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Add support for optional field pruning in verifier #1130

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24 changes: 14 additions & 10 deletions verifier/src/main/java/dev/cel/verifier/CelAstAlphaHasher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,9 @@
import dev.cel.common.ast.CelConstant;
import dev.cel.common.ast.CelExpr;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
Expand Down Expand Up @@ -83,16 +85,11 @@ private static void hashAst(CelExpr expr, @Nullable Scope scope, HasherContext c
context.hasher.putByte((byte) 0); // 0 = bound
context.hasher.putInt(bIdx);
} else {
int fIdx = -1;
for (int i = 0; i < context.freeVars.size(); i++) {
if (context.freeVars.get(i).ident().name().equals(name)) {
fIdx = i;
break;
}
}
if (fIdx == -1) {
Integer fIdx = context.freeVarIndices.get(name);
if (fIdx == null) {
fIdx = context.freeVars.size();
context.freeVars.add(expr);
fIdx = context.freeVars.size() - 1;
context.freeVarIndices.put(name, fIdx);
}
context.hasher.putByte((byte) 1); // 1 = free
context.hasher.putInt(fIdx);
Expand Down Expand Up @@ -121,6 +118,10 @@ private static void hashAst(CelExpr expr, @Nullable Scope scope, HasherContext c
for (CelExpr elem : expr.list().elements()) {
hashAst(elem, scope, context);
}
context.hasher.putInt(expr.list().optionalIndices().size());
for (int optIndex : expr.list().optionalIndices()) {
context.hasher.putInt(optIndex);
}
break;
case STRUCT:
context.hasher.putString(expr.struct().messageName(), UTF_8);
Expand Down Expand Up @@ -208,10 +209,13 @@ private static void hashConstant(CelConstant constant, HasherContext context) {

private static final class HasherContext {
final Hasher hasher;
final List<CelExpr> freeVars = new ArrayList<>();
final List<CelExpr> freeVars;
final Map<String, Integer> freeVarIndices;

HasherContext(HashFunction hashFunction) {
this.hasher = hashFunction.newHasher();
this.freeVars = new ArrayList<>();
this.freeVarIndices = new HashMap<>();
}
}

Expand Down
173 changes: 141 additions & 32 deletions verifier/src/main/java/dev/cel/verifier/CelAstToZ3Translator.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
Expand Down Expand Up @@ -88,7 +89,11 @@ final class CelAstToZ3Translator {
private final ImmutableSet<String> unknownIdentifiers;
private final int comprehensionUnrollLimit;
private final CelTypeProvider typeProvider;
private final List<BoolExpr> truncationConditions;
private final Set<BoolExpr> truncationConditions;
private final Set<SeqExpr<?>> boundedMapBijections;
private final Set<Expr<?>> appliedBijections;
private final Map<Long, TranslatedValue> pureExprCache;
private final Set<String> activeLoopVars;
private final Map<String, Expr<?>> emptyMessageCache;
private final Map<Object, Expr<?>> listLiteralCache;
private Expr<?> emptyListCache;
Expand All @@ -102,7 +107,7 @@ Set<BoolExpr> getTypeConstraints() {
}

BoolExpr hasTruncation() {
return CelZ3TypeSystem.mkOrFlattened(ctx, truncationConditions);
return CelZ3TypeSystem.mkOrFlattened(ctx, new ArrayList<>(truncationConditions));
}

CelZ3TypeSystem getTypeSystem() {
Expand Down Expand Up @@ -264,12 +269,14 @@ private TranslatedValue translateIdent(CelExpr celExpr, CelAbstractSyntaxTree as

return TranslatedValue.create(
v,
CelExpr.newBuilder().setIdent(ident).setId(exprId).build(),
Optional.of(CelExpr.newBuilder().setIdent(ident).setId(exprId).build()),
typeSystem,
/* isApproximate= */ ctx.mkFalse());
/* isApproximate= */ ctx.mkFalse(),
/* isLoopInvariant= */ true);
});

return TranslatedValue.create(tv.z3Expr(), celExpr, typeSystem, tv.isApproximate());
boolean isLoopInvariant = !activeLoopVars.contains(name) && tv.isLoopInvariant();
return TranslatedValue.create(tv.z3Expr(), Optional.of(celExpr), typeSystem, tv.isApproximate(), isLoopInvariant);
}

