Commit: patch 9.0.1968: cmdline completion should consider key option

[Christian Brabandt]

patch 9.0.1968: cmdline completion should consider key option

Commit: https://github.com/vim/vim/commit/6ee7b521fa7531ef356ececc8be7575c3800f872
Author: Yee Cheng Chin <ychi...@gmail.com>
Date: Sun Oct 1 09:13:22 2023 +0200

patch 9.0.1968: cmdline completion should consider key option

Problem: cmdline completion should consider key option
Solution: Disable cmdline completion for key option, slightly
refactor how P_NO_CMD_EXPAND is handled

Harden crypto 'key' option: turn off cmdline completion, disable set-=

"set-=" can be used maliciously with a crypto key, as it allows an
attacker (who either has access to the computer or a plugin author) to
guess a substring by observing the modified state. Simply turn off
set+=/-=/^= for this option as there is no good reason for them to be
used.

Update docs to make that clear as well.

Also, don't allow cmdline completion for 'key' as it just shows *****
which is not useful and confusing to the user what it means (if the user
accidentally hits enter they will have replaced their key with "*****"
instead).

Move logic to better location, don't use above 32-bit for flags

Move P_NO_CMD_EXPAND to use the unused 0x20 instead of going above
32-bits, as currently the flags parameter is only 32-bits on some
systems. Left a comment to warn that future additions will need to
change how the flags work either by making it 64-bit or split into two
member vars.

Also, move the logic for detecting P_NO_CMD_EXPAND earlier so it's not
up to each handler to decide, and you won't see the temporary "..." that
Vim shows while waiting for completion handler to complete.

closes: #13224

Signed-off-by: Christian Brabandt <c...@256bit.org>
Co-authored-by: Yee Cheng Chin <ychi...@gmail.com>

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 090399af0..a24dd0490 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4928,6 +4928,8 @@ A jump table for the options with a short description can be found at |Q_op|.
"echo &key". This is to avoid showing it to someone who shouldn't
know. It also means you cannot see it yourself once you have set it,
be careful not to make a typing error!
+ You also cannot use |:set-=|, |:set+=|, |:set^=| on this option to
+ prevent an attacker from guessing substrings in your key.
You can use "&key" in an expression to detect whether encryption is
enabled. When 'key' is set it returns "*****" (five stars).

diff --git a/src/option.c b/src/option.c
index d2096a5f0..c1d80fa81 100644
--- a/src/option.c
+++ b/src/option.c
@@ -1314,13 +1314,6 @@ ex_set(exarg_T *eap)
/*
* :set operator types
*/
-typedef enum {
- OP_NONE = 0,
- OP_ADDING, // "opt+=arg"
- OP_PREPENDING, // "opt^=arg"
- OP_REMOVING, // "opt-=arg"
-} set_op_T;
-
typedef enum {
PREFIX_NO = 0, // "no" prefix
PREFIX_NONE, // no prefix
@@ -1935,7 +1928,7 @@ do_set_option_string(
char_u **argp,
int nextchar,
set_op_T op_arg,
- int flags,
+ long_u flags,
int cp_val,
char_u *varp_arg,
char *errbuf,
@@ -2037,7 +2030,7 @@ do_set_option_string(
// be triggered that can cause havoc.
*errmsg = did_set_string_option(
opt_idx, (char_u **)varp, oldval, newval, errbuf,
- opt_flags, value_checked);
+ opt_flags, op, value_checked);

secure = secure_saved;
}
@@ -7376,6 +7369,15 @@ set_context_in_set_cmd(
else
expand_option_idx = opt_idx;

+ if (!is_term_option)
+ {
+ if (options[opt_idx].flags & P_NO_CMD_EXPAND)
+ {
+ xp->xp_context=EXPAND_UNSUCCESSFUL;
+ return;
+ }
+ }
+
xp->xp_pattern = p + 1;
expand_option_start_col = (int)(p + 1 - xp->xp_line);

