[git commit master] read_key,lineeedit: parse position answerback faster; sanitize its use
Denys Vlasenko
vda.linux at googlemail.com
Mon Oct 26 14:23:32 UTC 2009
commit: http://git.busybox.net/busybox/commit/?id=727e1b536e5478b8f28c93990a5bf34091144608
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master
it's still not reliable, and probably cannot be made so...
added comment with explanation.
function old new delta
put_prompt 52 110 +58
read_key 601 607 +6
lineedit_read_key 201 207 +6
win_changed 108 104 -4
read_line_input 4824 4809 -15
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/2 up/down: 70/-19) Total: 51 bytes
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
libbb/lineedit.c | 38 +++++++++++++++++++++++++++++++++-----
libbb/read_key.c | 53 +++++++++++++++++++++++++----------------------------
2 files changed, 58 insertions(+), 33 deletions(-)
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index bfd0e33..2e1bc5d 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -370,6 +370,7 @@ static void input_backward(unsigned num)
static void put_prompt(void)
{
out1str(cmdedit_prompt);
+ fflush(NULL);
if (ENABLE_FEATURE_EDITING_ASK_TERMINAL) {
/* Ask terminal where is the cursor now.
* lineedit_read_key handles response and corrects
@@ -380,7 +381,33 @@ static void put_prompt(void)
* Note: we print it _after_ prompt, because
* prompt may contain CR. Example: PS1='\[\r\n\]\w '
*/
- out1str("\033" "[6n");
+ /* Problem: if there is buffered input on stdin,
+ * the response will be delivered later,
+ * possibly to an unsuspecting application.
+ * Testcase: "sleep 1; busybox ash" + press and hold [Enter].
+ * Result:
+ * ~/srcdevel/bbox/fix/busybox.t4 #
+ * ~/srcdevel/bbox/fix/busybox.t4 #
+ * ^[[59;34~/srcdevel/bbox/fix/busybox.t4 # <-- garbage
+ * ~/srcdevel/bbox/fix/busybox.t4 #
+ *
+ * Checking for input with poll only makes the race narrower,
+ * I still can trigger it. Strace:
+ *
+ * write(1, "~/srcdevel/bbox/fix/busybox.t4 # ", 33) = 33
+ * poll([{fd=0, events=POLLIN}], 1, 0) = 0 (Timeout) <-- no input exists
+ * write(1, "\33[6n", 4) = 4 <-- send the ESC sequence, quick!
+ * poll([{fd=0, events=POLLIN}], 1, 4294967295) = 1 ([{fd=0, revents=POLLIN}])
+ * read(0, "\n", 1) = 1 <-- oh crap, user's input got in first
+ */
+ struct pollfd pfd;
+
+ pfd.fd = STDIN_FILENO;
+ pfd.events = POLLIN;
+ if (safe_poll(&pfd, 1, 0) == 0) {
+ out1str("\033" "[6n");
+ fflush(NULL); /* make terminal see it ASAP! */
+ }
}
cursor = 0;
{
@@ -1603,7 +1630,7 @@ static void cmdedit_setwidth(unsigned w, int redraw_flg)
int new_y = (cursor + cmdedit_prmt_len) / w;
/* redraw */
redraw((new_y >= cmdedit_y ? new_y : cmdedit_y), command_len - cursor);
- fflush(stdout);
+ fflush(NULL);
}
}
@@ -1640,6 +1667,7 @@ static int lineedit_read_key(char *read_key_buffer)
ic = read_key(STDIN_FILENO, read_key_buffer);
if (ENABLE_FEATURE_EDITING_ASK_TERMINAL
+ && cursor == 0 /* otherwise it may be bogus */
&& (int32_t)ic == KEYCODE_CURSOR_POS
) {
int col = ((ic >> 32) & 0x7fff) - 1;
@@ -1708,7 +1736,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
) {
/* Happens when e.g. stty -echo was run before */
parse_and_put_prompt(prompt);
- fflush(stdout);
+ /* fflush(stdout); - done by parse_and_put_prompt */
if (fgets(command, maxsize, stdin) == NULL)
len = -1; /* EOF or error */
else
@@ -2190,7 +2218,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
tcsetattr_stdin_TCSANOW(&initial_settings);
/* restore SIGWINCH handler */
signal(SIGWINCH, previous_SIGWINCH_handler);
- fflush(stdout);
+ fflush(NULL);
len = command_len;
DEINIT_S();
@@ -2204,7 +2232,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
int FAST_FUNC read_line_input(const char* prompt, char* command, int maxsize)
{
fputs(prompt, stdout);
- fflush(stdout);
+ fflush(NULL);
fgets(command, maxsize, stdin);
return strlen(command);
}
diff --git a/libbb/read_key.c b/libbb/read_key.c
index ec1b3a4..a2253ce 100644
--- a/libbb/read_key.c
+++ b/libbb/read_key.c
@@ -202,6 +202,31 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
break;
}
n++;
+ /* Try to decipher "ESC [ NNN ; NNN R" sequence */
+ if (ENABLE_FEATURE_EDITING_ASK_TERMINAL
+ && n >= 5
+ && buffer[0] == '['
+ && buffer[n-1] == 'R'
+ && isdigit(buffer[1])
+ ) {
+ char *end;
+ unsigned long row, col;
+
+ row = strtoul(buffer + 1, &end, 10);
+ if (*end != ';' || !isdigit(end[1]))
+ continue;
+ col = strtoul(end + 1, &end, 10);
+ if (*end != 'R')
+ continue;
+ if (row < 1 || col < 1 || (row | col) > 0x7fff)
+ continue;
+
+ buffer[-1] = 0;
+ /* Pack into "1 <row15bits> <col16bits>" 32-bit sequence */
+ col |= (((-1 << 15) | row) << 16);
+ /* Return it in high-order word */
+ return ((int64_t) col << 32) | (uint32_t)KEYCODE_CURSOR_POS;
+ }
}
got_all:
@@ -213,34 +238,6 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
return 27;
}
- /* Try to decipher "ESC [ NNN ; NNN R" sequence */
- if (ENABLE_FEATURE_EDITING_ASK_TERMINAL
- && n >= 5
- && buffer[0] == '['
- && isdigit(buffer[1])
- && buffer[n-1] == 'R'
- ) {
- char *end;
- unsigned long row, col;
-
- row = strtoul(buffer + 1, &end, 10);
- if (*end != ';' || !isdigit(end[1]))
- goto not_R;
- col = strtoul(end + 1, &end, 10);
- if (*end != 'R')
- goto not_R;
- if (row < 1 || col < 1 || (row | col) > 0x7fff)
- goto not_R;
-
- buffer[-1] = 0;
-
- /* Pack into "1 <row15bits> <col16bits>" 32-bit sequence */
- col |= (((-1 << 15) | row) << 16);
- /* Return it in high-order word */
- return ((int64_t) col << 32) | (uint32_t)KEYCODE_CURSOR_POS;
- }
- not_R:
-
/* We were doing "buffer[-1] = n; return c;" here, but this results
* in unknown key sequences being interpreted as ESC + garbage.
* This was not useful. Pretend there was no key pressed,
--
1.6.3.3
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