private TranslatedValue translateList(CelExpr celExpr, CelAbstractSyntaxTree ast) {
Expand All @@ -284,11 +291,23 @@ private TranslatedValue translateList(CelExpr celExpr, CelAbstractSyntaxTree ast
// check to a trivial identity check (e.g., `list_ref_0 == list_ref_0`).
if (listRef == null) {
SeqExpr seq = ctx.mkEmptySeq(ctx.mkSeqSort(typeSystem.celValueSort()));
for (CelExpr element : createList.elements()) {
ImmutableSet<Integer> optionalIndices = ImmutableSet.copyOf(createList.optionalIndices());
for (int i = 0; i < createList.elements().size(); i++) {
CelExpr element = createList.elements().get(i);
TranslatedValue elem = translateExpr(element, ast);
elementsTv.add(elem);

seq = typeSystem.mkConcatSafe(seq, ctx.mkUnit(elem.z3Expr()));
boolean isOptional = optionalIndices.contains(i);
OptionalUnwrap opt = unwrapOptional(elem.z3Expr(), isOptional);
SeqExpr optSeq =
isOptional
? (SeqExpr)
ctx.mkITE(
opt.isPresent,
ctx.mkUnit(opt.effectiveValue),
ctx.mkEmptySeq(ctx.mkSeqSort(typeSystem.celValueSort())))
: ctx.mkUnit(opt.effectiveValue);
seq = typeSystem.mkConcatSafe(seq, optSeq);
}
listRef = typeSystem.mkListRefConst(LIST_REF_PREFIX);
typeConstraints.add(ctx.mkEq(typeSystem.getSeq(listRef), seq));
Expand All @@ -297,7 +316,9 @@ private TranslatedValue translateList(CelExpr celExpr, CelAbstractSyntaxTree ast
}

Expr<?> result = typeSystem.wrapList(listRef);
return TranslatedValue.propagateStrict(ctx, typeSystem, result, celExpr, elementsTv);
BoolExpr baseTaint = ctx.mkFalse();
return TranslatedValue.propagateStrict(
ctx, typeSystem, result, Optional.of(celExpr), baseTaint, elementsTv);
}

private TranslatedValue translateMap(CelExpr celExpr, CelAbstractSyntaxTree ast) {
Expand All @@ -318,20 +339,31 @@ private TranslatedValue translateMap(CelExpr celExpr, CelAbstractSyntaxTree ast)
Expr<?> value = valueTv.z3Expr();
elementsTv.add(valueTv);

BoolExpr keyAlreadyPresent = (BoolExpr) ctx.mkSelect(mapPresence, key);
keysSeq =
ctx.mkITE(keyAlreadyPresent, keysSeq, typeSystem.mkConcatSafe(keysSeq, ctx.mkUnit(key)));
OptionalUnwrap opt = unwrapOptional(value, entryAst.optionalEntry());

mapValues = ctx.mkStore(mapValues, key, value);
mapPresence = ctx.mkStore(mapPresence, key, ctx.mkTrue());
BoolExpr keyAlreadyPresent = (BoolExpr) ctx.mkSelect(mapPresence, key);
BoolExpr shouldAddKey = ctx.mkAnd(opt.isPresent, ctx.mkNot(keyAlreadyPresent));

SeqExpr keyOptSeq =
(SeqExpr)
ctx.mkITE(
shouldAddKey,
ctx.mkUnit(key),
ctx.mkEmptySeq(ctx.mkSeqSort(typeSystem.celValueSort())));

keysSeq = typeSystem.mkConcatSafe(keysSeq, keyOptSeq);
mapValues = storeIf(opt.isPresent, mapValues, key, opt.effectiveValue);
mapPresence = storeIf(opt.isPresent, mapPresence, key, ctx.mkTrue());
}

typeConstraints.add(ctx.mkEq(typeSystem.getMapValues(mapRef), mapValues));
typeConstraints.add(ctx.mkEq(typeSystem.getMapPresence(mapRef), mapPresence));
typeConstraints.add(ctx.mkEq(typeSystem.getMapKeys(mapRef), keysSeq));

Expr<?> result = typeSystem.wrapMap(mapRef);
return TranslatedValue.propagateStrict(ctx, typeSystem, result, celExpr, elementsTv);
BoolExpr baseTaint = ctx.mkFalse();
return TranslatedValue.propagateStrict(
ctx, typeSystem, result, Optional.of(celExpr), baseTaint, elementsTv);
}

private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree ast) {
Expand Down Expand Up @@ -379,15 +411,15 @@ private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree a
// (`msg1 == msg2`) to work without using quantifiers (which avoids MBQI loops).
// Because proto3 singular primitives do not have field presence, we also skip setting
// `msgPresence`.
OptionalUnwrap opt = unwrapOptional(value, entryAst.optionalEntry());

