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Originally the code to im/export the EC pubkey was meant to be consumed only by the im/export functions when crossing the provider boundary. Having our providers exporting to a COMPRESSED format octet string made sense to avoid memory waste, as it wasn't exposed outside the provider API, and providers had all tools available to convert across the three formats. Later on, with #13139 deprecating the `EC_KEY_*` functions, more state was added among the params imported/exported on an EC provider-native key (including `OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT`, although it did not affect the format used to export `OSSL_PKEY_PARAM_PUB_KEY`). Finally, in #14800, `EVP_PKEY_todata()` was introduced and prominently exposed directly to users outside the provider API, and the choice of COMPRESSED over UNCOMPRESSED as the default became less sensible in light of usability, given the latter is more often needed by applications and protocols. This commit fixes it, by using `EC_KEY_get_conv_form()` to get the point format from the internal state (an `EC_KEY` under the hood) of the provider-side object, and using it on `EVP_PKEY_export()`/`EVP_PKEY_todata()` to format `OSSL_PKEY_PARAM_PUB_KEY`. The default for an `EC_KEY` was already UNCOMPRESSED, and it is altered if the user sets `OSSL_PKEY_PARAM_EC_POINT_CONVERSION_FORMAT` via `EVP_PKEY_fromdata()`, `EVP_PKEY_set_params()`, or one of the more specialized methods. For symmetry, this commit also alters `ec_pkey_export_to()` in `crypto/ec/ec_ameth.c`, part of the `EVP_PKEY_ASN1_METHOD` for legacy EC keys: it exclusively used COMPRESSED format, and now it honors the conversion format specified in the EC_KEY object being exported to a provider when this function is called. Expand documentation about `OSSL_PKEY_PARAM_PUB_KEY` and mention the 3.1 change in behavior for our providers. Fixes #16595 Reviewed-by: Hugo Landau <hlandau@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from https://github.com/openssl/openssl/pull/19681) (cherry picked from commit 926db476bc669fdcc4c4d2f1cb547060bdbfa153)
OpenSSL Documentation
README.md This file
fingerprints.txt PGP fingerprints of authorised release signers
standards.txt standards.txt Moved to the web, https://www.openssl.org/docs/standards.html
HOWTO/ A few how-to documents; not necessarily up-to-date
man1/ The openssl command-line tools; start with openssl.pod
man3/ The SSL library and the crypto library
man5/ File formats
man7/ Overviews; start with crypto.pod and ssl.pod, for example Algorithm specific EVP_PKEY documentation.
Formatted versions of the manpages (apps,ssl,crypto) can be found at https://www.openssl.org/docs/manpages.html