diff options
Diffstat (limited to 'vendor/github.com/authzed/cel-go/interpreter/runtimecost.go')
| -rw-r--r-- | vendor/github.com/authzed/cel-go/interpreter/runtimecost.go | 316 |
1 files changed, 316 insertions, 0 deletions
diff --git a/vendor/github.com/authzed/cel-go/interpreter/runtimecost.go b/vendor/github.com/authzed/cel-go/interpreter/runtimecost.go new file mode 100644 index 0000000..905aeea --- /dev/null +++ b/vendor/github.com/authzed/cel-go/interpreter/runtimecost.go @@ -0,0 +1,316 @@ +// Copyright 2022 Google LLC +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package interpreter + +import ( + "math" + + "github.com/authzed/cel-go/common" + "github.com/authzed/cel-go/common/overloads" + "github.com/authzed/cel-go/common/types" + "github.com/authzed/cel-go/common/types/ref" + "github.com/authzed/cel-go/common/types/traits" +) + +// WARNING: Any changes to cost calculations in this file require a corresponding change in checker/cost.go + +// ActualCostEstimator provides function call cost estimations at runtime +// CallCost returns an estimated cost for the function overload invocation with the given args, or nil if it has no +// estimate to provide. CEL attempts to provide reasonable estimates for its standard function library, so CallCost +// should typically not need to provide an estimate for CELs standard function. +type ActualCostEstimator interface { + CallCost(function, overloadID string, args []ref.Val, result ref.Val) *uint64 +} + +// CostObserver provides an observer that tracks runtime cost. +func CostObserver(tracker *CostTracker) EvalObserver { + observer := func(id int64, programStep any, val ref.Val) { + switch t := programStep.(type) { + case ConstantQualifier: + // TODO: Push identifiers on to the stack before observing constant qualifiers that apply to them + // and enable the below pop. Once enabled this can case can be collapsed into the Qualifier case. + tracker.cost++ + case InterpretableConst: + // zero cost + case InterpretableAttribute: + switch a := t.Attr().(type) { + case *conditionalAttribute: + // Ternary has no direct cost. All cost is from the conditional and the true/false branch expressions. + tracker.stack.drop(a.falsy.ID(), a.truthy.ID(), a.expr.ID()) + default: + tracker.stack.drop(t.Attr().ID()) + tracker.cost += common.SelectAndIdentCost + } + if !tracker.presenceTestHasCost { + if _, isTestOnly := programStep.(*evalTestOnly); isTestOnly { + tracker.cost -= common.SelectAndIdentCost + } + } + case *evalExhaustiveConditional: + // Ternary has no direct cost. All cost is from the conditional and the true/false branch expressions. + tracker.stack.drop(t.attr.falsy.ID(), t.attr.truthy.ID(), t.attr.expr.ID()) + + // While the field names are identical, the boolean operation eval structs do not share an interface and so + // must be handled individually. + case *evalOr: + for _, term := range t.terms { + tracker.stack.drop(term.ID()) + } + case *evalAnd: + for _, term := range t.terms { + tracker.stack.drop(term.ID()) + } + case *evalExhaustiveOr: + for _, term := range t.terms { + tracker.stack.drop(term.ID()) + } + case *evalExhaustiveAnd: + for _, term := range t.terms { + tracker.stack.drop(term.ID()) + } + case *evalFold: + tracker.stack.drop(t.iterRange.ID()) + case Qualifier: + tracker.cost++ + case InterpretableCall: + if argVals, ok := tracker.stack.dropArgs(t.Args()); ok { + tracker.cost += tracker.costCall(t, argVals, val) + } + case InterpretableConstructor: + tracker.stack.dropArgs(t.InitVals()) + switch t.Type() { + case types.ListType: + tracker.cost += common.ListCreateBaseCost + case types.MapType: + tracker.cost += common.MapCreateBaseCost + default: + tracker.cost += common.StructCreateBaseCost + } + } + tracker.stack.push(val, id) + + if tracker.Limit != nil && tracker.cost > *tracker.Limit { + panic(EvalCancelledError{Cause: CostLimitExceeded, Message: "operation cancelled: actual cost limit exceeded"}) + } + } + return observer +} + +// CostTrackerOption configures the behavior of CostTracker objects. +type CostTrackerOption func(*CostTracker) error + +// CostTrackerLimit sets the runtime limit on the evaluation cost during execution and will terminate