Commit af2db04c authored by Todd Short's avatar Todd Short Committed by Rich Salz
Browse files

Fix ALPN 



* Perform ALPN after the SNI callback; the SSL_CTX may change due to
  that processing
* Add flags to indicate that we actually sent ALPN, to properly error
  out if unexpectedly received.
* document ALPN functions
* unit tests

Backport of commit 817cd0d5

Reviewed-by: default avatarEmilia Käsper <emilia@openssl.org>
Reviewed-by: default avatarDr. Stephen Henson <steve@openssl.org>
parent 21211ade

CHANGES

+4 −0
Original line number Diff line number Diff line
@@ -4,6 +4,10 @@ 


 Changes between 1.0.2g and 1.0.2h [xx XXX xxxx]



  *) Modify behavior of ALPN to invoke callback after SNI/servername

     callback, such that updates to the SSL_CTX affect ALPN.

     [Todd Short]



  *) Remove LOW from the DEFAULT cipher list.  This removes singles DES from the

     default.

     [Kurt Roeckx]

doc/ssl/SSL_CTX_set_alpn_select_cb.pod

0 → 100644
+126 −0
Original line number Diff line number Diff line 
=pod



=head1 NAME



SSL_CTX_set_alpn_protos, SSL_set_alpn_protos, SSL_CTX_set_alpn_select_cb,

SSL_select_next_proto, SSL_get0_alpn_selected - handle application layer

protocol negotiation (ALPN)



=head1 SYNOPSIS



 #include <openssl/ssl.h>



 int SSL_CTX_set_alpn_protos(SSL_CTX *ctx, const unsigned char *protos,

                             unsigned protos_len);

 int SSL_set_alpn_protos(SSL *ssl, const unsigned char *protos,

                         unsigned protos_len);

 void SSL_CTX_set_alpn_select_cb(SSL_CTX *ctx,

                                 int (*cb) (SSL *ssl,

                                            const unsigned char **out,

                                            unsigned char *outlen,

                                            const unsigned char *in,

                                            unsigned int inlen,

                                            void *arg), void *arg);

 int SSL_select_next_proto(unsigned char **out, unsigned char *outlen,

                           const unsigned char *server,

                           unsigned int server_len,

                           const unsigned char *client,

                           unsigned int client_len)

 void SSL_get0_alpn_selected(const SSL *ssl, const unsigned char **data,

                             unsigned int *len);



=head1 DESCRIPTION



SSL_CTX_set_alpn_protos() and SSL_set_alpn_protos() are used by the client to

set the list of protocols available to be negotiated. The B<protos> must be in

protocol-list format, described below. The length of B<protos> is specified in

B<protos_len>.



SSL_CTX_set_alpn_select_cb() sets the application callback B<cb> used by a

server to select which protocol to use for the incoming connection. When B<cb>

is NULL, ALPN is not used. The B<arg> value is a pointer which is passed to

the application callback.



B<cb> is the application defined callback. The B<in>, B<inlen> parameters are a

vector in protocol-list format. The value of the B<out>, B<outlen> vector

should be set to the value of a single protocol selected from the B<in>,

B<inlen> vector. The B<arg> parameter is the pointer set via

SSL_CTX_set_alpn_select_cb().



SSL_select_next_proto() is a helper function used to select protocols. It

implements the standard protocol selection. It is expected that this function

is called from the application callback B<cb>. The protocol data in B<server>,

B<server_len> and B<client>, B<client_len> must be in the protocol-list format

described below. The first item in the B<server>, B<server_len> list that

matches an item in the B<client>, B<client_len> list is selected, and returned

in B<out>, B<outlen>. The B<out> value will point into either B<server> or

B<client>, so it should be copied immediately. If no match is found, the first

item in B<client>, B<client_len> is returned in B<out>, B<outlen>. This

function can also be used in the NPN callback.



SSL_get0_alpn_selected() returns a pointer to the selected protocol in B<data>

with length B<len>. It is not NUL-terminated. B<data> is set to NULL and B<len>

is set to 0 if no protocol has been selected. B<data> must not be freed.



