120 lines
5.3 KiB
Diff
120 lines
5.3 KiB
Diff
From c4b086fc4de06128695e1fe428f56d776d25e748 Mon Sep 17 00:00:00 2001
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From: Clemens Lang <cllang@redhat.com>
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Date: Thu, 11 Aug 2022 09:27:12 +0200
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Subject: [PATCH] Add FIPS indicator parameter to HKDF
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NIST considers HKDF only acceptable when used as in TLS 1.3, and
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otherwise unapproved. Add an explicit indicator attached to the
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EVP_KDF_CTX that can be queried using EVP_KDF_CTX_get_params() to
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determine whether the KDF operation was approved after performing it.
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Related: rhbz#2114772
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Signed-off-by: Clemens Lang <cllang@redhat.com>
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---
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include/openssl/core_names.h | 1 +
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include/openssl/kdf.h | 4 ++
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providers/implementations/kdfs/hkdf.c | 53 +++++++++++++++++++++++++++
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3 files changed, 58 insertions(+)
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diff --git a/include/openssl/core_names.h b/include/openssl/core_names.h
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index 21c94d0488..87786680d7 100644
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--- a/include/openssl/core_names.h
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+++ b/include/openssl/core_names.h
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@@ -223,6 +223,7 @@ extern "C" {
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#define OSSL_KDF_PARAM_X942_SUPP_PUBINFO "supp-pubinfo"
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#define OSSL_KDF_PARAM_X942_SUPP_PRIVINFO "supp-privinfo"
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#define OSSL_KDF_PARAM_X942_USE_KEYBITS "use-keybits"
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+#define OSSL_KDF_PARAM_HKDF_REDHAT_FIPS_INDICATOR "hkdf-fips-indicator"
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/* Known KDF names */
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#define OSSL_KDF_NAME_HKDF "HKDF"
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diff --git a/include/openssl/kdf.h b/include/openssl/kdf.h
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index 0983230a48..869f23d8fb 100644
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--- a/include/openssl/kdf.h
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+++ b/include/openssl/kdf.h
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@@ -63,6 +63,10 @@ int EVP_KDF_names_do_all(const EVP_KDF *kdf,
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# define EVP_KDF_HKDF_MODE_EXTRACT_ONLY 1
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# define EVP_KDF_HKDF_MODE_EXPAND_ONLY 2
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+# define EVP_KDF_HKDF_FIPS_INDICATOR_UNDETERMINED 0
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+# define EVP_KDF_HKDF_FIPS_INDICATOR_APPROVED 1
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+# define EVP_KDF_HKDF_FIPS_INDICATOR_NOT_APPROVED 2
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+
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#define EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV 65
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#define EVP_KDF_SSHKDF_TYPE_INITIAL_IV_SRV_TO_CLI 66
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#define EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_CLI_TO_SRV 67
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diff --git a/providers/implementations/kdfs/hkdf.c b/providers/implementations/kdfs/hkdf.c
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index afdb7138e1..9d28d292d8 100644
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--- a/providers/implementations/kdfs/hkdf.c
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+++ b/providers/implementations/kdfs/hkdf.c
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@@ -298,6 +298,56 @@ static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
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return 0;
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return OSSL_PARAM_set_size_t(p, sz);
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}
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+
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+#ifdef FIPS_MODULE
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+ if ((p = OSSL_PARAM_locate(params,
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+ OSSL_KDF_PARAM_HKDF_REDHAT_FIPS_INDICATOR)) != NULL) {
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+ int fips_indicator = EVP_KDF_HKDF_FIPS_INDICATOR_UNDETERMINED;
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+ switch (ctx->mode) {
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+ case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
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+ /* TLS 1.3 never uses extract-and-expand */
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+ fips_indicator = EVP_KDF_HKDF_FIPS_INDICATOR_NOT_APPROVED;
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+ break;
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+ case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
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+ {
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+ /* When TLS 1.3 uses extract, the following holds:
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+ * 1. The salt length matches the hash length, and either
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+ * 2.1. the key is all zeroes and matches the hash length, or
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+ * 2.2. the key originates from a PSK (resumption_master_secret
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+ * or some externally esablished key), or an ECDH or DH key
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+ * derivation. See
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+ * https://www.rfc-editor.org/rfc/rfc8446#section-7.1.
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+ * Unfortunately at this point, we cannot verify where the key
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+ * comes from, so all we can do is check the salt length.
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+ */
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+ const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
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+ if (md != NULL && ctx->salt_len == EVP_MD_get_size(md))
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+ fips_indicator = EVP_KDF_HKDF_FIPS_INDICATOR_APPROVED;
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+ else
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+ fips_indicator = EVP_KDF_HKDF_FIPS_INDICATOR_NOT_APPROVED;
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+ }
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+ break;
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+ case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
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+ /* When TLS 1.3 uses expand, it always provides a label that
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+ * contains an uint16 for the length, followed by between 7 and 255
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+ * bytes for a label string that starts with "tls13 " or "dtls13".
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+ * For compatibility with future versions, we only check for "tls"
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+ * or "dtls". See
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+ * https://www.rfc-editor.org/rfc/rfc8446#section-7.1 and
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+ * https://www.rfc-editor.org/rfc/rfc9147#section-5.9. */
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+ if (ctx->label != NULL
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+ && ctx->label_len >= 2 /* length */ + 4 /* "dtls" */
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+ && (strncmp("tls", (const char *)ctx->label + 2, 3) == 0 ||
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+ strncmp("dtls", (const char *)ctx->label + 2, 4) == 0))
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+ fips_indicator = EVP_KDF_HKDF_FIPS_INDICATOR_APPROVED;
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+ else
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+ fips_indicator = EVP_KDF_HKDF_FIPS_INDICATOR_NOT_APPROVED;
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+ break;
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+ }
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+ return OSSL_PARAM_set_int(p, fips_indicator);
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+ }
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+#endif /* defined(FIPS_MODULE) */
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+
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return -2;
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}
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@@ -306,6 +356,9 @@ static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(ossl_unused void *ctx,
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{
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static const OSSL_PARAM known_gettable_ctx_params[] = {
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OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
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+#ifdef FIPS_MODULE
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+ OSSL_PARAM_int(OSSL_KDF_PARAM_HKDF_REDHAT_FIPS_INDICATOR, NULL),
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+#endif /* defined(FIPS_MODULE) */
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OSSL_PARAM_END
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};
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return known_gettable_ctx_params;
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--
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2.37.1
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