Wrap servlet original PrintWriter on rum injector #9146
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| Original file line number | Diff line number | Diff line change | ||||
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| @@ -0,0 +1,160 @@ | ||||||
| package datadog.trace.bootstrap.instrumentation.buffer; | ||||||
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| import java.io.IOException; | ||||||
| import java.io.Writer; | ||||||
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| /** | ||||||
| * An Writer containing a circular buffer with a lookbehind buffer of n bytes. The first time that | ||||||
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| * the latest n bytes matches the marker, a content is injected before. | ||||||
| */ | ||||||
| public class InjectingPipeWriter extends Writer { | ||||||
| private final char[] lookbehind; | ||||||
| private int pos; | ||||||
| private boolean bufferFilled; | ||||||
| private final char[] marker; | ||||||
| private final char[] contentToInject; | ||||||
| private boolean found = false; | ||||||
| private int matchingPos = 0; | ||||||
| private final Runnable onContentInjected; | ||||||
| private final int bulkWriteThreshold; | ||||||
| private final Writer downstream; | ||||||
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| /** | ||||||
| * @param downstream the delegate writer | ||||||
| * @param marker the marker to find in the stream. Must at least be one char. | ||||||
| * @param contentToInject the content to inject once before the marker if found. | ||||||
| * @param onContentInjected callback called when and if the content is injected. | ||||||
| */ | ||||||
| public InjectingPipeWriter( | ||||||
| final Writer downstream, | ||||||
| final char[] marker, | ||||||
| final char[] contentToInject, | ||||||
| final Runnable onContentInjected) { | ||||||
| this.downstream = downstream; | ||||||
| this.marker = marker; | ||||||
| this.lookbehind = new char[marker.length]; | ||||||
| this.pos = 0; | ||||||
| this.contentToInject = contentToInject; | ||||||
| this.onContentInjected = onContentInjected; | ||||||
| this.bulkWriteThreshold = marker.length * 2 - 2; | ||||||
| } | ||||||
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| @Override | ||||||
| public void write(int b) throws IOException { | ||||||
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matches the |
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| if (found) { | ||||||
| downstream.write(b); | ||||||
| return; | ||||||
| } | ||||||
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| if (bufferFilled) { | ||||||
| downstream.write(lookbehind[pos]); | ||||||
| } | ||||||
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| lookbehind[pos] = (char) b; | ||||||
| pos = (pos + 1) % lookbehind.length; | ||||||
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| if (!bufferFilled) { | ||||||
| bufferFilled = pos == 0; | ||||||
| } | ||||||
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| if (marker[matchingPos++] == b) { | ||||||
| if (matchingPos == marker.length) { | ||||||
| found = true; | ||||||
| downstream.write(contentToInject); | ||||||
| if (onContentInjected != null) { | ||||||
| onContentInjected.run(); | ||||||
| } | ||||||
| drain(); | ||||||
| } | ||||||
| } else { | ||||||
| matchingPos = 0; | ||||||
| } | ||||||
| } | ||||||
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| @Override | ||||||
| public void flush() throws IOException { | ||||||
| downstream.flush(); | ||||||
|
There was a problem hiding this comment. I think we also need this in the updated There was a problem hiding this comment. Yes in the outputstream I didn't implement the first time since extending FilterOutputStream but now is not the case anymore thanks |
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| } | ||||||
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| @Override | ||||||
| public void write(char[] array, int off, int len) throws IOException { | ||||||
| if (found) { | ||||||
| downstream.write(array, off, len); | ||||||
| return; | ||||||
| } | ||||||
| if (len > bulkWriteThreshold) { | ||||||
| // if the content is large enough, we can bulk write everything but the N trail and tail. | ||||||
| // This because the buffer can already contain some byte from a previous single write. | ||||||
| // Also we need to fill the buffer with the tail since we don't know about the next write. | ||||||
| int idx = arrayContains(array, off, len, marker); | ||||||