the expression +// evaluation if the limit is exceeded. +func CostTrackerLimit(limit uint64) CostTrackerOption { + return func(tracker *CostTracker) error { + tracker.Limit = &limit + return nil + } +} + +// PresenceTestHasCost determines whether presence testing has a cost of one or zero. +// Defaults to presence test has a cost of one. +func PresenceTestHasCost(hasCost bool) CostTrackerOption { + return func(tracker *CostTracker) error { + tracker.presenceTestHasCost = hasCost + return nil + } +} + +// NewCostTracker creates a new CostTracker with a given estimator and a set of functional CostTrackerOption values. +func NewCostTracker(estimator ActualCostEstimator, opts ...CostTrackerOption) (*CostTracker, error) { + tracker := &CostTracker{ + Estimator: estimator, + overloadTrackers: map[string]FunctionTracker{}, + presenceTestHasCost: true, + } + for _, opt := range opts { + err := opt(tracker) + if err != nil { + return nil, err + } + } + return tracker, nil +} + +// OverloadCostTracker binds an overload ID to a runtime FunctionTracker implementation. +// +// OverloadCostTracker instances augment or override ActualCostEstimator decisions, allowing for versioned and/or +// optional cost tracking changes. +func OverloadCostTracker(overloadID string, fnTracker FunctionTracker) CostTrackerOption { + return func(tracker *CostTracker) error { + tracker.overloadTrackers[overloadID] = fnTracker + return nil + } +} + +// FunctionTracker computes the actual cost of evaluating the functions with the given arguments and result. +type FunctionTracker func(args []ref.Val, result ref.Val) *uint64 + +// CostTracker represents the information needed for tracking runtime cost. +type CostTracker struct { + Estimator ActualCostEstimator + overloadTrackers map[string]FunctionTracker + Limit *uint64 + presenceTestHasCost bool + + cost uint64 + stack refValStack +} + +// ActualCost returns the runtime cost +func (c *CostTracker) ActualCost() uint64 { + return c.cost +} + +func (c *CostTracker) costCall(call InterpretableCall, args []ref.Val, result ref.Val) uint64 { + var cost uint64 + if len(c.overloadTrackers) != 0 { + if tracker, found := c.overloadTrackers[call.OverloadID()]; found { + callCost := tracker(args, result) + if callCost != nil { + cost += *callCost + return cost + } + } + } + if c.Estimator != nil { + callCost := c.Estimator.CallCost(call.Function(), call.OverloadID(), args, result) + if callCost != nil { + cost += *callCost + return cost + } + } + // if user didn't specify, the default way of calculating runtime cost would be used. + // if user has their own implementation of ActualCostEstimator, make sure to cover the mapping between overloadId and cost calculation + switch call.OverloadID() { + // O(n) functions + case overloads.StartsWithString, overloads.EndsWithString, overloads.StringToBytes, overloads.BytesToString, overloads.ExtQuoteString, overloads.ExtFormatString: + cost += uint64(math.Ceil(float64(c.actualSize(args[0])) * common.StringTraversalCostFactor)) + case overloads.InList: + // If a list is composed entirely of constant values this is O(1), but we don't account for that here. + // We just assume all list containment checks are O(n). + cost += c.actualSize(args[1]) + // O(min(m, n)) functions + case overloads.LessString, overloads.GreaterString, overloads.LessEqualsString, overloads.GreaterEqualsString, + overloads.LessBytes, overloads.GreaterBytes, overloads.LessEqualsBytes, overloads.GreaterEqualsBytes, + overloads.Equals, overloads.NotEquals: + // When we check the equality of 2 scalar values (e.g. 2 integers, 2 floating-point numbers, 2 booleans etc.), + // the CostTracker.actualSize() function by definition returns 1 for each operand, resulting in an overall cost + // of 1. + lhsSize := c.actualSize(args[0]) + rhsSize := c.actualSize(args[1]) + minSize := lhsSize + if rhsSize < minSize { + minSize = rhsSize + } + cost += uint64(math.Ceil(float64(minSize) * common.StringTraversalCostFactor)) + // O(m+n) functions + case overloads.AddString, overloads.AddBytes: + // In the worst case scenario, we would need to reallocate a new backing store and copy both operands over. + cost += uint64(math.Ceil(float64(c.actualSize(args[0])+c.actualSize(args[1])) * common.StringTraversalCostFactor)) + // O(nm) functions + case overloads.MatchesString: + // https://swtch.com/~rsc/regexp/regexp1.html applies to RE2 implementation supported by CEL + // Add one to string length for purposes of cost calculation to prevent product of string and regex to be 0 + // in case where string is empty but regex is still expensive. + strCost := uint64(math.Ceil((1.0 + float64(c.actualSize(args[0]))) * common.StringTraversalCostFactor)) + // We don't know how many expressions are in the regex, just the string length (a huge + // improvement here would be to somehow get a count the number of expressions in the regex or + // how many states are in the regex state machine and use that to measure regex cost). + // For now, we're making a guess that each expression in a regex is typically at least 4 chars + // in length. + regexCost := uint64(math.Ceil(float64(c.actualSize(args[1])) * common.RegexStringLengthCostFactor)) + cost += strCost * regexCost + case overloads.ContainsString: + strCost := uint64(math.Ceil(float64(c.actualSize(args[0])) * common.StringTraversalCostFactor)) + substrCost := uint64(math.Ceil(float64(c.actualSize(args[1])) * common.StringTraversalCostFactor)) + cost += strCost * substrCost + + default: + // The following operations are assumed to have O(1) complexity. + // - AddList due to the implementation. Index lookup can be O(c) the + // number of concatenated lists, but we don't track that is cost calculations. + // - Conversions, since none perform a traversal of a type of unbound length. + // - Computing the size of strings, byte sequences, lists and maps. + // - Logical operations and all operators on fixed width scalars (comparisons, equality) + // - Any functions that don't have a declared cost either here or in provided ActualCostEstimator. + cost++ + + } + return cost +} + +// actualSize returns the size of value +func (c *CostTracker) actualSize(value ref.Val) uint64 { + if sz, ok := value.(traits.Sizer); ok { + return uint64(sz.Size().(types.Int)) + } + return 1 +} + +type stackVal struct { + Val ref.Val + ID int64 +} + +// refValStack keeps track of values of the stack for cost calculation purposes +type refValStack []stackVal + +func (s *refValStack) push(val ref.Val, id int64) { + value := stackVal{Val: val, ID: id} + *s = append(*s, value) +} + +// TODO: Allowing drop and dropArgs to remove stack items above the IDs they are provided is a workaround. drop and dropArgs +// should find and remove only the stack items matching the provided IDs once all attributes are properly pushed and popped from stack. + +// drop searches the stack for each ID and removes the ID and all stack items above it. +// If none of the IDs are found, the stack is not modified. +// WARNING: It is possible for multiple expressions with the same ID to exist (due to how macros are implemented) so it's +// possible that a dropped ID will remain on the stack. They should be removed when IDs on the stack are popped. +func (s *refValStack) drop(ids ...int64) { + for _, id := range ids { + for idx := len(*s) - 1; idx >= 0; idx-- { + if (*s)[idx].ID == id { + *s = (*s)[:idx] + break + } + } + } +} + +// dropArgs searches the stack for all the args by their IDs, accumulates their associated ref.Vals and drops any +// stack items above any of the arg IDs. If any of the IDs are not found the stack, false is returned. +// Args are assumed to be found in the stack in reverse order, i.e. the last arg is expected to be found highest in +// the stack. +// WARNING: It is possible for multiple expressions with the same ID to exist (due to how macros are implemented) so it's +// possible that a dropped ID will remain on the stack. They should be removed when IDs on the stack are popped. +func (s *refValStack) dropArgs(args []Interpretable) ([]ref.Val, bool) { + result := make([]ref.Val, len(args)) +argloop: + for nIdx := len(args) - 1; nIdx >= 0; nIdx-- { + for idx := len(*s) - 1; idx >= 0; idx-- { + if (*s)[idx].ID == args[nIdx].ID() { + el := (*s)[idx] + *s = (*s)[:idx] + result[nIdx] = el.Val + continue argloop + } + } + return nil, false + } + return result, true +} |