vulncheck/witness.go - vuln - Git at Google

 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package vulncheck

 import (
 	"container/list"
 	"fmt"
 	"go/token"
 	"sort"
 	"strings"
 	"sync"
 )

 // ImportChain is a slice of packages where each
 // subsequent package is imported by its immediate
 // predecessor. The chain starts with a client package
 // and ends in a package with some known vulnerabilities.
 type ImportChain []*PkgNode

 // ImportChains returns a slice of representative import chains for
 // each vulnerability in res. The returned chains are ordered
 // increasingly by their length.
 //
 // ImportChains performs a breadth-first search of res.RequireGraph starting
 // at a vulnerable package and going up until reaching an entry package
 // in res.ImportGraph.Entries. During this search, a package is visited
 // only once to avoid analyzing every possible import chain. Hence, not
 // all import chains are analyzed.
 //
 // Note that vulnerabilities from the same package will have the same
 // slice of identified import chains.
 func ImportChains(res *Result) map[*Vuln][]ImportChain {
 	// Group vulns per package.
 	vPerPkg := make(map[int][]*Vuln)
 	for _, v := range res.Vulns {
 		vPerPkg[v.ImportSink] = append(vPerPkg[v.ImportSink], v)
 	}

 	// Collect chains in parallel for every package path.
 	var wg sync.WaitGroup
 	var mu sync.Mutex
 	chains := make(map[*Vuln][]ImportChain)
 	for pkgID, vulns := range vPerPkg {
 		pID := pkgID
 		vs := vulns
 		wg.Add(1)
 		go func() {
 			pChains := importChains(pID, res)
 			mu.Lock()
 			for _, v := range vs {
 				chains[v] = pChains
 			}
 			mu.Unlock()
 			wg.Done()
 		}()
 	}
 	wg.Wait()
 	return chains
 }

 // importChains finds representative chains of package imports
 // leading to vulnerable package identified with vulnSinkID.
 func importChains(vulnSinkID int, res *Result) []ImportChain {
 	if vulnSinkID == 0 {
 		return nil
 	}

 	// Entry packages, needed for finalizing chains.
 	entries := make(map[int]bool)
 	for _, e := range res.Imports.Entries {
 		entries[e] = true
 	}

 	var chains []ImportChain
 	seen := make(map[int]bool)

 	queue := list.New()
 	queue.PushBack(&importChain{pkg: res.Imports.Packages[vulnSinkID]})
 	for queue.Len() > 0 {
 		front := queue.Front()
 		c := front.Value.(*importChain)
 		queue.Remove(front)

 		pkg := c.pkg
 		if seen[pkg.ID] {
 			continue
 		}
 		seen[pkg.ID] = true

 		for _, impBy := range pkg.ImportedBy {
 			imp := res.Imports.Packages[impBy]
 			newC := &importChain{pkg: imp, child: c}
 			// If the next package is an entry, we have
 			// a chain to report.
 			if entries[imp.ID] {
 				chains = append(chains, newC.ImportChain())
 			}
 			queue.PushBack(newC)
 		}
 	}
 	return chains
 }

 // importChain models an chain of package imports.
 type importChain struct {
 	pkg   *PkgNode
 	child *importChain
 }

 // ImportChain converts importChain to ImportChain type.
 func (r *importChain) ImportChain() ImportChain {
 	if r == nil {
 		return nil
 	}
 	return append([]*PkgNode{r.pkg}, r.child.ImportChain()...)
 }

 // CallStack is a call stack starting with a client
 // function or method and ending with a call to a
 // vulnerable symbol.
 type CallStack []StackEntry

 // StackEntry is an element of a call stack.
 type StackEntry struct {
 	// Function whose frame is on the stack.
 	Function *FuncNode

 	// Call is the call site inducing the stack frame.
 	// nil when the frame represents the stack entry point.
 	Call *CallSite
 }

