Observations
The file packages/electron-updater/src/windowsExecutableCodeSignatureVerifier.ts implements the signature validation routine for Electron applications on Windows. It executes the following command in a new shell (process.env.ComSpec on Windows, usually C:\Windows\System32\cmd.exe):
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execFile( |
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`set "PSModulePath="; chcp 65001 >NUL & powershell.exe`, |
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["-NoProfile", "-NonInteractive", "-InputFormat", "None", "-Command", `"Get-AuthenticodeSignature -LiteralPath '${tempUpdateFile}' | ConvertTo-Json -Compress"`], |
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{ |
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shell: true, |
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timeout: 20 * 1000, |
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}, |
Because of the surrounding shell, a first pass by cmd.exe expands any environment variable found in command-line above.
Exploitation
This creates a situation where verifySignature() can be tricked into validating the certificate of a different file than the one that was just downloaded. If the step is successful, the malicious update will be executed even if its signature is invalid.
Impact
This attack assumes a compromised update manifest (server compromise, Man-in-the-Middle attack if fetched over HTTP, Cross-Site Scripting to point the application to a malicious updater server, etc.).
Patch
This vulnerability was patched in #8295, by comparing the path in the output of Get-AuthenticodeSignature with the intended one. The patch is available starting from 6.3.0-alpha.6.
mmaietta Remediation developer
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Observations
The file
packages/electron-updater/src/windowsExecutableCodeSignatureVerifier.tsimplements the signature validation routine for Electron applications on Windows. It executes the following command in a new shell (process.env.ComSpecon Windows, usuallyC:\Windows\System32\cmd.exe):electron-builder/packages/electron-updater/src/windowsExecutableCodeSignatureVerifier.ts
Lines 35 to 41 in 140e2f0
Because of the surrounding shell, a first pass by
cmd.exeexpands any environment variable found in command-line above.Exploitation
This creates a situation where
verifySignature()can be tricked into validating the certificate of a different file than the one that was just downloaded. If the step is successful, the malicious update will be executed even if its signature is invalid.Impact
This attack assumes a compromised update manifest (server compromise, Man-in-the-Middle attack if fetched over HTTP, Cross-Site Scripting to point the application to a malicious updater server, etc.).
Patch
This vulnerability was patched in #8295, by comparing the path in the output of
Get-AuthenticodeSignaturewith the intended one. The patch is available starting from 6.3.0-alpha.6.