From b8237707d483719e527313cc007c09e96ef7d778 Mon Sep 17 00:00:00 2001
From: Shane Lontis <shane.lontis@oracle.com>
Date: Sat, 29 Aug 2020 12:54:00 +1000
Subject: Add fips checks for dh key agreement

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/12745)
---
 providers/implementations/exchange/build.info |  5 ++-
 providers/implementations/exchange/dh_exch.c  | 47 +++++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 5 deletions(-)

(limited to 'providers')

diff --git a/providers/implementations/exchange/build.info b/providers/implementations/exchange/build.info
index 92932b9d28..3ae86309c7 100644
--- a/providers/implementations/exchange/build.info
+++ b/providers/implementations/exchange/build.info
@@ -1,13 +1,12 @@
 # We make separate GOAL variables for each algorithm, to make it easy to
 # switch each to the Legacy provider when needed.
 
-$DH_GOAL=../../libimplementations.a
 $ECX_GOAL=../../libimplementations.a
-$ECDH_GOAL=../../libimplementations.a
 $KDF_GOAL=../../libimplementations.a
 
 IF[{- !$disabled{dh} -}]
-  SOURCE[$DH_GOAL]=dh_exch.c
+  SOURCE[../../libfips.a]=dh_exch.c
+  SOURCE[../../libnonfips.a]=dh_exch.c
 ENDIF
 
 IF[{- !$disabled{asm} -}]
diff --git a/providers/implementations/exchange/dh_exch.c b/providers/implementations/exchange/dh_exch.c
index fad38ec93d..a8a0d43319 100644
--- a/providers/implementations/exchange/dh_exch.c
+++ b/providers/implementations/exchange/dh_exch.c
@@ -23,6 +23,7 @@
 #include "prov/providercommon.h"
 #include "prov/implementations.h"
 #include "prov/provider_ctx.h"
+#include "prov/provider_util.h"
 #include "crypto/dh.h"
 
 static OSSL_FUNC_keyexch_newctx_fn dh_newctx;
@@ -91,6 +92,43 @@ static void *dh_newctx(void *provctx)
     return pdhctx;
 }
 
+/*
+ * For DH key agreement refer to SP800-56A
+ * https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar3.pdf
+ * "Section 5.5.1.1FFC Domain Parameter Selection/Generation" and
+ * "Appendix D" FFC Safe-prime Groups
+ */
+static int dh_check_key(const DH *dh)
+{
+#ifdef FIPS_MODULE
+    size_t L, N;
+    const BIGNUM *p, *q;
+
+    if (dh == NULL)
+        return 0;
+
+    p = DH_get0_p(dh);
+    q = DH_get0_q(dh);
+    if (p == NULL || q == NULL)
+        return 0;
+
+    L = BN_num_bits(p);
+    if (L < 2048)
+        return 0;
+
+    /* If it is a safe prime group then it is ok */
+    if (DH_get_nid(dh))
+        return 1;
+
+    /* If not then it must be FFC, which only allows certain sizes. */
+    N = BN_num_bits(q);
+
+    return (L == 2048 && (N == 224 || N == 256));
+#else
+    return 1;
+#endif
+}
+
 static int dh_init(void *vpdhctx, void *vdh)
 {
     PROV_DH_CTX *pdhctx = (PROV_DH_CTX *)vpdhctx;
@@ -103,7 +141,7 @@ static int dh_init(void *vpdhctx, void *vdh)
     DH_free(pdhctx->dh);
     pdhctx->dh = vdh;
     pdhctx->kdf_type = PROV_DH_KDF_NONE;
-    return 1;
+    return dh_check_key(vdh);
 }
 
 static int dh_set_peer(void *vpdhctx, void *vdh)
@@ -320,7 +358,12 @@ static int dh_set_ctx_params(void *vpdhctx, const OSSL_PARAM params[])
 
         EVP_MD_free(pdhctx->kdf_md);
         pdhctx->kdf_md = EVP_MD_fetch(pdhctx->libctx, name, mdprops);
-
+#ifdef FIPS_MODULE
+        if (!ossl_prov_digest_get_approved_nid(pdhctx->kdf_md, 1)) {
+            EVP_MD_free(pdhctx->kdf_md);
+            pdhctx->kdf_md = NULL;
+        }
+#endif
         if (pdhctx->kdf_md == NULL)
             return 0;
     }
-- 
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