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pageant: fall back to GetUserNameA when GetUserNameExA fails #726

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Merged
Eugeny merged 2 commits into from
Aug 17, 2026
Merged

pageant: fall back to GetUserNameA when GetUserNameExA fails #726

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9963571
pageant: fall back to USERNAME env var when GetUserNameExA fails
cwatanab Jun 17, 2026
b8034c0
fall back to GetUserNameExA instead like putty does
Eugeny Aug 17, 2026
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1 change: 1 addition & 0 deletions pageant/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -45,4 +45,5 @@ namedpipes = [
"dep:windows-strings",
"windows/Win32_Security_Authentication_Identity",
"windows/Win32_Security_Cryptography",
"windows/Win32_System_WindowsProgramming",
]
17 changes: 12 additions & 5 deletions pageant/src/namedpipes.rs
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Expand Up @@ -14,6 +14,7 @@ use windows::Win32::Security::Authentication::Identity::{GetUserNameExA, NameUse
use windows::Win32::Security::Cryptography::{
CRYPTPROTECTMEMORY_BLOCK_SIZE, CRYPTPROTECTMEMORY_CROSS_PROCESS, CryptProtectMemory,
};
use windows::Win32::System::WindowsProgramming::GetUserNameA;
use windows_strings::PSTR;

use crate::Error;
Expand Down Expand Up @@ -65,11 +66,17 @@ impl PageantStream {
Some(PSTR(name_buf.as_mut_ptr())),
&mut name_length,
) {
// Pageant falls back to GetUserNameA here,
// but as far as I can tell, all Versions of Windows supported by Rust today
// should be able to answer the UserNameEx request - the comments in Pageant source
// point to Windows XP and earlier compatibility...
return Err(Error::from_win32());
// GetUserNameExA fails on non-domain-joined machines, where no UPN
// (NameUserPrincipal) is configured. Fall back to GetUserNameA
// (the SAM account name), like the original PuTTY Pageant.
debug!("GetUserNameExA failed, falling back to GetUserNameA");

let mut name_length = 0;
// don't check result on this, always returns ERROR_INSUFFICIENT_BUFFER
let _ = GetUserNameA(None, &mut name_length);

name_buf = vec![0u8; name_length as usize];
GetUserNameA(Some(PSTR(name_buf.as_mut_ptr())), &mut name_length)?;
}

//remove terminating null
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