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Fix dangerous command splicing

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This commit is contained in:
Robert Estelle 2020-07-29 13:50:35 -07:00 committed by Ferran Basora
parent b355406972
commit f48029fb50
1 changed files with 32 additions and 2 deletions
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34
src/swapper.rs
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@ -298,8 +298,38 @@ impl<'a> Swapper<'a> {
self.command.clone()
};
let final_command = str::replace(execute_command.as_str(), "{}", text.trim_end());
let retrieve_command = vec!["bash", "-c", final_command.as_str()];
// The command we run has two arguments:
// * The first arg is the (trimmed) text. This gets stored in a variable, in order to
// preserve quoting and special characters.
//
// * The second argument is the user's command, with the '{}' token replaced with an
// unquoted reference to the variable containing the text.
//
// The reference is unquoted, unfortunately, because the token may already have been
// spliced into a string (e.g 'tmux display-message "Copied {}"'), and it's impossible (or
// at least exceedingly difficult) to determine the correct quoting level.
//
// The alternative of literally splicing the text into the command is bad and it causes all
// kinds of harmful escaping issues that the user cannot reasonable avoid.
//
// For example, imagine some pattern matched the text "foo;rm *" and the user's command was
// an innocuous "echo {}". With literal splicing, we would run the command "echo foo;rm *".
// That's BAD. Without splicing, instead we execute "echo ${THUMB}" which does mostly the
// right thing regardless the contents of the text. (At worst, bash will word-separate the
// unquoted variable; but it won't _execute_ those words in common scenarios).
//
// Ideally user commands would just use "${THUMB}" to begin with rather than having any
// sort of ad-hoc string splicing here at all, and then they could specify the quoting they
// want, but that would break backwards compatibility.
let final_command = str::replace(execute_command.as_str(), "{}", "${THUMB}");
let retrieve_command = vec![
"bash",
"-c",
"THUMB=\"$1\"; eval \"$2\"",
"--",
text.trim_end(),
final_command.as_str(),
];
let params = retrieve_command.iter().map(|arg| arg.to_string()).collect();
self.executor.execute(params);