patch 8.2.3022: available encryption methods are not strong enoughv8.2.3022

Problem:    Available encryption methods are not strong enough.
Solution:   Add initial support for xchaha20. (Christian Brabandt,
            closes #8394)

29 files changed, 820 insertions, 64 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9127455bc1..e569b42397 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -71,7 +71,8 @@ jobs:
             cscope \
             libgtk2.0-dev \
             desktop-file-utils \
-            libtool-bin
+            libtool-bin \
+            libsodium-dev
 
       - name: Install clang-11
         if: matrix.compiler == 'clang'
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index dd2d24232a..4620623c63 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -11971,6 +11971,7 @@ scrollbind		Compiled with 'scrollbind' support. (always true)
 showcmd			Compiled with 'showcmd' support.
 signs			Compiled with |:sign| support.
 smartindent		Compiled with 'smartindent' support.
+sodium			Compiled with libsodium for better crypt support
 sound			Compiled with sound support, e.g. `sound_playevent()`
 spell			Compiled with spell checking support |spell|.
 startuptime		Compiled with |--startuptime| support.
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index e600dd91dd..19ddd9cb5f 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -2384,6 +2384,23 @@ A jump table for the options with a short description can be found at |Q_op|.
 			you write the file the encrypted bytes will be
 			different.  The whole undo file is encrypted, not just
 			the pieces of text.
+					*E1193* *E1194* *E1195* *E1196*
+					*E1197* *E1198* *E1199* *E1200* *E1201*
+	   xchacha20	XChaCha20 Cipher with Poly1305 Message Authentication
+			Code.  Medium strong till strong encryption.
+			Encryption is provided by the libsodium library, it
+			requires Vim to be built with |+sodium|
+			It adds a seed and a message authentication code (MAC)
+			to the file.  This needs at least a Vim 8.2.3022 to
+			read the encrypted file.
+			Encryption of swap files is not supported, therefore
+			no swap file will be used when xchacha20 encryption is
+			enabled.
+			Encryption of undo files is not yet supported,
+			therefore no undo file will currently be written.
+			CURRENTLY EXPERIMENTAL: Files written with this method
+			might have to be read back with the same version of
+			Vim if the binary format changes later.
 
 	You should use "blowfish2", also to re-encrypt older files.
 
diff --git a/runtime/doc/various.txt b/runtime/doc/various.txt
index eb45922ccf..0ad12e8042 100644
--- a/runtime/doc/various.txt
+++ b/runtime/doc/various.txt
@@ -444,6 +444,7 @@ m  *+ruby/dyn*		Ruby interface |ruby-dynamic| |/dyn|
 T  *+scrollbind*	|'scrollbind'|
 B  *+signs*		|:sign|
 N  *+smartindent*	|'smartindent'|
+B  *+sodium*		compiled with libsodium for better encryption support
 B  *+sound*		|sound_playevent()|, |sound_playfile()| functions, etc.
 N  *+spell*		spell checking support, see |spell|
 N  *+startuptime*	|--startuptime| argument
diff --git a/src/INSTALLpc.txt b/src/INSTALLpc.txt
index b5c1a0b58c..d5516c891a 100644
--- a/src/INSTALLpc.txt
+++ b/src/INSTALLpc.txt
@@ -322,6 +322,9 @@ MSYS2 has its own git package, and you can also install it via pacman:
 
     $ pacman -S git
 
+For enabling libsodium support, you also need to install the package
+
+    $ pacman -S mingw-w64-x86_64-libsodium
 
 2.3. Keep the build environment up-to-date
 
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index c33200b33e..e93165dbf4 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -41,6 +41,9 @@ DEBUG=no
 # set to yes to measure code coverage
 COVERAGE=no
 
+# better encryption support using libsodium
+#SODIUM=yes
+
 # set to SIZE for size, SPEED for speed, MAXSPEED for maximum optimization
 OPTIMIZE=MAXSPEED
 
@@ -517,6 +520,10 @@ CXXFLAGS = -std=gnu++11
 WINDRES_FLAGS =
 EXTRA_LIBS =
 
+ifdef SODIUM
+DEFINES += -DHAVE_SODIUM
+endif
+
 ifdef GETTEXT
 DEFINES += -DHAVE_GETTEXT -DHAVE_LOCALE_H
 GETTEXTINCLUDE = $(GETTEXT)/include
@@ -660,6 +667,10 @@ DEFINES += -DFEAT_DIRECTX_COLOR_EMOJI
  endif
 endif
 
