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fix: Command Injection Fix for entrabot #76

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fix: Command Injection Fix for entrabot #76

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14 changes: 12 additions & 2 deletions scripts/generate_windows_cert.py
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Original file line number Diff line number Diff line change
Expand Up @@ -87,9 +87,13 @@ def _build_command(*, subject: str, days_valid: int, ksp: str) -> list[str]:
# user profile either way. We add it on TPM because the plan's threat
# model assumes the TPM key is the strongest baseline.
extra = "-KeyExportPolicy NonExportable " if ksp == KSP_TPM else ""

# Escape single quotes for PowerShell single-quoted strings to prevent RCE
safe_subject = subject.replace("'", "''")

pwsh_block = (
"$ErrorActionPreference = 'Stop'; "
f"$cert = New-SelfSignedCertificate -Subject '{subject}' "
f"$cert = New-SelfSignedCertificate -Subject '{safe_subject}' "
f"-CertStoreLocation Cert:\\CurrentUser\\My "
f"-Provider '{provider}' "
f"{extra}"
Expand Down Expand Up @@ -146,10 +150,16 @@ def generate(*, subject: str, days_valid: int, ksp: str) -> GenerateResult:

def export_der(thumbprint: str, dest: Path) -> Path:
"""Export the public cert DER bytes for upload to the Blueprint app."""
# Security fix: Validate thumbprint format and escape single quotes in dest
# to prevent arbitrary PowerShell command injection.
if not THUMBPRINT_RE.match(thumbprint):
raise ThumbprintValidationError(f"Invalid thumbprint format: {thumbprint!r}")

safe_dest = str(dest).replace("'", "''")
pwsh = (
"$ErrorActionPreference = 'Stop'; "
f"$c = Get-Item Cert:\\CurrentUser\\My\\{thumbprint}; "
f"[IO.File]::WriteAllBytes('{dest}', $c.GetRawCertData())"
f"[IO.File]::WriteAllBytes('{safe_dest}', $c.GetRawCertData())"
)
result = _run_pwsh(pwsh)
if result.returncode != 0:
Expand Down