BoolExpr shouldBypass =
fieldType.kind().isPrimitive() ? ctx.mkEq(value, defaultVal) : ctx.mkFalse();
fieldType.kind().isPrimitive() ? ctx.mkEq(opt.effectiveValue, defaultVal) : ctx.mkFalse();

msgValues =
(ArrayExpr) ctx.mkITE(shouldBypass, msgValues, ctx.mkStore(msgValues, key, value));
BoolExpr shouldStore = ctx.mkAnd(opt.isPresent, ctx.mkNot(shouldBypass));

msgPresence =
(ArrayExpr)
ctx.mkITE(shouldBypass, msgPresence, ctx.mkStore(msgPresence, key, ctx.mkTrue()));
msgValues = storeIf(shouldStore, msgValues, key, opt.effectiveValue);
msgPresence = storeIf(shouldStore, msgPresence, key, ctx.mkTrue());
}

typeConstraints.add(
Expand All @@ -396,7 +428,9 @@ private TranslatedValue translateStruct(CelExpr celExpr, CelAbstractSyntaxTree a
typeConstraints.add(ctx.mkEq(typeSystem.getMsgPresence(msgRef), msgPresence));

Expr<?> result = typeSystem.wrapMessage(msgRef);
return TranslatedValue.propagateStrict(ctx, typeSystem, result, celExpr, elementsTv);
BoolExpr baseTaint = ctx.mkFalse();
return TranslatedValue.propagateStrict(
ctx, typeSystem, result, Optional.of(celExpr), baseTaint, elementsTv);
}

private Expr<?> getDefaultValueForType(CelType type) {
Expand Down Expand Up @@ -472,6 +506,28 @@ private Expr<?> getDefaultValueForType(CelType type) {
return typeSystem.mkUnknown();
}

private static final class OptionalUnwrap {
final BoolExpr isPresent;
final Expr<?> effectiveValue;

OptionalUnwrap(BoolExpr isPresent, Expr<?> effectiveValue) {
this.isPresent = isPresent;
this.effectiveValue = effectiveValue;
}
}

private OptionalUnwrap unwrapOptional(Expr<?> value, boolean isOptional) {
if (!isOptional) {
return new OptionalUnwrap(ctx.mkTrue(), value);
}
Expr<?> optRef = typeSystem.getOptionalRef(value);
return new OptionalUnwrap(typeSystem.optHasValue(optRef), typeSystem.getOptionalValue(optRef));
}

private ArrayExpr storeIf(BoolExpr condition, ArrayExpr array, Expr<?> key, Expr<?> value) {
return (ArrayExpr) ctx.mkITE(condition, ctx.mkStore(array, key, value), array);
}

