org.bouncycastle.openpgp.api

Class OpenPGPMessageOutputStream

java.lang.Object

java.io.OutputStream

org.bouncycastle.openpgp.api.OpenPGPMessageOutputStream

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable

public class OpenPGPMessageOutputStream
extends java.io.OutputStream

Implementation of an OutputStream tailored to creating OpenPGP messages. Since not all OpenPGP-related OutputStreams forward close() calls, we need to keep track of nested streams and close them in order. This stream can create OpenPGP messages following the following EBNF (which is a subset of the EBNF defined in RFC9580):

• OpenPGP Message := ASCII-Armor(Optionally Encrypted Message) | Optionally Encrypted Message
• Literal Message := LiteralDataPacket
• Optionally Compressed Message := Literal Message | CompressedDataPacket(Literal Message)
• Optionally Signed Message := Optionally Compressed Message | OnePassSignaturePacket + Optionally Signed Message + SignaturePacket
• Optionally Padded Message := Optionally Signed Message | Optionally Signed Message + PaddingPacket
• Encrypted Message := SEIPDv1(Optionally Padded Message) | SEIPDv2(Optionally Padded Message) | OED(Optionally Padded Message)
• Optionally Encrypted Message := Optionally Padded Message | Encrypted Message

Therefore, this stream is capable of creating a wide variety of OpenPGP message, from simply LiteralDataPacket-wrapped plaintext over signed messages to encrypted, signed and padded messages. The following considerations lead to why this particular subset was chosen:

• An encrypted message is not distinguishable from randomness, so it makes no sense to compress it
• Since signatures also consist of data which is not distinguishable from randomness, it makes no sense to compress them either
• Padding packets are used to prevent traffic analysis. Since they contain random data, we do not compress them. If a message is encrypted, we want to encrypt the padding packet to prevent an intermediate from stripping it
• Since (v4) signatures leak some metadata about the message plaintext (the hash and the issuer), for encrypted messages we always place signatures inside the encryption container (sign-then-encrypt)
• Prefix-signed messages (where a SignaturePacket is prefixed to an OpenPGP message) are inferior to One-Pass-Signed messages, so this stream cannot produce those.
• Messages using the Cleartext-Signature Framework are "different enough" to deserve their own message generator / stream.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	OpenPGPMessageOutputStream.OutputStreamFactory Factory class for wrapping output streams.
static interface	OpenPGPMessageOutputStream.PaddingPacketFactory Factory interface for creating PGPPadding objects.

Method Summary

Modifier and Type	Method and Description
void	close()
void	flush()
void	write(byte[] b)
void	write(byte[] b, int off, int len)
void	write(int i)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

write

public void write(int i)
           throws java.io.IOException

Specified by:

write in class java.io.OutputStream

Throws:

java.io.IOException

write

public void write(byte[] b)
           throws java.io.IOException

Overrides:

write in class java.io.OutputStream

Throws:

java.io.IOException

write

public void write(byte[] b,
                  int off,
                  int len)
           throws java.io.IOException

Overrides:

write in class java.io.OutputStream

Throws:

java.io.IOException

flush

public void flush()
           throws java.io.IOException

Specified by:

flush in interface java.io.Flushable

Overrides:

flush in class java.io.OutputStream

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.OutputStream

Throws:

java.io.IOException