=head1 NOTES



The protocol-lists must be in wire-format, which is defined as a vector of

non-empty, 8-bit length-prefixed, byte strings. The length-prefix byte is not

included in the length. Each string is limited to 255 bytes. A byte-string

length of 0 is invalid. A truncated byte-string is invalid. The length of the

vector is not in the vector itself, but in a separate variable.



Example:



 unsigned char vector[] = {

     6, 's', 'p', 'd', 'y', '/', '1',

     8, 'h', 't', 't', 'p', '/', '1', '.', '1'

 };

 unsigned int length = sizeof(vector);



The ALPN callback is executed after the servername callback; as that servername

callback may update the SSL_CTX, and subsequently, the ALPN callback.



If there is no ALPN proposed in the ClientHello, the ALPN callback is not

invoked.



=head1 RETURN VALUES



SSL_CTX_set_alpn_protos() and SSL_set_alpn_protos() return 0 on success, and

non-0 on failure. WARNING: these functions reverse the return value convention.



SSL_select_next_proto() returns one of the following:



=over 4



=item OPENSSL_NPN_NEGOTIATED



A match was found and is returned in B<out>, B<outlen>.



=item OPENSSL_NPN_NO_OVERLAP



No match was found. The first item in B<client>, B<client_len> is returned in

B<out>, B<outlen>.



=back



The ALPN select callback B<cb>, must return one of the following:



=over 4



=item SSL_TLSEXT_ERR_OK



ALPN protocol selected.



=item SSL_TLSEXT_ERR_NOACK



ALPN protocol not selected.



=back



=head1 SEE ALSO



L<ssl(3)>, L<SSL_CTX_set_tlsext_servername_callback(3)>,

L<SSL_CTX_set_tlsext_servername_arg(3)>



=cut

ssl/ssl_cert.c

+2 −0
Original line number Diff line number Diff line
@@ -504,6 +504,8 @@ void ssl_cert_free(CERT *c) 
#ifndef OPENSSL_NO_TLSEXT

    custom_exts_free(&c->cli_ext);

    custom_exts_free(&c->srv_ext);

    if (c->alpn_proposed)

        OPENSSL_free(c->alpn_proposed);

#endif

    OPENSSL_free(c);

}

ssl/ssl_lib.c

+16 −1
Original line number Diff line number Diff line
@@ -244,7 +244,16 @@ int SSL_clear(SSL *s) 
    ssl_clear_hash_ctx(&s->write_hash);



    s->first_packet = 0;



#ifndef OPENSSL_NO_TLSEXT

    if (s->cert != NULL) {

        if (s->cert->alpn_proposed) {

            OPENSSL_free(s->cert->alpn_proposed);

            s->cert->alpn_proposed = NULL;

        }

        s->cert->alpn_proposed_len = 0;

        s->cert->alpn_sent = 0;

    }

#endif

#if 1

    /*

     * Check to see if we were changed into a different method, if so, revert
@@ -3174,6 +3183,12 @@ SSL_CTX *SSL_set_SSL_CTX(SSL *ssl, SSL_CTX *ctx) 
            ssl->cert->ciphers_rawlen = ocert->ciphers_rawlen;

            ocert->ciphers_raw = NULL;

        }

#ifndef OPENSSL_NO_TLSEXT

        ssl->cert->alpn_proposed = ocert->alpn_proposed;

        ssl->cert->alpn_proposed_len = ocert->alpn_proposed_len;

        ocert->alpn_proposed = NULL;

        ssl->cert->alpn_sent = ocert->alpn_sent;

#endif

        ssl_cert_free(ocert);

    }

ssl/ssl_locl.h

+4 −0
Original line number Diff line number Diff line
@@ -688,6 +688,10 @@ typedef struct cert_st { 
    custom_ext_methods cli_ext;

    custom_ext_methods srv_ext;

    int references;             /* >1 only if SSL_copy_session_id is used */

    /* non-optimal, but here due to compatibility */

    unsigned char *alpn_proposed;   /* server */

    unsigned int alpn_proposed_len;

    int alpn_sent;                  /* client */

} CERT;



typedef struct sess_cert_st {