank = false;
+
+	SMB_VFS_HANDLE_GET_DATA(ad->ad_handle, config,
+				struct fruit_config_data, return false);
+
+	if (!config->wipe_intentionally_left_blank_rfork) {
+		return true;
+	}
+
+	if (ad_getentrylen(ad, ADEID_RFORK) != sizeof(empty_resourcefork)) {
+		return true;
+	}
+
+	maplen = ad_getentryoff(ad, ADEID_RFORK) +
+		ad_getentrylen(ad, ADEID_RFORK);
+
+	/* FIXME: direct use of mmap(), vfs_aio_fork does it too */
+	map = mmap(NULL, maplen, PROT_READ|PROT_WRITE, MAP_SHARED,
+		   ad->ad_fd, 0);
+	if (map == MAP_FAILED) {
+		DBG_ERR("mmap AppleDouble: %s\n", strerror(errno));
+		return false;
+	}
+
+	cmp = memcmp(map + ADEDOFF_RFORK_DOT_UND,
+		     empty_resourcefork,
+		     sizeof(empty_resourcefork));
+	rc = munmap(map, maplen);
+	if (rc != 0) {
+		DBG_ERR("munmap failed: %s\n", strerror(errno));
+		return false;
+	}
+
+	if (cmp != 0) {
+		return true;
+	}
+
+	ad_setentrylen(ad, ADEID_RFORK, 0);
+
+	ok = ad_pack(ad);
+	if (!ok) {
+		return false;
+	}
+
+	len = sys_pwrite(ad->ad_fd, ad->ad_data, AD_DATASZ_DOT_UND, 0);
+	if (len != AD_DATASZ_DOT_UND) {
+		return false;
+	}
+
+	*blank = true;
+	return true;
+}
+
 /**
  * Convert from Apple's ._ file to Netatalk
  *
@@ -1296,13 +1399,19 @@ static int ad_convert(struct adouble *ad,
 {
 	bool ok;
 	bool converted_xattr = false;
+	bool blank;
 
 	ok = ad_convert_xattr(ad, smb_fname, &converted_xattr);
 	if (!ok) {
 		return -1;
 	}
 
-	if (converted_xattr) {
+	ok = ad_convert_blank_rfork(ad, &blank);
+	if (!ok) {
+		return -1;
+	}
+
+	if (converted_xattr || blank) {
 		ok = ad_convert_truncate(ad, smb_fname);
 		if (!ok) {
 			return -1;