reconcile AES errors with crypto/aes

aes.go

@@ -56,11 +56,17 @@ func (c *aesCipher) BlockSize() int {
 }
 
 func (c *aesCipher) Encrypt(dst, src []byte) {
-	c.encrypt(dst, src)
+	if err := c.encrypt(dst, src); err != nil {
+		// Go expects that the panic message starts with "crypto/aes: ".
+		panic("crypto/aes: " + err.Error())
+	}
 }
 
 func (c *aesCipher) Decrypt(dst, src []byte) {
-	c.decrypt(dst, src)
+	if err := c.decrypt(dst, src); err != nil {
+		// Go expects that the panic message starts with "crypto/aes: ".
+		panic("crypto/aes: " + err.Error())
+	}
 }
 
 func (c *aesCipher) NewCBCEncrypter(iv []byte) cipher.BlockMode {

aes_test.go

@@ -9,6 +9,31 @@ import (
 	"github.com/golang-fips/openssl/v2"
 )
 
+func TestAESShortBlocks(t *testing.T) {
+	bytes := func(n int) []byte { return make([]byte, n) }
+
+	c, _ := openssl.NewAESCipher(bytes(16))
+
+	mustPanic(t, "crypto/aes: input not full block", func() { c.Encrypt(bytes(1), bytes(1)) })
+	mustPanic(t, "crypto/aes: input not full block", func() { c.Decrypt(bytes(1), bytes(1)) })
+	mustPanic(t, "crypto/aes: input not full block", func() { c.Encrypt(bytes(100), bytes(1)) })
+	mustPanic(t, "crypto/aes: input not full block", func() { c.Decrypt(bytes(100), bytes(1)) })
+	mustPanic(t, "crypto/aes: output not full block", func() { c.Encrypt(bytes(1), bytes(100)) })
+	mustPanic(t, "crypto/aes: output not full block", func() { c.Decrypt(bytes(1), bytes(100)) })
+}
+
+func mustPanic(t *testing.T, msg string, f func()) {
+	defer func() {
+		err := recover()
+		if err == nil {
+			t.Errorf("function did not panic, wanted %q", msg)
+		} else if err != msg {
+			t.Errorf("got panic %v, wanted %q", err, msg)
+		}
+	}()
+	f()
+}
+
 func TestNewGCMNonce(t *testing.T) {
 	key := []byte("D249BF6DEC97B1EBD69BC4D6B3A3C49D")
 	ci, err := openssl.NewAESCipher(key)

cipher.go

@@ -166,57 +166,59 @@ func (c *evpCipher) finalize() {
 	}
 }
 
-func (c *evpCipher) encrypt(dst, src []byte) {
+func (c *evpCipher) encrypt(dst, src []byte) error {
 	if len(src) < c.blockSize {
-		panic("crypto/cipher: input not full block")
+		return errors.New("input not full block")
 	}
 	if len(dst) < c.blockSize {
-		panic("crypto/cipher: output not full block")
+		return errors.New("output not full block")
 	}
 	// Only check for overlap between the parts of src and dst that will actually be used.
 	// This matches Go standard library behavior.
 	if inexactOverlap(dst[:c.blockSize], src[:c.blockSize]) {
-		panic("crypto/cipher: invalid buffer overlap")
+		return errors.New("invalid buffer overlap")
 	}
 	if c.enc_ctx == nil {
 		var err error
 		c.enc_ctx, err = newCipherCtx(c.kind, cipherModeECB, cipherOpEncrypt, c.key, nil)
 		if err != nil {
-			panic(err)
+			return err
 		}
 	}
 
 	if C.go_openssl_EVP_EncryptUpdate_wrapper(c.enc_ctx, base(dst), base(src), C.int(c.blockSize)) != 1 {
-		panic("crypto/cipher: EncryptUpdate failed")
+		return errors.New("EncryptUpdate failed")
 	}
 	runtime.KeepAlive(c)
+	return nil
 }
 
-func (c *evpCipher) decrypt(dst, src []byte) {
+func (c *evpCipher) decrypt(dst, src []byte) error {
 	if len(src) < c.blockSize {
-		panic("crypto/cipher: input not full block")
+		return errors.New("input not full block")
 	}
 	if len(dst) < c.blockSize {
-		panic("crypto/cipher: output not full block")
+		return errors.New("output not full block")
 	}
 	// Only check for overlap between the parts of src and dst that will actually be used.
 	// This matches Go standard library behavior.
 	if inexactOverlap(dst[:c.blockSize], src[:c.blockSize]) {
-		panic("crypto/cipher: invalid buffer overlap")
+		return errors.New("invalid buffer overlap")
 	}
 	if c.dec_ctx == nil {
 		var err error
 		c.dec_ctx, err = newCipherCtx(c.kind, cipherModeECB, cipherOpDecrypt, c.key, nil)
 		if err != nil {
-			panic(err)
+			return err
 		}
 		if C.go_openssl_EVP_CIPHER_CTX_set_padding(c.dec_ctx, 0) != 1 {
-			panic("crypto/cipher: could not disable cipher padding")
+			return errors.New("could not disable cipher padding")
 		}
 	}
 
 	C.go_openssl_EVP_DecryptUpdate_wrapper(c.dec_ctx, base(dst), base(src), C.int(c.blockSize))
 	runtime.KeepAlive(c)
+	return nil
 }
 
 type cipherCBC struct {