82 lines
3.1 KiB
Java
82 lines
3.1 KiB
Java
/*
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* Copyright 2021 Paul Schaub.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.pgpainless.signature.cleartext_signatures;
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import java.io.ByteArrayOutputStream;
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import java.io.File;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.OutputStream;
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/**
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* Since the {@link CleartextSignatureProcessor} needs to read the whole data twice in order to verify signatures,
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* a strategy for how to cache the read data is required.
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* Otherwise large data kept in memory could cause {@link OutOfMemoryError OutOfMemoryErrors} or other issues.
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*
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* This is an Interface that describes a strategy to deal with the fact that detached signatures require multiple passes
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* to do verification.
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*
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* This interface can be used to write the signed data stream out via {@link #getMessageOutputStream()} and later
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* get access to the data again via {@link #getMessageInputStream()}.
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* Thereby the detail where the data is being stored (memory, file, etc.) can be abstracted away.
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*/
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public interface MultiPassStrategy {
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/**
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* Provide an {@link OutputStream} into which the signed data can be read into.
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*
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* @return output stream
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* @throws IOException io error
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*/
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OutputStream getMessageOutputStream() throws IOException;
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/**
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* Provide an {@link InputStream} which contains the data that was previously written away in
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* {@link #getMessageOutputStream()}.
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*
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* As there may be multiple signatures that need to be processed, each call of this method MUST return
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* a new {@link InputStream}.
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*
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* @return input stream
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* @throws IOException io error
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*/
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InputStream getMessageInputStream() throws IOException;
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/**
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* Write the message content out to a file and re-read it to verify signatures.
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* This strategy is best suited for larger messages (eg. plaintext signed files) which might not fit into memory.
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* After the message has been processed completely, the messages content are available at the provided file.
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*
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* @param file target file
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* @return strategy
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*/
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static MultiPassStrategy writeMessageToFile(File file) {
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return new WriteToFileMultiPassStrategy(file);
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}
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/**
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* Read the message content into memory.
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* This strategy is best suited for small messages which fit into memory.
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* After the message has been processed completely, the message content can be accessed by calling
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* {@link ByteArrayOutputStream#toByteArray()} on {@link #getMessageOutputStream()}.
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*
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* @return strategy
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*/
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static InMemoryMultiPassStrategy keepMessageInMemory() {
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return new InMemoryMultiPassStrategy();
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}
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}
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