+ifeq ($(SODIUM),yes)
+SODIUMLIB = -lsodium
+endif
+
 # Only allow XPM for a GUI build.
 ifeq (yes, $(GUI))
 
@@ -1064,7 +1075,7 @@ $(EXEOBJC): | $(OUTDIR)
 
 ifeq ($(VIMDLL),yes)
 $(TARGET): $(OBJ)
-	$(LINK) $(CFLAGS) $(LFLAGS) -o $@ $(OBJ) $(LIB) -lole32 -luuid -lgdi32 $(LUA_LIB) $(MZSCHEME_LIBDIR) $(MZSCHEME_LIB) $(PYTHONLIB) $(PYTHON3LIB) $(RUBYLIB)
+	$(LINK) $(CFLAGS) $(LFLAGS) -o $@ $(OBJ) $(LIB) -lole32 -luuid -lgdi32 $(LUA_LIB) $(MZSCHEME_LIBDIR) $(MZSCHEME_LIB) $(PYTHONLIB) $(PYTHON3LIB) $(RUBYLIB) $(SODIUMLIB)
 
 $(GVIMEXE): $(EXEOBJG) $(VIMDLLBASE).dll
 	$(CC) -L. $(EXELFLAGS) -mwindows -o $@ $(EXEOBJG) -l$(VIMDLLBASE)
@@ -1073,7 +1084,7 @@ $(VIMEXE): $(EXEOBJC) $(VIMDLLBASE).dll
 	$(CC) -L. $(EXELFLAGS) -o $@ $(EXEOBJC) -l$(VIMDLLBASE)
 else
 $(TARGET): $(OBJ)
-	$(LINK) $(CFLAGS) $(LFLAGS) -o $@ $(OBJ) $(LIB) -lole32 -luuid $(LUA_LIB) $(MZSCHEME_LIBDIR) $(MZSCHEME_LIB) $(PYTHONLIB) $(PYTHON3LIB) $(RUBYLIB)
+	$(LINK) $(CFLAGS) $(LFLAGS) -o $@ $(OBJ) $(LIB) -lole32 -luuid $(LUA_LIB) $(MZSCHEME_LIBDIR) $(MZSCHEME_LIB) $(PYTHONLIB) $(PYTHON3LIB) $(RUBYLIB) $(SODIUMLIB)
 endif
 
 upx: exes
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 42b6f8ddf6..c61bb27ab7 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -41,6 +41,9 @@
 #
 #	Sound support: SOUND=yes (default is yes)
 #
+#	Sodium support: SODIUM=[Path to Sodium directory]
+#	 You need to install the msvc package from https://download.libsodium.org/libsodium/releases/
+#
 #	DLL support (EXPERIMENTAL): VIMDLL=yes (default is no)
 #	  Creates vim{32,64}.dll, and stub gvim.exe and vim.exe.
 #	  The shared codes between the GUI and the console are built into
@@ -372,6 +375,26 @@ SOUND = no
 ! endif
 !endif
 
+!ifndef SODIUM
+SODIUM = no
+!endif
+
+!if "$(SODIUM)" != "no"
+! if "$(CPU)" == "AMD64"
+SOD_LIB		= $(SODIUM)\x64\Release\v140\dynamic
+! elseif "$(CPU)" == "i386"
+SOD_LIB		= $(SODIUM)\x86\Release\v140\dynamic
+! else
+SODIUM = no
+! endif
+!endif
+
+!if "$(SODIUM)" != "no"
+SOD_INC		= -I $(SODIUM)\include
+SOD_DEFS	= -DFEAT_SODIUM
+SOD_LIB		= $(SOD_LIB)\libsodium.lib
+!endif
+
 !ifndef NETBEANS
 NETBEANS = $(GUI)
 !endif
@@ -491,7 +514,7 @@ CON_LIB = $(CON_LIB) /DELAYLOAD:comdlg32.dll /DELAYLOAD:ole32.dll DelayImp.lib
 
 CFLAGS = -c /W3 /GF /nologo $(CVARS) -I. -Iproto -DHAVE_PATHDEF -DWIN32 \
 		$(CSCOPE_DEFS) $(TERM_DEFS) $(SOUND_DEFS) $(NETBEANS_DEFS) $(CHANNEL_DEFS) \
-		$(NBDEBUG_DEFS) $(XPM_DEFS) \
+		$(NBDEBUG_DEFS) $(XPM_DEFS) $(SOD_DEFS) \
 		$(DEFINES) -DWINVER=$(WINVER) -D_WIN32_WINNT=$(WINVER)
 
