3 issues found by coverity

[chipitsine]

** CID 345245:    (UNINIT)


________________________________________________________________________________________________________
*** CID 345245:    (UNINIT)
/gost_prov.c: 71 in provider_ctx_new()
65             && populate_gost_engine(ctx->e)) {
66             ctx->core_handle = core;
67     
68             /* Ugly hack */
69             err_handle = ctx->proverr_handle;
70         } else {
>>>     CID 345245:    (UNINIT)
>>>     Using uninitialized value "ctx->e" when calling "provider_ctx_free".
71             provider_ctx_free(ctx);
72             ctx = NULL;
73         }
74         return ctx;
75     }
76     
/gost_prov.c: 71 in provider_ctx_new()
65             && populate_gost_engine(ctx->e)) {
66             ctx->core_handle = core;
67     
68             /* Ugly hack */
69             err_handle = ctx->proverr_handle;
70         } else {
>>>     CID 345245:    (UNINIT)
>>>     Using uninitialized value "ctx->e" when calling "provider_ctx_free".
71             provider_ctx_free(ctx);
72             ctx = NULL;
73         }
74         return ctx;
75     }
76     

** CID 345244:    (CHECKED_RETURN)
/test_tlstree.c: 155 in main()
/test_tlstree.c: 114 in main()


________________________________________________________________________________________________________
*** CID 345244:    (CHECKED_RETURN)
/test_tlstree.c: 155 in main()
149             if (memcmp(enc0_etl, data0_processed, sizeof(data0_processed)) != 0) {
150                     fprintf(stderr, "ENC0 mismatch");
151                     exit(1);
152             }
153     
154             mdctx = EVP_MD_CTX_new();
>>>     CID 345244:    (CHECKED_RETURN)
>>>     Calling "EVP_DigestInit_ex" without checking return value (as is done elsewhere 9 out of 11 times).
155             EVP_DigestInit_ex(mdctx, md, NULL);
156       mac_key = EVP_PKEY_new_mac_key(NID_grasshopper_mac, NULL, mac_secret, 32);
157       EVP_DigestSignInit(mdctx, NULL, md, NULL, mac_key);
158       EVP_PKEY_free(mac_key);
159     
160             EVP_MD_CTX_ctrl(mdctx, EVP_MD_CTRL_TLSTREE, 0, seq63);
/test_tlstree.c: 114 in main()
108             OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CONFIG, NULL);
109     
110             memset(data63, 0, 4096);
111     
112             md = EVP_get_digestbynid(NID_grasshopper_mac);
113     
>>>     CID 345244:    (CHECKED_RETURN)
>>>     Calling "EVP_DigestInit_ex" without checking return value (as is done elsewhere 9 out of 11 times).
114             EVP_DigestInit_ex(mdctx, md, NULL);
115       mac_key = EVP_PKEY_new_mac_key(NID_grasshopper_mac, NULL, mac_secret, 32);
116       EVP_DigestSignInit(mdctx, NULL, md, NULL, mac_key);
117       EVP_PKEY_free(mac_key);
118     
119             EVP_MD_CTX_ctrl(mdctx, EVP_MD_CTRL_TLSTREE, 0, seq0);

** CID 345243:  Null pointer dereferences  (REVERSE_INULL)
/gost_ec_keyx.c: 681 in pkey_gost2018_decrypt()


________________________________________________________________________________________________________
*** CID 345243:  Null pointer dereferences  (REVERSE_INULL)
/gost_ec_keyx.c: 681 in pkey_gost2018_decrypt()
675        o  Q_eph is on the same curve as server public key;
676     
677        o  Q_eph is not equal to zero point;
678     
679        o  q * Q_eph is not equal to zero point.
680     */
>>>     CID 345243:  Null pointer dereferences  (REVERSE_INULL)
>>>     Null-checking "data" suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
681         if (eph_key == NULL || priv == NULL || data == NULL) {
682            GOSTerr(GOST_F_PKEY_GOST2018_DECRYPT,
683                    GOST_R_ERROR_COMPUTING_EXPORT_KEYS);
684            ret = 0;
685            goto err;
686         }

[se-prok]

As for unnecessary data == NULL check:

This if (eph_key == NULL ...) fragment was my patch against the real segmentation fault observed due to the dereference of the null eph_key.
I added this unnecessary check of the data pointer as an extra precaution. )