s3: smbd: Create and use a common function for generating a fileid - …

…create_clock_itime().

This first gets the clock_gettime_mono() value, converts to an NTTIME (as
this is what is stored in the dos attribute EA), then mixes in 8 bits of
randomness shifted up by 55 bits to cope with poor resolution clocks to
avoid duplicate inodes.

Using 8 bits of randomness on top of an NTTIME gives us around 114
years headroom. We can now guarentee returning a itime-based
fileid in a normal share (storing dos attributes in an EA).

Remove knownfail.d/fileid-unique

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14928

Signed-off-by: Jeremy Allison <[email protected]>
Reviewed-by: Christof Schmitt <[email protected]>

Autobuild-User(master): Jeremy Allison <[email protected]>
Autobuild-Date(master): Sat Jan  8 06:35:22 UTC 2022 on sn-devel-184

source3/include/proto.h

@@ -175,6 +175,7 @@ void update_stat_ex_create_time(struct stat_ex *dst, struct timespec create_time
 void update_stat_ex_file_id(struct stat_ex *dst, uint64_t file_id);
 void update_stat_ex_from_saved_stat(struct stat_ex *dst,
 				    const struct stat_ex *src);
+void create_clock_itime(struct stat_ex *dst);
 int sys_stat(const char *fname, SMB_STRUCT_STAT *sbuf,
 	     bool fake_dir_create_times);
 int sys_fstat(int fd, SMB_STRUCT_STAT *sbuf,

source3/lib/system.c

@@ -310,6 +310,58 @@ void init_stat_ex_from_stat (struct stat_ex *dst,
 	dst->st_ex_iflags |= ST_EX_IFLAG_CALCULATED_FILE_ID;
 }
 
+/*******************************************************************
+ Create a clock-derived itime (imaginary) time. Used to generate
+ the fileid.
+********************************************************************/
+
+void create_clock_itime(struct stat_ex *dst)
+{
+	NTTIME tval;
+	struct timespec itime;
+	uint64_t mixin;
+	uint8_t rval;
+
+	/* Start with the system clock. */
+	clock_gettime_mono(&itime);
+
+	/* Convert to NTTIME. */
+	tval = unix_timespec_to_nt_time(itime);
+
+	/*
+	 * In case the system clock is poor granularity
+	 * (happens on VM or docker images) then mix in
+	 * 8 bits of randomness.
+	 */
+	generate_random_buffer((unsigned char *)&rval, 1);
+	mixin = rval;
+
+	/*
+	 * Shift up by 55 bits. This gives us approx 114 years
+	 * of headroom.
+	 */
+	mixin <<= 55;
+
+	/* And OR into the nttime. */
+	tval |= mixin;
+
+	/*
+	 * Convert to a unix timespec, ignoring any
+	 * constraints on seconds being higher than
+	 * TIME_T_MAX or lower than TIME_T_MIN. These
+	 * are only needed to allow unix display time functions
+	 * to work correctly, and this is being used to
+	 * generate a fileid. All we care about is the
+	 * NTTIME being valid across all NTTIME ranges
+	 * (which we carefully ensured above).
+	 */
+
+	itime = nt_time_to_unix_timespec_raw(tval);
+
+	/* And set as a generated itime. */
+	update_stat_ex_itime(dst, itime);
+}
+
 /*******************************************************************
 A stat() wrapper.
 ********************************************************************/

source3/smbd/open.c

@@ -4129,13 +4129,13 @@ static NTSTATUS open_file_ntcreate(connection_struct *conn,
 	 * If we created a file and it's not a stream, this is the point where
 	 * we set the itime (aka invented time) that get's stored in the DOS
 	 * attribute xattr. The value is going to be either what the filesystem
-	 * provided or a copy of the creation date.
+	 * provided or a generated itime value.
 	 *
 	 * Either way, we turn the itime into a File-ID, unless the filesystem
 	 * provided one (unlikely).
 	 */
 	if (info == FILE_WAS_CREATED && !is_named_stream(smb_fname)) {
-		smb_fname->st.st_ex_iflags &= ~ST_EX_IFLAG_CALCULATED_ITIME;
+		create_clock_itime(&smb_fname->st);
 
 		if (lp_store_dos_attributes(SNUM(conn)) &&
 		    smb_fname->st.st_ex_iflags & ST_EX_IFLAG_CALCULATED_FILE_ID)
@@ -4317,7 +4317,7 @@ static NTSTATUS mkdir_internal(connection_struct *conn,
 		return NT_STATUS_NOT_A_DIRECTORY;
 	}
 
-	smb_dname->st.st_ex_iflags &= ~ST_EX_IFLAG_CALCULATED_ITIME;
+	create_clock_itime(&smb_dname->st);
 
 	if (lp_store_dos_attributes(SNUM(conn))) {
 		if (smb_dname->st.st_ex_iflags & ST_EX_IFLAG_CALCULATED_FILE_ID)