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boringssl / boringssl / e9fc3e547e557492316932b62881c3386973ceb2 / . / ssl / ssl_ciph.c
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
/* ====================================================================
* Copyright (c) 1998-2007 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@openssl.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com).
*
*/
/* ====================================================================
* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
* ECC cipher suite support in OpenSSL originally developed by
* SUN MICROSYSTEMS, INC., and contributed to the OpenSSL project.
*/
/* ====================================================================
* Copyright 2005 Nokia. All rights reserved.
*
* The portions of the attached software ("Contribution") is developed by
* Nokia Corporation and is licensed pursuant to the OpenSSL open source
* license.
*
* The Contribution, originally written by Mika Kousa and Pasi Eronen of
* Nokia Corporation, consists of the "PSK" (Pre-Shared Key) ciphersuites
* support (see RFC 4279) to OpenSSL.
*
* No patent licenses or other rights except those expressly stated in
* the OpenSSL open source license shall be deemed granted or received
* expressly, by implication, estoppel, or otherwise.
*
* No assurances are provided by Nokia that the Contribution does not
* infringe the patent or other intellectual property rights of any third
* party or that the license provides you with all the necessary rights
* to make use of the Contribution.
*
* THE SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. IN
* ADDITION TO THE DISCLAIMERS INCLUDED IN THE LICENSE, NOKIA
* SPECIFICALLY DISCLAIMS ANY LIABILITY FOR CLAIMS BROUGHT BY YOU OR ANY
* OTHER ENTITY BASED ON INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OR
* OTHERWISE. */
#include <stdio.h>
#include <assert.h>
#include <openssl/engine.h>
#include <openssl/md5.h>
#include <openssl/mem.h>
#include <openssl/obj.h>
#include <openssl/sha.h>
#include "ssl_locl.h"
struct handshake_digest {
long mask;
const EVP_MD *(*md_func)(void);
};
static const struct handshake_digest ssl_handshake_digests[SSL_MAX_DIGEST] = {
{SSL_HANDSHAKE_MAC_MD5, EVP_md5},
{SSL_HANDSHAKE_MAC_SHA, EVP_sha1},
{SSL_HANDSHAKE_MAC_SHA256, EVP_sha256},
{SSL_HANDSHAKE_MAC_SHA384, EVP_sha384},
};
#define CIPHER_ADD 1
#define CIPHER_KILL 2
#define CIPHER_DEL 3
#define CIPHER_ORD 4
#define CIPHER_SPECIAL 5
typedef struct cipher_order_st {
const SSL_CIPHER *cipher;
int active;
int dead;
int in_group;
struct cipher_order_st *next, *prev;
} CIPHER_ORDER;
static const SSL_CIPHER cipher_aliases[] =
{
{0, SSL_TXT_ALL, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
/* "COMPLEMENTOFDEFAULT" (does *not* include ciphersuites not found in
ALL!) */
{0, SSL_TXT_CMPDEF, 0, SSL_kEDH | SSL_kEECDH, SSL_aNULL, 0, 0, 0, 0, 0, 0,
0},
/* key exchange aliases
* (some of those using only a single bit here combine
* multiple key exchange algs according to the RFCs,
* e.g. kEDH combines DHE_DSS and DHE_RSA) */
{0, SSL_TXT_kRSA, 0, SSL_kRSA, 0, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_kEDH, 0, SSL_kEDH, 0, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_DH, 0, SSL_kEDH, 0, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_kEECDH, 0, SSL_kEECDH, 0, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_ECDH, 0, SSL_kEECDH, 0, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_kPSK, 0, SSL_kPSK, 0, 0, 0, 0, 0, 0, 0, 0},
/* server authentication aliases */
{0, SSL_TXT_aRSA, 0, 0, SSL_aRSA, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_aNULL, 0, 0, SSL_aNULL, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_aECDSA, 0, 0, SSL_aECDSA, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_ECDSA, 0, 0, SSL_aECDSA, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_aPSK, 0, 0, SSL_aPSK, 0, 0, 0, 0, 0, 0, 0},
/* aliases combining key exchange and server authentication */