 // CallStacks returns representative call stacks for each
 // vulnerability in res. The returned call stacks are heuristically
 // ordered by how seemingly easy is to understand them: shorter
 // call stacks with less dynamic call sites appear earlier in the
 // returned slices.
 //
 // CallStacks performs a breadth-first search of res.CallGraph starting
 // at the vulnerable symbol and going up until reaching an entry
 // function or method in res.CallGraph.Entries. During this search,
 // each function is visited at most once to avoid potential
 // exponential explosion. Hence, not all call stacks are analyzed.
 func CallStacks(res *Result) map[*Vuln][]CallStack {
 	var (
 		wg sync.WaitGroup
 		mu sync.Mutex
 	)
 	stacksPerVuln := make(map[*Vuln][]CallStack)
 	for _, vuln := range res.Vulns {
 		vuln := vuln
 		wg.Add(1)
 		go func() {
 			cs := callStacks(vuln.CallSink, res)
 			// sort call stacks by the estimated value to the user
 			sort.SliceStable(cs, func(i int, j int) bool { return stackLess(cs[i], cs[j]) })
 			mu.Lock()
 			stacksPerVuln[vuln] = cs
 			mu.Unlock()
 			wg.Done()
 		}()
 	}

 	wg.Wait()
 	return stacksPerVuln
 }

 // callStacks finds representative call stacks
 // for vulnerable symbol identified with vulnSinkID.
 func callStacks(vulnSinkID int, res *Result) []CallStack {
 	if vulnSinkID == 0 {
 		return nil
 	}

 	entries := make(map[int]bool)
 	for _, e := range res.Calls.Entries {
 		entries[e] = true
 	}

 	var stacks []CallStack
 	seen := make(map[int]bool)

 	queue := list.New()
 	queue.PushBack(&callChain{f: res.Calls.Functions[vulnSinkID]})

 	for queue.Len() > 0 {
 		front := queue.Front()
 		c := front.Value.(*callChain)
 		queue.Remove(front)

 		f := c.f
 		if seen[f.ID] {
 			continue
 		}
 		seen[f.ID] = true

 		// Pick a single call site for each function in determinstic order.
 		// A single call site is sufficient as we visit a function only once.
 		for _, cs := range callsites(f.CallSites, res, seen) {
 			callee := res.Calls.Functions[cs.Parent]
 			nStack := &callChain{f: callee, call: cs, child: c}
 			if entries[callee.ID] {
 				stacks = append(stacks, nStack.CallStack())
 			}
 			queue.PushBack(nStack)
 		}
 	}
 	return stacks
 }

 // callsites picks a call site from sites for each non-visited function.
 // For each such function, the smallest (posLess) call site is chosen. The
 // returned slice is sorted by caller functions (funcLess). Assumes callee
 // of each call site is the same.
 func callsites(sites []*CallSite, result *Result, visited map[int]bool) []*CallSite {
 	minCs := make(map[int]*CallSite)
 	for _, cs := range sites {
 		if visited[cs.Parent] {
 			continue
 		}
 		if csLess(cs, minCs[cs.Parent]) {
 			minCs[cs.Parent] = cs
 		}
 	}

 	var fs []*FuncNode
 	for id := range minCs {
 		fs = append(fs, result.Calls.Functions[id])
 	}
 	sort.SliceStable(fs, func(i, j int) bool { return funcLess(fs[i], fs[j]) })

 	var css []*CallSite
 	for _, f := range fs {
 		css = append(css, minCs[f.ID])
 	}
 	return css
 }

 // callChain models a chain of function calls.
 type callChain struct {
 	call  *CallSite // nil for entry points
 	f     *FuncNode
 	child *callChain
 }

 // CallStack converts callChain to CallStack type.
 func (c *callChain) CallStack() CallStack {
 	if c == nil {
 		return nil
 	}
 	return append(CallStack{StackEntry{Function: c.f, Call: c.call}}, c.child.CallStack()...)
 }

