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Fall back properly if chosen factory class isn't working. #28

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merged 6 commits into from
Sep 22, 2020
Merged

Fall back properly if chosen factory class isn't working. #28

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6a41646
Fall back properly to automatically-chosen factory classes if the cho…
JonathanLennox Sep 21, 2020
0eaa602
Check if key is unchanged before checking validity.
JonathanLennox Sep 18, 2020
5a8073e
Document that null is a valid value for Aes.setFactoryClassName.
JonathanLennox Sep 21, 2020
3124f92
Modify CTR benchmark to be (slightly) more similar to the actual usag…
JonathanLennox Sep 18, 2020
9573540
Remove superfluous parentheses.
JonathanLennox Sep 22, 2020
932b706
Cleanups after PR review.
JonathanLennox Sep 22, 2020
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106 changes: 65 additions & 41 deletions src/main/java/org/jitsi/srtp/crypto/Aes.java
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Original file line number Diff line number Diff line change
Expand Up @@ -266,8 +266,7 @@ public void run(Cipher cipher) throws Exception
private static CipherFactory benchmark(
CipherFactory[] factories,
int keySize,
String transformation,
boolean warmup
String transformation
)
{
long minTime = Long.MAX_VALUE;
Expand All @@ -282,6 +281,14 @@ private static CipherFactory benchmark(
if (factory == null)
continue;

// The user may have specified a specific CipherFactory class
// (name) through setFactoryClassName(String), Practically, FACTORY_CLASS_NAME may override
// minFactory and, consequently, it may appear that the benchmark is
// unnecessary. Technically though, the specified CipherFactory may
// malfunction. That is why FACTORY_CLASS_NAME is selected after it has
// proven itself functional.
boolean chosenFactoryClass = (factory.getClass().equals(Aes.factoryClass));
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Extra parens on purpose?

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Ah, no, I reorganized this from an if statement.


try
{
Cipher cipher = factory.createCipher(transformation);
Expand All @@ -295,18 +302,24 @@ private static CipherFactory benchmark(
}
else
{
/* If this is the user-chosen factory class, we don't really
* need to benchmark it; just verify that it's working.
*/
int numWarmups = chosenFactoryClass ? 0 : NUM_WARMUPS;
int numBenchmarks = chosenFactoryClass ? 1 : NUM_BENCHMARKS;

BenchmarkOperation benchmark = BenchmarkOperation.getBenchmark(transformation, keySize);
if (warmup)
if (!chosenFactoryClass)
{
// Let the JVM "warm up" (do JIT compilation and the like)
for (int i = 0; i < NUM_WARMUPS; i++)
for (int i = 0; i < numWarmups; i++)
{
benchmark.run(cipher);
}
}

long startTime = System.nanoTime();
for (int i = 0; i < NUM_BENCHMARKS; i++)
for (int i = 0; i < numBenchmarks; i++)
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Should line 329 use numBenchmarks instead of NUM_BENCHMARKS? I guess in practice it doesn't matter

{
benchmark.run(cipher);
}
Expand Down Expand Up @@ -335,6 +348,19 @@ private static CipherFactory benchmark(
else if (t instanceof ThreadDeath)
throw (ThreadDeath) t;
}

if (chosenFactoryClass)
{
if (minFactory != null)
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I'm not sure I understand this well. If this loop iteration is for the user-configured factory class, return the fastest factory. If a previous non-user-configured factory was faster, we short-circuit and return it (the faster one)?

Should that return factory instead of minFactory?

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Well, elsewhere in the code I reorganize the list so the user-configured factory class is always first, so we avoid profiling factories we don't need to. But I agree that's fragile and confusing.

I've reorganized it now, is it clearer?

{
return minFactory;
}
else
{
logger.warn("Chosen factory class \"" + FACTORY_CLASS_NAME +
"\" not working for " + transformation);
}
}
}

if (log.length() != 0)
Expand Down Expand Up @@ -537,26 +563,47 @@ else if (t instanceof ThreadDeath)

// If FACTORY_CLASS_NAME does not specify a well-known Class, add the
// new Class to FACTORY_CLASSES.
if (add && (factoryClass != null))
if (factoryClass != null)
{
for (Class<?> clazz : factoryClasses)
Class<?>[] newFactoryClasses;
if (add)
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I think all of this is equivalent to factoryClasses = ArrayUtils.add(factoryClasses, Class.class, factoryClass); (from jitsi-utils)

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Not quite - I want to put the new factory class first, whereas ArrayUtils.add would seem to put it last.

{
if (factoryClass.equals(clazz))
for (Class<?> clazz : factoryClasses)
{
add = false;
break;
if (factoryClass.equals(clazz))
{
add = false;
break;
}
}
}
if (add)
{
Class<?>[] newFactoryClasses
= new Class<?>[1 + factoryClasses.length];
if (add)
{
newFactoryClasses
= new Class<?>[1 + factoryClasses.length];

newFactoryClasses[0] = factoryClass;
System.arraycopy(
newFactoryClasses[0] = factoryClass;
System.arraycopy(
factoryClasses, 0,
newFactoryClasses, 1,
factoryClasses.length);
}
}
else
{
/* Otherwise, move the FACTORY_CLASS to the beginning of the list. */
newFactoryClasses
= new Class<?>[factoryClasses.length];

newFactoryClasses[0] = factoryClass;
int i = 1;
for (Class<?> clazz : factoryClasses)
{
if (!factoryClass.equals(clazz))
{
newFactoryClasses[i] = clazz;
i++;
}
}
factoryClasses = newFactoryClasses;
}
}
Expand Down Expand Up @@ -639,30 +686,7 @@ private static CipherFactory getCipherFactory(String transformation, boolean war
// Benchmark the StreamCiphers provided by the available
// StreamCipherFactories in order to select the fastest-performing
// CipherFactory.
CipherFactory minFactory = benchmark(factories, keySize, transformation, warmup);

// The user may have specified a specific CipherFactory class
// (name) through setFactoryClassName(String), Practically, FACTORY_CLASS_NAME may override
// minFactory and, consequently, it may appear that the benchmark is
// unnecessary. Technically though, the specified CipherFactory may
// malfunction. That is why FACTORY_CLASS_NAME is selected after it has
// proven itself functional.
{
Class<? extends CipherFactory> factoryClass = Aes.factoryClass;

if (factoryClass != null)
{
for (CipherFactory factory : factories)
{
if ((factory != null)
&& factory.getClass().equals(factoryClass))
{
minFactory = factory;
break;
}
}
}
}
CipherFactory minFactory = benchmark(factories, keySize, transformation);

return minFactory;
}
Expand Down