private static final class FieldAccess {
final Expr<?> presence;
final Expr<?> value;
Expand Down Expand Up @@ -657,24 +713,53 @@ private TranslatedValue translateComprehension(CelExpr celExpr, CelAbstractSynta
// For statically known list/map literals, unroll them exactly.
if (iterRangeExpr.exprKind().getKind() == ExprKind.Kind.LIST) {
ImmutableList<CelExpr> elements = iterRangeExpr.list().elements();
ImmutableList<Integer> optionalIndices = iterRangeExpr.list().optionalIndices();
for (int i = 0; i < elements.size(); i++) {
TranslatedValue valueTv = translateExpr(elements.get(i), ast);
Expr<?> value = valueTv.z3Expr();
taints.add(valueTv.isApproximate());
iterationElements.add(new IterationElement(typeSystem.mkInt(i), value));
allRangeElems.add(value);
boolean isOptional = optionalIndices.contains(i);
OptionalUnwrap opt = unwrapOptional(valueTv.z3Expr(), isOptional);
if (isOptional && ctx.mkFalse().equals(opt.isPresent)) {
continue;
}
taints.add(
isOptional
? CelZ3TypeSystem.mkAndFlattened(ctx, opt.isPresent, valueTv.isApproximate())
: valueTv.isApproximate());
iterationElements.add(
new IterationElement(
typeSystem.mkInt(i),
opt.effectiveValue,
isOptional ? Optional.of(opt.isPresent) : Optional.empty()));
allRangeElems.add(
isOptional
? ctx.mkITE(opt.isPresent, opt.effectiveValue, typeSystem.mkInt(0))
: opt.effectiveValue);
}
} else if (iterRangeExpr.exprKind().getKind() == ExprKind.Kind.MAP) {
for (CelExpr.CelMap.Entry entry : iterRangeExpr.map().entries()) {
TranslatedValue keyTv = translateExpr(entry.key(), ast);
Expr<?> key = keyTv.z3Expr();
taints.add(keyTv.isApproximate());
TranslatedValue valueTv = translateExpr(entry.value(), ast);
Expr<?> value = valueTv.z3Expr();
taints.add(valueTv.isApproximate());
iterationElements.add(new IterationElement(key, value));
boolean isOptional = entry.optionalEntry();
OptionalUnwrap opt = unwrapOptional(valueTv.z3Expr(), isOptional);
if (isOptional && ctx.mkFalse().equals(opt.isPresent)) {
continue;
}
taints.add(
isOptional
? CelZ3TypeSystem.mkAndFlattened(ctx, opt.isPresent, valueTv.isApproximate())
: valueTv.isApproximate());
iterationElements.add(
new IterationElement(
key,
opt.effectiveValue,
isOptional ? Optional.of(opt.isPresent) : Optional.empty()));
allRangeElems.add(key);
allRangeElems.add(value);
allRangeElems.add(
isOptional
? ctx.mkITE(opt.isPresent, opt.effectiveValue, typeSystem.mkInt(0))
: opt.effectiveValue);
}
} else {
return translateDynamicComprehension(celExpr, ast);
Expand All @@ -693,13 +778,23 @@ private TranslatedValue translateComprehension(CelExpr celExpr, CelAbstractSynta
comp, ast, iterElem.keyOrIndex, iterElem.value, currentAccu, isMap, isTwoVar);
Expr<?> condition = condAndStep[0].z3Expr();
Expr<?> step = condAndStep[1].z3Expr();
taints.add(condAndStep[1].isApproximate());
if (iterElem.hasValue.isPresent()) {
taints.add(
CelZ3TypeSystem.mkAndFlattened(
ctx, iterElem.hasValue.get(), condAndStep[1].isApproximate()));
} else {
taints.add(condAndStep[1].isApproximate());
}

Expr<?> stepVal = ctx.mkITE((BoolExpr) typeSystem.unwrapBool(condition), step, currentAccu);
Expr<?> typeErrorOrStep =
typeSystem.withRuntimeError(stepVal, ctx.mkNot(typeSystem.isBool(condition)));

accu = typeSystem.propagateErrorAndUnknown(typeErrorOrStep, condition);
Expr<?> updatedAccu = typeSystem.propagateErrorAndUnknown(typeErrorOrStep, condition);
accu =
iterElem.hasValue.isPresent()
? ctx.mkITE(iterElem.hasValue.get(), updatedAccu, currentAccu)
: updatedAccu;
}

TranslatedValue resultTv =
Expand Down Expand Up @@ -773,6 +868,9 @@ private TranslatedValue translateDynamicComprehension(

private void applyBoundedMapBijection(
ArrayExpr mapPresence, SeqExpr<?> seq, ArithExpr lengthExpr) {
if (!boundedMapBijections.add(seq)) {
return;
}
for (int i = 0; i < comprehensionUnrollLimit; i++) {
for (int j = i + 1; j < comprehensionUnrollLimit; j++) {
BoolExpr validPair = ctx.mkLt(ctx.mkInt(j), lengthExpr);
Expand Down Expand Up @@ -1223,16 +1321,26 @@ private BoolExpr createTypeConstraintForType(Expr<?> val, CelType type) {
this.emptyMessageCache = new HashMap<>();
this.listLiteralCache = new HashMap<>();
this.typeProvider = typeProvider;
this.truncationConditions = new ArrayList<>();
this.truncationConditions = new LinkedHashSet<>();
this.boundedMapBijections = new LinkedHashSet<>();
this.appliedBijections = new HashSet<>();
this.pureExprCache = new HashMap<>();
this.activeLoopVars = new LinkedHashSet<>();
}

private static class IterationElement {
final Expr<?> keyOrIndex;
final Expr<?> value;
final Optional<BoolExpr> hasValue;

IterationElement(Expr<?> keyOrIndex, Expr<?> value) {
this(keyOrIndex, value, Optional.empty());
}

IterationElement(Expr<?> keyOrIndex, Expr<?> value, Optional<BoolExpr> hasValue) {
this.keyOrIndex = keyOrIndex;
this.value = value;
this.hasValue = hasValue;
}
}

Expand All @@ -1249,6 +1357,7 @@ private Optional<Object> toCacheKey(CelExpr expr) {
}
builder.add(elemKey.get());
}
builder.add(expr.list().optionalIndices());
return Optional.of(builder.build());
default:
return Optional.empty();
Expand Down
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