diff --git a/src/option.h b/src/option.h
index ced4f3e4b..396c568d4 100644
--- a/src/option.h
+++ b/src/option.h
@@ -25,6 +25,7 @@
// the same.
#define P_EXPAND 0x10 // environment expansion. NOTE: P_EXPAND can
// never be used for local or hidden options!
+#define P_NO_CMD_EXPAND 0x20 // don't perform cmdline completions
#define P_NODEFAULT 0x40 // don't set to default value
#define P_DEF_ALLOCED 0x80 // default value is in allocated memory, must
// use vim_free() when assigning new value
@@ -61,6 +62,10 @@
#define P_MLE 0x20000000L // under control of 'modelineexpr'
#define P_FUNC 0x40000000L // accept a function reference or a lambda
#define P_COLON 0x80000000L // values use colons to create sublists
+// Warning: Currently we have used all 32 bits for option flags. On some 32-bit
+// systems, the flags are stored as a 32-bit integer, and adding more
+// flags will overflow it. Adding another flag will need to change how
+// it's stored first.

// Returned by get_option_value().
typedef enum {
diff --git a/src/optiondefs.h b/src/optiondefs.h
index 08de5bf40..f850d19b1 100644
--- a/src/optiondefs.h
+++ b/src/optiondefs.h
@@ -1467,7 +1467,7 @@ static struct vimoption options[] =
{"jumpoptions", "jop", P_STRING|P_VI_DEF|P_VIM|P_ONECOMMA|P_NODUP,
(char_u *)&p_jop, PV_NONE, did_set_jumpoptions, expand_set_jumpoptions,
{(char_u *)"", (char_u *)0L} SCTX_INIT},
- {"key", NULL, P_STRING|P_ALLOCED|P_VI_DEF|P_NO_MKRC,
+ {"key", NULL, P_STRING|P_ALLOCED|P_VI_DEF|P_NO_MKRC|P_NO_CMD_EXPAND,
#ifdef FEAT_CRYPT
(char_u *)&p_key, PV_KEY, did_set_cryptkey, NULL,
{(char_u *)"", (char_u *)0L}
diff --git a/src/optionstr.c b/src/optionstr.c
index 88532ee59..5a3dd6e75 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -579,7 +579,7 @@ set_string_option(
}
#endif
if ((errmsg = did_set_string_option(opt_idx, varp, oldval, value, errbuf,
- opt_flags, &value_checked)) == NULL)
+ opt_flags, OP_NONE, &value_checked)) == NULL)
did_set_option(opt_idx, opt_flags, TRUE, value_checked);

#if defined(FEAT_EVAL)
@@ -1578,6 +1578,10 @@ did_set_cryptkey(optset_T *args)
// history.
remove_key_from_history();

+ if (args->os_op != OP_NONE)
+ // Don't allow set+=/-=/^= as they can allow for substring guessing
+ return e_invalid_argument;
+
if (STRCMP(curbuf->b_p_key, args->os_oldval.string) != 0)
{
// Need to update the swapfile.
@@ -4209,6 +4213,7 @@ did_set_string_option(
char_u *value, // new value of the option
char *errbuf, // buffer for errors, or NULL
int opt_flags, // OPT_LOCAL and/or OPT_GLOBAL
+ set_op_T op, // OP_ADDING/OP_PREPENDING/OP_REMOVING
int *value_checked) // value was checked to be safe, no
// need to set P_INSECURE
{
@@ -4247,6 +4252,7 @@ did_set_string_option(
args.os_varp = (char_u *)varp;
args.os_idx = opt_idx;
args.os_flags = opt_flags;
+ args.os_op = op;
args.os_oldval.string = oldval;
args.os_newval.string = value;
args.os_errbuf = errbuf;
diff --git a/src/proto/optionstr.pro b/src/proto/optionstr.pro
index b4d9dfc95..48cccea8c 100644
--- a/src/proto/optionstr.pro
+++ b/src/proto/optionstr.pro
@@ -121,7 +121,7 @@ char *did_set_wildmode(optset_T *args);
char *did_set_wildoptions(optset_T *args);
char *did_set_winaltkeys(optset_T *args);
char *did_set_wincolor(optset_T *args);
-char *did_set_string_option(int opt_idx, char_u **varp, char_u *oldval, char_u *value, char *errbuf, int opt_flags, int *value_checked);
+char *did_set_string_option(int opt_idx, char_u **varp, char_u *oldval, char_u *value, char *errbuf, int opt_flags, set_op_T op, int *value_checked);
int expand_set_ambiwidth(optexpand_T *args, int *numMatches, char_u ***matches);
int expand_set_background(optexpand_T *args, int *numMatches, char_u ***matches);
int expand_set_backspace(optexpand_T *args, int *numMatches, char_u ***matches);
diff --git a/src/structs.h b/src/structs.h
index d05ae872d..1508f4791 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -588,6 +588,13 @@ typedef enum {
XP_PREFIX_INV, // "inv" prefix for bool option
} xp_prefix_T;

