C 中的 x509 证书验证

我确实有 DER 和 PEM 格式的证书，我的目标是检索颁发者和主题字段并使用 CA 公钥验证证书，同时使用根公钥验证 CA 证书。 我能够检索颁发者和主题的所有详细信息，但无法验证证书。
使用的API：

x509 = d2i_X509_fp (fp, &x509); //READING DER Format
x509 = PEM_read_X509 (fp, &x509, NULL, NULL); //READING PEM Format
//to retrieve the Subject:
X509_NAME_oneline(X509_get_subject_name(x509), subject, sizeof (subject));
//to retrieve the Issuer:
X509_NAME_oneline(X509_get_issuer_name(x509), issuer, sizeof (issuer));

//To store the CA public key (in unsigned char *key) that will be used to verify the 
//certificate (in my case always sha1WithRSAEncryption):
RSA *x = X509_get_pubkey(x509)->pkey.rsa;
bn = x->n;
//extracts the bytes from public key & convert into unsigned char buffer
buf_len = (size_t) BN_num_bytes (bn);
stored_CA_pubKey = (unsigned char *)malloc (buf_len);
i_n = BN_bn2bin (bn, (unsigned char *)stored_CA_pubKey);
if (i_n != buf_len)
  LOG(ERROR," : key error\n");
if (key[0] & 0x80)
  LOG(DEBUG, "00\n");

stored_CA_pubKeyLen = EVP_PKEY_size(X509_get_pubkey(x509));

对于验证，我采用了不同的方法，但无法验证：

a)

i_x509_verify = X509_verify(cert_x509, ca_pubkey);

b)

/* verify the signature */
int iRet1, iRet2, iReason;
iRet1 = EVP_VerifyInit(&md_ctx, EVP_sha1());
iRet2 = EVP_VerifyUpdate(&md_ctx, cert_code, cert_code_len);
rv = EVP_VerifyFinal(&md_ctx, (const unsigned char *)stored_CA_pubKey,
     stored_CA_pubKeyLen, cert_pubkey);

注意：cert_code 和stored_CA_pubKey 是无符号字符缓冲区。

我使用以下代码来验证证书

初始化证书存储：

X509_STORE* m_store = X509_STORE_new();
X509_LOOKUP* m_lookup = X509_STORE_add_lookup(m_store,X509_LOOKUP_file());    
X509_STORE_load_locations(m_store, "CAFile.pem", NULL);
X509_STORE_set_default_paths(m_store);
X509_LOOKUP_load_file(m_lookup,"CAFile.pem",X509_FILETYPE_PEM)
// alternative lookup by hashdir
// X509_LOOKUP* m_lookup=X509_STORE_add_lookup(m_store,X509_LOOKUP_hash_dir());

验证证书：

X509_STORE_CTX *storeCtx = X509_STORE_CTX_new();
X509_STORE_CTX_init(storeCtx,m_store,cert,NULL);
X509_STORE_CTX_set_flags(storeCtx, X509_V_FLAG_CB_ISSUER_CHECK);
if (X509_verify_cert(storeCtx) == 1)
{
  printf("success");
}
else
{
  printf("Verificatione rror: %s",X509_verify_cert_error_string(storeCtx->error));
}
X509_STORE_CTX_free(storeCtx);

您还需要清理 m_store

if(m_store != NULL)
{
   X509_STORE_free(m_store);
   m_store = NULL;
}