From d530fbd400c88fa54c856d958963d77669ac9cf2 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Mon, 1 Nov 2021 14:44:32 +0100
Subject: docs: names longer than 175 bytes (not 176) are stored in longnames

Quoting fusefrontend_reverse/node_helpers.go :

	// File names are padded to 16-byte multiples, encrypted and
	// base64-encoded. We can encode at most 176 bytes to stay below the 255
	// bytes limit:
	// * base64(176 bytes) = 235 bytes
	// * base64(192 bytes) = 256 bytes (over 255!)
	// But the PKCS#7 padding is at least one byte. This means we can only use
	// 175 bytes for the file name.

Noticed by @bailey27 at https://github.com/rfjakob/gocryptfs/issues/499#issuecomment-955790427
---
 Documentation/MANPAGE.md             | 7 ++++---
 cli_args.go                          | 2 +-
 internal/configfile/feature_flags.go | 2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/Documentation/MANPAGE.md b/Documentation/MANPAGE.md
index b9c72dd..ffed44e 100644
--- a/Documentation/MANPAGE.md
+++ b/Documentation/MANPAGE.md
@@ -318,9 +318,10 @@ the directories. Example:
     gocryptfs -ko noexec /tmp/foo /tmp/bar
 
 #### -longnames
-Store names longer than 176 bytes in extra files (default true)
-This flag is useful when recovering old gocryptfs filesystems using
-"-masterkey". It is ignored (stays at the default) otherwise.
+Store names that are longer than 175 bytes in extra files (default true).
+
+This flag is only useful when recovering very old gocryptfs filesystems (gocryptfs v0.8 and earlier)
+using "-masterkey". It is ignored (stays at the default) otherwise.
 
 #### -nodev
 See `-dev, -nodev`.
diff --git a/cli_args.go b/cli_args.go
index e925345..6b97744 100644
--- a/cli_args.go
+++ b/cli_args.go
@@ -163,7 +163,7 @@ func parseCliOpts(osArgs []string) (args argContainer) {
 	flagSet.BoolVar(&args.quiet, "quiet", false, "Quiet - silence informational messages")
 	flagSet.BoolVar(&args.nosyslog, "nosyslog", false, "Do not redirect output to syslog when running in the background")
 	flagSet.BoolVar(&args.wpanic, "wpanic", false, "When encountering a warning, panic and exit immediately")
-	flagSet.BoolVar(&args.longnames, "longnames", true, "Store names longer than 176 bytes in extra files")
+	flagSet.BoolVar(&args.longnames, "longnames", true, "Store names longer than 175 bytes in extra files")
 	flagSet.BoolVar(&args.allow_other, "allow_other", false, "Allow other users to access the filesystem. "+
 		"Only works if user_allow_other is set in /etc/fuse.conf.")
 	flagSet.BoolVar(&args.reverse, "reverse", false, "Reverse mode")
diff --git a/internal/configfile/feature_flags.go b/internal/configfile/feature_flags.go
index e45b20c..d6627a5 100644
--- a/internal/configfile/feature_flags.go
+++ b/internal/configfile/feature_flags.go
@@ -14,7 +14,7 @@ const (
 	// This flag is mandatory since gocryptfs v1.0,
 	// except when XChaCha20Poly1305 is used.
 	FlagGCMIV128
-	// FlagLongNames allows file names longer than 176 bytes.
+	// FlagLongNames allows file names longer than 175 bytes.
 	FlagLongNames
 	// FlagLongNameMax sets a custom name length limit, names longer than that
 	// will be hashed.
-- 
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