Fix validation of SSH public keys #1090
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Previously, the algorithm name was not correctly parsed from the base64 encoded public key if the name was longer than 0x1F bytes. The first four bytes of the decoded public key specify the length of the following algorithm name. Since we already know the expected length, we do not need to parse this and can directly get the algorithm name starting at the fifth (decoded) byte.
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We may find a cleaner way to check if the key is valid. Maybe with phpseclib: https://stackoverflow.com/a/65993238 |
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Using a proper library for the purpose certainly makes sense. |
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I found a bug in
check_sshkey. Key using algorithms with long names (longer than 0x1F characters) get incorrectly rejected.One example for such an algorithm is
[email protected](0x22 characters). This results in an extra"in$check, which then obviously does not match$algorithm.The first four bytes of the decoded public key specify the length of the following algorithm name.
preg_replaceremoves these four bytes if they are in the non-printable range. Otherwise some of the length bytes end up in$check.This PR fixes this by always discarding the first four bytes and comparing the expected number of bytes.