 #>>>>> end of choices
@@ -703,7 +726,7 @@ CFLAGS = $(CFLAGS) $(CFLAGS_DEPR)
 
 INCL =	vim.h alloc.h ascii.h ex_cmds.h feature.h errors.h globals.h \
 	keymap.h macros.h option.h os_dos.h os_win32.h proto.h regexp.h \
-	spell.h structs.h term.h beval.h $(NBDEBUG_INCL)
+	spell.h structs.h term.h beval.h $(NBDEBUG_INCL) $(SOD_INC)
 
 OBJ = \
 	$(OUTDIR)\arabic.obj \
@@ -1282,7 +1305,7 @@ conflags = $(conflags) /map /mapinfo:lines
 LINKARGS1 = $(linkdebug) $(conflags)
 LINKARGS2 = $(CON_LIB) $(GUI_LIB) $(NODEFAULTLIB) $(LIBC) $(OLE_LIB) user32.lib \
 		$(LUA_LIB) $(MZSCHEME_LIB) $(PERL_LIB) $(PYTHON_LIB) $(PYTHON3_LIB) $(RUBY_LIB) \
-		$(TCL_LIB) $(SOUND_LIB) $(NETBEANS_LIB) $(XPM_LIB) $(LINK_PDB)
+		$(TCL_LIB) $(SOUND_LIB) $(NETBEANS_LIB) $(XPM_LIB) $(SOD_LIB) $(LINK_PDB)
 
 # Report link time code generation progress if used. 
 !ifdef NODEBUG
diff --git a/src/auto/configure b/src/auto/configure
index 7ecc40ca51..cd678fd9f1 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -839,6 +839,7 @@ with_motif_lib
 with_tlib
 enable_largefile
 enable_canberra
+enable_libsodium
 enable_acl
 enable_gpm
 enable_sysmouse
@@ -1513,6 +1514,7 @@ Optional Features:
   --disable-desktop-database-update  update disabled
   --disable-largefile     omit support for large files
   --disable-canberra      Do not use libcanberra.
+  --disable-libsodium      Do not use libsodium.
   --disable-acl           No check for ACL support.
   --disable-gpm           Don't use gpm (Linux mouse daemon).
   --disable-sysmouse      Don't use sysmouse (mouse in *BSD console).
@@ -13005,6 +13007,70 @@ rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking --enable-libsodium argument" >&5
+$as_echo_n "checking --enable-libsodium argument... " >&6; }
+# Check whether --enable-libsodium was given.
+if test "${enable_libsodium+set}" = set; then :
+  enableval=$enable_libsodium;
+else
+  enable_libsodium="maybe"
+fi
+
+
+if test "$enable_libsodium" = "maybe"; then
+  if test "$features" = "big" -o "$features" = "huge"; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: Defaulting to yes" >&5
+$as_echo "Defaulting to yes" >&6; }
+    enable_libsodium="yes"
+  else
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: Defaulting to no" >&5
+$as_echo "Defaulting to no" >&6; }
+    enable_libsodium="no"
+  fi
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $enable_libsodium" >&5
+$as_echo "$enable_libsodium" >&6; }
+fi
+if test "$enable_libsodium" = "yes"; then
+  if test "x$PKG_CONFIG" != "xno"; then
+    libsodium_lib=`$PKG_CONFIG --libs libsodium 2>/dev/null`
+    libsodium_cflags=`$PKG_CONFIG --cflags libsodium 2>/dev/null`
+  fi
+  if test "x$libsodium_lib" = "x"; then
+    libsodium_lib=-lsodium
+    libsodium_cflags=
+  fi
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for libcanberra" >&5
+$as_echo_n "checking for libcanberra... " >&6; }
+  ac_save_CFLAGS="$CFLAGS"
+  ac_save_LIBS="$LIBS"
+  CFLAGS="$CFLAGS $libsodium_cflags"
+  LIBS="$LIBS $libsodium_lib"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+  # include <sodium.h>
+
+int
+main ()
+{
+
+     printf("%d", sodium_init());
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }; $as_echo "#define HAVE_SODIUM 1" >>confdefs.h
+
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no; try installing libsodium-dev" >&5
+$as_echo "no; try installing libsodium-dev" >&6; }; CFLAGS="$ac_save_CFLAGS"; LIBS="$ac_save_LIBS"
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for st_blksize" >&5
 $as_echo_n "checking for st_blksize... " >&6; }
diff --git a/src/blowfish.c b/src/blowfish.c
index 342bcc406e..4502a1c5db 100644
--- a/src/blowfish.c
+++ b/src/blowfish.c
@@ -596,7 +596,8 @@ crypt_blowfish_encode(
     cryptstate_T *state,
     char_u	*from,
     size_t	len,
-    char_u	*to)
+    char_u	*to,
+    int		last UNUSED)
 {
     bf_state_T *bfs = state->method_state;
     size_t	i;
@@ -619,7 +620,8 @@ crypt_blowfish_decode(
     cryptstate_T *state,
     char_u	*from,
     size_t	len,
-    char_u	*to)
+    char_u	*to,
+    int		last UNUSED)
 {
     bf_state_T *bfs = state->method_state;
     size_t	i;
@@ -680,5 +682,4 @@ blowfish_self_test(void)
     }
     return OK;
 }
-
 #endif // FEAT_CRYPT
diff --git a/src/bufwrite.c b/src/bufwrite.c
index c7c832cff7..c91bcd9958 100644
--- a/src/bufwrite.c
+++ b/src/bufwrite.c
@@ -30,6 +30,7 @@ struct bw_info
     int		bw_flags;	// FIO_ flags
 #ifdef FEAT_CRYPT
     buf_T	*bw_buffer;	// buffer being written
+    int         bw_finish;      // finish encrypting
 #endif
     char_u	bw_rest[CONV_RESTLEN]; // not converted bytes
     int		bw_restlen;	// nr of bytes in bw_rest[]
@@ -493,14 +494,14 @@ buf_write_bytes(struct bw_info *ip)
 	if (crypt_works_inplace(ip->bw_buffer->b_cryptstate))
 	{
 # endif
-	    crypt_encode_inplace(ip->bw_buffer->b_cryptstate, buf, len);
+	    crypt_encode_inplace(ip->bw_buffer->b_cryptstate, buf, len, ip->bw_finish);
 # ifdef CRYPT_NOT_INPLACE
 	}
 	else
 	{
 	    char_u *outbuf;
 
