cmd/vulnreport: resolve package references with "go mod tidy".

When resolving vulnerable symbols, we create a temporary module which
depends on the vulnerable package. Construct this temporary module's
go.mod file with "go mod tidy" rather than "go get -u", which seems
to do a better of job of resolving the dependencies for packages
in the Kubernetes ecosystem. Allows vulnreport fix to work on
GO-2023-1549.

Change-Id: I50a71807411a3bab896b5982186d3e57fa1d941b
Reviewed-on: https://go-review.googlesource.com/c/vulndb/+/470376
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Damien Neil <[email protected]>
Reviewed-by: Tatiana Bradley <[email protected]>

cmd/vulnreport/main.go

@@ -7,6 +7,7 @@
 package main
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"flag"
@@ -705,15 +706,37 @@ func findExportedSymbols(m *report.Module, p *report.Package, c *reportClient) (
 		return nil, err
 	}
 	defer cleanup()
+
+	// This procedure was developed through trial and error finding a way
+	// to load symbols for GO-2023-1549, which has a dependency tree that
+	// includes go.mod files that reference v0.0.0 versions which do not exist.
+	//
+	// Create an empty go.mod.
 	if err := run("go", "mod", "init", "go.dev/_"); err != nil {
 		return nil, err
 	}
-	if !m.IsStdLib() {
-		pkgPathAndVersion := p.Package + "@" + m.VulnerableAt.V()
-		if err := run("go", "get", pkgPathAndVersion); err != nil {
+	// Require the module we're interested in at the vulnerable_at version.
+	if err := run("go", "mod", "edit", "-require", m.Module+"@"+m.VulnerableAt.V()); err != nil {
+		return nil, err
+	}
+	for _, req := range m.VulnerableAtRequires {
+		if err := run("go", "mod", "edit", "-require", req); err != nil {
 			return nil, err
 		}
 	}
+	// Create a package that imports the package we're interested in.
+	var content bytes.Buffer
+	fmt.Fprintf(&content, "package p\n")
+	fmt.Fprintf(&content, "import _ %q\n", p.Package)
+	for _, req := range m.VulnerableAtRequires {
+		pkg, _, _ := strings.Cut(req, "@")
+		fmt.Fprintf(&content, "import _ %q", pkg)
+	}
+	os.WriteFile("p.go", content.Bytes(), 0666)
+	// Run go mod tidy.
+	if err := run("go", "mod", "tidy"); err != nil {
+		return nil, err
+	}
 
 	pkgs, err := loadPackage(&packages.Config{}, p.Package)
 	if err != nil {

data/osv/GO-2021-0072.json

@@ -34,8 +34,10 @@
           {
             "path": "github.com/docker/distribution/registry/handlers",
             "symbols": [
+              "NewApp",
               "blobUploadHandler.PatchBlobData",
               "blobUploadHandler.PutBlobUploadComplete",
+              "catalogHandler.GetCatalog",
               "copyFullPayload",
               "imageManifestHandler.GetImageManifest",
               "imageManifestHandler.PutImageManifest"

data/reports/GO-2021-0072.yaml

@@ -3,13 +3,17 @@ modules:
     versions:
       - fixed: 2.7.0-rc.0+incompatible
     vulnerable_at: 2.6.2+incompatible
+    vulnerable_at_requires:
+      - github.com/Sirupsen/[email protected]
     packages:
       - package: github.com/docker/distribution/registry/handlers
         symbols:
           - copyFullPayload
         derived_symbols:
+          - NewApp
           - blobUploadHandler.PatchBlobData
           - blobUploadHandler.PutBlobUploadComplete
+          - catalogHandler.GetCatalog
           - imageManifestHandler.GetImageManifest
           - imageManifestHandler.PutImageManifest
       - package: github.com/docker/distribution/registry/storage

internal/report/report.go

@@ -59,8 +59,11 @@ type Module struct {
 	// In general, we want to use the most recent vulnerable version of
 	// the package. Determining this programmatically is difficult, especially
 	// for packages without tagged versions, so we specify it manually here.
-	VulnerableAt Version    `yaml:"vulnerable_at,omitempty"`
-	Packages     []*Package `yaml:",omitempty"`
+	VulnerableAt Version `yaml:"vulnerable_at,omitempty"`
+	// Additional list of module@version to require when performing static analysis.
+	// It is rare that we need to specify this.
+	VulnerableAtRequires []string   `yaml:"vulnerable_at_requires,omitempty"`
+	Packages             []*Package `yaml:",omitempty"`
 }
 
 type Package struct {