forked from stripe-archive/safesql
/
safesql.go
329 lines (292 loc) · 7.98 KB
/
safesql.go
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// Command safesql is a tool for performing static analysis on programs to
// ensure that SQL injection attacks are not possible. It does this by ensuring
// package database/sql is only used with compile-time constant queries.
package main
import (
"flag"
"fmt"
"go/build"
"go/types"
"os"
"path/filepath"
"strings"
"golang.org/x/tools/go/callgraph"
"golang.org/x/tools/go/loader"
"golang.org/x/tools/go/pointer"
"golang.org/x/tools/go/ssa"
"golang.org/x/tools/go/ssa/ssautil"
)
type sqlPackage struct {
packageName string
paramNames []string
enable bool
}
var sqlPackages = []sqlPackage{
{
packageName: "database/sql",
paramNames: []string{"query"},
},
{
packageName: "github.com/jinzhu/gorm",
paramNames: []string{"sql", "query"},
},
{
packageName: "github.com/jmoiron/sqlx",
paramNames: []string{"query"},
},
}
func main() {
var verbose, quiet bool
flag.BoolVar(&verbose, "v", false, "Verbose mode")
flag.BoolVar(&quiet, "q", false, "Only print on failure")
flag.Usage = func() {
fmt.Fprintf(os.Stderr, "Usage: %s [-q] [-v] package1 [package2 ...]\n", os.Args[0])
flag.PrintDefaults()
}
flag.Parse()
pkgs := flag.Args()
if len(pkgs) == 0 {
flag.Usage()
os.Exit(2)
}
c := loader.Config{
FindPackage: FindPackage,
}
for _, pkg := range pkgs {
c.Import(pkg)
}
p, err := c.Load()
if err != nil {
fmt.Printf("error loading packages %v: %v\n", pkgs, err)
os.Exit(2)
}
imports := getImports(p)
existOne := false
for i := range sqlPackages {
if _, exist := imports[sqlPackages[i].packageName]; exist {
if verbose {
fmt.Printf("Enabling support for %s\n", sqlPackages[i].packageName)
}
sqlPackages[i].enable = true
existOne = true
}
}
if !existOne {
fmt.Printf("No packages in %v include a supported database driver", pkgs)
os.Exit(2)
}
s := ssautil.CreateProgram(p, 0)
s.Build()
qms := make([]*QueryMethod, 0)
for i := range sqlPackages {
if sqlPackages[i].enable {
qms = append(qms, FindQueryMethods(sqlPackages[i], p.Package(sqlPackages[i].packageName).Pkg, s)...)
}
}
if verbose {
fmt.Println("database driver functions that accept queries:")
for _, m := range qms {
fmt.Printf("- %s (param %d)\n", m.Func, m.Param)
}
fmt.Println()
}
mains := FindMains(p, s)
if len(mains) == 0 {
fmt.Println("Did not find any commands (i.e., main functions).")
os.Exit(2)
}
res, err := pointer.Analyze(&pointer.Config{
Mains: mains,
BuildCallGraph: true,
})
if err != nil {
fmt.Printf("error performing pointer analysis: %v\n", err)
os.Exit(2)
}
bad := FindNonConstCalls(res.CallGraph, qms)
if len(bad) == 0 {
if !quiet {
fmt.Println(`You're safe from SQL injection! Yay \o/`)
}
return
}
if verbose {
fmt.Printf("Found %d potentially unsafe SQL statements:\n", len(bad))
}
for _, ci := range bad {
pos := p.Fset.Position(ci.Pos())
fmt.Printf("- %s\n", pos)
}
if verbose {
fmt.Println("Please ensure that all SQL queries you use are compile-time constants.")
fmt.Println("You should always use parameterized queries or prepared statements")
fmt.Println("instead of building queries from strings.")
}
os.Exit(1)
}
// QueryMethod represents a method on a type which has a string parameter named
// "query".
type QueryMethod struct {
Func *types.Func
SSA *ssa.Function
ArgCount int
Param int
}
// FindQueryMethods locates all methods in the given package (assumed to be
// package database/sql) with a string parameter named "query".