-	    len = crypt_encode_alloc(curbuf->b_cryptstate, buf, len, &outbuf);
+	    len = crypt_encode_alloc(curbuf->b_cryptstate, buf, len, &outbuf, ip->bw_finish);
 	    if (len == 0)
 		return OK;  // Crypt layer is buffering, will flush later.
 	    wlen = write_eintr(ip->bw_fd, outbuf, len);
@@ -724,6 +725,7 @@ buf_write(
 #endif
 #ifdef FEAT_CRYPT
     write_info.bw_buffer = buf;
+    write_info.bw_finish = FALSE;
 #endif
 
     // After writing a file changedtick changes but we don't want to display
@@ -2015,6 +2017,13 @@ restore_backup:
 		++s;
 		if (++len != bufsize)
 		    continue;
+#ifdef FEAT_CRYPT
+		if (write_info.bw_fd > 0 && lnum == end
+			&& (write_info.bw_flags & FIO_ENCRYPTED)
+			&& *buf->b_p_key != NUL && !filtering
+			&& *ptr == NUL)
+		    write_info.bw_finish = TRUE;
+ #endif
 		if (buf_write_bytes(&write_info) == FAIL)
 		{
 		    end = 0;		// write error: break loop
@@ -2118,6 +2127,12 @@ restore_backup:
 	if (len > 0 && end > 0)
 	{
 	    write_info.bw_len = len;
+#ifdef FEAT_CRYPT
+	    if (write_info.bw_fd > 0 && lnum >= end
+		    && (write_info.bw_flags & FIO_ENCRYPTED)
+		    && *buf->b_p_key != NUL && !filtering)
+		write_info.bw_finish = TRUE;
+ #endif
 	    if (buf_write_bytes(&write_info) == FAIL)
 		end = 0;		    // write error
 	    nchars += len;
diff --git a/src/config.h.in b/src/config.h.in
index fbf4b2449c..0808cc3587 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -208,6 +208,7 @@
 #undef HAVE_STRPTIME
 #undef HAVE_STRTOL
 #undef HAVE_CANBERRA
+#undef HAVE_SODIUM
 #undef HAVE_ST_BLKSIZE
 #undef HAVE_SYSCONF
 #undef HAVE_SYSCTL
diff --git a/src/configure.ac b/src/configure.ac
index 9810ea1fc4..84b54dbf0a 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3767,6 +3767,43 @@ if test "$enable_canberra" = "yes"; then
        AC_MSG_RESULT(no; try installing libcanberra-dev); CFLAGS="$ac_save_CFLAGS"; LIBS="$ac_save_LIBS")
 fi
 
