openssl和md2的问题

Since 2004, MD2 is not considered safe; it is vulnerable to a preimage attack with time complexity. Some Certificate Authorities and vendors are starting to not support MD2.
当然也包括verisign。
Sun released the Java SE version 1.6.0_17, they have removed the support for MD2 hash algorithm in certificates。
如果使用，Caused by: java.security.cert.CertPathValidatorException: algorithm check failed: MD2withRSA is disabled
Internet Explorer 8+ on Windows 7 SP1+ no longer accepts Authenticode signatures that use the MD2 or MD4 hashing algorithms in the certificate chain. (MD2 and MD4 on the root itself isn’t a worry, because the root itself is installed on the machine).
OpenSSL 1.0 and later does not include the MD2 digest algorithm in the default configuration due to its security weaknesses.
如果支持md2，需要编译时加上enable-md2
如果使用
  md = EVP_get_digestbyname (digest);
digets是md2时，一直返回NULL。
但是EVP_md2();还是可以使用的
代码改为
 const EVP_MD *md = NULL;
  ASSERT (digest);
  if(0 == strcasecmp(digest,"md2")||0 == strcasecmp(digest,"rsa-md2"))
  {
 md = EVP_md2();
  }
  else
  {
    md = EVP_get_digestbyname (digest);
  }

或者

在 OpenSSL_add_all_digests();后面添加

EVP_add_digest(EVP_md2());