mirror of https://github.com/qpdf/qpdf.git
34 lines
1.5 KiB
ReStructuredText
34 lines
1.5 KiB
ReStructuredText
.. _weak-crypto:
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Weak Cryptography
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=================
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Start with version 10.4, qpdf is taking steps to reduce the likelihood
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of a user *accidentally* creating PDF files with insecure cryptography
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but will continue to allow creation of such files indefinitely with
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explicit acknowledgment.
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The PDF file format makes use of RC4, which is known to be a weak
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cryptography algorithm, and MD5, which is a weak hashing algorithm. In
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version 10.4, qpdf generates warnings for some (but not all) cases of
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writing files with weak cryptography when invoked from the command-line.
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These warnings can be suppressed using the
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:samp:`--allow-weak-crypto` option.
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It is planned for qpdf version 11 to be stricter, making it an error to
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write files with insecure cryptography from the command-line tool in
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most cases without specifying the
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:samp:`--allow-weak-crypto` flag and also to require
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explicit steps when using the C++ library to enable use of insecure
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cryptography.
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Note that qpdf must always retain support for weak cryptographic
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algorithms since this is required for reading older PDF files that use
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it. Additionally, qpdf will always retain the ability to create files
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using weak cryptographic algorithms since, as a development tool, qpdf
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explicitly supports creating older or deprecated types of PDF files
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since these are sometimes needed to test or work with older versions of
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software. Even if other cryptography libraries drop support for RC4 or
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MD5, qpdf can always fall back to its internal implementations of those
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algorithms, so they are not going to disappear from qpdf.
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