On Thu, 3 Mar 2022 15:38:44 GMT, Olga Mikhaltsova <omikhaltc...@openjdk.org> 
wrote:

>> This fix made equal processing of strings such as ""C:\\Program 
>> Files\\Git\\"" before and after JDK-8250568.
>> 
>> For example, it's needed to execute the following command on Windows:
>> `C:\Windows\SysWOW64\WScript.exe "MyVB.vbs" "C:\Program Files\Git" "Test"`
>> it's equal to:
>> `new ProcessBuilder("C:\\Windows\\SysWOW64\\WScript.exe", "MyVB.vbs", 
>> ""C:\\Program Files\\Git\\"", "Test").start();`
>> 
>> While processing, the 3rd argument ""C:\\Program Files\\Git\\"" treated as 
>> unquoted due to the condition added in JDK-8250568.
>> 
>>     private static String unQuote(String str) {
>>     .. 
>>        if (str.endsWith("\\"")) {
>>             return str;    // not properly quoted, treat as unquoted
>>         }
>>     ..
>>     }
>> 
>> 
>> that leads to the additional surrounding by quotes in 
>> ProcessImpl::createCommandLine(..) because needsEscaping(..) returns true 
>> due to the space inside the string argument.
>> As a result the native function CreateProcessW 
>> (src/java.base/windows/native/libjava/ProcessImpl_md.c) gets the incorrectly 
>> quoted argument: 
>> 
>> pcmd = C:\Windows\SysWOW64\WScript.exe MyVB.vbs ""C:\Program Files\Git"" Test
>> (jdk.lang.Process.allowAmbiguousCommands = true)
>> pcmd = "C:\Windows\SysWOW64\WScript.exe" MyVB.vbs ""C:\Program Files\Git\\"" 
>> Test
>> (jdk.lang.Process.allowAmbiguousCommands = false)
>> 
>> 
>> Obviously, a string ending with `"\\""` must not be started with `"""` to 
>> treat as unquoted overwise it’s should be treated as properly quoted.
>
> Olga Mikhaltsova has updated the pull request incrementally with one 
> additional commit since the last revision:
> 
>   Reverted addition of the test via echo

As an alternative fix, please take a look at Draft PR: 
https://github.com/openjdk/jdk/pull/7709.

In the default handling of arguments, the check for what is quoted is reverted 
to prior to 8255068. First and last quotes are sufficient to identify a 
"quoted" string. The check for a backslash ("\") is removed.
This original check is sufficient for `jdk.lang.Process.allowAmbiguousCommands 
= true`.

For the case where the system property `jdk.lang.Process.allowAmbiguousCommands 
= false`
and the argument has first and last quotes, a backslash ("\") before the final 
quote must not allow the quote to interpreted as a literal quote and merge the 
following argument.  The backslashes will doubled to prevent the interpretation 
of the quote as a literal.  This is the correct encoding if the command uses 
the ".exe" encoding, when reparsing the arguments the doubled backslashes are 
reduced to the original contents.
When the command is using the simpler parsing that does not support literal 
quotes, the backslash before the quote is typically is a trailing backslash on 
a file path and in that case the additional backslash is redundant and has no 
effect on the interpretation of the argument as a directory path.

The PR includes a test of the 12 combinations of invoking an "java"/.exe 
program, a .cmd script, and a Visual Basic script (which uses the .exe rules 
but different command line parser); with and without application quotes and 
compares the actual results with the expected arguments.

-------------

PR: https://git.openjdk.java.net/jdk/pull/7504

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