 // weight computes an approximate measure of how easy is to understand the call
 // stack when presented to the client as a witness. The smaller the value, the more
 // understandable the stack is. Currently defined as the number of unresolved
 // call sites in the stack.
 func weight(stack CallStack) int {
 	w := 0
 	for _, e := range stack {
 		if e.Call != nil && !e.Call.Resolved {
 			w += 1
 		}
 	}
 	return w
 }

 func isStdPackage(pkg string) bool {
 	if pkg == "" {
 		return false
 	}
 	// std packages do not have a "." in their path. For instance, see
 	// Contains in pkgsite/+/refs/heads/master/internal/stdlbib/stdlib.go.
 	if i := strings.IndexByte(pkg, '/'); i != -1 {
 		pkg = pkg[:i]
 	}
 	return !strings.Contains(pkg, ".")
 }

 // confidence computes an approximate measure of whether the stack
 // is realizeable in practice. Currently, it equals the number of call
 // sites in stack that go through standard libraries. Such call stacks
 // have been experimentally shown to often result in false positives.
 func confidence(stack CallStack) int {
 	c := 0
 	for _, e := range stack {
 		if isStdPackage(e.Function.PkgPath) {
 			c += 1
 		}
 	}
 	return c
 }

 // stackLess compares two call stacks in terms of their estimated
 // value to the user. Shorter stacks generally come earlier in the ordering.
 //
 // Two stacks are lexicographically ordered by:
 // 1) their estimated level of confidence in being a real call stack,
 // 2) their length, and 3) the number of dynamic call sites in the stack.
 func stackLess(s1, s2 CallStack) bool {
 	if c1, c2 := confidence(s1), confidence(s2); c1 != c2 {
 		return c1 < c2
 	}

 	if len(s1) != len(s2) {
 		return len(s1) < len(s2)
 	}

 	if w1, w2 := weight(s1), weight(s2); w1 != w2 {
 		return w1 < w2
 	}

 	// At this point, the stableness/determinism of
 	// sorting is guaranteed by the determinism of
 	// the underlying call graph and the call stack
 	// search algorithm.
 	return true
 }

 // csLess compares two call sites by their locations and, if needed,
 // their string representation.
 func csLess(cs1, cs2 *CallSite) bool {
 	if cs2 == nil {
 		return true
 	}

 	// fast code path
 	if p1, p2 := cs1.Pos, cs2.Pos; p1 != nil && p2 != nil {
 		if posLess(*p1, *p2) {
 			return true
 		}
 		if posLess(*p2, *p1) {
 			return false
 		}
 		// for sanity, should not occur in practice
 		return fmt.Sprintf("%v.%v", cs1.RecvType, cs2.Name) < fmt.Sprintf("%v.%v", cs2.RecvType, cs2.Name)
 	}

 	// code path rarely exercised
 	if cs2.Pos == nil {
 		return true
 	}
 	if cs1.Pos == nil {
 		return false
 	}
 	// should very rarely occur in practice
 	return fmt.Sprintf("%v.%v", cs1.RecvType, cs2.Name) < fmt.Sprintf("%v.%v", cs2.RecvType, cs2.Name)
 }

 // posLess compares two positions by their line and column number,
 // and filename if needed.
 func posLess(p1, p2 token.Position) bool {
 	if p1.Line < p2.Line {
 		return true
 	}
 	if p2.Line < p1.Line {
 		return false
 	}

 	if p1.Column < p2.Column {
 		return true
 	}
 	if p2.Column < p1.Column {
 		return false
 	}

 	return strings.Compare(p1.Filename, p2.Filename) == -1
 }

 // funcLess compares two function nodes by locations of
 // corresponding functions and, if needed, their string representation.
 func funcLess(f1, f2 *FuncNode) bool {
 	if p1, p2 := f1.Pos, f2.Pos; p1 != nil && p2 != nil {
 		if posLess(*p1, *p2) {
 			return true
 		}
 		if posLess(*p2, *p1) {
 			return false
 		}
 		// for sanity, should not occur in practice
 		return f1.String() < f2.String()
 	}

 	if f2.Pos == nil {
 		return true
 	}
 	if f1.Pos == nil {
 		return false
 	}
 	// should happen only for inits
 	return f1.String() < f2.String()
 }
	// Copyright 2021 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package vulncheck

	import (
	"container/list"
	"fmt"
	"go/token"
	"sort"
	"strings"
	"sync"
	)