{0, SSL_TXT_EDH, 0, SSL_kEDH, ~SSL_aNULL, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_EECDH, 0, SSL_kEECDH, ~SSL_aNULL, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_RSA, 0, SSL_kRSA, SSL_aRSA, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_ADH, 0, SSL_kEDH, SSL_aNULL, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_AECDH, 0, SSL_kEECDH, SSL_aNULL, 0, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_PSK, 0, SSL_kPSK, SSL_aPSK, 0, 0, 0, 0, 0, 0, 0},
/* symmetric encryption aliases */
{0, SSL_TXT_3DES, 0, 0, 0, SSL_3DES, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_RC4, 0, 0, 0, SSL_RC4, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_AES128, 0, 0, 0, SSL_AES128 | SSL_AES128GCM, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_AES256, 0, 0, 0, SSL_AES256 | SSL_AES256GCM, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_AES, 0, 0, 0, SSL_AES, 0, 0, 0, 0, 0, 0},
{0, SSL_TXT_AES_GCM, 0, 0, 0, SSL_AES128GCM | SSL_AES256GCM, 0, 0, 0, 0, 0,
0},
{0, SSL_TXT_CHACHA20, 0, 0, 0, SSL_CHACHA20POLY1305, 0, 0, 0, 0, 0, 0},
/* MAC aliases */
{0, SSL_TXT_MD5, 0, 0, 0, 0, SSL_MD5, 0, 0, 0, 0, 0},
{0, SSL_TXT_SHA1, 0, 0, 0, 0, SSL_SHA1, 0, 0, 0, 0, 0},
{0, SSL_TXT_SHA, 0, 0, 0, 0, SSL_SHA1, 0, 0, 0, 0, 0},
{0, SSL_TXT_SHA256, 0, 0, 0, 0, SSL_SHA256, 0, 0, 0, 0, 0},
{0, SSL_TXT_SHA384, 0, 0, 0, 0, SSL_SHA384, 0, 0, 0, 0, 0},
/* protocol version aliases */
{0, SSL_TXT_SSLV3, 0, 0, 0, 0, 0, SSL_SSLV3, 0, 0, 0, 0},
{0, SSL_TXT_TLSV1, 0, 0, 0, 0, 0, SSL_TLSV1, 0, 0, 0, 0},
{0, SSL_TXT_TLSV1_2, 0, 0, 0, 0, 0, SSL_TLSV1_2, 0, 0, 0, 0},
/* strength classes */
{0, SSL_TXT_MEDIUM, 0, 0, 0, 0, 0, 0, SSL_MEDIUM, 0, 0, 0},
{0, SSL_TXT_HIGH, 0, 0, 0, 0, 0, 0, SSL_HIGH, 0, 0, 0},
/* FIPS 140-2 approved ciphersuite */
{0, SSL_TXT_FIPS, 0, 0, 0, 0, 0, 0, SSL_FIPS, 0, 0, 0},
};
int ssl_cipher_get_evp_aead(const EVP_AEAD **out_aead,
size_t *out_mac_secret_len,
size_t *out_fixed_iv_len,
const SSL_CIPHER *cipher, uint16_t version) {
*out_aead = NULL;
*out_mac_secret_len = 0;
*out_fixed_iv_len = 0;
switch (cipher->algorithm_enc) {
case SSL_AES128GCM:
*out_aead = EVP_aead_aes_128_gcm();
*out_fixed_iv_len = 4;
return 1;
case SSL_AES256GCM:
*out_aead = EVP_aead_aes_256_gcm();
*out_fixed_iv_len = 4;
return 1;
case SSL_CHACHA20POLY1305:
*out_aead = EVP_aead_chacha20_poly1305();
*out_fixed_iv_len = 0;
return 1;
case SSL_RC4:
switch (cipher->algorithm_mac) {
case SSL_MD5:
if (version == SSL3_VERSION) {
*out_aead = EVP_aead_rc4_md5_ssl3();
} else {
*out_aead = EVP_aead_rc4_md5_tls();
}
*out_mac_secret_len = MD5_DIGEST_LENGTH;
return 1;
case SSL_SHA1:
if (version == SSL3_VERSION) {
*out_aead = EVP_aead_rc4_sha1_ssl3();
} else {
*out_aead = EVP_aead_rc4_sha1_tls();
}
*out_mac_secret_len = SHA_DIGEST_LENGTH;
return 1;
default:
return 0;
}
case SSL_AES128:
switch (cipher->algorithm_mac) {
case SSL_SHA1:
if (version == SSL3_VERSION) {
*out_aead = EVP_aead_aes_128_cbc_sha1_ssl3();
*out_fixed_iv_len = 16;
} else if (version == TLS1_VERSION) {
*out_aead = EVP_aead_aes_128_cbc_sha1_tls_implicit_iv();
*out_fixed_iv_len = 16;
} else {
*out_aead = EVP_aead_aes_128_cbc_sha1_tls();
}
*out_mac_secret_len = SHA_DIGEST_LENGTH;
return 1;
case SSL_SHA256:
*out_aead = EVP_aead_aes_128_cbc_sha256_tls();
*out_mac_secret_len = SHA256_DIGEST_LENGTH;
return 1;
default:
return 0;
}
case SSL_AES256:
switch (cipher->algorithm_mac) {
case SSL_SHA1:
if (version == SSL3_VERSION) {
*out_aead = EVP_aead_aes_256_cbc_sha1_ssl3();
*out_fixed_iv_len = 16;
} else if (version == TLS1_VERSION) {
*out_aead = EVP_aead_aes_256_cbc_sha1_tls_implicit_iv();
*out_fixed_iv_len = 16;
} else {
*out_aead = EVP_aead_aes_256_cbc_sha1_tls();
}
*out_mac_secret_len = SHA_DIGEST_LENGTH;
return 1;
case SSL_SHA256:
*out_aead = EVP_aead_aes_256_cbc_sha256_tls();
*out_mac_secret_len = SHA256_DIGEST_LENGTH;
return 1;
case SSL_SHA384:
*out_aead = EVP_aead_aes_256_cbc_sha384_tls();
*out_mac_secret_len = SHA384_DIGEST_LENGTH;
return 1;
default:
return 0;
}
case SSL_3DES:
switch (cipher->algorithm_mac) {
case SSL_SHA1:
if (version == SSL3_VERSION) {
*out_aead = EVP_aead_des_ede3_cbc_sha1_ssl3();
*out_fixed_iv_len = 8;
} else if (version == TLS1_VERSION) {
*out_aead = EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv();
*out_fixed_iv_len = 8;
} else {
