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Do not allow dropping Extended Master Secret extension on renegotiaton #81

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merged 1 commit into from Sep 22, 2021
Merged

Do not allow dropping Extended Master Secret extension on renegotiaton #81

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3 changes: 3 additions & 0 deletions include/openssl/ssl3.h
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Expand Up @@ -292,6 +292,9 @@ extern "C" {

# define TLS1_FLAGS_STATELESS 0x0800

/* Set if extended master secret extension required on renegotiation */
# define TLS1_FLAGS_REQUIRED_EXTMS 0x1000

# define SSL3_MT_HELLO_REQUEST 0
# define SSL3_MT_CLIENT_HELLO 1
# define SSL3_MT_SERVER_HELLO 2
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14 changes: 13 additions & 1 deletion ssl/statem/extensions.c
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Expand Up @@ -1225,14 +1225,26 @@ static int init_etm(SSL *s, unsigned int context)

static int init_ems(SSL *s, unsigned int context)
{
if (!s->server)
if (s->s3->flags & TLS1_FLAGS_RECEIVED_EXTMS) {
s->s3->flags &= ~TLS1_FLAGS_RECEIVED_EXTMS;
s->s3->flags |= TLS1_FLAGS_REQUIRED_EXTMS;
}

return 1;
}

static int final_ems(SSL *s, unsigned int context, int sent)
{
/*
* Check extended master secret extension is not dropped on
* renegotiation.
*/
if (!(s->s3->flags & TLS1_FLAGS_RECEIVED_EXTMS)
&& (s->s3->flags & TLS1_FLAGS_REQUIRED_EXTMS)) {
SSLfatal(s, SSL_AD_HANDSHAKE_FAILURE, SSL_F_FINAL_EMS,
SSL_R_INCONSISTENT_EXTMS);
return 0;
}
if (!s->server && s->hit) {
/*
* Check extended master secret extension is consistent with
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