fix(submit): 审阅绑定上下文 sha256，批准须带摘要，构建只从内部 API 取上下文并校验字节

cmd/felis/api.go

@@ -469,6 +469,9 @@ func buildConfig(cfg *config.Config) build.Config {
 		// the internal DB mirror (see config.RegistryConfig.TrivyDBRepository).
 		TrivyDBRepository:     cfg.Registry.TrivyDBRepository,
 		TrivyJavaDBRepository: cfg.Registry.TrivyJavaDBRepository,
+		// The submit lane's derived context URLs live here; the fetch step's
+		// service token goes nowhere else.
+		ContextOrigin: internalAPIBaseURL(),
 	}
 }
 

cmd/felis/fetchcontext.go

@@ -4,6 +4,8 @@ import (
 	"archive/tar"
 	"compress/gzip"
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"errors"
 	"flag"
 	"fmt"
@@ -15,6 +17,8 @@ import (
 	"strings"
 	"syscall"
 	"time"
+
+	"felis.lolicon.best/internal/build"
 )
 
 // cmdFetchContext is the in-Pod entrypoint the build Job's context-fetch
@@ -41,9 +45,14 @@ func cmdFetchContext(args []string, _, stderr io.Writer) int {
 	fs.SetOutput(stderr)
 	url := fs.String("url", "", "internal-face URL of the submission's build-context tarball")
 	out := fs.String("out", "/context", "directory to extract the build context into")
+	want := fs.String("sha256", "", "refuse the context unless the tarball's sha256 is this lowercase hex digest")
 	if err := fs.Parse(args); err != nil {
 		return 2
 	}
+	if *want != "" && !build.IsSHA256Hex(*want) {
+		fmt.Fprintf(stderr, "felis fetch-context: --sha256 %q is not a lowercase hex sha256\n", *want)
+		return 2
+	}
 	if *url == "" {
 		fmt.Fprintln(stderr, "felis fetch-context: --url is required")
 		return 2
@@ -66,7 +75,12 @@ func cmdFetchContext(args []string, _, stderr io.Writer) int {
 	// No overall client timeout: a legitimate modpack context can be large and the
 	// Job's activeDeadlineSeconds is the real bound. The header timeout catches a
 	// wedged endpoint without capping a healthy download.
-	client := &http.Client{Transport: &http.Transport{ResponseHeaderTimeout: time.Minute}}
+	// Redirects are refused: the request carries the service token, and the
+	// internal face never redirects, so a 3xx is someone steering the token.
+	client := &http.Client{
+		Transport:     &http.Transport{ResponseHeaderTimeout: time.Minute},
+		CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse },
+	}
 	resp, err := fetchContextWithRetry(ctx, client, *url, token, stderr)
 	if err != nil {
 		fmt.Fprintf(stderr, "felis fetch-context: %v\n", err)
@@ -74,10 +88,28 @@ func cmdFetchContext(args []string, _, stderr io.Writer) int {
 	}
 	defer resp.Body.Close()
 
-	if err := extractTarGz(resp.Body, *out); err != nil {
+	h := sha256.New()
+	body := io.TeeReader(resp.Body, h)
+	if err := extractTarGz(body, *out); err != nil {
 		fmt.Fprintf(stderr, "felis fetch-context: %v\n", err)
 		return 1
 	}
+	if *want == "" {
+		return 0
+	}
+	// The tar end marker comes before the gzip trailer and whatever follows it,
+	// so read to EOF: the digest must cover every byte the blob holds. The blob
+	// itself is size-capped at upload, which bounds this read.
+	if _, err := io.Copy(io.Discard, io.LimitReader(body, maxContextBytes)); err != nil {
+		fmt.Fprintf(stderr, "felis fetch-context: %v\n", err)
+		return 1
+	}
+	if got := hex.EncodeToString(h.Sum(nil)); got != *want {
+		// The init container failing is what keeps Kaniko from ever starting on
+		// the extracted tree.
+		fmt.Fprintf(stderr, "felis fetch-context: the context's sha256 is %s, the approved digest is %s: it changed after approval; refusing to build\n", got, *want)
+		return 1
+	}
 	return 0
 }
 

cmd/felis/fetchcontext_test.go

@@ -4,6 +4,8 @@ import (
 	"archive/tar"
 	"bytes"
 	"compress/gzip"
+	"crypto/sha256"
+	"encoding/hex"
 	"io"
 	"net"
 	"net/http"
@@ -187,6 +189,69 @@ func TestCmdFetchContextFetchAndExtract(t *testing.T) {
 	}
 }
 
+// With --sha256 the fetch refuses any bytes but the approved ones, including
+// a tarball that extracts cleanly: that is exactly the context an uploader
+// swapped in after the review.
+func TestCmdFetchContextChecksDigest(t *testing.T) {
+	body := tgzBody(t, tarEntry{name: "Dockerfile", body: "FROM scratch\n"})
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write(body)
+	}))
+	defer srv.Close()
+	t.Setenv("FELIS_SERVICE_TOKEN", "test-token")
+	sum := sha256.Sum256(body)
+	good := hex.EncodeToString(sum[:])
+	args := func(digest string) []string {
+		return []string{"--url=" + srv.URL + "/sub-1/context", "--out=" + t.TempDir(), "--sha256=" + digest}
+	}
+
+	if code := cmdFetchContext(args(good), io.Discard, io.Discard); code != 0 {
+		t.Fatalf("matching digest exit = %d, want 0", code)
+	}
+	var stderr bytes.Buffer
+	other := strings.Repeat("0", 64)
+	if code := cmdFetchContext(args(other), io.Discard, &stderr); code != 1 || !strings.Contains(stderr.String(), "changed after approval") {
+		t.Fatalf("mismatched digest exit = %d, stderr %q; want 1 naming the change", code, stderr.String())
+	}
+	stderr.Reset()
+	if code := cmdFetchContext(args("ABC"), io.Discard, &stderr); code != 2 {
+		t.Fatalf("malformed digest exit = %d, want 2 (stderr %q)", code, stderr.String())
+	}
+
+	// Bytes after the tar end marker still count: appending to an approved blob
+	// must change what the fetch accepts.
+	padded := append(append([]byte{}, body...), "trailing"...)
+	srvPadded := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write(padded)
+	}))
+	defer srvPadded.Close()
+	if code := cmdFetchContext([]string{"--url=" + srvPadded.URL + "/c", "--out=" + t.TempDir(), "--sha256=" + good}, io.Discard, io.Discard); code != 1 {
+		t.Fatalf("padded blob exit = %d, want 1", code)
+	}
+}
+
+// The request carries the service token, so a redirect is a failure: the token
+// never follows it to another host (build-supply-chain-13).
+func TestCmdFetchContextRefusesRedirects(t *testing.T) {
+	var leaked bool
+	elsewhere := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		leaked = true
+	}))
+	defer elsewhere.Close()
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, elsewhere.URL+"/steal", http.StatusFound)
+	}))
+	defer srv.Close()
+	t.Setenv("FELIS_SERVICE_TOKEN", "test-token")
+	var stderr bytes.Buffer
+	if code := cmdFetchContext([]string{"--url=" + srv.URL + "/c", "--out=" + t.TempDir()}, io.Discard, &stderr); code != 1 {
+		t.Fatalf("redirect exit = %d, want 1 (stderr %q)", code, stderr.String())
+	}
+	if leaked {
+		t.Fatal("the fetch followed the redirect")
+	}
+}
+
 // A body that is not a gzip tarball must fail the extraction rather than produce
 // an empty (or partial) context Kaniko would then try to build.
 func TestExtractTarGzRejectsNonGzip(t *testing.T) {