yq/pkg/yqlib/operator_slice.go
Jan Dubois 1b549962b2 Fix panic on negative slice indices that underflow after adjustment
sliceArrayOperator adjusts negative indices by adding Content length,
but does not clamp the result. When the absolute value of a negative
index exceeds Content length (e.g. .[-99999:3] on a 3-element array),
the adjusted index remains negative and causes an out-of-bounds access
in the Content slice loop.

Extract the adjust-and-clamp logic into clampSliceIndex and use it for
both index positions.

Reproducer (panics before this fix, returns full array after):

    echo '[a, b, c]' | yq '.[-99999:3]'

Found by OSS-Fuzz via the lima project's FuzzEvaluateExpression target.
https://issues.oss-fuzz.com/issues/438776028

Signed-off-by: Jan Dubois <jan@jandubois.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-05 22:35:04 -07:00

75 lines
2.2 KiB
Go

package yqlib
import (
"container/list"
"fmt"
)
func getSliceNumber(d *dataTreeNavigator, context Context, node *CandidateNode, expressionNode *ExpressionNode) (int, error) {
result, err := d.GetMatchingNodes(context.SingleChildContext(node), expressionNode)
if err != nil {
return 0, err
}
if result.MatchingNodes.Len() != 1 {
return 0, fmt.Errorf("expected to find 1 number, got %v instead", result.MatchingNodes.Len())
}
return parseInt(result.MatchingNodes.Front().Value.(*CandidateNode).Value)
}
// clampSliceIndex resolves a possibly-negative slice index against
// length and clamps the result to [0, length].
func clampSliceIndex(index, length int) int {
if index < 0 {
index += length
}
if index < 0 {
return 0
}
if index > length {
return length
}
return index
}
func sliceArrayOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
log.Debug("slice array operator!")
log.Debugf("lhs: %v", expressionNode.LHS.Operation.toString())
log.Debugf("rhs: %v", expressionNode.RHS.Operation.toString())
results := list.New()
for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
lhsNode := el.Value.(*CandidateNode)
firstNumber, err := getSliceNumber(d, context, lhsNode, expressionNode.LHS)
if err != nil {
return Context{}, err
}
relativeFirstNumber := clampSliceIndex(firstNumber, len(lhsNode.Content))
secondNumber, err := getSliceNumber(d, context, lhsNode, expressionNode.RHS)
if err != nil {
return Context{}, err
}
relativeSecondNumber := clampSliceIndex(secondNumber, len(lhsNode.Content))
log.Debugf("calculateIndicesToTraverse: slice from %v to %v", relativeFirstNumber, relativeSecondNumber)
var newResults []*CandidateNode
for i := relativeFirstNumber; i < relativeSecondNumber; i++ {
newResults = append(newResults, lhsNode.Content[i])
}
sliceArrayNode := lhsNode.CreateReplacement(SequenceNode, lhsNode.Tag, "")
sliceArrayNode.AddChildren(newResults)
results.PushBack(sliceArrayNode)
}
// result is now the context that has the nodes we need to put back into a sequence.
//what about multiple arrays in the context? I think we need to create an array for each one
return context.ChildContext(results), nil
}