ENV#[]=: Disallow null bytes in key and value #5216
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Before this, a call to `ENV[k] = v` would not check for NUL-bytes.
`setenv(3)` would then take the key and value, and as it doesn't know
about the embedded NUL-byte(s) in the key and/or value, would truncate
at the NUL-byte.
This may not sound too terrible at first. But it can turn into a
security issue:
```cr
from_user = "DO-SOMETHING-BAD\0GOOD" # Received from user input
if from_user.ends_with?("GOOD") # Will match
ENV["FOO"] = from_user # Will set "FOO" to "DO-SOMETHING-BAD"
end
```
Papierkorb
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asterite
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Oct 31, 2017
| def self.[]=(key : String, value : String?) | ||
| raise ArgumentError.new("Key contains null byte") if key.byte_index(0) |
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You can simply do key.check_no_null_byte
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Same applies to value, of course
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Yes I had that at first, but then chose to tell if the key or the value is the culprit
asterite
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Oct 31, 2017
RX14
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Oct 31, 2017
asterite
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Make
ENV#[]=raise anArgumentErrorif key or value contain a NUL byte.Before this, a call to
ENV[k] = vwould not check for NUL-bytes.setenv(3)would then take the key and value, and as it doesn't knowabout the embedded NUL-byte(s) in the key and/or value, would truncate
at the NUL-byte.
This may not sound too terrible at first. But it can turn into a
security issue:
Truncating user input is a real issue, with exploitation in the wild: https://mathiasbynens.be/notes/mysql-utf8mb4
Regards,
Korb