	// ImportChain is a slice of packages where each
	// subsequent package is imported by its immediate
	// predecessor. The chain starts with a client package
	// and ends in a package with some known vulnerabilities.
	type ImportChain []*PkgNode

	// ImportChains returns a slice of representative import chains for
	// each vulnerability in res. The returned chains are ordered
	// increasingly by their length.
	//
	// ImportChains performs a breadth-first search of res.RequireGraph starting
	// at a vulnerable package and going up until reaching an entry package
	// in res.ImportGraph.Entries. During this search, a package is visited
	// only once to avoid analyzing every possible import chain. Hence, not
	// all import chains are analyzed.
	//
	// Note that vulnerabilities from the same package will have the same
	// slice of identified import chains.
	func ImportChains(res Result) map[Vuln][]ImportChain {
	// Group vulns per package.
	vPerPkg := make(map[int][]*Vuln)
	for _, v := range res.Vulns {
	vPerPkg[v.ImportSink] = append(vPerPkg[v.ImportSink], v)
	}

	// Collect chains in parallel for every package path.
	var wg sync.WaitGroup
	var mu sync.Mutex
	chains := make(map[*Vuln][]ImportChain)
	for pkgID, vulns := range vPerPkg {
	pID := pkgID
	vs := vulns
	wg.Add(1)
	go func() {
	pChains := importChains(pID, res)
	mu.Lock()
	for _, v := range vs {
	chains[v] = pChains
	}
	mu.Unlock()
	wg.Done()
	}()
	}
	wg.Wait()
	return chains
	}

	// importChains finds representative chains of package imports
	// leading to vulnerable package identified with vulnSinkID.
	func importChains(vulnSinkID int, res *Result) []ImportChain {
	if vulnSinkID == 0 {
	return nil
	}

	// Entry packages, needed for finalizing chains.
	entries := make(map[int]bool)
	for _, e := range res.Imports.Entries {
	entries[e] = true
	}

	var chains []ImportChain
	seen := make(map[int]bool)

	queue := list.New()
	queue.PushBack(&importChain{pkg: res.Imports.Packages[vulnSinkID]})
	for queue.Len() > 0 {
	front := queue.Front()
	c := front.Value.(*importChain)
	queue.Remove(front)

	pkg := c.pkg
	if seen[pkg.ID] {
	continue
	}
	seen[pkg.ID] = true

	for _, impBy := range pkg.ImportedBy {
	imp := res.Imports.Packages[impBy]
	newC := &importChain{pkg: imp, child: c}
	// If the next package is an entry, we have
	// a chain to report.
	if entries[imp.ID] {
	chains = append(chains, newC.ImportChain())
	}
	queue.PushBack(newC)
	}
	}
	return chains
	}

	// importChain models an chain of package imports.
	type importChain struct {
	pkg *PkgNode
	child *importChain
	}

	// ImportChain converts importChain to ImportChain type.
	func (r *importChain) ImportChain() ImportChain {
	if r == nil {
	return nil
	}
	return append([]*PkgNode{r.pkg}, r.child.ImportChain()...)
	}

	// CallStack is a call stack starting with a client
	// function or method and ending with a call to a
	// vulnerable symbol.
	type CallStack []StackEntry

	// StackEntry is an element of a call stack.
	type StackEntry struct {
	// Function whose frame is on the stack.
	Function *FuncNode