func FindQueryMethods(sqlPackages sqlPackage, sql *types.Package, ssa *ssa.Program) []*QueryMethod {
methods := make([]*QueryMethod, 0)
scope := sql.Scope()
for _, name := range scope.Names() {
o := scope.Lookup(name)
if !o.Exported() {
continue
}
if _, ok := o.(*types.TypeName); !ok {
continue
}
n := o.Type().(*types.Named)
for i := 0; i < n.NumMethods(); i++ {
m := n.Method(i)
if !m.Exported() {
continue
}
s := m.Type().(*types.Signature)
if num, ok := FuncHasQuery(sqlPackages, s); ok {
methods = append(methods, &QueryMethod{
Func: m,
SSA: ssa.FuncValue(m),
ArgCount: s.Params().Len(),
Param: num,
})
}
}
}
return methods
}
// FuncHasQuery returns the offset of the string parameter named "query", or
// none if no such parameter exists.
func FuncHasQuery(sqlPackages sqlPackage, s *types.Signature) (offset int, ok bool) {
params := s.Params()
for i := 0; i < params.Len(); i++ {
v := params.At(i)
for _, paramName := range sqlPackages.paramNames {
if v.Name() == paramName {
return i, true
}
}
}
return 0, false
}
// FindMains returns the set of all packages loaded into the given
// loader.Program which contain main functions
func FindMains(p *loader.Program, s *ssa.Program) []*ssa.Package {
ips := p.InitialPackages()
mains := make([]*ssa.Package, 0, len(ips))
for _, info := range ips {
ssaPkg := s.Package(info.Pkg)
if ssaPkg.Func("main") != nil {
mains = append(mains, ssaPkg)
}
}
return mains
}
func getImports(p *loader.Program) map[string]interface{} {
pkgs := make(map[string]interface{})
for _, pkg := range p.AllPackages {
if pkg.Importable {
pkgs[pkg.Pkg.Path()] = nil
}
}
return pkgs
}
// FindNonConstCalls returns the set of callsites of the given set of methods
// for which the "query" parameter is not a compile-time constant.
func FindNonConstCalls(cg *callgraph.Graph, qms []*QueryMethod) []ssa.CallInstruction {
cg.DeleteSyntheticNodes()
// package database/sql has a couple helper functions which are thin
// wrappers around other sensitive functions. Instead of handling the
// general case by tracing down callsites of wrapper functions
// recursively, let's just whitelist the functions we're already
// tracking, since it happens to be good enough for our use case.
okFuncs := make(map[*ssa.Function]struct{}, len(qms))
for _, m := range qms {
okFuncs[m.SSA] = struct{}{}
}
bad := make([]ssa.CallInstruction, 0)
for _, m := range qms {
node := cg.CreateNode(m.SSA)
for _, edge := range node.In {
if _, ok := okFuncs[edge.Site.Parent()]; ok {
continue
}
isInternalSQLPkg := false
for _, pkg := range sqlPackages {
if pkg.packageName == edge.Caller.Func.Pkg.Pkg.Path() {
isInternalSQLPkg = true
break
}
}
if isInternalSQLPkg {
continue
}
cc := edge.Site.Common()
args := cc.Args
// The first parameter is occasionally the receiver.
if len(args) == m.ArgCount+1 {
args = args[1:]
} else if len(args) != m.ArgCount {
panic("arg count mismatch")
}
v := args[m.Param]
if _, ok := v.(*ssa.Const); !ok {
if inter, ok := v.(*ssa.MakeInterface); ok && types.IsInterface(v.(*ssa.MakeInterface).Type()) {
if inter.X.Referrers() == nil || inter.X.Type() != types.Typ[types.String] {
continue
}
}
bad = append(bad, edge.Site)
}
}
}
return bad
}
// Deal with GO15VENDOREXPERIMENT
func FindPackage(ctxt *build.Context, path, dir string, mode build.ImportMode) (*build.Package, error) {
if !useVendor {
return ctxt.Import(path, dir, mode)
}
// First, walk up the filesystem from dir looking for vendor directories
var vendorDir string
for tmp := dir; vendorDir == "" && tmp != "/"; tmp = filepath.Dir(tmp) {
dname := filepath.Join(tmp, "vendor", filepath.FromSlash(path))
fd, err := os.Open(dname)
if err != nil {
continue
}
// Directories are only valid if they contain at least one file
// with suffix ".go" (this also ensures that the file descriptor
// we have is in fact a directory)
names, err := fd.Readdirnames(-1)
if err != nil {
continue
}
for _, name := range names {
if strings.HasSuffix(name, ".go") {
vendorDir = filepath.ToSlash(dname)
break
}
}
}
if vendorDir != "" {
pkg, err := ctxt.ImportDir(vendorDir, mode)
if err != nil {
return nil, err
}
// Go tries to derive a valid import path for the package, but
// it's wrong (it includes "/vendor/"). Overwrite it here.
pkg.ImportPath = path
return pkg, nil
}
return ctxt.Import(path, dir, mode)
}