+AC_MSG_CHECKING(--enable-libsodium argument)
+AC_ARG_ENABLE(libsodium,
+	[  --disable-libsodium      Do not use libsodium.],
+	, [enable_libsodium="maybe"])
+
+if test "$enable_libsodium" = "maybe"; then
+  if test "$features" = "big" -o "$features" = "huge"; then
+    AC_MSG_RESULT(Defaulting to yes)
+    enable_libsodium="yes"
+  else
+    AC_MSG_RESULT(Defaulting to no)
+    enable_libsodium="no"
+  fi
+else
+  AC_MSG_RESULT($enable_libsodium)
+fi
+if test "$enable_libsodium" = "yes"; then
+  if test "x$PKG_CONFIG" != "xno"; then
+    libsodium_lib=`$PKG_CONFIG --libs libsodium 2>/dev/null`
+    libsodium_cflags=`$PKG_CONFIG --cflags libsodium 2>/dev/null`
+  fi
+  if test "x$libsodium_lib" = "x"; then
+    libsodium_lib=-lsodium
+    libsodium_cflags=
+  fi
+  AC_MSG_CHECKING(for libcanberra)
+  ac_save_CFLAGS="$CFLAGS"
+  ac_save_LIBS="$LIBS"
+  CFLAGS="$CFLAGS $libsodium_cflags"
+  LIBS="$LIBS $libsodium_lib"
+  AC_TRY_LINK([
+  # include <sodium.h>
+      ], [
+     printf("%d", sodium_init()); ],
+       AC_MSG_RESULT(yes); AC_DEFINE(HAVE_SODIUM),
+       AC_MSG_RESULT(no; try installing libsodium-dev); CFLAGS="$ac_save_CFLAGS"; LIBS="$ac_save_LIBS")
+fi
 
 dnl fstatfs() can take 2 to 4 arguments, try to use st_blksize if possible
 AC_MSG_CHECKING(for st_blksize)
diff --git a/src/crypt.c b/src/crypt.c
index 0164f1ce9d..35d4e14dc3 100644
--- a/src/crypt.c
+++ b/src/crypt.c
@@ -12,6 +12,10 @@
  */
 #include "vim.h"
 
+#ifdef FEAT_SODIUM
+# include <sodium.h>
+#endif
+
 #if defined(FEAT_CRYPT) || defined(PROTO)
 /*
  * Optional encryption support.
@@ -33,7 +37,7 @@ typedef struct {
     char    *name;	// encryption name as used in 'cryptmethod'
     char    *magic;	// magic bytes stored in file header
     int	    salt_len;	// length of salt, or 0 when not using salt
-    int	    seed_len;	// length of seed, or 0 when not using salt
+    int	    seed_len;	// length of seed, or 0 when not using seed
 #ifdef CRYPT_NOT_INPLACE
     int	    works_inplace; // encryption/decryption can be done in-place
 #endif
@@ -49,16 +53,16 @@ typedef struct {
     // Function pointers for encoding/decoding from one buffer into another.
     // Optional, however, these or the _buffer ones should be configured.
     void (*encode_fn)(cryptstate_T *state, char_u *from, size_t len,
-								  char_u *to);
+							char_u *to, int last);
     void (*decode_fn)(cryptstate_T *state, char_u *from, size_t len,
-								  char_u *to);
+							char_u *to, int last);
 
     // Function pointers for encoding and decoding, can buffer data if needed.
     // Optional (however, these or the above should be configured).
     long (*encode_buffer_fn)(cryptstate_T *state, char_u *from, size_t len,
-							     char_u **newptr);
+						    char_u **newptr, int last);
     long (*decode_buffer_fn)(cryptstate_T *state, char_u *from, size_t len,
-							     char_u **newptr);
+						    char_u **newptr, int last);
 
     // Function pointers for in-place encoding and decoding, used for
     // crypt_*_inplace(). "from" and "to" arguments will be equal.
@@ -68,9 +72,9 @@ typedef struct {
     // padding to files).
     // This method is used for swap and undo files which have a rigid format.
     void (*encode_inplace_fn)(cryptstate_T *state, char_u *p1, size_t len,
-								  char_u *p2);
+							char_u *p2, int last);
     void (*decode_inplace_fn)(cryptstate_T *state, char_u *p1, size_t len,
-								  char_u *p2);
+							char_u *p2, int last);
 } cryptmethod_T;
 
