Remove the following subclasses of OpenSSL::PKey::PKeyError and make
them aliases of it.

 - OpenSSL::PKey::DHError
 - OpenSSL::PKey::DSAError
 - OpenSSL::PKey::ECError
 - OpenSSL::PKey::RSAError

Historically, methods defined on OpenSSL::PKey and OpenSSL::PKey::PKey
raise OpenSSL::PKey::PKeyError, while methods on the subclasses raise
their respective exception classes. However, this distinction is not
particularly useful since all those exception classes represent the
same kind of errors from the underlying EVP_PKEY API.

I think this convention comes from the fact that OpenSSL::PKey::{DH,
DSA,RSA} originally wrapped the corresponding OpenSSL structs DH, DSA,
and RSA, before they were unified to wrap EVP_PKEY, way back in 2002.

OpenSSL::PKey::EC::Group::Error and OpenSSL::PKey::EC::Point::Error
are out of scope of this change, as they are not subclasses of
OpenSSL::PKey::PKeyError and do not represent errors from the EVP_PKEY
API.

https://github.com/ruby/openssl/commit/e74ff3e272

Use generic keys whenever possible.

https://github.com/ruby/openssl/commit/90d6af60b9

This reverts commit https://github.com/ruby/openssl/commit/5347880c6eb0 and
https://github.com/ruby/openssl/commit/985ba27d6339.

These commits attempted to stop processing after the first relevant PEM
block, whether it is successful or not, when the input contains multiple
keys.

It turned out that it cannot be reliably determined using the
OSSL_DECODER API. There is an edge case where OSSL_DECODER_from_bio()
reports "unsupported" even though the input actually contains an error:

https://redirect.github.com/ruby/openssl/pull/931#discussion_r2347813807

Revert the changes for now and keep the existing behavior, as partial
support does not seem worth the added complexity.

https://github.com/ruby/openssl/commit/319cd4952a

Continue processing only when OSSL_DECODER_from_bio() returns the error
code ERR_R_UNSUPPORTED. Otherwise, raise an exception without retrying
decoding the input in another format.

This fixes another case where OpenSSL::PKey.read prompts for a
passphrase multiple times when the input contains multiple
passphrase-protected PEM blocks and the first one cannot be decoded.

I am not entirely sure if the error code ERR_R_UNSUPPORTED is considered
part of the public interface of OpenSSL, but this seems to be the only
option available and is the approach used internally by the
PEM_read_bio_*() functions.

Fixes https://github.com/ruby/openssl/issues/927

https://github.com/ruby/openssl/commit/985ba27d63

Specify OSSL_DECODER_CTX_set_pem_password_cb() only when we expect a
passphrase-protected private key.

OSSL_DECODER appears to try to decrypt every PEM block in the input even
when the PEM header does not match the requested selection. This can
cause repeated prompts for a passphrase in a single OpenSSL::PKey.read
call.

https://github.com/ruby/openssl/commit/933503f49f

Add tests covering edge cases in the current behavior to prevent
accidental regressions. The next patches will update the OpenSSL 3.x
path.

https://github.com/ruby/openssl/commit/468f8ceea2

Algorithms implemented only in OpenSSL 3 providers may not have a
corresponding NID. The *_ex() variants have been added in OpenSSL 3.0
to handle such algorithms, by taking algorithm names as a string.

https://github.com/ruby/openssl/commit/e730e457cc

For algorithms implemented solely in an OpenSSL 3 provider, without an
associated EVP_PKEY_METHOD, EVP_PKEY_id() returns a special value
EVP_PKEY_KEYMGMT.

Let OpenSSL::PKey::PKey#oid raise an exception as necessary.
Update PKey#inspect to include the string returned by
EVP_PKEY_get0_type_name(), if available.

https://github.com/ruby/openssl/commit/bd3e32270e

Drop support for OpenSSL 1.1.0. OpenSSL 1.1.0 was a non-LTS release and
it has reached upstream EOL in 2019-12 along with OpenSSL 1.0.2.
Distributions that shipped with OpenSSL 1.1.0 include:

 - Debian 9 (EOL 2022-06)
 - Ubuntu 18.04 LTS (EOL 2023-04)

https://github.com/ruby/openssl/commit/ba83abe920

Drop support for OpenSSL 1.0.2. It has reached upstream EOL in 2019-12.

Most distributions that shipped with OpenSSL 1.0.2 have also reached
EOL, or provide a newer version in the package repository:

 - RHEL 7 (EOL 2024-06)
 - Ubuntu 16.04 LTS (EOL 2021-04)
 - Amazon Linux 2 (EOL 2026-06, but OpenSSL 1.1.1 can be installed via
   the openssl11{,-devel} package)

https://github.com/ruby/openssl/commit/38ec6fd50e