	// Call is the call site inducing the stack frame.
	// nil when the frame represents the stack entry point.
	Call *CallSite
	}

	// CallStacks returns representative call stacks for each
	// vulnerability in res. The returned call stacks are heuristically
	// ordered by how seemingly easy is to understand them: shorter
	// call stacks with less dynamic call sites appear earlier in the
	// returned slices.
	//
	// CallStacks performs a breadth-first search of res.CallGraph starting
	// at the vulnerable symbol and going up until reaching an entry
	// function or method in res.CallGraph.Entries. During this search,
	// each function is visited at most once to avoid potential
	// exponential explosion. Hence, not all call stacks are analyzed.
	func CallStacks(res Result) map[Vuln][]CallStack {
	var (
	wg sync.WaitGroup
	mu sync.Mutex
	)
	stacksPerVuln := make(map[*Vuln][]CallStack)
	for _, vuln := range res.Vulns {
	vuln := vuln
	wg.Add(1)
	go func() {
	cs := callStacks(vuln.CallSink, res)
	// sort call stacks by the estimated value to the user
	sort.SliceStable(cs, func(i int, j int) bool { return stackLess(cs[i], cs[j]) })
	mu.Lock()
	stacksPerVuln[vuln] = cs
	mu.Unlock()
	wg.Done()
	}()
	}

	wg.Wait()
	return stacksPerVuln
	}

	// callStacks finds representative call stacks
	// for vulnerable symbol identified with vulnSinkID.
	func callStacks(vulnSinkID int, res *Result) []CallStack {
	if vulnSinkID == 0 {
	return nil
	}

	entries := make(map[int]bool)
	for _, e := range res.Calls.Entries {
	entries[e] = true
	}

	var stacks []CallStack
	seen := make(map[int]bool)

	queue := list.New()
	queue.PushBack(&callChain{f: res.Calls.Functions[vulnSinkID]})

	for queue.Len() > 0 {
	front := queue.Front()
	c := front.Value.(*callChain)
	queue.Remove(front)

	f := c.f
	if seen[f.ID] {
	continue
	}
	seen[f.ID] = true

	// Pick a single call site for each function in determinstic order.
	// A single call site is sufficient as we visit a function only once.
	for _, cs := range callsites(f.CallSites, res, seen) {
	callee := res.Calls.Functions[cs.Parent]
	nStack := &callChain{f: callee, call: cs, child: c}
	if entries[callee.ID] {
	stacks = append(stacks, nStack.CallStack())
	}
	queue.PushBack(nStack)
	}
	}
	return stacks
	}

	// callsites picks a call site from sites for each non-visited function.
	// For each such function, the smallest (posLess) call site is chosen. The
	// returned slice is sorted by caller functions (funcLess). Assumes callee
	// of each call site is the same.
	func callsites(sites []CallSite, result Result, visited map[int]bool) []*CallSite {
	minCs := make(map[int]*CallSite)
	for _, cs := range sites {
	if visited[cs.Parent] {
	continue
	}
	if csLess(cs, minCs[cs.Parent]) {
	minCs[cs.Parent] = cs
	}
	}

	var fs []*FuncNode
	for id := range minCs {
	fs = append(fs, result.Calls.Functions[id])
	}
	sort.SliceStable(fs, func(i, j int) bool { return funcLess(fs[i], fs[j]) })

	var css []*CallSite
	for _, f := range fs {
	css = append(css, minCs[f.ID])
	}
	return css
	}

	// callChain models a chain of function calls.
	type callChain struct {
	call *CallSite // nil for entry points
	f *FuncNode
	child *callChain
	}

	// CallStack converts callChain to CallStack type.
	func (c *callChain) CallStack() CallStack {
	if c == nil {
	return nil
	}
	return append(CallStack{StackEntry{Function: c.f, Call: c.call}}, c.child.CallStack()...)
	}

