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/*
* Copyright 2024-2026 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/ssl.h>
#include <openssl/ech.h>
#include "../ssl_local.h"
#include "ech_local.h"
#include "internal/ech_helpers.h"
/* used in ECH crypto derivations (odd format for EBCDIC goodness) */
/* "tls ech" */
static const char OSSL_ECH_CONTEXT_STRING[] = "\x74\x6c\x73\x20\x65\x63\x68";
/*
* Construct HPKE "info" input as per spec
* encoding is the ECHconfig being used
* encoding_length is the length of ECHconfig being used
* info is a caller-allocated buffer for results
* info_len is the buffer size on input, used-length on output
* return 1 for success, zero otherwise
*/
int ossl_ech_make_enc_info(const unsigned char *encoding,
size_t encoding_length,
unsigned char *info, size_t *info_len)
{
WPACKET ipkt = { 0 };
if (encoding == NULL || info == NULL || info_len == NULL)
return 0;
if (!WPACKET_init_static_len(&ipkt, info, *info_len, 0)
|| !WPACKET_memcpy(&ipkt, OSSL_ECH_CONTEXT_STRING,
sizeof(OSSL_ECH_CONTEXT_STRING) - 1)
/*
* the zero valued octet is required by the spec, section 7.1 so
* a tiny bit better to add it explicitly rather than depend on
* the context string being NUL terminated
*/
|| !WPACKET_put_bytes_u8(&ipkt, 0)
|| !WPACKET_memcpy(&ipkt, encoding, encoding_length)
|| !WPACKET_get_total_written(&ipkt, info_len)) {
WPACKET_cleanup(&ipkt);
return 0;
}
WPACKET_cleanup(&ipkt);
return 1;
}
/*
* Given a CH find the offsets of the session id, extensions and ECH
* ch is the encoded client hello
* ch_len is the length of ch
* sessid_off returns offset of session_id length
* exts_off points to offset of extensions
* exts_len returns length of extensions
* ech_off returns offset of ECH
* echtype returns the ext type of the ECH
* ech_len returns the length of the ECH
* sni_off returns offset of (outer) SNI
* sni_len returns the length of the SNI
* inner 1 if the ECH is marked as an inner, 0 for outer
* return 1 for success, other otherwise
*
* Offsets are set to zero if relevant thing not found.
* Offsets are returned to the type or length field in question.
*
* Note: input here is untrusted!
*/
int ossl_ech_helper_get_ch_offsets(const unsigned char *ch, size_t ch_len,
size_t *sessid_off, size_t *exts_off,
size_t *exts_len,
size_t *ech_off, uint16_t *echtype,
size_t *ech_len, size_t *sni_off,
size_t *sni_len, int *inner)
{
unsigned int elen = 0, etype = 0, pi_tmp = 0;
const unsigned char *pp_tmp = NULL, *chstart = NULL, *estart = NULL;
PACKET pkt;
int done = 0;
if (ch == NULL || ch_len == 0 || sessid_off == NULL || exts_off == NULL
|| ech_off == NULL || echtype == NULL || ech_len == NULL
|| sni_off == NULL || inner == NULL || exts_len == NULL)
return 0;
*sessid_off = *exts_off = *ech_off = *sni_off = *sni_len = *ech_len = 0;
*exts_len = 0;
*inner = OSSL_ECH_UNKNOWN_CH_TYPE;
*echtype = 0xffff;
if (!PACKET_buf_init(&pkt, ch, ch_len))
return 0;
chstart = PACKET_data(&pkt);
if (!PACKET_get_net_2(&pkt, &pi_tmp))
return 0;
/* if we're not TLSv1.2+ then we can bail, but it's not an error */
if (pi_tmp != TLS1_2_VERSION)
return 1;
/* chew up the packet to extensions */
if (!PACKET_get_bytes(&pkt, &pp_tmp, SSL3_RANDOM_SIZE)
|| (*sessid_off = PACKET_data(&pkt) - chstart) == 0
|| !PACKET_get_1(&pkt, &pi_tmp) /* sessid len */
|| !PACKET_get_bytes(&pkt, &pp_tmp, pi_tmp) /* sessid */
|| !PACKET_get_net_2(&pkt, &pi_tmp) /* ciphersuite len */
|| !PACKET_get_bytes(&pkt, &pp_tmp, pi_tmp) /* suites */
|| !PACKET_get_1(&pkt, &pi_tmp) /* compression meths */
|| !PACKET_get_bytes(&pkt, &pp_tmp, pi_tmp) /* comp meths */
|| (*exts_off = PACKET_data(&pkt) - chstart) == 0
|| !PACKET_get_net_2(&pkt, &pi_tmp) /* len(extensions) */
|| (*exts_len = (size_t)pi_tmp) == 0)
/*
* unexpectedly, we return 1 here, as doing otherwise will
* break some non-ECH test code that truncates CH messages
* The same is true below when looking through extensions.
* That's ok though, we'll only set those offsets we've
* found.
*/
return 1;
/* no extensions is theoretically ok, if uninteresting */
if (*exts_len == 0)
return 1;
/* find what we want from extensions */
estart = PACKET_data(&pkt);
while (PACKET_remaining(&pkt) > 0
&& (size_t)(PACKET_data(&pkt) - estart) < *exts_len
&& done < 2) {
if (!PACKET_get_net_2(&pkt, &etype)
|| !PACKET_get_net_2(&pkt, &elen))
return 1; /* see note above */
if (etype == TLSEXT_TYPE_ech) {
if (elen == 0)
return 0;
*ech_off = PACKET_data(&pkt) - chstart - 4;
*echtype = etype;
*ech_len = elen;
done++;
}
if (etype == TLSEXT_TYPE_server_name) {
*sni_off = PACKET_data(&pkt) - chstart - 4;
*sni_len = elen;
done++;
}
if (!PACKET_get_bytes(&pkt, &pp_tmp, elen))
return 1; /* see note above */
if (etype == TLSEXT_TYPE_ech)
*inner = pp_tmp[0];
}
return 1;
}
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