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Provide a callback interface that gives the application the ability to adjust the nascent SSL object at the earliest stage of ClientHello processing, immediately after extensions have been collected but before they have been processed. This is akin to BoringSSL's "select_certificate_cb" (though it is not API compatible), and as the name indicates, one major use is to examine the supplied server name indication and select what certificate to present to the client. However, it can also be used to make more sweeping configuration changes to the SSL object according to the selected server identity and configuration. That may include adjusting the permitted TLS versions, swapping out the SSL_CTX object (as is traditionally done in a tlsext_servername_callback), changing the server's cipher list, and more. We also wish to allow an early callback to indicate that it needs to perform additional work asynchronously and resume processing later. To that effect, refactor the second half of tls_process_client_hello() into a subroutine to be called at the post-processing stage (including the early callback itself), to allow the callback to result in remaining in the same work stage for a later call to succeed. This requires allocating for and storing the CLIENTHELLO_MSG in the SSL object to be preserved across such calls, but the storage is reclaimed after ClientHello processing finishes. Information about the CliehtHello is available to the callback by means of accessor functions that can only be used from the early callback. This allows extensions to make use of the existing internal parsing machinery without exposing structure internals (e.g., of PACKET), so that applications do not have to write fragile parsing code. Applications are encouraged to utilize an early callback and not use a servername_callback, in order to avoid unexpected behavior that occurs due to the relative order of processing between things like session resumption and the historical servername callback. Also tidy up nearby style by removing unnecessary braces around one-line conditional bodies. Reviewed-by: Matt Caswell <matt@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/2279) |
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| HOWTO | ||
| man1 | ||
| man3 | ||
| man5 | ||
| man7 | ||
| dir-locals.example.el | ||
| fingerprints.txt | ||
| openssl-c-indent.el | ||
| README | ||
README This file
fingerprints.txt
PGP fingerprints of authoried release signers
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
Formatted versions of the manpages (apps,ssl,crypto) can be found at
https://www.openssl.org/docs/manpages.html