From fb35cd0ef496fee9aa65daadf542057f18d6063f Mon Sep 17 00:00:00 2001
From: Ryan Dahl <ry@tinyclouds.org>
Date: Thu, 9 Sep 2021 08:38:47 -0400
Subject: fix: permission prompt stuffing (#11931)

Fixes #9750
---
 runtime/Cargo.toml     |  2 +-
 runtime/permissions.rs | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

(limited to 'runtime')

diff --git a/runtime/Cargo.toml b/runtime/Cargo.toml
index 98983b5de..03a58fdd0 100644
--- a/runtime/Cargo.toml
+++ b/runtime/Cargo.toml
@@ -85,7 +85,7 @@ uuid = { version = "0.8.2", features = ["v4"] }
 
 [target.'cfg(windows)'.dependencies]
 fwdansi = "1.1.0"
-winapi = { version = "0.3.9", features = ["knownfolders", "mswsock", "objbase", "shlobj", "tlhelp32", "winbase", "winerror", "winsock2"] }
+winapi = { version = "0.3.9", features = ["commapi", "knownfolders", "mswsock", "objbase", "shlobj", "tlhelp32", "winbase", "winerror", "winsock2"] }
 
 [target.'cfg(unix)'.dependencies]
 nix = "0.22.1"
diff --git a/runtime/permissions.rs b/runtime/permissions.rs
index 9e97ac234..d1ee7f999 100644
--- a/runtime/permissions.rs
+++ b/runtime/permissions.rs
@@ -1194,6 +1194,29 @@ fn permission_prompt(message: &str) -> bool {
   if !atty::is(atty::Stream::Stdin) || !atty::is(atty::Stream::Stderr) {
     return false;
   };
+
+  #[cfg(unix)]
+  fn clear_stdin() {
+    let r = unsafe { libc::tcflush(0, libc::TCIFLUSH) };
+    assert_eq!(r, 0);
+  }
+
+  #[cfg(not(unix))]
+  fn clear_stdin() {
+    unsafe {
+      let stdin = winapi::um::processenv::GetStdHandle(
+        winapi::um::winbase::STD_INPUT_HANDLE,
+      );
+      let flags =
+        winapi::um::winbase::PURGE_TXCLEAR | winapi::um::winbase::PURGE_RXCLEAR;
+      winapi::um::commapi::PurgeComm(stdin, flags);
+    }
+  }
+
+  // For security reasons we must consume everything in stdin so that previously
+  // buffered data cannot effect the prompt.
+  clear_stdin();
+
   let opts = "[y/n (y = yes allow, n = no deny)] ";
   let msg = format!(
     "{}  ️Deno requests {}. Allow? {}",
-- 
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