Fix DH/DHX named groups to not overwrite the private key length.

The only reason(s) the DH private key length should be set are:
(1) The user sets it during key generation via EVP_PKEY_CTX_set_params
    using OSSL_PKEY_PARAM_DH_PRIV_LEN.
(2) When loading a PKCS3 (DH) key the optional value
    'privateValueLength' is set.

Now that the named groups contain a value for 'q' there is no reason to
automatically overwrite the private key length.

Issue detected by @davidmakepeace

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15695)

2 files changed, 74 insertions, 7 deletions

diff --git a/crypto/dh/dh_group_params.c b/crypto/dh/dh_group_params.c
index ff6d7cdd66..c71f4053da 100644
--- a/crypto/dh/dh_group_params.c
+++ b/crypto/dh/dh_group_params.c
@@ -34,7 +34,6 @@ static DH *dh_param_init(OSSL_LIB_CTX *libctx, const DH_NAMED_GROUP *group)
 
     ossl_ffc_named_group_set_pqg(&dh->params, group);
     dh->params.nid = ossl_ffc_named_group_get_uid(group);
-    dh->length = BN_num_bits(dh->params.q);
     dh->dirty_cnt++;
     return dh;
 }
@@ -76,7 +75,6 @@ void ossl_dh_cache_named_group(DH *dh)
             dh->params.q = (BIGNUM *)ossl_ffc_named_group_get_q(group);
         /* cache the nid */
         dh->params.nid = ossl_ffc_named_group_get_uid(group);
-        dh->length = BN_num_bits(dh->params.q);
         dh->dirty_cnt++;
     }
 }
diff --git a/test/dhtest.c b/test/dhtest.c
index b5ff81a319..adbe3afd78 100644
--- a/test/dhtest.c
+++ b/test/dhtest.c
@@ -24,6 +24,7 @@
 #include <openssl/rand.h>
 #include <openssl/err.h>
 #include <openssl/obj_mac.h>
+#include <openssl/core_names.h>
 #include "testutil.h"
 
 #ifndef OPENSSL_NO_DH
@@ -706,7 +707,6 @@ static int dh_test_prime_groups(int index)
     int ok = 0;
     DH *dh = NULL;
     const BIGNUM *p, *q, *g;
-    long len;
 
     if (!TEST_ptr(dh = DH_new_by_nid(prime_groups[index])))
         goto err;
@@ -717,9 +717,8 @@ static int dh_test_prime_groups(int index)
     if (!TEST_int_eq(DH_get_nid(dh), prime_groups[index]))
         goto err;
 
-    len = DH_get_length(dh);
-    if (!TEST_true(len > 0)
-        || !TEST_true(len <= BN_num_bits(q)))
+    /* Since q is set there is no need for the private length to be set */
+    if (!TEST_int_eq((int)DH_get_length(dh), 0))
         goto err;
 