*out_aead = EVP_aead_des_ede3_cbc_sha1_tls();
}
*out_mac_secret_len = SHA_DIGEST_LENGTH;
return 1;
default:
return 0;
}
default:
return 0;
}
}
int ssl_get_handshake_digest(size_t idx, long *mask, const EVP_MD **md) {
if (idx >= SSL_MAX_DIGEST) {
return 0;
}
*mask = ssl_handshake_digests[idx].mask;
*md = ssl_handshake_digests[idx].md_func();
return 1;
}
#define ITEM_SEP(a) \
(((a) == ':') || ((a) == ' ') || ((a) == ';') || ((a) == ','))
static void ll_append_tail(CIPHER_ORDER **head, CIPHER_ORDER *curr,
CIPHER_ORDER **tail) {
if (curr == *tail) {
return;
}
if (curr == *head) {
*head = curr->next;
}
if (curr->prev != NULL) {
curr->prev->next = curr->next;
}
if (curr->next != NULL) {
curr->next->prev = curr->prev;
}
(*tail)->next = curr;
curr->prev = *tail;
curr->next = NULL;
*tail = curr;
}
static void ll_append_head(CIPHER_ORDER **head, CIPHER_ORDER *curr,
CIPHER_ORDER **tail) {
if (curr == *head) {
return;
}
if (curr == *tail) {
*tail = curr->prev;
}
if (curr->next != NULL) {
curr->next->prev = curr->prev;
}
if (curr->prev != NULL) {
curr->prev->next = curr->next;
}
(*head)->prev = curr;
curr->next = *head;
curr->prev = NULL;
*head = curr;
}
static void ssl_cipher_collect_ciphers(const SSL_PROTOCOL_METHOD *ssl_method,
int num_of_ciphers,
CIPHER_ORDER *co_list,
CIPHER_ORDER **head_p,
CIPHER_ORDER **tail_p) {
int i, co_list_num;
const SSL_CIPHER *c;
/* We have num_of_ciphers descriptions compiled in, depending on the method
* selected (SSLv2 and/or SSLv3, TLSv1 etc). These will later be sorted in a
* linked list with at most num entries. */
/* Get the initial list of ciphers */
co_list_num = 0; /* actual count of ciphers */
for (i = 0; i < num_of_ciphers; i++) {
c = ssl_method->get_cipher(i);
/* drop those that use any of that is not available */
if (c != NULL && c->valid) {
co_list[co_list_num].cipher = c;
co_list[co_list_num].next = NULL;
co_list[co_list_num].prev = NULL;
co_list[co_list_num].active = 0;
co_list[co_list_num].in_group = 0;
co_list_num++;
}
}
/* Prepare linked list from list entries. */
if (co_list_num > 0) {
co_list[0].prev = NULL;
if (co_list_num > 1) {
co_list[0].next = &co_list[1];
for (i = 1; i < co_list_num - 1; i++) {
co_list[i].prev = &co_list[i - 1];
co_list[i].next = &co_list[i + 1];
}
co_list[co_list_num - 1].prev = &co_list[co_list_num - 2];
}
co_list[co_list_num - 1].next = NULL;
*head_p = &co_list[0];
*tail_p = &co_list[co_list_num - 1];
}
}
static void ssl_cipher_collect_aliases(const SSL_CIPHER **ca_list,
int num_of_group_aliases,
CIPHER_ORDER *head) {
CIPHER_ORDER *ciph_curr;
const SSL_CIPHER **ca_curr;
int i;
/* First, add the real ciphers as already collected. */
ciph_curr = head;
ca_curr = ca_list;
while (ciph_curr != NULL) {
*ca_curr = ciph_curr->cipher;
ca_curr++;
ciph_curr = ciph_curr->next;
}
/* Now we add the available ones from the cipher_aliases[] table. They
* represent either one or more algorithms, some of which in any affected
* category must be supported (set in enabled_mask), or represent a cipher
* strength value (will be added in any case because algorithms=0). */
for (i = 0; i < num_of_group_aliases; i++) {
*ca_curr = cipher_aliases + i;
ca_curr++;
}
*ca_curr = NULL; /* end of list */
}
static void ssl_cipher_apply_rule(
unsigned long cipher_id, unsigned long alg_mkey, unsigned long alg_auth,
unsigned long alg_enc, unsigned long alg_mac, unsigned long alg_ssl,
unsigned long algo_strength, int rule, int strength_bits, int in_group,
CIPHER_ORDER **head_p, CIPHER_ORDER **tail_p) {
CIPHER_ORDER *head, *tail, *curr, *next, *last;
const SSL_CIPHER *cp;
int reverse = 0;
if (rule == CIPHER_DEL) {
/* needed to maintain sorting between currently deleted ciphers */
reverse = 1;
}
head = *head_p;
tail = *tail_p;
if (reverse) {
next = tail;
last = head;
} else {
next = head;
last = tail;
}
curr = NULL;
for (;;) {
if (curr == last) {
break;
}
curr = next;
if (curr == NULL) {
break;
}
next = reverse ? curr->prev : curr->next;
cp = curr->cipher;
/* Selection criteria is either the value of strength_bits
* or the algorithms used. */
if (strength_bits >= 0) {
if (strength_bits != cp->strength_bits) {
continue;
}
