[release/6.0-staging] Disable implicit rejection for RSA PKCS#1 v1.5 #95218
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Tagging subscribers to this area: @dotnet/area-system-security, @bartonjs, @vcsjones Issue DetailsBackport of #95157 to release/6.0-staging /cc @vcsjones Customer ImpactTestingRiskIMPORTANT: If this backport is for a servicing release, please verify that:
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leecow
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Servicing-approved
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Just to make sure that this doesn't end up being merged just because nobody saw the original comment: This re-enables a Bleichenbacher timing oracle attack against PKCS#1v1.5 decryption. See https://people.redhat.com/~hkario/marvin/ for details and #95157 (comment) for a comment by the researcher who published the vulnerability and proposed the change in OpenSSL. I don't think this should be merged. |
carlossanlop
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@GrabYourPitchforks addressed the above feedback in detail in the other backport PR. We are good to merge. |
carlossanlop
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This reverts commit e3500b8. To quote Clemens Lang: > [Disabling implcit rejection] re-enables a Bleichenbacher timing oracle > attack against PKCS#1v1.5 decryption. See > https://people.redhat.com/~hkario/marvin/ for details and > dotnet#95157 (comment) for a > comment by the researcher who published the vulnerability and proposed the > change in OpenSSL. For more details, see: dotnet#95216 (comment)
Backport of #95157 to release/6.0-staging
/cc @vcsjones @bartonjs
Customer Impact
OpenSSL introduced a behavior change in
EVP_PKEY_decryptwhere RSA decryption with PKCS#1 v1.5 padding no longer produces an error with invalid padding. Instead, it returns “random” data.Customers using affected versions of OpenSSL will no longer get consistent and documented behavior from
RSA.Decrypt.This change is reacting to a breaking behavioral change in a dependency, OpenSSL, so that RSA.Decrypt continues to function as it is documented to, and to be consistent with Windows and other platforms.
Testing
This behavior change was identified with a test in #95115. Additional tests were added.
Risk
Low. This is reacting to a change in OpenSSL by settings a particular flag. Existing tests cover RSA.Decrypt’s behavior.