From ed371b8cbac0d0349667558c061c1ae380cf75eb Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Mon, 3 Dec 2018 18:14:57 +0000 Subject: [PATCH] Revert "Reduce stack usage in tls13_hkdf_expand" This reverts commit ec0c5f5693e39c5a013f81e6dd9dfd09ec65162d. SSL_export_keying_material() may use longer label lengths. Fixes #7712 Reviewed-by: Tim Hudson (Merged from https://github.com/openssl/openssl/pull/7755) --- ssl/tls13_enc.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff --git a/ssl/tls13_enc.c b/ssl/tls13_enc.c index b6825d20c2..f7ab0fa470 100644 --- a/ssl/tls13_enc.c +++ b/ssl/tls13_enc.c @@ -13,14 +13,7 @@ #include #include -/* - * 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 -- 2.25.1