     ok = 1;
@@ -790,8 +789,77 @@ err:
     return ok;
 }
 
-#endif
+static const unsigned char dh_pub_der[] = {
+    0x30, 0x82, 0x02, 0x28, 0x30, 0x82, 0x01, 0x1b, 0x06, 0x09, 0x2a, 0x86,
+    0x48, 0x86, 0xf7, 0x0d, 0x01, 0x03, 0x01, 0x30, 0x82, 0x01, 0x0c, 0x02,
+    0x82, 0x01, 0x01, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+    0xc9, 0x0f, 0xda, 0xa2, 0x21, 0x68, 0xc2, 0x34, 0xc4, 0xc6, 0x62, 0x8b,
+    0x80, 0xdc, 0x1c, 0xd1, 0x29, 0x02, 0x4e, 0x08, 0x8a, 0x67, 0xcc, 0x74,
+    0x02, 0x0b, 0xbe, 0xa6, 0x3b, 0x13, 0x9b, 0x22, 0x51, 0x4a, 0x08, 0x79,
+    0x8e, 0x34, 0x04, 0xdd, 0xef, 0x95, 0x19, 0xb3, 0xcd, 0x3a, 0x43, 0x1b,
+    0x30, 0x2b, 0x0a, 0x6d, 0xf2, 0x5f, 0x14, 0x37, 0x4f, 0xe1, 0x35, 0x6d,
+    0x6d, 0x51, 0xc2, 0x45, 0xe4, 0x85, 0xb5, 0x76, 0x62, 0x5e, 0x7e, 0xc6,
+    0xf4, 0x4c, 0x42, 0xe9, 0xa6, 0x37, 0xed, 0x6b, 0x0b, 0xff, 0x5c, 0xb6,
+    0xf4, 0x06, 0xb7, 0xed, 0xee, 0x38, 0x6b, 0xfb, 0x5a, 0x89, 0x9f, 0xa5,
+    0xae, 0x9f, 0x24, 0x11, 0x7c, 0x4b, 0x1f, 0xe6, 0x49, 0x28, 0x66, 0x51,
+    0xec, 0xe4, 0x5b, 0x3d, 0xc2, 0x00, 0x7c, 0xb8, 0xa1, 0x63, 0xbf, 0x05,
+    0x98, 0xda, 0x48, 0x36, 0x1c, 0x55, 0xd3, 0x9a, 0x69, 0x16, 0x3f, 0xa8,
+    0xfd, 0x24, 0xcf, 0x5f, 0x83, 0x65, 0x5d, 0x23, 0xdc, 0xa3, 0xad, 0x96,
+    0x1c, 0x62, 0xf3, 0x56, 0x20, 0x85, 0x52, 0xbb, 0x9e, 0xd5, 0x29, 0x07,
+    0x70, 0x96, 0x96, 0x6d, 0x67, 0x0c, 0x35, 0x4e, 0x4a, 0xbc, 0x98, 0x04,
+    0xf1, 0x74, 0x6c, 0x08, 0xca, 0x18, 0x21, 0x7c, 0x32, 0x90, 0x5e, 0x46,
+    0x2e, 0x36, 0xce, 0x3b, 0xe3, 0x9e, 0x77, 0x2c, 0x18, 0x0e, 0x86, 0x03,
+    0x9b, 0x27, 0x83, 0xa2, 0xec, 0x07, 0xa2, 0x8f, 0xb5, 0xc5, 0x5d, 0xf0,
+    0x6f, 0x4c, 0x52, 0xc9, 0xde, 0x2b, 0xcb, 0xf6, 0x95, 0x58, 0x17, 0x18,
+    0x39, 0x95, 0x49, 0x7c, 0xea, 0x95, 0x6a, 0xe5, 0x15, 0xd2, 0x26, 0x18,
+    0x98, 0xfa, 0x05, 0x10, 0x15, 0x72, 0x8e, 0x5a, 0x8a, 0xac, 0xaa, 0x68,
+    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x02, 0x01, 0x02, 0x02,
+    0x02, 0x04, 0x00, 0x03, 0x82, 0x01, 0x05, 0x00, 0x02, 0x82, 0x01, 0x00,
+    0x08, 0x87, 0x8a, 0x5f, 0x4f, 0x3b, 0xef, 0xe1, 0x77, 0x13, 0x3b, 0xd7,
+    0x58, 0x76, 0xc9, 0xeb, 0x7e, 0x2d, 0xcc, 0x7e, 0xed, 0xc5, 0xee, 0xf9,
+    0x2d, 0x55, 0xb0, 0xe2, 0x37, 0x8c, 0x51, 0x87, 0x6a, 0x8e, 0x0d, 0xb2,
+    0x08, 0xed, 0x4f, 0x88, 0x9b, 0x63, 0x19, 0x7a, 0x67, 0xa1, 0x61, 0xd8,