| if (idx >= 0) { | ||||||
| // we have a full match. just write everything | ||||||
| found = true; | ||||||
| drain(); | ||||||
| downstream.write(array, off, idx); | ||||||
| downstream.write(contentToInject); | ||||||
| if (onContentInjected != null) { | ||||||
| onContentInjected.run(); | ||||||
| } | ||||||
| downstream.write(array, off + idx, len - idx); | ||||||
| } else { | ||||||
| // we don't have a full match. write everything in a bulk except the lookbehind buffer | ||||||
| // sequentially | ||||||
| for (int i = off; i < off + marker.length - 1; i++) { | ||||||
| write(array[i]); | ||||||
| } | ||||||
| drain(); | ||||||
| downstream.write(array, off + marker.length - 1, len - bulkWriteThreshold); | ||||||
| for (int i = len - marker.length + 1; i < len; i++) { | ||||||
| write(array[i]); | ||||||
| } | ||||||
| } | ||||||
| } else { | ||||||
| // use slow path because the length to write is small and within the lookbehind buffer size | ||||||
| for (int i = off; i < off + len; i++) { | ||||||
| write(array[i]); | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
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| private int arrayContains(char[] array, int off, int len, char[] search) { | ||||||
| for (int i = off; i < len - search.length; i++) { | ||||||
| if (array[i] == search[0]) { | ||||||
| boolean found = true; | ||||||
| int k = i; | ||||||
| for (int j = 1; j < search.length; j++) { | ||||||
| k++; | ||||||
| if (array[k] != search[j]) { | ||||||
| found = false; | ||||||
| break; | ||||||
| } | ||||||
| } | ||||||
| if (found) { | ||||||
| return i; | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
| return -1; | ||||||
| } | ||||||
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| private void drain() throws IOException { | ||||||
| if (bufferFilled) { | ||||||
| for (int i = 0; i < lookbehind.length; i++) { | ||||||
| downstream.write(lookbehind[(pos + i) % lookbehind.length]); | ||||||
| } | ||||||
| } else { | ||||||
| downstream.write(this.lookbehind, 0, pos); | ||||||
| } | ||||||
| pos = 0; | ||||||
| matchingPos = 0; | ||||||
| bufferFilled = false; | ||||||
| } | ||||||
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| @Override | ||||||
| public void close() throws IOException { | ||||||
| if (!found) { | ||||||
| drain(); | ||||||
| } | ||||||
| downstream.close(); | ||||||
| } | ||||||
| } | ||||||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| package datadog.trace.bootstrap.instrumentation.buffer | ||
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| import datadog.trace.test.util.DDSpecification | ||
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| class InjectingPipeWriterTest extends DDSpecification { | ||
| def 'should filter a buffer and inject if found #found using write'() { | ||
| setup: | ||
| def downstream = new StringWriter() | ||
| def piped = new PrintWriter(new InjectingPipeWriter(downstream, marker.toCharArray(), contentToInject.toCharArray(), null)) | ||
| when: | ||
| try (def closeme = piped) { | ||
| piped.write(body) | ||
| } | ||
| then: | ||
| assert downstream.toString() == expected | ||
| where: | ||
| body | marker | contentToInject | found | expected | ||
| "<html><head><foo/></head><body/></html>" | "</head>" | "<script>true</script>" | true | "<html><head><foo/><script>true</script></head><body/></html>" | ||
| "<html><body/></html>" | "</head>" | "<something/>" | false | "<html><body/></html>" | ||
| "<foo/>" | "<longerThanFoo>" | "<nothing>" | false | "<foo/>" | ||
| } | ||
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| def 'should filter a buffer and inject if found #found using append'() { | ||
| setup: | ||
| def downstream = new StringWriter() | ||
| def piped = new PrintWriter(new InjectingPipeWriter(downstream, marker.toCharArray(), contentToInject.toCharArray(), null)) | ||
| when: | ||
| try (def closeme = piped) { | ||
| piped.append(body) | ||
| } | ||
| then: | ||
| assert downstream.toString() == expected | ||
| where: | ||
| body | marker | contentToInject | found | expected | ||
| "<html><head><foo/></head><body/></html>" | "</head>" | "<script>true</script>" | true | "<html><head><foo/><script>true</script></head><body/></html>" | ||
| "<html><body/></html>" | "</head>" | "<something/>" | false | "<html><body/></html>" | ||
| "<foo/>" | "<longerThanFoo>" | "<nothing>" | false | "<foo/>" | ||
| } | ||
| } |
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@mcculls added the loop not to delegate to super