} else {
if ((alg_mkey && !(alg_mkey & cp->algorithm_mkey)) ||
(alg_auth && !(alg_auth & cp->algorithm_auth)) ||
(alg_enc && !(alg_enc & cp->algorithm_enc)) ||
(alg_mac && !(alg_mac & cp->algorithm_mac)) ||
(alg_ssl && !(alg_ssl & cp->algorithm_ssl)) ||
(algo_strength && !(algo_strength & cp->algo_strength))) {
continue;
}
}
/* add the cipher if it has not been added yet. */
if (rule == CIPHER_ADD) {
/* reverse == 0 */
if (!curr->active) {
ll_append_tail(&head, curr, &tail);
curr->active = 1;
curr->in_group = in_group;
}
}
/* Move the added cipher to this location */
else if (rule == CIPHER_ORD) {
/* reverse == 0 */
if (curr->active) {
ll_append_tail(&head, curr, &tail);
curr->in_group = 0;
}
} else if (rule == CIPHER_DEL) {
/* reverse == 1 */
if (curr->active) {
/* most recently deleted ciphersuites get best positions
* for any future CIPHER_ADD (note that the CIPHER_DEL loop
* works in reverse to maintain the order) */
ll_append_head(&head, curr, &tail);
curr->active = 0;
curr->in_group = 0;
}
} else if (rule == CIPHER_KILL) {
/* reverse == 0 */
if (head == curr) {
head = curr->next;
} else {
curr->prev->next = curr->next;
}
if (tail == curr) {
tail = curr->prev;
}
curr->active = 0;
if (curr->next != NULL) {
curr->next->prev = curr->prev;
}
if (curr->prev != NULL) {
curr->prev->next = curr->next;
}
curr->next = NULL;
curr->prev = NULL;
}
}
*head_p = head;
*tail_p = tail;
}
static int ssl_cipher_strength_sort(CIPHER_ORDER **head_p,
CIPHER_ORDER **tail_p) {
int max_strength_bits, i, *number_uses;
CIPHER_ORDER *curr;
/* This routine sorts the ciphers with descending strength. The sorting must
* keep the pre-sorted sequence, so we apply the normal sorting routine as
* '+' movement to the end of the list. */
max_strength_bits = 0;
curr = *head_p;
while (curr != NULL) {
if (curr->active && curr->cipher->strength_bits > max_strength_bits) {
max_strength_bits = curr->cipher->strength_bits;
}
curr = curr->next;
}
number_uses = OPENSSL_malloc((max_strength_bits + 1) * sizeof(int));
if (!number_uses) {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_strength_sort, ERR_R_MALLOC_FAILURE);
return 0;
}
memset(number_uses, 0, (max_strength_bits + 1) * sizeof(int));
/* Now find the strength_bits values actually used. */
curr = *head_p;
while (curr != NULL) {
if (curr->active) {
number_uses[curr->cipher->strength_bits]++;
}
curr = curr->next;
}
/* Go through the list of used strength_bits values in descending order. */
for (i = max_strength_bits; i >= 0; i--) {
if (number_uses[i] > 0) {
ssl_cipher_apply_rule(0, 0, 0, 0, 0, 0, 0, CIPHER_ORD, i, 0, head_p,
tail_p);
}
}
OPENSSL_free(number_uses);
return 1;
}
static int ssl_cipher_process_rulestr(const char *rule_str,
CIPHER_ORDER **head_p,
CIPHER_ORDER **tail_p,
const SSL_CIPHER **ca_list) {
unsigned long alg_mkey, alg_auth, alg_enc, alg_mac, alg_ssl, algo_strength;
const char *l, *buf;
int j, multi, found, rule, retval, ok, buflen, in_group = 0, has_group = 0;
unsigned long cipher_id = 0;
char ch;
retval = 1;
l = rule_str;
for (;;) {
ch = *l;
if (ch == '\0') {
break; /* done */
}
if (in_group) {
if (ch == ']') {
if (!in_group) {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr,
SSL_R_UNEXPECTED_GROUP_CLOSE);
retval = found = in_group = 0;
break;
}
if (*tail_p) {
(*tail_p)->in_group = 0;
}
in_group = 0;
l++;
continue;
}
if (ch == '|') {
rule = CIPHER_ADD;
l++;
continue;
} else if (!(ch >= 'a' && ch <= 'z') && !(ch >= 'A' && ch <= 'Z') &&
!(ch >= '0' && ch <= '9')) {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr,
SSL_R_UNEXPECTED_OPERATOR_IN_GROUP);
retval = found = in_group = 0;
break;
} else {
rule = CIPHER_ADD;
}
} else if (ch == '-') {
rule = CIPHER_DEL;
l++;
} else if (ch == '+') {
rule = CIPHER_ORD;
l++;
} else if (ch == '!') {
rule = CIPHER_KILL;
l++;
} else if (ch == '@') {
rule = CIPHER_SPECIAL;
l++;
} else if (ch == '[') {
if (in_group) {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr, SSL_R_NESTED_GROUP);
retval = found = in_group = 0;
break;
}
in_group = 1;
has_group = 1;
l++;
continue;
} else {
rule = CIPHER_ADD;
}
/* If preference groups are enabled, the only legal operator is +.