 // index is method_nr of cryptstate_T, CRYPT_M_*
@@ -126,10 +130,41 @@ static cryptmethod_T cryptmethods[CRYPT_M_COUNT] = {
 	crypt_blowfish_encode, crypt_blowfish_decode,
     },
 
+    // XChaCha20 using libsodium
+    {
+	"xchacha20",
+	"VimCrypt~04!",
+#ifdef FEAT_SODIUM
+	crypto_pwhash_argon2id_SALTBYTES, // 16
+#else
+	16,
+#endif
+	8,
+#ifdef CRYPT_NOT_INPLACE
+	FALSE,
+#endif
+	FALSE,
+	NULL,
+	crypt_sodium_init,
+	crypt_sodium_encode, crypt_sodium_decode,
+	crypt_sodium_buffer_encode, crypt_sodium_buffer_decode,
+	crypt_sodium_encode, crypt_sodium_decode,
+    },
+
     // NOTE: when adding a new method, use some random bytes for the magic key,
     // to avoid that a text file is recognized as encrypted.
 };
 
+#ifdef FEAT_SODIUM
+typedef struct {
+    size_t	    count;
+    unsigned char   key[crypto_box_SEEDBYTES];
+		  // 32, same as crypto_secretstream_xchacha20poly1305_KEYBYTES
+    crypto_secretstream_xchacha20poly1305_state
+		    state;
+} sodium_state_T;
+#endif
+
 #define CRYPT_MAGIC_LEN	12	// cannot change
 static char	crypt_magic_head[] = "VimCrypt~";
 
@@ -260,7 +295,7 @@ crypt_create(
 
     state->method_nr = method_nr;
     if (cryptmethods[method_nr].init_fn(
-			   state, key, salt, salt_len, seed, seed_len) == FAIL)
+	state, key, salt, salt_len, seed, seed_len) == FAIL)
     {
         vim_free(state);
         return NULL;
@@ -365,9 +400,16 @@ crypt_create_for_writing(
 	// TODO: Should this be crypt method specific? (Probably not worth
 	// it).  sha2_seed is pretty bad for large amounts of entropy, so make
 	// that into something which is suitable for anything.
-	sha2_seed(salt, salt_len, seed, seed_len);
+#ifdef FEAT_SODIUM
+	if (sodium_init() >= 0)
+	{
+	    randombytes_buf(salt, salt_len);
+	    randombytes_buf(seed, seed_len);
+	}
+	else
+#endif
+	    sha2_seed(salt, salt_len, seed, seed_len);
     }
-
     state = crypt_create(method_nr, key, salt, salt_len, seed, seed_len);
     if (state == NULL)
 	VIM_CLEAR(*header);
@@ -380,7 +422,15 @@ crypt_create_for_writing(
     void
 crypt_free_state(cryptstate_T *state)
 {
-    vim_free(state->method_state);
+#ifdef FEAT_SODIUM
+    if (state->method_nr == CRYPT_M_SOD)
+    {
+	sodium_memzero(state->method_state, sizeof(sodium_state_T));
+	sodium_free(state->method_state);
+    }
+    else
+#endif
+	vim_free(state->method_state);
     vim_free(state);
 }
 
@@ -395,21 +445,22 @@ crypt_encode_alloc(
     cryptstate_T *state,
     char_u	*from,
     size_t	len,
-    char_u	**newptr)
+    char_u	**newptr,
+    int		last)
 {
     cryptmethod_T *method = &cryptmethods[state->method_nr];
 
     if (method->encode_buffer_fn != NULL)
 	// Has buffer function, pass through.
-	return method->encode_buffer_fn(state, from, len, newptr);
+	return method->encode_buffer_fn(state, from, len, newptr, last);
     if (len == 0)
 	// Not buffering, just return EOF.
 	return (long)len;
 
-    *newptr = alloc(len);
+    *newptr = alloc(len + 50);
     if (*newptr == NULL)
 	return -1;
-    method->encode_fn(state, from, len, *newptr);
+    method->encode_fn(state, from, len, *newptr, last);
     return (long)len;
 }
 