	// weight computes an approximate measure of how easy is to understand the call
	// stack when presented to the client as a witness. The smaller the value, the more
	// understandable the stack is. Currently defined as the number of unresolved
	// call sites in the stack.
	func weight(stack CallStack) int {
	w := 0
	for _, e := range stack {
	if e.Call != nil && !e.Call.Resolved {
	w += 1
	}
	}
	return w
	}

	func isStdPackage(pkg string) bool {
	if pkg == "" {
	return false
	}
	// std packages do not have a "." in their path. For instance, see
	// Contains in pkgsite/+/refs/heads/master/internal/stdlbib/stdlib.go.
	if i := strings.IndexByte(pkg, '/'); i != -1 {
	pkg = pkg[:i]
	}
	return !strings.Contains(pkg, ".")
	}

	// confidence computes an approximate measure of whether the stack
	// is realizeable in practice. Currently, it equals the number of call
	// sites in stack that go through standard libraries. Such call stacks
	// have been experimentally shown to often result in false positives.
	func confidence(stack CallStack) int {
	c := 0
	for _, e := range stack {
	if isStdPackage(e.Function.PkgPath) {
	c += 1
	}
	}
	return c
	}

	// stackLess compares two call stacks in terms of their estimated
	// value to the user. Shorter stacks generally come earlier in the ordering.
	//
	// Two stacks are lexicographically ordered by:
	// 1) their estimated level of confidence in being a real call stack,
	// 2) their length, and 3) the number of dynamic call sites in the stack.
	func stackLess(s1, s2 CallStack) bool {
	if c1, c2 := confidence(s1), confidence(s2); c1 != c2 {
	return c1 < c2
	}

	if len(s1) != len(s2) {
	return len(s1) < len(s2)
	}

	if w1, w2 := weight(s1), weight(s2); w1 != w2 {
	return w1 < w2
	}

	// At this point, the stableness/determinism of
	// sorting is guaranteed by the determinism of
	// the underlying call graph and the call stack
	// search algorithm.
	return true
	}

	// csLess compares two call sites by their locations and, if needed,
	// their string representation.
	func csLess(cs1, cs2 *CallSite) bool {
	if cs2 == nil {
	return true
	}

	// fast code path
	if p1, p2 := cs1.Pos, cs2.Pos; p1 != nil && p2 != nil {
	if posLess(p1, p2) {
	return true
	}
	if posLess(p2, p1) {
	return false
	}
	// for sanity, should not occur in practice
	return fmt.Sprintf("%v.%v", cs1.RecvType, cs2.Name) < fmt.Sprintf("%v.%v", cs2.RecvType, cs2.Name)
	}

	// code path rarely exercised
	if cs2.Pos == nil {
	return true
	}
	if cs1.Pos == nil {
	return false
	}
	// should very rarely occur in practice
	return fmt.Sprintf("%v.%v", cs1.RecvType, cs2.Name) < fmt.Sprintf("%v.%v", cs2.RecvType, cs2.Name)
	}

	// posLess compares two positions by their line and column number,
	// and filename if needed.
	func posLess(p1, p2 token.Position) bool {
	if p1.Line < p2.Line {
	return true
	}
	if p2.Line < p1.Line {
	return false
	}

	if p1.Column < p2.Column {
	return true
	}
	if p2.Column < p1.Column {
	return false
	}

	return strings.Compare(p1.Filename, p2.Filename) == -1
	}

	// funcLess compares two function nodes by locations of
	// corresponding functions and, if needed, their string representation.
	func funcLess(f1, f2 *FuncNode) bool {
	if p1, p2 := f1.Pos, f2.Pos; p1 != nil && p2 != nil {
	if posLess(p1, p2) {
	return true
	}
	if posLess(p2, p1) {
	return false
	}
	// for sanity, should not occur in practice
	return f1.String() < f2.String()
	}

	if f2.Pos == nil {
	return true
	}
	if f1.Pos == nil {
	return false
	}
	// should happen only for inits
	return f1.String() < f2.String()
	}