PROV: Fix DSA and DH private key serializers

If those private key serializer were given a key structure with just
the public key material, they crashed, because they tried to
de-reference NULL.  This adds better checking.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/12679)

4 files changed, 32 insertions, 8 deletions

diff --git a/providers/common/include/prov/providercommonerr.h b/providers/common/include/prov/providercommonerr.h
index 3f3c39ba52..4c356fc5c6 100644
--- a/providers/common/include/prov/providercommonerr.h
+++ b/providers/common/include/prov/providercommonerr.h
@@ -128,6 +128,8 @@ int ERR_load_PROV_strings(void);
 # define PROV_R_MISSING_TYPE                              134
 # define PROV_R_MISSING_XCGHASH                           135
 # define PROV_R_MODULE_INTEGRITY_FAILURE                  214
+# define PROV_R_NOT_A_PRIVATE_KEY                         221
+# define PROV_R_NOT_A_PUBLIC_KEY                          220
 # define PROV_R_NOT_INSTANTIATED                          193
 # define PROV_R_NOT_SUPPORTED                             136
 # define PROV_R_NOT_XOF_OR_INVALID_LENGTH                 113
diff --git a/providers/common/provider_err.c b/providers/common/provider_err.c
index ad7ae57157..3ea41f3c25 100644
--- a/providers/common/provider_err.c
+++ b/providers/common/provider_err.c
@@ -133,6 +133,8 @@ static const ERR_STRING_DATA PROV_str_reasons[] = {
     {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_MISSING_XCGHASH), "missing xcghash"},
     {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_MODULE_INTEGRITY_FAILURE),
     "module integrity failure"},
+    {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_NOT_A_PRIVATE_KEY), "not a private key"},
+    {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_NOT_A_PUBLIC_KEY), "not a public key"},
     {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_NOT_INSTANTIATED), "not instantiated"},
     {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_NOT_SUPPORTED), "not supported"},
     {ERR_PACK(ERR_LIB_PROV, 0, PROV_R_NOT_XOF_OR_INVALID_LENGTH),
diff --git a/providers/implementations/serializers/serializer_dh.c b/providers/implementations/serializers/serializer_dh.c
index d63c8402f9..d1b1d27cf6 100644
--- a/providers/implementations/serializers/serializer_dh.c
+++ b/providers/implementations/serializers/serializer_dh.c
@@ -119,10 +119,15 @@ int ossl_prov_prepare_dh_params(const void *dh, int nid,
 
 int ossl_prov_dh_pub_to_der(const void *dh, unsigned char **pder)
 {
-    ASN1_INTEGER *pub_key = BN_to_ASN1_INTEGER(DH_get0_pub_key(dh), NULL);
+    const BIGNUM *bn = NULL;
+    ASN1_INTEGER *pub_key = NULL;
     int ret;
 
-    if (pub_key == NULL) {
+    if ((bn = DH_get0_pub_key(dh)) == NULL) {
+        ERR_raise(ERR_LIB_PROV, PROV_R_NOT_A_PUBLIC_KEY);
+        return 0;
+    }
+    if ((pub_key = BN_to_ASN1_INTEGER(bn, NULL)) == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_BN_ERROR);
         return 0;
     }
@@ -135,10 +140,15 @@ int ossl_prov_dh_pub_to_der(const void *dh, unsigned char **pder)
 
 int ossl_prov_dh_priv_to_der(const void *dh, unsigned char **pder)
 {
-    ASN1_INTEGER *priv_key = BN_to_ASN1_INTEGER(DH_get0_priv_key(dh), NULL);
+    const BIGNUM *bn = NULL;
+    ASN1_INTEGER *priv_key = NULL;
     int ret;
 
-    if (priv_key == NULL) {
+    if ((bn = DH_get0_priv_key(dh)) == NULL) {
+        ERR_raise(ERR_LIB_PROV, PROV_R_NOT_A_PRIVATE_KEY);
+        return 0;
+    }
+    if ((priv_key = BN_to_ASN1_INTEGER(bn, NULL)) == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_BN_ERROR);
         return 0;
     }
diff --git a/providers/implementations/serializers/serializer_dsa.c b/providers/implementations/serializers/serializer_dsa.c
index 4389bded99..1f986b62d5 100644
--- a/providers/implementations/serializers/serializer_dsa.c
+++ b/providers/implementations/serializers/serializer_dsa.c
@@ -132,10 +132,15 @@ int ossl_prov_prepare_all_dsa_params(const void *dsa, int nid,
 
 int ossl_prov_dsa_pub_to_der(const void *dsa, unsigned char **pder)
 {
-    ASN1_INTEGER *pub_key = BN_to_ASN1_INTEGER(DSA_get0_pub_key(dsa), NULL);
+    const BIGNUM *bn = NULL;
+    ASN1_INTEGER *pub_key = NULL;
     int ret;
 
-    if (pub_key == NULL) {
+    if ((bn = DSA_get0_pub_key(dsa)) == NULL) {
+        ERR_raise(ERR_LIB_PROV, PROV_R_NOT_A_PUBLIC_KEY);
+        return 0;
+    }
+    if ((pub_key = BN_to_ASN1_INTEGER(bn, NULL)) == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_BN_ERROR);
         return 0;
     }
@@ -148,10 +153,15 @@ int ossl_prov_dsa_pub_to_der(const void *dsa, unsigned char **pder)
 
 int ossl_prov_dsa_priv_to_der(const void *dsa, unsigned char **pder)
 {
-    ASN1_INTEGER *priv_key = BN_to_ASN1_INTEGER(DSA_get0_priv_key(dsa), NULL);
+    const BIGNUM *bn = NULL;
+    ASN1_INTEGER *priv_key = NULL;
     int ret;
 
-    if (priv_key == NULL) {
+    if ((bn = DSA_get0_priv_key(dsa)) == NULL) {
+        ERR_raise(ERR_LIB_PROV, PROV_R_NOT_A_PRIVATE_KEY);
+        return 0;
+    }
+    if ((priv_key = BN_to_ASN1_INTEGER(bn, NULL)) == NULL) {
         ERR_raise(ERR_LIB_PROV, PROV_R_BN_ERROR);
         return 0;
     }