* Otherwise the in_group bits will get mixed up. */
if (has_group && rule != CIPHER_ADD) {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr,
SSL_R_MIXED_SPECIAL_OPERATOR_WITH_GROUPS);
retval = found = in_group = 0;
break;
}
if (ITEM_SEP(ch)) {
l++;
continue;
}
alg_mkey = 0;
alg_auth = 0;
alg_enc = 0;
alg_mac = 0;
alg_ssl = 0;
algo_strength = 0;
for (;;) {
ch = *l;
buf = l;
buflen = 0;
while (((ch >= 'A') && (ch <= 'Z')) || ((ch >= '0') && (ch <= '9')) ||
((ch >= 'a') && (ch <= 'z')) || (ch == '-') || (ch == '.')) {
ch = *(++l);
buflen++;
}
if (buflen == 0) {
/* We hit something we cannot deal with, it is no command or separator
* nor alphanumeric, so we call this an error. */
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr,
SSL_R_INVALID_COMMAND);
retval = found = in_group = 0;
l++;
break;
}
if (rule == CIPHER_SPECIAL) {
found = 0; /* unused -- avoid compiler warning */
break; /* special treatment */
}
/* check for multi-part specification */
if (ch == '+') {
multi = 1;
l++;
} else {
multi = 0;
}
/* Now search for the cipher alias in the ca_list. Be careful with the
* strncmp, because the "buflen" limitation will make the rule "ADH:SOME"
* and the cipher "ADH-MY-CIPHER" look like a match for buflen=3. So
* additionally check whether the cipher name found has the correct
* length. We can save a strlen() call: just checking for the '\0' at the
* right place is sufficient, we have to strncmp() anyway. (We cannot use
* strcmp(), because buf is not '\0' terminated.) */
j = found = 0;
cipher_id = 0;
while (ca_list[j]) {
if (!strncmp(buf, ca_list[j]->name, buflen) &&
(ca_list[j]->name[buflen] == '\0')) {
found = 1;
break;
} else {
j++;
}
}
if (!found) {
break; /* ignore this entry */
}
if (ca_list[j]->algorithm_mkey) {
if (alg_mkey) {
alg_mkey &= ca_list[j]->algorithm_mkey;
if (!alg_mkey) {
found = 0;
break;
}
} else {
alg_mkey = ca_list[j]->algorithm_mkey;
}
}
if (ca_list[j]->algorithm_auth) {
if (alg_auth) {
alg_auth &= ca_list[j]->algorithm_auth;
if (!alg_auth) {
found = 0;
break;
}
} else {
alg_auth = ca_list[j]->algorithm_auth;
}
}
if (ca_list[j]->algorithm_enc) {
if (alg_enc) {
alg_enc &= ca_list[j]->algorithm_enc;
if (!alg_enc) {
found = 0;
break;
}
} else {
alg_enc = ca_list[j]->algorithm_enc;
}
}
if (ca_list[j]->algorithm_mac) {
if (alg_mac) {
alg_mac &= ca_list[j]->algorithm_mac;
if (!alg_mac) {
found = 0;
break;
}
} else {
alg_mac = ca_list[j]->algorithm_mac;
}
}
if (ca_list[j]->algo_strength) {
if (algo_strength) {
algo_strength &= ca_list[j]->algo_strength;
if (!algo_strength) {
found = 0;
break;
}
} else {
algo_strength |= ca_list[j]->algo_strength;
}
}
if (ca_list[j]->valid) {
/* explicit ciphersuite found; its protocol version does not become
* part of the search pattern! */
cipher_id = ca_list[j]->id;
} else {
/* not an explicit ciphersuite; only in this case, the protocol version
* is considered part of the search pattern. */
if (ca_list[j]->algorithm_ssl) {
if (alg_ssl) {
alg_ssl &= ca_list[j]->algorithm_ssl;
if (!alg_ssl) {
found = 0;
break;
}
} else {
alg_ssl = ca_list[j]->algorithm_ssl;
}
}
}
if (!multi) {
break;
}
}
/* Ok, we have the rule, now apply it. */
if (rule == CIPHER_SPECIAL) {
/* special command */
ok = 0;
if (buflen == 8 && !strncmp(buf, "STRENGTH", 8)) {
ok = ssl_cipher_strength_sort(head_p, tail_p);
} else {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr,
SSL_R_INVALID_COMMAND);
}
if (ok == 0) {
retval = 0;
}
/* We do not support any "multi" options together with "@", so throw away
* the rest of the command, if any left, until end or ':' is found. */
while (*l != '\0' && !ITEM_SEP(*l)) {
l++;
}
} else if (found) {
ssl_cipher_apply_rule(cipher_id, alg_mkey, alg_auth, alg_enc, alg_mac,
alg_ssl, algo_strength, rule, -1, in_group, head_p,
tail_p);
} else {
while (*l != '\0' && !ITEM_SEP(*l)) {
l++;
}
}
}
if (in_group) {
OPENSSL_PUT_ERROR(SSL, ssl_cipher_process_rulestr, SSL_R_INVALID_COMMAND);
retval = 0;
}
return retval;
}
STACK_OF(SSL_CIPHER) *
ssl_create_cipher_list(const SSL_PROTOCOL_METHOD *ssl_method,
struct ssl_cipher_preference_list_st **cipher_list,
STACK_OF(SSL_CIPHER) * *cipher_list_by_id,
const char *rule_str, CERT *c) {
int ok, num_of_ciphers, num_of_alias_max, num_of_group_aliases;
STACK_OF(SSL_CIPHER) *cipherstack = NULL, *tmp_cipher_list = NULL;
const char *rule_p;
CIPHER_ORDER *co_list = NULL, *head = NULL, *tail = NULL, *curr;
const SSL_CIPHER **ca_list = NULL;
uint8_t *in_group_flags = NULL;
unsigned int num_in_group_flags = 0;
struct ssl_cipher_preference_list_st *pref_list = NULL;
/* Return with error if nothing to do. */
if (rule_str == NULL || cipher_list == NULL) {
return NULL;
}
/* Now we have to collect the available ciphers from the compiled in ciphers.
