MINOR: quic: Add a function to derive the key update secrets
This is the function used to derive an n+1th secret from the nth one as
described in RFC9001 par. 6.1.
diff --git a/include/haproxy/quic_tls.h b/include/haproxy/quic_tls.h
index bf23823..5a73611 100644
--- a/include/haproxy/quic_tls.h
+++ b/include/haproxy/quic_tls.h
@@ -75,6 +75,10 @@
unsigned char *hp_key, size_t hp_keylen,
const unsigned char *secret, size_t secretlen);
+int quic_tls_sec_update(const EVP_MD *md,
+ unsigned char *new_sec, size_t new_seclen,
+ const unsigned char *sec, size_t seclen);
+
int quic_aead_iv_build(unsigned char *iv, size_t ivlen,
unsigned char *aead_iv, size_t aead_ivlen, uint64_t pn);
diff --git a/src/quic_tls.c b/src/quic_tls.c
index 491a1bc..2e35443 100644
--- a/src/quic_tls.c
+++ b/src/quic_tls.c
@@ -261,6 +261,19 @@
return 1;
}
+/* Update <sec> secret key into <new_sec> according to RFC 9001 6.1.
+ * Always succeeds.
+ */
+int quic_tls_sec_update(const EVP_MD *md,
+ unsigned char *new_sec, size_t new_seclen,
+ const unsigned char *sec, size_t seclen)
+{
+ const unsigned char ku_label[] = "quic ku";
+
+ return quic_hkdf_expand_label(md, new_sec, new_seclen, sec, seclen,
+ ku_label, sizeof ku_label - 1);
+}
+
/*
* Build an IV into <iv> buffer with <ivlen> as size from <aead_iv> with
* <aead_ivlen> as size depending on <pn> packet number.