Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

When decrypted with a different private key, OpenSSL::PKey::RSAError does not occur #732

Closed
seconoid opened this issue Mar 21, 2024 · 2 comments
Closed

When decrypted with a different private key, OpenSSL::PKey::RSAError does not occur #732

seconoid opened this issue Mar 21, 2024 · 2 comments

Comments

@seconoid
Copy link

seconoid commented Mar 21, 2024 •
edited
Loading

Hi,

Is there a way to determine if the wrong key is being used when decrypting a string?
In ruby 2.7, when a different key was used, it would raise OpenSSL::PKey::RSAError .

ruby 2.7.6 and OpenSSL 2.1.3

RUBY_VERSION #=> "2.7.6"
OpenSSL::VERSION #=> "2.1.3"
OpenSSL::OPENSSL_LIBRARY_VERSION #=> "OpenSSL 1.1.1n  15 Mar 2022"

correct_private_key = OpenSSL::PKey::RSA.new(correct_private_key.pem)
wrong_private_key = OpenSSL::PKey::RSA.new(wrong_private_key.pem)

str = "PLAIN TEXT"
encrypted_str = correct_private_key.public_encrypt(str)
correct_private_key.private_decrypt(encrypted_str) #=> "PLAIN TEXT"
wrong_private_key.private_decrypt(encrypted_str) #=> OpenSSL::PKey::RSAError: padding check failed

However, when upgrading to ruby 3, even if the wrong key is used, OpenSSL::PKey::RSAError no longer occurs.

ruby 3.2.3 and OpenSSL 3.1.0

RUBY_VERSION #=> "3.2.3"
OpenSSL::VERSION #=> "3.1.0"
OpenSSL::OPENSSL_LIBRARY_VERSION #=> "OpenSSL 3.2.1 30 Jan 2024"

correct_private_key = OpenSSL::PKey::RSA.new(correct_private_key.pem)
wrong_private_key = OpenSSL::PKey::RSA.new(wrong_private_key.pem)

str = "PLAIN TEXT"
encrypted_str = correct_private_key.public_encrypt(str)
correct_private_key.private_decrypt(encrypted_str) #=> "PLAIN TEXT"
wrong_private_key.private_decrypt(encrypted_str) #=> "\x96h\xE4\xFF\xFD?4|h-g!\xECu\xB1\xC3\x02;\f?\xD5-M\x9D\xF0\xF1\xEC\b\xE0\x9D\xA3ps\xE0\xE3\xDD\xCF\xDBG5\xE1\xDE\x89N\xA2\x97\x95\x00\xA75\xE0h\xF1\xF0&L\xF7\x85\ni\xC1\xD9\x91\xCB\xF4\a\xE1FpG\xF0\x18\x1C\xD2\xD8\x1A\xD6\xFD\xAA\xEF9\x95?\x10\xCA\xA5@\x8A\x88\x91n\x81q\xA5a\xD9`\x8D\xAD|\xB9\xFB\xEF[\xD6#\x94CiU\xC5\x13L\xEB\xCC\xC4\xAE\xD0\x90\ao\x12\xC1\xF5\xF4$s\x8E\x12\x8D\xDBL\xE4\xC5\xE9\x15\xD5\r<\xCE\xFD\x8B\xDC\x03\x93"
wrong_private_key.decrypt(encrypted_str)         #=> "\x96h\xE4\xFF\xFD?4|h-g!\xECu\xB1\xC3\x02;\f?\xD5-M\x9D\xF0\xF1\xEC\b\xE0\x9D\xA3ps\xE0\xE3\xDD\xCF\xDBG5\xE1\xDE\x89N\xA2\x97\x95\x00\xA75\xE0h\xF1\xF0&L\xF7\x85\ni\xC1\xD9\x91\xCB\xF4\a\xE1FpG\xF0\x18\x1C\xD2\xD8\x1A\xD6\xFD\xAA\xEF9\x95?\x10\xCA\xA5@\x8A\x88\x91n\x81q\xA5a\xD9`\x8D\xAD|\xB9\xFB\xEF[\xD6#\x94CiU\xC5\x13L\xEB\xCC\xC4\xAE\xD0\x90\ao\x12\xC1\xF5\xF4$s\x8E\x12\x8D\xDBL\xE4\xC5\xE9\x15\xD5\r<\xCE\xFD\x8B\xDC\x03\x93"

I'm not sure if this is a specification or a bug, but I would like to know if there is a way to determine it.
@rhenium
Copy link
Member

rhenium commented Mar 21, 2024

This is a change in OpenSSL 3.2 (the C library, not ruby/openssl) to mitigate a timing attack with PKCS#1 v1.5 padding. It is also backported to older versions as a security fix in some distributions, such as Fedora or Ubuntu.

https://www.openssl.org/docs/man3.2/man3/EVP_PKEY_decrypt.html

You can use wrong_private_key.decrypt(encrypted_str, rsa_pkcs1_implicit_rejection: 0) if the old behavior is absolutely necessary. This option is documented in https://www.openssl.org/docs/man3.2/man1/openssl-pkeyutl.html

@rhenium rhenium closed this as completed Mar 21, 2024
@seconoid
Copy link
Author

thanks!

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
None yet
Milestone
No milestone
Development

No branches or pull requests
2 participants
@rhenium @seconoid