* We cannot get more than the number compiled in, so it is used for
* allocation. */
num_of_ciphers = ssl_method->num_ciphers();
co_list =
(CIPHER_ORDER *)OPENSSL_malloc(sizeof(CIPHER_ORDER) * num_of_ciphers);
if (co_list == NULL) {
OPENSSL_PUT_ERROR(SSL, ssl_create_cipher_list, ERR_R_MALLOC_FAILURE);
return NULL;
}
ssl_cipher_collect_ciphers(ssl_method, num_of_ciphers, co_list, &head, &tail);
/* Now arrange all ciphers by preference:
* TODO(davidben): Compute this order once and copy it. */
/* Everything else being equal, prefer ECDHE_ECDSA then ECDHE_RSA over other
* key exchange mechanisms */
ssl_cipher_apply_rule(0, SSL_kEECDH, SSL_aECDSA, 0, 0, 0, 0, CIPHER_ADD, -1,
0, &head, &tail);
ssl_cipher_apply_rule(0, SSL_kEECDH, 0, 0, 0, 0, 0, CIPHER_ADD, -1, 0, &head,
&tail);
ssl_cipher_apply_rule(0, SSL_kEECDH, 0, 0, 0, 0, 0, CIPHER_DEL, -1, 0, &head,
&tail);
/* Order the bulk ciphers. First the preferred AEAD ciphers. We prefer
* CHACHA20 unless there is hardware support for fast and constant-time
* AES_GCM. */
if (EVP_has_aes_hardware()) {
ssl_cipher_apply_rule(0, 0, 0, SSL_AES256GCM, 0, 0, 0, CIPHER_ADD, -1, 0,
&head, &tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_AES128GCM, 0, 0, 0, CIPHER_ADD, -1, 0,
&head, &tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_CHACHA20POLY1305, 0, 0, 0, CIPHER_ADD,
-1, 0, &head, &tail);
} else {
ssl_cipher_apply_rule(0, 0, 0, SSL_CHACHA20POLY1305, 0, 0, 0, CIPHER_ADD,
-1, 0, &head, &tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_AES256GCM, 0, 0, 0, CIPHER_ADD, -1, 0,
&head, &tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_AES128GCM, 0, 0, 0, CIPHER_ADD, -1, 0,
&head, &tail);
}
/* Then the legacy non-AEAD ciphers: AES_256_CBC, AES-128_CBC, RC4_128_SHA,
* RC4_128_MD5, 3DES_EDE_CBC_SHA. */
ssl_cipher_apply_rule(0, 0, 0, SSL_AES256, 0, 0, 0, CIPHER_ADD, -1, 0, &head,
&tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_AES128, 0, 0, 0, CIPHER_ADD, -1, 0, &head,
&tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_RC4, ~SSL_MD5, 0, 0, CIPHER_ADD, -1, 0,
&head, &tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_RC4, SSL_MD5, 0, 0, CIPHER_ADD, -1, 0,
&head, &tail);
ssl_cipher_apply_rule(0, 0, 0, SSL_3DES, 0, 0, 0, CIPHER_ADD, -1, 0, &head,
&tail);
/* Temporarily enable everything else for sorting */
ssl_cipher_apply_rule(0, 0, 0, 0, 0, 0, 0, CIPHER_ADD, -1, 0, &head, &tail);
/* Move ciphers without forward secrecy to the end. */
ssl_cipher_apply_rule(0, ~(SSL_kEDH | SSL_kEECDH), 0, 0, 0, 0, 0, CIPHER_ORD,
-1, 0, &head, &tail);
/* Move anonymous ciphers to the end. Usually, these will remain disabled.
* (For applications that allow them, they aren't too bad, but we prefer
* authenticated ciphers.)