+    0x17, 0xa0, 0x2c, 0xdb, 0xc2, 0xfa, 0xb3, 0x4f, 0xe7, 0xcb, 0x16, 0xf2,
+    0xe7, 0xd0, 0x2c, 0xf8, 0xcc, 0x97, 0xd3, 0xe7, 0xae, 0xc2, 0x71, 0xd8,
+    0x2b, 0x12, 0x83, 0xe9, 0x5a, 0x45, 0xfe, 0x66, 0x5c, 0xa2, 0xb6, 0xce,
+    0x2f, 0x04, 0x05, 0xe7, 0xa7, 0xbc, 0xe5, 0x63, 0x1a, 0x93, 0x3d, 0x4d,
+    0xf4, 0x77, 0xdd, 0x2a, 0xc9, 0x51, 0x7b, 0xf5, 0x54, 0xa2, 0xab, 0x26,
+    0xee, 0x16, 0xd3, 0x83, 0x92, 0x85, 0x40, 0x67, 0xa3, 0xa9, 0x31, 0x16,
+    0x64, 0x45, 0x5a, 0x2a, 0x9d, 0xa8, 0x1a, 0x84, 0x2f, 0x59, 0x57, 0x6b,
+    0xbb, 0x51, 0x28, 0xbd, 0x91, 0x60, 0xd9, 0x8f, 0x54, 0x6a, 0xa0, 0x6b,
+    0xb2, 0xf6, 0x78, 0x79, 0xd2, 0x3a, 0x8f, 0xa6, 0x24, 0x7e, 0xe9, 0x6e,
+    0x66, 0x30, 0xed, 0xbf, 0x55, 0x71, 0x9c, 0x89, 0x81, 0xf0, 0xa7, 0xe7,
+    0x05, 0x87, 0x51, 0xc1, 0xff, 0xe5, 0xcf, 0x1f, 0x19, 0xe4, 0xeb, 0x7c,
+    0x1c, 0x1a, 0x58, 0xd5, 0x22, 0x3d, 0x31, 0x22, 0xc7, 0x8b, 0x60, 0xf5,
+    0xe8, 0x95, 0x73, 0xe0, 0x20, 0xe2, 0x4f, 0x03, 0x9e, 0x89, 0x34, 0x91,
+    0x5e, 0xda, 0x4f, 0x60, 0xff, 0xc9, 0x4f, 0x5a, 0x37, 0x1e, 0xb0, 0xed,
+    0x26, 0x4c, 0xa4, 0xc6, 0x26, 0xc9, 0xcc, 0xab, 0xd2, 0x1a, 0x3a, 0x82,
+    0x68, 0x03, 0x49, 0x8f, 0xb0, 0xb9, 0xc8, 0x48, 0x9d, 0xc7, 0xdf, 0x8b,
+    0x1c, 0xbf, 0xda, 0x89, 0x78, 0x6f, 0xd3, 0x62, 0xad, 0x35, 0xb9, 0xd3,
+    0x9b, 0xd0, 0x25, 0x65
+};
+
+/*
+ * Load PKCS3 DH Parameters that contain an optional private value length.
+ * Loading a named group should not overwrite the private value length field.
+ */
+static int dh_load_pkcs3_namedgroup_privlen_test(void)
+{
+    int ret, privlen = 0;
+    EVP_PKEY *pkey = NULL;
+    const unsigned char *p = dh_pub_der;
 
+    ret = TEST_ptr(pkey = d2i_PUBKEY_ex(NULL, &p, sizeof(dh_pub_der),
+                                        NULL, NULL))
+          && TEST_true(EVP_PKEY_get_int_param(pkey, OSSL_PKEY_PARAM_DH_PRIV_LEN,
+                                              &privlen))
+          && TEST_int_eq(privlen, 1024);
+
+    EVP_PKEY_free(pkey);
+    return ret;
+}
+
+#endif
 
 int setup_tests(void)
 {
@@ -804,6 +872,7 @@ int setup_tests(void)
     ADD_TEST(rfc7919_test);
     ADD_ALL_TESTS(dh_test_prime_groups, OSSL_NELEM(prime_groups));
     ADD_TEST(dh_get_nid);
+    ADD_TEST(dh_load_pkcs3_namedgroup_privlen_test);
 #endif
     return 1;
 }