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Revert "Reduce stack usage in tls13_hkdf_expand"

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This reverts commit ec0c5f5693.

SSL_export_keying_material() may use longer label lengths.

Fixes #7712

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7755)
This commit is contained in:
Matt Caswell 2018-12-03 18:14:57 +00:00
parent 3a4a88f436
commit ed371b8cba
1 changed files with 4 additions and 12 deletions
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16
ssl/tls13_enc.c
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@ -13,14 +13,7 @@
#include <openssl/evp.h>
#include <openssl/kdf.h>
/*
* RFC 8446, 7.1 Key Schedule, says:
* Note: With common hash functions, any label longer than 12 characters
* requires an additional iteration of the hash function to compute.
* The labels in this specification have all been chosen to fit within
* this limit.
*/
#define TLS13_MAX_LABEL_LEN 12
#define TLS13_MAX_LABEL_LEN 246
/* Always filled with zeros */
static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
@ -36,15 +29,14 @@ int tls13_hkdf_expand(SSL *s, const EVP_MD *md, const unsigned char *secret,
const unsigned char *data, size_t datalen,
unsigned char *out, size_t outlen)
{
static const unsigned char label_prefix[] = "tls13 ";
const unsigned char label_prefix[] = "tls13 ";
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
int ret;
size_t hkdflabellen;
size_t hashlen;
/*
* 2 bytes for length of derived secret + 1 byte for length of combined
* prefix and label + bytes for the label itself + 1 byte length of hash
* + bytes for the hash itself
* 2 bytes for length of whole HkdfLabel + 1 byte for length of combined
* prefix and label + bytes for the label itself + bytes for the hash
*/
unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
+ sizeof(label_prefix) + TLS13_MAX_LABEL_LEN