* TODO(davidben): Remove them altogether? */
ssl_cipher_apply_rule(0, 0, SSL_aNULL, 0, 0, 0, 0, CIPHER_ORD, -1, 0, &head,
&tail);
/* Now disable everything (maintaining the ordering!) */
ssl_cipher_apply_rule(0, 0, 0, 0, 0, 0, 0, CIPHER_DEL, -1, 0, &head, &tail);
/* We also need cipher aliases for selecting based on the rule_str. There
* might be two types of entries in the rule_str: 1) names of ciphers
* themselves 2) aliases for groups of ciphers. For 1) we need the available
* ciphers and for 2) the cipher groups of cipher_aliases added together in
* one list (otherwise we would be happy with just the cipher_aliases
* table). */
num_of_group_aliases = sizeof(cipher_aliases) / sizeof(SSL_CIPHER);
num_of_alias_max = num_of_ciphers + num_of_group_aliases + 1;
ca_list = OPENSSL_malloc(sizeof(SSL_CIPHER *) * num_of_alias_max);
if (ca_list == NULL) {
OPENSSL_PUT_ERROR(SSL, ssl_create_cipher_list, ERR_R_MALLOC_FAILURE);
goto err;
}
ssl_cipher_collect_aliases(ca_list, num_of_group_aliases, head);
/* If the rule_string begins with DEFAULT, apply the default rule before
* using the (possibly available) additional rules. */
ok = 1;
rule_p = rule_str;
if (strncmp(rule_str, "DEFAULT", 7) == 0) {
ok = ssl_cipher_process_rulestr(SSL_DEFAULT_CIPHER_LIST, &head, &tail,
ca_list);
rule_p += 7;
if (*rule_p == ':') {
rule_p++;
}
}
if (ok && strlen(rule_p) > 0) {
ok = ssl_cipher_process_rulestr(rule_p, &head, &tail, ca_list);
}
OPENSSL_free((void *)ca_list); /* Not needed anymore */
if (!ok) {
goto err;
}
/* Allocate new "cipherstack" for the result, return with error
* if we cannot get one. */
cipherstack = sk_SSL_CIPHER_new_null();
if (cipherstack == NULL) {
goto err;
}
in_group_flags = OPENSSL_malloc(num_of_ciphers);
if (!in_group_flags) {
goto err;
}
/* The cipher selection for the list is done. The ciphers are added
* to the resulting precedence to the STACK_OF(SSL_CIPHER). */
for (curr = head; curr != NULL; curr = curr->next) {
if (curr->active) {
if (!sk_SSL_CIPHER_push(cipherstack, curr->cipher)) {
goto err;
}
in_group_flags[num_in_group_flags++] = curr->in_group;
}
}
OPENSSL_free(co_list); /* Not needed any longer */
co_list = NULL;
tmp_cipher_list = sk_SSL_CIPHER_dup(cipherstack);
if (tmp_cipher_list == NULL) {
goto err;
}
pref_list = OPENSSL_malloc(sizeof(struct ssl_cipher_preference_list_st));
if (!pref_list) {
goto err;
}
pref_list->ciphers = cipherstack;
pref_list->in_group_flags = OPENSSL_malloc(num_in_group_flags);
if (!pref_list->in_group_flags) {
goto err;
}
memcpy(pref_list->in_group_flags, in_group_flags, num_in_group_flags);
OPENSSL_free(in_group_flags);
in_group_flags = NULL;
if (*cipher_list != NULL) {
ssl_cipher_preference_list_free(*cipher_list);
}
*cipher_list = pref_list;
pref_list = NULL;
if (cipher_list_by_id != NULL) {
if (*cipher_list_by_id != NULL) {
sk_SSL_CIPHER_free(*cipher_list_by_id);
}
*cipher_list_by_id = tmp_cipher_list;
tmp_cipher_list = NULL;
(void) sk_SSL_CIPHER_set_cmp_func(*cipher_list_by_id, ssl_cipher_ptr_id_cmp);
sk_SSL_CIPHER_sort(*cipher_list_by_id);
} else {
sk_SSL_CIPHER_free(tmp_cipher_list);
tmp_cipher_list = NULL;
}
return cipherstack;
err:
if (co_list) {
OPENSSL_free(co_list);
}
if (in_group_flags) {
OPENSSL_free(in_group_flags);
}
if (cipherstack) {
sk_SSL_CIPHER_free(cipherstack);
}
if (tmp_cipher_list) {
sk_SSL_CIPHER_free(tmp_cipher_list);
}
if (pref_list && pref_list->in_group_flags) {
OPENSSL_free(pref_list->in_group_flags);
}
if (pref_list) {
OPENSSL_free(pref_list);
}
return NULL;
}
const char *SSL_CIPHER_description(const SSL_CIPHER *cipher, char *buf,
int len) {
const char *ver;
const char *kx, *au, *enc, *mac;
unsigned long alg_mkey, alg_auth, alg_enc, alg_mac, alg_ssl;
static const char *format = "%-23s %s Kx=%-8s Au=%-4s Enc=%-9s Mac=%-4s\n";
alg_mkey = cipher->algorithm_mkey;
alg_auth = cipher->algorithm_auth;
alg_enc = cipher->algorithm_enc;
alg_mac = cipher->algorithm_mac;
alg_ssl = cipher->algorithm_ssl;
if (alg_ssl & SSL_SSLV3) {
ver = "SSLv3";
} else if (alg_ssl & SSL_TLSV1_2) {
ver = "TLSv1.2";
} else {
ver = "unknown";
}
switch (alg_mkey) {
case SSL_kRSA:
kx = "RSA";
break;
case SSL_kEDH:
kx = "DH";
break;
case SSL_kEECDH:
kx = "ECDH";
break;
case SSL_kPSK:
kx = "PSK";
break;
default:
kx = "unknown";
}
switch (alg_auth) {
case SSL_aRSA:
au = "RSA";
break;
case SSL_aNULL:
au = "None";
break;
case SSL_aECDSA:
au = "ECDSA";
break;
case SSL_aPSK:
au = "PSK";
break;
default:
au = "unknown";
break;
}
switch (alg_enc) {
case SSL_3DES:
enc = "3DES(168)";
break;
case SSL_RC4:
enc = "RC4(128)";
break;
case SSL_AES128:
enc = "AES(128)";
break;
case SSL_AES256:
enc = "AES(256)";
break;
case SSL_AES128GCM:
enc = "AESGCM(128)";
break;
case SSL_AES256GCM:
enc = "AESGCM(256)";
break;
case SSL_CHACHA20POLY1305:
enc = "ChaCha20-Poly1305";
break;
default:
enc = "unknown";
break;
}
switch (alg_mac) {
case SSL_MD5:
mac = "MD5";
break;
case SSL_SHA1:
mac = "SHA1";
break;
case SSL_SHA256:
mac = "SHA256";
break;
case SSL_SHA384:
mac = "SHA384";
break;
case SSL_AEAD:
mac = "AEAD";
break;
default:
mac = "unknown";
break;
}
if (buf == NULL) {
len = 128;
buf = OPENSSL_malloc(len);
if (buf == NULL)
return "OPENSSL_malloc Error";
} else if (len < 128) {
return "Buffer too small";
}
BIO_snprintf(buf, len, format, cipher->name, ver, kx, au, enc, mac);
return buf;
}
int SSL_CIPHER_is_AES(const SSL_CIPHER *c) {
return (c->algorithm_enc & SSL_AES) != 0;
}
int SSL_CIPHER_has_MD5_HMAC(const SSL_CIPHER *c) {
return (c->algorithm_mac & SSL_MD5) != 0;
}
int SSL_CIPHER_is_AESGCM(const SSL_CIPHER *c) {
return (c->algorithm_mac & (SSL_AES128GCM | SSL_AES256GCM)) != 0;
}
int SSL_CIPHER_is_CHACHA20POLY1305(const SSL_CIPHER *c) {
return (c->algorithm_enc & SSL_CHACHA20POLY1305) != 0;
}
const char *SSL_CIPHER_get_version(const SSL_CIPHER *c) {
int i;
if (c == NULL) {
return "(NONE)";
}
i = (int)(c->id >> 24L);
if (i == 3) {
return "TLSv1/SSLv3";
} else if (i == 2) {
return "SSLv2";
} else {
return "unknown";
}
}
/* return the actual cipher being used */
const char *SSL_CIPHER_get_name(const SSL_CIPHER *c) {
if (c != NULL) {
return c->name;
}
return "(NONE)";
}
const char *SSL_CIPHER_get_kx_name(const SSL_CIPHER *cipher) {
if (cipher == NULL) {
return "";
}
switch (cipher->algorithm_mkey) {
case SSL_kRSA:
return SSL_TXT_RSA;
case SSL_kEDH:
switch (cipher->algorithm_auth) {
case SSL_aRSA:
return "DHE_" SSL_TXT_RSA;
case SSL_aNULL:
return SSL_TXT_DH "_anon";
default:
return "UNKNOWN";
}
case SSL_kEECDH:
switch (cipher->algorithm_auth) {
case SSL_aECDSA:
return "ECDHE_" SSL_TXT_ECDSA;
case SSL_aRSA:
return "ECDHE_" SSL_TXT_RSA;
case SSL_aNULL:
return SSL_TXT_ECDH "_anon";
default:
return "UNKNOWN";
}
default:
return "UNKNOWN";
}
}
/* number of bits for symmetric cipher */
int SSL_CIPHER_get_bits(const SSL_CIPHER *c, int *alg_bits) {
int ret = 0;
if (c != NULL) {
if (alg_bits != NULL) {
*alg_bits = c->alg_bits;
}
ret = c->strength_bits;
}
return ret;
}
unsigned long SSL_CIPHER_get_id(const SSL_CIPHER *c) { return c->id; }
void *SSL_COMP_get_compression_methods(void) { return NULL; }
int SSL_COMP_add_compression_method(int id, void *cm) { return 1; }
const char *SSL_COMP_get_name(const void *comp) { return NULL; }
/* For a cipher return the index corresponding to the certificate type */
int ssl_cipher_get_cert_index(const SSL_CIPHER *c) {
unsigned long alg_a = c->algorithm_auth;
if (alg_a & SSL_aECDSA) {
return SSL_PKEY_ECC;
} else if (alg_a & SSL_aRSA) {
return SSL_PKEY_RSA_ENC;
}
return -1;
}
/* ssl_cipher_has_server_public_key returns 1 if |cipher| involves a server
* public key in the key exchange, sent in a server Certificate message.
* Otherwise it returns 0. */
int ssl_cipher_has_server_public_key(const SSL_CIPHER *cipher) {
/* Anonymous ciphers do not include a server certificate. */
if (cipher->algorithm_auth & SSL_aNULL) {
return 0;
}
/* Neither do PSK ciphers, except for RSA_PSK. */
if ((cipher->algorithm_auth & SSL_aPSK) &&
!(cipher->algorithm_mkey & SSL_kRSA)) {
return 0;
}
/* All other ciphers include it. */
return 1;
}
/* ssl_cipher_requires_server_key_exchange returns 1 if |cipher| requires a
* ServerKeyExchange message. Otherwise it returns 0.
*
* Unlike ssl_cipher_has_server_public_key, some ciphers take optional
* ServerKeyExchanges. PSK and RSA_PSK only use the ServerKeyExchange to
* communicate a psk_identity_hint, so it is optional. */
int ssl_cipher_requires_server_key_exchange(const SSL_CIPHER *cipher) {
/* Ephemeral Diffie-Hellman key exchanges require a ServerKeyExchange. */
if (cipher->algorithm_mkey & SSL_kEDH || cipher->algorithm_mkey & SSL_kEECDH) {
return 1;
}
/* It is optional in all others. */
return 0;
}