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| author | Bernd Edlinger <bernd.edlinger@hotmail.de> | 2018-09-23 09:20:54 +0200 |
|---|---|---|
| committer | Bernd Edlinger <bernd.edlinger@hotmail.de> | 2018-09-24 15:58:24 +0200 |
| commit | ec0c5f5693e39c5a013f81e6dd9dfd09ec65162d (patch) | |
| tree | 956f19e5fb22f4baf0f2a2435decf56167eb8b63 /ssl | |
| parent | Document OPENSSL_VERSION_TEXT macro (diff) | |
| download | openssl-ec0c5f5693e39c5a013f81e6dd9dfd09ec65162d.tar.xz openssl-ec0c5f5693e39c5a013f81e6dd9dfd09ec65162d.zip | |
Reduce stack usage in tls13_hkdf_expand
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7297)
Diffstat (limited to 'ssl')
| -rw-r--r-- | ssl/tls13_enc.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/ssl/tls13_enc.c b/ssl/tls13_enc.c index f7ab0fa470..b6825d20c2 100644 --- a/ssl/tls13_enc.c +++ b/ssl/tls13_enc.c @@ -13,7 +13,14 @@ #include <openssl/evp.h> #include <openssl/kdf.h> -#define TLS13_MAX_LABEL_LEN 246 +/* + * 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 /* Always filled with zeros */ static const unsigned char default_zeros[EVP_MAX_MD_SIZE]; @@ -29,14 +36,15 @@ 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) { - const unsigned char label_prefix[] = "tls13 "; + static 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 whole HkdfLabel + 1 byte for length of combined - * prefix and label + bytes for the label itself + bytes for the hash + * 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 */ unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) + + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN |