Merge pull request #111 from corhere/fix-aes-gcm-102fips

Fix AES-GCM decryption on OpenSSL 1.0.2-fips

Author: qmuntal

aes_test.go

@@ -81,25 +81,52 @@ func TestNewGCMNonce(t *testing.T) {
 }
 
 func TestSealAndOpen(t *testing.T) {
-	key := []byte("D249BF6DEC97B1EBD69BC4D6B3A3C49D")
-	ci, err := openssl.NewAESCipher(key)
-	if err != nil {
-		t.Fatal(err)
-	}
-	gcm, err := cipher.NewGCM(ci)
-	if err != nil {
-		t.Fatal(err)
-	}
-	nonce := []byte{0x91, 0xc7, 0xa7, 0x54, 0x52, 0xef, 0x10, 0xdb, 0x91, 0xa8, 0x6c, 0xf9}
-	plainText := []byte{0x01, 0x02, 0x03}
-	additionalData := []byte{0x05, 0x05, 0x07}
-	sealed := gcm.Seal(nil, nonce, plainText, additionalData)
-	decrypted, err := gcm.Open(nil, nonce, sealed, additionalData)
-	if err != nil {
-		t.Error(err)
-	}
-	if !bytes.Equal(decrypted, plainText) {
-		t.Errorf("unexpected decrypted result\ngot: %#v\nexp: %#v", decrypted, plainText)
+	for _, tt := range aesGCMTests {
+		t.Run(tt.description, func(t *testing.T) {
+			ci, err := openssl.NewAESCipher(tt.key)
+			if err != nil {
+				t.Fatalf("NewAESCipher() err = %v", err)
+			}
+			gcm, err := cipher.NewGCM(ci)
+			if err != nil {
+				t.Fatalf("cipher.NewGCM() err = %v", err)
+			}
+
+			sealed := gcm.Seal(nil, tt.nonce, tt.plaintext, tt.aad)
+			if !bytes.Equal(sealed, tt.ciphertext) {
+				t.Errorf("unexpected sealed result\ngot: %#v\nexp: %#v", sealed, tt.ciphertext)
+			}
+
+			decrypted, err := gcm.Open(nil, tt.nonce, tt.ciphertext, tt.aad)
+			if err != nil {
+				t.Errorf("gcm.Open() err = %v", err)
+			}
+			if !bytes.Equal(decrypted, tt.plaintext) {
+				t.Errorf("unexpected decrypted result\ngot: %#v\nexp: %#v", decrypted, tt.plaintext)
+			}
+
+			// Test that open fails if the ciphertext is modified.
+			tt.ciphertext[0] ^= 0x80
+			_, err = gcm.Open(nil, tt.nonce, tt.ciphertext, tt.aad)
+			if err != openssl.ErrOpen {
+				t.Errorf("expected authentication error for tampered message\ngot: %#v", err)
+			}
+			tt.ciphertext[0] ^= 0x80
+
+			// Test that the ciphertext can be opened using a fresh context
+			// which was not previously used to seal the same message.
+			gcm, err = cipher.NewGCM(ci)
+			if err != nil {
+				t.Fatalf("cipher.NewGCM() err = %v", err)
+			}
+			decrypted, err = gcm.Open(nil, tt.nonce, tt.ciphertext, tt.aad)
+			if err != nil {
+				t.Errorf("fresh GCM instance: gcm.Open() err = %v", err)
+			}
+			if !bytes.Equal(decrypted, tt.plaintext) {
+				t.Errorf("fresh GCM instance: unexpected decrypted result\ngot: %#v\nexp: %#v", decrypted, tt.plaintext)
+			}
+		})
 	}
 }
 

cipher.go

@@ -513,7 +513,7 @@ func newCipherCtx(kind cipherKind, mode cipherMode, encrypt cipherOp, key, iv []
 		cipher = nil
 	}
 	if C.go_openssl_EVP_CipherInit_ex(ctx, cipher, nil, base(key), base(iv), C.int(encrypt)) != 1 {
-		return nil, fail("unable to initialize EVP cipher ctx")
+		return nil, newOpenSSLError("unable to initialize EVP cipher ctx")
 	}
 	return ctx, nil
 }

cmd/gentestvectors/main.go

@@ -0,0 +1,116 @@
+// gentestvectors emits cryptographic test vectors using the Go standard library
+// cryptographic routines to test the OpenSSL bindings.
+package main
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"log"
+	"math/rand"
+	"os"
+	"path/filepath"
+)
+
+var outputPath = flag.String("out", "", "output path (default stdout)")
+
+func init() {
+	log.SetFlags(log.Llongfile)
+	log.SetOutput(os.Stderr)
+}
+
+func main() {
+	flag.Parse()
+
+	var b bytes.Buffer
+	fmt.Fprint(&b, "// Code generated by cmd/gentestvectors. DO NOT EDIT.\n\n")
+	if *outputPath != "" {
+		fmt.Fprintf(&b, "//go"+":generate go run github.com/golang-fips/openssl/v2/cmd/gentestvectors -out %s\n\n", filepath.Base(*outputPath))
+	}
+
+	pkg := "openssl_test"
+	if gopackage := os.Getenv("GOPACKAGE"); gopackage != "" {
+		pkg = gopackage + "_test"
+	}
+	fmt.Fprintf(&b, "package %s\n\n", pkg)
+
+	aesGCM(&b)
+
+	generated, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatalf("failed to format generated code: %v", err)
+	}
+
+	if *outputPath != "" {
+		err := os.WriteFile(*outputPath, generated, 0o644)
+		if err != nil {
+			log.Fatalf("failed to write output file: %v\n", err)
+		}
+	} else {
+		_, _ = os.Stdout.Write(generated)
+	}
+}
+
+func aesGCM(w io.Writer) {
+	r := rand.New(rand.NewSource(0))
+
+	fmt.Fprintln(w, `var aesGCMTests = []struct {
+	description string
+	key, nonce, plaintext, aad, ciphertext []byte
+}{`)
+
+	for _, keyLen := range []int{16, 24, 32} {
+		for _, aadLen := range []int{0, 1, 3, 13, 30} {
+			for _, plaintextLen := range []int{0, 1, 3, 13, 16, 51} {
+				if aadLen == 0 && plaintextLen == 0 {
+					continue
+				}
+
+				key := randbytes(r, keyLen)
+				nonce := randbytes(r, 12)
+				plaintext := randbytes(r, plaintextLen)
+				aad := randbytes(r, aadLen)
+
+				c, err := aes.NewCipher(key)
+				if err != nil {
+					panic(err)
+				}
+				aead, err := cipher.NewGCM(c)
+				if err != nil {
+					panic(err)
+				}
+				ciphertext := aead.Seal(nil, nonce, plaintext, aad)
+
+				fmt.Fprint(w, "\t{\n")
+				fmt.Fprintf(w, "\t\tdescription: \"AES-%d/AAD=%d/Plaintext=%d\",\n", keyLen*8, aadLen, plaintextLen)
+				printBytesField(w, "key", key)
+				printBytesField(w, "nonce", nonce)
+				printBytesField(w, "plaintext", plaintext)
+				printBytesField(w, "aad", aad)
+				printBytesField(w, "ciphertext", ciphertext)
+				fmt.Fprint(w, "\t},\n")
+			}
+		}
+	}
+	fmt.Fprintln(w, "}")
+}
+
+func randbytes(r *rand.Rand, n int) []byte {
+	if n == 0 {
+		return nil
+	}
+	b := make([]byte, n)
+	r.Read(b)
+	return b
+}
+
+func printBytesField(w io.Writer, name string, b []byte) {
+	if len(b) == 0 {
+		return
+	}
+	fmt.Fprintf(w, "\t\t%s: %#v,\n", name, b)
+}

des.go

@@ -14,9 +14,9 @@ import (
 // If CBC is also supported, then the returned cipher.Block
 // will also implement NewCBCEncrypter and NewCBCDecrypter.
 func SupportsDESCipher() bool {
-	// True for stock OpenSSL 1.
+	// True for stock OpenSSL 1 w/o FIPS.
 	// False for stock OpenSSL 3 unless the legacy provider is available.
-	return loadCipher(cipherDES, cipherModeECB) != nil
+	return (versionAtOrAbove(1, 1, 0) || !FIPS()) && loadCipher(cipherDES, cipherModeECB) != nil
 }
 
 // SupportsTripleDESCipher returns true if NewTripleDESCipher is supported,

ed25519.go

@@ -37,7 +37,7 @@ func SupportsEd25519() bool {
 	onceSupportsEd25519.Do(func() {
 		switch vMajor {
 		case 1:
-			supportsEd25519 = version1_1_1_or_above()
+			supportsEd25519 = versionAtOrAbove(1, 1, 1)
 		case 3:
 			name := C.CString("ED25519")
 			defer C.free(unsafe.Pointer(name))

evp.go

@@ -72,9 +72,13 @@ func cryptoHashToMD(ch crypto.Hash) (md C.GO_EVP_MD_PTR) {
 	}
 	switch ch {
 	case crypto.MD4:
-		return C.go_openssl_EVP_md4()
+		if versionAtOrAbove(1, 1, 0) || !FIPS() {
+			return C.go_openssl_EVP_md4()
+		}
 	case crypto.MD5:
-		return C.go_openssl_EVP_md5()
+		if versionAtOrAbove(1, 1, 0) || !FIPS() {
+			return C.go_openssl_EVP_md5()
+		}
 	case crypto.SHA1:
 		return C.go_openssl_EVP_sha1()
 	case crypto.SHA224:
@@ -86,19 +90,19 @@ func cryptoHashToMD(ch crypto.Hash) (md C.GO_EVP_MD_PTR) {
 	case crypto.SHA512:
 		return C.go_openssl_EVP_sha512()
 	case crypto.SHA3_224:
-		if version1_1_1_or_above() {
+		if versionAtOrAbove(1, 1, 1) {
 			return C.go_openssl_EVP_sha3_224()
 		}
 	case crypto.SHA3_256:
-		if version1_1_1_or_above() {
+		if versionAtOrAbove(1, 1, 1) {
 			return C.go_openssl_EVP_sha3_256()
 		}
 	case crypto.SHA3_384:
-		if version1_1_1_or_above() {
+		if versionAtOrAbove(1, 1, 1) {
 			return C.go_openssl_EVP_sha3_384()
 		}
 	case crypto.SHA3_512:
-		if version1_1_1_or_above() {
+		if versionAtOrAbove(1, 1, 1) {
 			return C.go_openssl_EVP_sha3_512()
 		}
 	}

goopenssl.c

@@ -60,12 +60,12 @@ go_openssl_fips_enabled(void* handle)
 // and assign them to their corresponding function pointer
 // defined in goopenssl.h.
 void
-go_openssl_load_functions(void* handle, int major, int minor, int patch)
+go_openssl_load_functions(void* handle, unsigned int major, unsigned int minor, unsigned int patch)
 {
 #define DEFINEFUNC_INTERNAL(name, func)                                                                         \
     _g_##name = dlsym(handle, func);                                                                            \
     if (_g_##name == NULL) {                                                                                    \
-        fprintf(stderr, "Cannot get required symbol " #func " from libcrypto version %d.%d\n", major, minor);   \
+        fprintf(stderr, "Cannot get required symbol " #func " from libcrypto version %u.%u\n", major, minor);   \
         abort();                                                                                                \
     }
 #define DEFINEFUNC(ret, func, args, argscall) \

goopenssl.h

@@ -24,7 +24,7 @@ int go_openssl_version_major(void* handle);
 int go_openssl_version_minor(void* handle);
 int go_openssl_version_patch(void* handle);
 int go_openssl_thread_setup(void);
-void go_openssl_load_functions(void* handle, int major, int minor, int patch);
+void go_openssl_load_functions(void* handle, unsigned int major, unsigned int minor, unsigned int patch);
 const GO_EVP_MD_PTR go_openssl_EVP_md5_sha1_backport(void);
 
 // Define pointers to all the used OpenSSL functions.
@@ -144,22 +144,40 @@ go_openssl_EVP_CIPHER_CTX_open_wrapper(const GO_EVP_CIPHER_CTX_PTR ctx,
                                        const unsigned char *aad, int aad_len,
                                        const unsigned char *tag)
 {
-    if (in_len == 0) in = (const unsigned char *)"";
+    if (in_len == 0) {
+        in = (const unsigned char *)"";
+        // OpenSSL 1.0.2 in FIPS mode contains a bug: it will fail to verify
+        // unless EVP_DecryptUpdate is called at least once with a non-NULL
+        // output buffer.  OpenSSL will not dereference the output buffer when
+        // the input length is zero, so set it to an arbitrary non-NULL pointer
+        // to satisfy OpenSSL when the caller only has authenticated additional
+        // data (AAD) to verify. While a stack-allocated buffer could be used,
+        // that would risk a stack-corrupting buffer overflow if OpenSSL
+        // unexpectedly dereferenced it. Instead pass a value which would
+        // segfault if dereferenced on any modern platform where a NULL-pointer
+        // dereference would also segfault.
+        if (out == NULL) out = (unsigned char *)1;
+    }
     if (aad_len == 0) aad = (const unsigned char *)"";
 
     if (go_openssl_EVP_DecryptInit_ex(ctx, NULL, NULL, NULL, nonce) != 1)
         return 0;
 
+    // OpenSSL 1.0.x FIPS Object Module 2.0 versions below 2.0.5 require that
+    // the tag be set before the ciphertext, otherwise EVP_DecryptUpdate returns
+    // an error. At least one extant commercially-supported, FIPS validated
+    // build of OpenSSL 1.0.2 uses FIPS module version 2.0.1. Set the tag first
+    // to maximize compatibility with all OpenSSL version combinations.
+    if (go_openssl_EVP_CIPHER_CTX_ctrl(ctx, GO_EVP_CTRL_GCM_SET_TAG, 16, (unsigned char *)(tag)) != 1)
+        return 0;
+
     int discard_len, out_len;
     if (go_openssl_EVP_DecryptUpdate(ctx, NULL, &discard_len, aad, aad_len) != 1
         || go_openssl_EVP_DecryptUpdate(ctx, out, &out_len, in, in_len) != 1)
     {
         return 0;
     }
 
-    if (go_openssl_EVP_CIPHER_CTX_ctrl(ctx, GO_EVP_CTRL_GCM_SET_TAG, 16, (unsigned char *)(tag)) != 1)
-        return 0;
-
     if (go_openssl_EVP_DecryptFinal_ex(ctx, out + out_len, &discard_len) != 1)
         return 0;
 

hkdf.go

@@ -13,7 +13,7 @@ import (
 )
 
 func SupportsHKDF() bool {
-	return version1_1_1_or_above()
+	return versionAtOrAbove(1, 1, 1)
 }
 
 func newHKDF(h func() hash.Hash, mode C.int) (*hkdf, error) {

init.go

@@ -13,7 +13,7 @@ import (
 // as reported by the OpenSSL API.
 //
 // See Init() for details about file.
-func opensslInit(file string) (major, minor, patch int, err error) {
+func opensslInit(file string) (major, minor, patch uint, err error) {
 	// Load the OpenSSL shared library using dlopen.
 	handle, err := dlopen(file)
 	if err != nil {
@@ -24,12 +24,13 @@ func opensslInit(file string) (major, minor, patch int, err error) {
 	// Notice that major and minor could not match with the version parameter
 	// in case the name of the shared library file differs from the OpenSSL
 	// version it contains.
-	major = int(C.go_openssl_version_major(handle))
-	minor = int(C.go_openssl_version_minor(handle))
-	patch = int(C.go_openssl_version_patch(handle))
-	if major == -1 || minor == -1 || patch == -1 {
+	imajor := int(C.go_openssl_version_major(handle))
+	iminor := int(C.go_openssl_version_minor(handle))
+	ipatch := int(C.go_openssl_version_patch(handle))
+	if imajor < 0 || iminor < 0 || ipatch < 0 {
 		return 0, 0, 0, errors.New("openssl: can't retrieve OpenSSL version")
 	}
+	major, minor, patch = uint(imajor), uint(iminor), uint(ipatch)
 	var supported bool
 	if major == 1 {
 		supported = minor == 0 || minor == 1
@@ -43,7 +44,7 @@ func opensslInit(file string) (major, minor, patch int, err error) {
 
 	// Load the OpenSSL functions.
 	// See shims.go for the complete list of supported functions.
-	C.go_openssl_load_functions(handle, C.int(major), C.int(minor), C.int(patch))
+	C.go_openssl_load_functions(handle, C.uint(major), C.uint(minor), C.uint(patch))
 
 	// Initialize OpenSSL.
 	C.go_openssl_OPENSSL_init()