SSL: external groups support in $ssl_curve and $ssl_curves. #609
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bavshin-f5
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Apr 8, 2025
Starting with OpenSSL 3.0, groups may be added externally with pluggable KEM providers. Using SSL_get_negotiated_group(), which makes lookup in a static table with known groups, doesn't allow to list such groups by names leaving them in hex. Adding X25519MLKEM768 to the default group list in OpenSSL 3.5 made this problem more visible. SSL_get0_group_name() and, apparently, SSL_group_to_name() allow to resolve such provider-implemented groups, which is also "generally preferred" over SSL_get_negotiated_group() as documented in OpenSSL git commit 93d4f6133f. This change makes external groups listing by name using SSL_group_to_name() available since OpenSSL 3.0. To preserve "prime256v1" naming for the group 0x0017, and to avoid breaking BoringSSL and older OpenSSL versions support, it is used supplementary for a group that appears to be unknown. See openssl/openssl#27137 for related discussion.
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Starting with OpenSSL 3.0, groups may be added externally with pluggable KEM providers. Using SSL_get_negotiated_group(), which makes lookup in a static table with known groups, doesn't allow to list such groups by names leaving them in hex. Adding X25519MLKEM768 to the default group list in OpenSSL 3.5 made this problem more visible. SSL_get0_group_name() and, apparently, SSL_group_to_name() allow to resolve such provider-implemented groups, which is also "generally preferred" over SSL_get_negotiated_group() as documented in OpenSSL git commit 93d4f6133f.
This change makes external groups listing by name using SSL_group_to_name() available since OpenSSL 3.0. To preserve "prime256v1" naming for the group 0x0017, and to avoid breaking BoringSSL and older OpenSSL versions support, it is used supplementary for a group that appears to be unknown.
See openssl/openssl#27137 for related discussion.