解密smime.p7m

Question

我正在尝试使用Bouncycastle解密Android上的s / mime加密附件（来自Outlook / Exchange，smime.p7m）。

我可以在Windows上使用p7mViewer解密/查看内容。

代码，如bc-java的ReadEncryptedMail.java：

ByteArrayInputStream inputStream = new ByteArrayInputStream(encryptedContent);
Session session = Session.getInstance(new Properties());
MimeMessage mimeMessage = new MimeMessage(session, inputStream);    
SMIMEEnveloped smimeEnveloped = new SMIMEEnveloped(mimeMessage);

结果我得到java.io.IOException：DER长度超过4个字节：75 org.bouncycastle.asn1.ASN1InputStream.readLength（未知来源：53）

我缺少什么？

Answer 1

经过大量挖掘后，我在bouncycastle邮件列表http://bouncy-castle.1462172.n4.nabble.com/how-to-generically-parse-a-PKCS7-object-td1467990.html上找到了“如何一般地解析PKCS7对象”

使用代码我获得了ENVELOPEDDATA的内容类型，这导致我尝试成功解析内容的CMSEnvelopedDataParser。

CMSEnvelopedDataParser cmsEnvelopedDataParser = new CMSEnvelopedDataParser(encryptedContent);
Collection recInfos = cmsEnvelopedDataParser.getRecipientInfos().getRecipients();
Iterator recipientIterator = recInfos.iterator();
if (recipientIterator.hasNext()) {
    RecipientInformation recipientInformation = (RecipientInformation) recipientIterator.next();
    byte[] contentBytes = recipientInformation.getContent(new JceKeyTransEnvelopedRecipient(privateKey));
    String content = new String(contentBytes);
}