+typedef enum {
+ OP_NONE = 0,
+ OP_ADDING, // "opt+=arg"
+ OP_PREPENDING, // "opt^=arg"
+ OP_REMOVING, // "opt-=arg"
+} set_op_T;
+
/*
* used for completion on the command line
*/
@@ -4876,6 +4883,7 @@ typedef struct
char_u *os_varp;
int os_idx;
int os_flags;
+ set_op_T os_op;

// old value of the option (can be a string, number or a boolean)
union
diff --git a/src/testdir/test_crypt.vim b/src/testdir/test_crypt.vim
index 1782d83f3..85ed5740a 100644
--- a/src/testdir/test_crypt.vim
+++ b/src/testdir/test_crypt.vim
@@ -438,4 +438,27 @@ func Test_crypt_set_key_segfault()
bwipe!
endfunc

+func Test_crypt_set_key_disallow_append_subtract()
+ new Xtest4
+
+ set key=foobar
+ call assert_true(&modified)
+ setl nomodified
+
+ call assert_fails('set key-=foo', 'E474:')
+ call assert_fails('set key-=bar', 'E474:')
+ call assert_fails('set key-=foobar', 'E474:')
+ call assert_fails('set key-=test1', 'E474:')
+
+ call assert_false(&modified)
+ call assert_equal('*****', &key)
+
+ call assert_fails('set key+=test2', 'E474:')
+ call assert_fails('set key^=test3', 'E474:')
+
+ call assert_false(&modified)
+ set key=
+ bwipe!
+endfunc
+
" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_history.vim b/src/testdir/test_history.vim
index f1c31dee0..bb6d67172 100644
--- a/src/testdir/test_history.vim
+++ b/src/testdir/test_history.vim
@@ -244,8 +244,13 @@ endfunc
" Test for making sure the key value is not stored in history
func Test_history_crypt_key()
CheckFeature cryptv
+
call feedkeys(":set bs=2 key=abc ts=8\<CR>", 'xt')
call assert_equal('set bs=2 key= ts=8', histget(':'))
+
+ call assert_fails("call feedkeys(':set bs=2 key-=abc ts=8\<CR>', 'xt')")
+ call assert_equal('set bs=2 key-= ts=8', histget(':'))
+
set key& bs& ts&
endfunc

diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index 32d4910cc..8cd50694c 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -365,13 +365,15 @@ func Test_set_completion()
call feedkeys(":set spellsuggest=best,file:test_options.v\<Tab>\<C-B>\"\<CR>", 'xt')
call assert_equal("\"set spellsuggest=best,file:test_options.vim", @:)

- " Expand value for 'key'
- set key=abcd
- call feedkeys(":set key=\<Tab>\<C-B>\"\<CR>", 'xt')
- call assert_equal('"set key=*****', @:)
- call feedkeys(":set key-=\<Tab>\<C-B>\"\<CR>", 'xt')
- call assert_equal('"set key-=*****', @:)
- set key=
+ " Expanding value for 'key' is disallowed
+ if exists('+key')
+ set key=abcd
+ call feedkeys(":set key=\<Tab>\<C-B>\"\<CR>", 'xt')
+ call assert_equal('"set key=', @:)
+ call feedkeys(":set key-=\<Tab>\<C-B>\"\<CR>", 'xt')
+ call assert_equal('"set key-=', @:)
+ set key=
+ endif

" Expand values for 'filetype'
call feedkeys(":set filetype=sshdconfi\<Tab>\<C-B>\"\<CR>", 'xt')
diff --git a/src/version.c b/src/version.c
index a46db2a85..1be146276 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =

static int included_patches[] =
{ /* Add new patch number below this line */
+/**/
+ 1968,
/**/
1967,
/**/