@@ -423,13 +474,14 @@ crypt_decode_alloc(
     cryptstate_T *state,
     char_u	*ptr,
     long	len,
-    char_u      **newptr)
+    char_u      **newptr,
+    int		last)
 {
     cryptmethod_T *method = &cryptmethods[state->method_nr];
 
     if (method->decode_buffer_fn != NULL)
 	// Has buffer function, pass through.
-	return method->decode_buffer_fn(state, ptr, len, newptr);
+	return method->decode_buffer_fn(state, ptr, len, newptr, last);
 
     if (len == 0)
 	// Not buffering, just return EOF.
@@ -438,7 +490,7 @@ crypt_decode_alloc(
     *newptr = alloc(len);
     if (*newptr == NULL)
 	return -1;
-    method->decode_fn(state, ptr, len, *newptr);
+    method->decode_fn(state, ptr, len, *newptr, last);
     return len;
 }
 #endif
@@ -451,9 +503,10 @@ crypt_encode(
     cryptstate_T *state,
     char_u	*from,
     size_t	len,
-    char_u	*to)
+    char_u	*to,
+    int		last)
 {
-    cryptmethods[state->method_nr].encode_fn(state, from, len, to);
+    cryptmethods[state->method_nr].encode_fn(state, from, len, to, last);
 }
 
 #if 0  // unused
@@ -465,9 +518,10 @@ crypt_decode(
     cryptstate_T *state,
     char_u	*from,
     size_t	len,
-    char_u	*to)
+    char_u	*to,
+    int		last)
 {
-    cryptmethods[state->method_nr].decode_fn(state, from, len, to);
+    cryptmethods[state->method_nr].decode_fn(state, from, len, to, last);
 }
 #endif
 
@@ -478,9 +532,11 @@ crypt_decode(
 crypt_encode_inplace(
     cryptstate_T *state,
     char_u	*buf,
-    size_t	len)
+    size_t	len,
+    int         last)
 {
-    cryptmethods[state->method_nr].encode_inplace_fn(state, buf, len, buf);
+    cryptmethods[state->method_nr].encode_inplace_fn(state, buf, len,
+								    buf, last);
 }
 
 /*
@@ -490,9 +546,11 @@ crypt_encode_inplace(
 crypt_decode_inplace(
     cryptstate_T *state,
     char_u	*buf,
-    size_t	len)
+    size_t	len,
+    int		last)
 {
-    cryptmethods[state->method_nr].decode_inplace_fn(state, buf, len, buf);
+    cryptmethods[state->method_nr].decode_inplace_fn(state, buf, len,
+								    buf, last);
 }
 
 /*
@@ -523,6 +581,19 @@ crypt_check_method(int method)
 	msg_scroll = TRUE;
 	msg(_("Warning: Using a weak encryption method; see :help 'cm'"));
     }
+    if (method == CRYPT_M_SOD)
+    {
+	// encryption uses padding and MAC, that does not work very well with
+	// swap and undo files, so disable them
+	mf_close_file(curbuf, TRUE);	// remove the swap file
+	set_option_value((char_u *)"swf", 0, NULL, OPT_LOCAL);
+#ifdef FEAT_PERSISTENT_UNDO
+	set_option_value((char_u *)"udf", 0, NULL, OPT_LOCAL);
+#endif
+
+	msg_scroll = TRUE;
+	msg(_("Note: Encryption of swapfile not supported, disabling swap- and undofile"));
+    }
 }
 
