用Java生成X509Certificate的主题哈希

Question

我目前正在尝试使用Java安全API和BouncyCastle生成主题哈希。

使用Openssl库时，这是我的工作：

openssl x509 -in  /Users/Sn0wfreezeDev/Downloads/Test.pem -hash

这会生成一个短的8位数字哈希1817886a

这是我的Java代码

X509Certificate cert = CertManager.getCertificate(number, c);  
MessageDigest sha1 = MessageDigest.getInstance("SHA1");
System.out.println("  Subject " + cert.getSubjectDN());
System.out.println("   Issuer  " + cert.getIssuerDN());
sha1.update(cert.getSubjectDN().getName().getBytes());
String hexString =  bytesToHex(sha1.digest());
System.out.println("   sha1    " + hexString);
System.out.println();

Answer 1

这会生成一个短的8位数字哈希1817886a

OpenSSL有两种形式：

$ cd openssl-1.0.2-src
$ grep -R X509_subject_name_hash *
...
crypto/x509/x509.h:unsigned long X509_subject_name_hash(X509 *x);
crypto/x509/x509.h:unsigned long X509_subject_name_hash_old(X509 *x);
crypto/x509/x509_cmp.c:unsigned long X509_subject_name_hash(X509 *x)
crypto/x509/x509_cmp.c:unsigned long X509_subject_name_hash_old(X509 *x)
...

在Java中生成X509Certificate的主题哈希...

这是他们的来源crypto/x509/x509_cmp.c：

unsigned long X509_subject_name_hash(X509 *x)
{
    return (X509_NAME_hash(x->cert_info->subject));
}

#ifndef OPENSSL_NO_MD5
unsigned long X509_subject_name_hash_old(X509 *x)
{
    return (X509_NAME_hash_old(x->cert_info->subject));
}
#endif

最后：

unsigned long X509_NAME_hash(X509_NAME *x)
{
    unsigned long ret = 0;
    unsigned char md[SHA_DIGEST_LENGTH];

    /* Make sure X509_NAME structure contains valid cached encoding */
    i2d_X509_NAME(x, NULL);
    if (!EVP_Digest(x->canon_enc, x->canon_enclen, md, NULL, EVP_sha1(),
                    NULL))
        return 0;

    ret = (((unsigned long)md[0]) | ((unsigned long)md[1] << 8L) |
           ((unsigned long)md[2] << 16L) | ((unsigned long)md[3] << 24L)
        ) & 0xffffffffL;
    return (ret);
}

#ifndef OPENSSL_NO_MD5
unsigned long X509_NAME_hash_old(X509_NAME *x)
{
    EVP_MD_CTX md_ctx;
    unsigned long ret = 0;
    unsigned char md[16];

    /* Make sure X509_NAME structure contains valid cached encoding */
    i2d_X509_NAME(x, NULL);
    EVP_MD_CTX_init(&md_ctx);
    EVP_MD_CTX_set_flags(&md_ctx, EVP_MD_CTX_FLAG_NON_FIPS_ALLOW);
    if (EVP_DigestInit_ex(&md_ctx, EVP_md5(), NULL)
        && EVP_DigestUpdate(&md_ctx, x->bytes->data, x->bytes->length)
        && EVP_DigestFinal_ex(&md_ctx, md, NULL))
        ret = (((unsigned long)md[0]) | ((unsigned long)md[1] << 8L) |
               ((unsigned long)md[2] << 16L) | ((unsigned long)md[3] << 24L)
            ) & 0xffffffffL;
    EVP_MD_CTX_cleanup(&md_ctx);

    return (ret);
}
#endif

i2d_X509_NAMEX509_NAME使用RFC 2459（和其他地方）将a编码为标准表示形式。例如，它用于证书主题和颁发者名称。

您可以使用类似的命令查看OpenSSL用于名称字符串的内容openssl x509 -in <cert> -text -noout。它看起来类似于C=US, ST=California, L=Mountain View, O=Google Inc, CN=www.google.com（取自Google证书）。

在Java中生成X509Certificate的主题哈希...

在大图中，您正在生成主题的专有名称字符串的哈希，并返回无符号的long。unsigned long实际上是一个截断的哈希。

X509_subject_name_hash使用SHA-1，并X509_subject_name_hash_old使用MD5。

（评论）...他们如何使用sha1哈希生成短哈希

OpenSSL提供了截断的哈希的十六进制编码。整个哈希在中md。md将为16个字节（MD5）或20个字节（SHA-1）。

截断与字节选择发生[0,3]和对位操作md[0]，md[1]，md[2]和md[3]。

8位数字来自对4个字节进行十六进制编码。