OPENSSL PKCS7 认证哪位大神会啊！！！

我用C++写了一个安卓APK的认证。
主要就是解析里面的CERT.RSA
解析：
PKCS7 *p7 = NULL;
BIO *in = BIO_new(BIO_s_file());
STACK_OF(X509) *certs = NULL;
int i;

    BIO_read_filename(in, rsa_path);
    p7 = d2i_PKCS7_bio(in, NULL);
    if(p7) {
        i = OBJ_obj2nid(p7->type);
    } else {
        BIO_free(in);
        break;
    }
    if(i == NID_pkcs7_signed) {
        certs = p7->d.sign->cert;
    } else if(i == NID_pkcs7_signedAndEnveloped) {
        certs = p7->d.signed_and_enveloped->cert;
    }
    BIO_free(in);
    if(sk_X509_num(certs) != 1) {
        PKCS7_free(p7);
        break;
    }

认证：
BIO *p7bio = NULL;
int res = 0;
char buf[1024*4] = {0};
STACK_OF(PKCS7_SIGNER_INFO) *sk;
PKCS7_SIGNER_INFO *si;
X509 * x509;
int i;

PKCS7 *pkcs7 = (PKCS7 *)m_pkcs7;
p7bio = PKCS7_dataDecode(pkcs7, 0, 0, 0);
    //这里得到的p7bio是空的！！！！为什么
    //这段代码是我从网上面找到的
for (;;)
{
    i=BIO_read(p7bio,buf,sizeof(buf));
    if (i <= 0)
        break;
}

// We can now verify signatures
sk = PKCS7_get_signer_info(pkcs7);
if (sk == NULL)
{
    goto end;
}
else
{
    if (sk_PKCS7_SIGNER_INFO_num(sk) == 0)
    {
        goto end;
    }
    /* Ok, first we need to, for each subject entry,
     * see if we can verify */
    for (i=0; i<sk_PKCS7_SIGNER_INFO_num(sk); i++)
    {
        si = sk_PKCS7_SIGNER_INFO_value(sk, i);
        x509 = X509_find_by_issuer_and_serial(pkcs7->d.sign->cert,si->issuer_and_serial->issuer,si->issuer_and_serial->serial);
        int ret;

        ret = PKCS7_signatureVerify(p7bio, pkcs7, si, x509);
        if (ret <= 0)
            goto end;
    }
}
res = 1;

end:
if (p7bio)
BIO_free_all(p7bio);
return res;

m_pkcs7数据是否正确。

获取m_pkcs7
bool Certificate::parse(const char *rsa_path) {
bool ret = false;
do {
if(m_pkcs7) {
clear();
}
PKCS7 *p7 = NULL;
BIO *in = BIO_new(BIO_s_file());
STACK_OF(X509) *certs = NULL;
int i;

    BIO_read_filename(in, rsa_path);
    p7 = d2i_PKCS7_bio(in, NULL);
    if(p7) {
        i = OBJ_obj2nid(p7->type);
    } else {
        BIO_free(in);
        break;
    }
    if(i == NID_pkcs7_signed) {
        certs = p7->d.sign->cert;
    } else if(i == NID_pkcs7_signedAndEnveloped) {
        certs = p7->d.signed_and_enveloped->cert;
    }
    BIO_free(in);
    if(sk_X509_num(certs) != 1) {
        PKCS7_free(p7);
        break;
    }
    m_rsa_path = rsa_path;
    m_certs = certs;
    m_pkcs7 = p7;
    ret = true;
}while(0);
return ret;

}

验证：
bool Certificate::VerifyPkcs7Signature() {
if(m_pkcs7 == NULL) {
return false;
}
BIO *p7bio = NULL;
int res = 0;
char buf[1024*4] = {0};
STACK_OF(PKCS7_SIGNER_INFO) *sk;
PKCS7_SIGNER_INFO *si;
X509 * x509;
int i;

PKCS7 *pkcs7 = (PKCS7 *)m_pkcs7;

//    p7bio = PKCS7_dataInit(pkcs7,NULL);
p7bio = PKCS7_dataDecode(pkcs7, 0, 0, 0);
// We now have to 'read' from p7bio to calculate digests etc.
do {
    i = BIO_read(p7bio, buf, sizeof(buf));

    //we can now verify signatures
    sk = PKCS7_get_signer_info(pkcs7);
    if(sk == NULL) {
        break;
    }
    if(0 == sk_PKCS7_SIGNER_INFO_num(sk)) {
        break;
    }
    for(i = 0; i < sk_PKCS7_SIGNER_INFO_num(sk); i++) {
        si = sk_PKCS7_SIGNER_INFO_value(sk, i);
        x509 = X509_find_by_issuer_and_serial(pkcs7->d.sign->cert,
                                              si->issuer_and_serial->issuer,
                                              si->issuer_and_serial->serial);
        int ret = PKCS7_signatureVerify(p7bio, pkcs7, si, x509);
        if(ret < 0) {
            res = -1;
            break;
        }
    }
}while(0);
if(p7bio) {
    BIO_free_all(p7bio);
}
return res != 1;

}
你看看有什么问题
现在是能用了，但是不知道为什么PKCS7_dataDecode仍然是空。
如果你了解怎么用PKCS7来得到签名的话，我就真的谢谢你了！！！！