     void
@@ -610,4 +681,266 @@ crypt_append_msg(
     }
 }
 
+    int
+crypt_sodium_init(
+    cryptstate_T	*state UNUSED,
+    char_u		*key UNUSED,
+    char_u		*salt UNUSED,
+    int			salt_len UNUSED,
+    char_u		*seed UNUSED,
+    int			seed_len UNUSED)
+{
+# ifdef FEAT_SODIUM
+    // crypto_box_SEEDBYTES ==  crypto_secretstream_xchacha20poly1305_KEYBYTES
+    unsigned char	dkey[crypto_box_SEEDBYTES]; // 32
+    sodium_state_T	*sd_state;
+
+    if (sodium_init() < 0)
+	return FAIL;
+
+    sd_state = (sodium_state_T *)sodium_malloc(sizeof(sodium_state_T));
+    sodium_memzero(sd_state, sizeof(sodium_state_T));
+
+    // derive a key from the password
+    if (crypto_pwhash(dkey, sizeof(dkey), (const char *)key, STRLEN(key), salt,
+	crypto_pwhash_OPSLIMIT_INTERACTIVE, crypto_pwhash_MEMLIMIT_INTERACTIVE,
+	crypto_pwhash_ALG_DEFAULT) != 0)
+    {
+	// out of memory
+	sodium_free(sd_state);
+	return FAIL;
+    }
+    memcpy(sd_state->key, dkey, crypto_box_SEEDBYTES);
+    sd_state->count = 0;
+    state->method_state = sd_state;
+
+    return OK;
+# else
+    emsg(e_libsodium_not_built_in);
+    return FAIL;
+# endif
+}
+
+/*
+ * Encrypt "from[len]" into "to[len]".
+ * "from" and "to" can be equal to encrypt in place.
+ * Call needs to ensure that there is enough space in to (for the header)
+ */
+    void
+crypt_sodium_encode(
+    cryptstate_T *state UNUSED,
+    char_u	*from UNUSED,
+    size_t	len UNUSED,
+    char_u	*to UNUSED,
+    int		last UNUSED)
+{
+# ifdef FEAT_SODIUM
+    // crypto_box_SEEDBYTES == crypto_secretstream_xchacha20poly1305_KEYBYTES
+    sodium_state_T *sod_st = state->method_state;
+    unsigned char  tag = last
+			? crypto_secretstream_xchacha20poly1305_TAG_FINAL  : 0;
+
+    if (sod_st->count == 0)
+    {
+	if (len <= crypto_secretstream_xchacha20poly1305_HEADERBYTES)
+	{
+	    emsg(e_libsodium_cannot_encrypt_header);
+	    return;
+	}
+	crypto_secretstream_xchacha20poly1305_init_push(&sod_st->state,
+							      to, sod_st->key);
+	to += crypto_secretstream_xchacha20poly1305_HEADERBYTES;
+    }
+
+    if (sod_st->count && len <= crypto_secretstream_xchacha20poly1305_ABYTES)
+    {
+	emsg(e_libsodium_cannot_encrypt_buffer);
+	return;
+    }
+
+    crypto_secretstream_xchacha20poly1305_push(&sod_st->state, to, NULL,
+						      from, len, NULL, 0, tag);
+
+    sod_st->count++;
+# endif
+}
+
+/* TODO: Unused
+ * Decrypt "from[len]" into "to[len]".
+ * "from" and "to" can be equal to encrypt in place.
+ */
+    void
+crypt_sodium_decode(
+    cryptstate_T *state UNUSED,
+    char_u	*from UNUSED,
+    size_t	len UNUSED,
+    char_u	*to UNUSED,
+    int		last UNUSED)
+{
+# ifdef FEAT_SODIUM
+    // crypto_box_SEEDBYTES ==  crypto_secretstream_xchacha20poly1305_KEYBYTES
+    sodium_state_T *sod_st = state->method_state;
+    unsigned char  tag;
+    unsigned long long buf_len;
+    char_u *p1 = from;
+    char_u *p2 = to;
+    char_u *buf_out;
+
+    if (sod_st->count == 0
+		   && len <= crypto_secretstream_xchacha20poly1305_HEADERBYTES)
+    {
+	emsg(e_libsodium_cannot_decrypt_header);
+	return;
+    }
+
+    buf_out = (char_u *)alloc(len);
+
+    if (buf_out == NULL)
+    {
+	emsg(e_libsodium_cannot_allocate_buffer);
+	return;
+    }
+    if (sod_st->count == 0)
+    {
+	if (crypto_secretstream_xchacha20poly1305_init_pull(
+				       &sod_st->state, from, sod_st->key) != 0)
+	{
+	    emsg(e_libsodium_decryption_failed_header_incomplete);
+	    goto fail;
+	}
+
+	from += crypto_secretstream_xchacha20poly1305_HEADERBYTES;
+	len -= crypto_secretstream_xchacha20poly1305_HEADERBYTES;
+
+	if (p1 == p2)
+	    to += crypto_secretstream_xchacha20poly1305_HEADERBYTES;
+    }
+
+    if (sod_st->count && len <= crypto_secretstream_xchacha20poly1305_ABYTES)
+    {
+	emsg(e_libsodium_cannot_decrypt_buffer);
+	return;
+    }
+    if (crypto_secretstream_xchacha20poly1305_pull(&sod_st->state,
+			     buf_out, &buf_len, &tag, from, len, NULL, 0) != 0)
+    {
+	emsg(e_libsodium_decription_failed);
+	goto fail;
+    }
+    sod_st->count++;
+
+    if (tag == crypto_secretstream_xchacha20poly1305_TAG_FINAL && !last)
+    {
+	emsg(e_libsodium_decyption_failed_premature);
+	goto fail;
+    }
+    if (p1 == p2)
+	mch_memmove(p2, buf_out, buf_len);
+
+fail:
+    vim_free(buf_out);
+# e