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Allow savefig to save SVGs on FIPS enabled systems #18192#18193

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jkseppan merged 2 commits intomatplotlib:masterfrom
daytonb:fips-compatible
Aug 7, 2020
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Allow savefig to save SVGs on FIPS enabled systems #18192#18193
jkseppan merged 2 commits intomatplotlib:masterfrom
daytonb:fips-compatible

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@daytonb daytonb commented Aug 6, 2020 •
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PR Summary

This pull request resolves #18192.

If you use a FIPS (Federal Information Processing Standards) enabled system, then you cannot use plt.savefig to save an image in SVG format. This is because the RenderSVG._make_id method takes the first 10 characters of a hashlib.md5 digest of entries in the SVG as the ID for entries in the SVG file.

The Python docs for hashlib includes the following note:

Constructors for hash algorithms that are always present in this module are sha1(), sha224(), sha256(), sha384(), sha512(), blake2b(), and blake2s(). md5() is normally available as well, though it may be missing if you are using a rare “FIPS compliant” build of Python.

PR Checklist

  • [na ] Has Pytest style unit tests
    - Not sure if this is applicable to my change
  • Code is Flake 8 compliant
  • [na] New features are documented, with examples if plot related
  • Documentation is sphinx and numpydoc compliant
  • [na] Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
    - Not a major feature
  • Documented in doc/api/next_api_changes/* if API changed in a backward-incompatible way

@daytonb daytonb mentioned this pull request Aug 6, 2020
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dstansby
dstansby reviewed Aug 6, 2020
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Seems like a reasonable approach. Is this injected into the .svg files? If so it would be good to add a quick note to doc/api/next_api_changes/behavior to say that the contents will be slightly different, just in case there is anybody comparing the hashes of matplotlib generated .svg files.

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daytonb commented Aug 6, 2020 via email

@dopplershift dopplershift added this to the v3.4.0 milestone Aug 7, 2020
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daytonb commented Aug 7, 2020

Alright I've added a file to the doc/api/next_api_changes/behavior. Let me know if the description seems unclear and needs tweaking.

QuLogic
QuLogic reviewed Aug 7, 2020
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daytonb commented Aug 7, 2020

I re-wrote the behavior change note to no longer reference the private method. I was also previously getting an error from the circleci doc tests that I think was from the warnings Sphinx gave about my references to hashlib.md5 and RenderSVG._make_id. The warnings said that Sphinx couldn't find these pyobjs to link to them. Obviously I removed the reference to RenderSVG._make_id so that won't be a problem any more, but I also reworded my note about hashlib.md5 to avoid having to do a intersphinx reference.

jklymak
jklymak approved these changes Aug 7, 2020
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This seems fine to me. I don't know that it really needs an API change note - the origin of the hash is just an implementation detail of the unique ID, and its not like the user needs to know that. But, I guess it doesn't hurt.

@jkseppan jkseppan merged commit 9b7f94f into matplotlib:master Aug 7, 2020
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jkseppan commented Aug 7, 2020

Thanks @daytonb!

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daytonb commented Aug 7, 2020

It's been a pleasure!

@martinky24 martinky24 mentioned this pull request Feb 12, 2025
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@jkseppan jkseppan jkseppan approved these changes

@jklymak jklymak jklymak approved these changes

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Cannot save SVG file with FIPS compliant Python

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