crypto: replace 'des-rfb' cipher with 'des'

Currently the crypto layer exposes support for a 'des-rfb'
algorithm which is just normal single-DES, with the bits
in each key byte reversed. This special key munging is
required by the RFB protocol password authentication
mechanism.

Since the crypto layer is generic shared code, it makes
more sense to do the key byte munging in the VNC server
code, and expose normal single-DES support.

Replacing cipher 'des-rfb' by 'des' looks like an incompatible
interface change, but it doesn't matter.  While the QMP schema
allows any QCryptoCipherAlgorithm for the 'cipher-alg' field
in QCryptoBlockCreateOptionsLUKS, the code restricts what can
be used at runtime. Thus the only effect is a change in error
message.

Original behaviour:

 $ qemu-img create -f luks --object secret,id=sec0,data=123 -o cipher-alg=des-rfb,key-secret=sec0 demo.luks 1G
 Formatting 'demo.luks', fmt=luks size=1073741824 key-secret=sec0 cipher-alg=des-rfb
 qemu-img: demo.luks: Algorithm 'des-rfb' not supported

New behaviour:

 $ qemu-img create -f luks --object secret,id=sec0,data=123 -o cipher-alg=des-rfb,key-secret=sec0 demo.luks 1G
 Formatting 'demo.luks', fmt=luks size=1073741824 key-secret=sec0 cipher-alg=des-fish
 qemu-img: demo.luks: Invalid parameter 'des-rfb'

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

crypto/cipher-gcrypt.c.inc

@@ -24,7 +24,7 @@ bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg,
                              QCryptoCipherMode mode)
 {
     switch (alg) {
-    case QCRYPTO_CIPHER_ALG_DES_RFB:
+    case QCRYPTO_CIPHER_ALG_DES:
     case QCRYPTO_CIPHER_ALG_3DES:
     case QCRYPTO_CIPHER_ALG_AES_128:
     case QCRYPTO_CIPHER_ALG_AES_192:
@@ -186,7 +186,7 @@ static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgorithm alg,
     }
 
     switch (alg) {
-    case QCRYPTO_CIPHER_ALG_DES_RFB:
+    case QCRYPTO_CIPHER_ALG_DES:
         gcryalg = GCRY_CIPHER_DES;
         break;
     case QCRYPTO_CIPHER_ALG_3DES:
@@ -257,17 +257,7 @@ static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgorithm alg,
     }
     ctx->blocksize = gcry_cipher_get_algo_blklen(gcryalg);
 
-    if (alg == QCRYPTO_CIPHER_ALG_DES_RFB) {
-        /* We're using standard DES cipher from gcrypt, so we need
-         * to munge the key so that the results are the same as the
-         * bizarre RFB variant of DES :-)
-         */
-        uint8_t *rfbkey = qcrypto_cipher_munge_des_rfb_key(key, nkey);
-        err = gcry_cipher_setkey(ctx->handle, rfbkey, nkey);
-        g_free(rfbkey);
-    } else {
-        err = gcry_cipher_setkey(ctx->handle, key, nkey);
-    }
+    err = gcry_cipher_setkey(ctx->handle, key, nkey);
     if (err != 0) {
         error_setg(errp, "Cannot set key: %s", gcry_strerror(err));
         goto error;

crypto/cipher-nettle.c.inc

@@ -235,11 +235,11 @@ static const struct QCryptoCipherDriver NAME##_driver_xts = {   \
     DEFINE_XTS(NAME, TYPE, BLEN, ENCRYPT, DECRYPT)
 
 
-typedef struct QCryptoNettleDESRFB {
+typedef struct QCryptoNettleDES {
     QCryptoCipher base;
     struct des_ctx key;
     uint8_t iv[DES_BLOCK_SIZE];
-} QCryptoNettleDESRFB;
+} QCryptoNettleDES;
 
 static void des_encrypt_native(const void *ctx, size_t length,
                                uint8_t *dst, const uint8_t *src)
@@ -253,7 +253,7 @@ static void des_decrypt_native(const void *ctx, size_t length,
     des_decrypt(ctx, length, dst, src);
 }
 
-DEFINE_ECB_CBC_CTR(qcrypto_nettle_des_rfb, QCryptoNettleDESRFB,
+DEFINE_ECB_CBC_CTR(qcrypto_nettle_des, QCryptoNettleDES,
                    DES_BLOCK_SIZE, des_encrypt_native, des_decrypt_native)
 
 
@@ -431,7 +431,7 @@ bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg,
                              QCryptoCipherMode mode)
 {
     switch (alg) {
-    case QCRYPTO_CIPHER_ALG_DES_RFB:
+    case QCRYPTO_CIPHER_ALG_DES:
     case QCRYPTO_CIPHER_ALG_3DES:
     case QCRYPTO_CIPHER_ALG_AES_128:
     case QCRYPTO_CIPHER_ALG_AES_192:
@@ -480,32 +480,28 @@ static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgorithm alg,
     }
 
     switch (alg) {
-    case QCRYPTO_CIPHER_ALG_DES_RFB:
+    case QCRYPTO_CIPHER_ALG_DES:
         {
-            QCryptoNettleDESRFB *ctx;
+            QCryptoNettleDES *ctx;
             const QCryptoCipherDriver *drv;
-            uint8_t *rfbkey;
 
             switch (mode) {
             case QCRYPTO_CIPHER_MODE_ECB:
-                drv = &qcrypto_nettle_des_rfb_driver_ecb;
+                drv = &qcrypto_nettle_des_driver_ecb;
                 break;
             case QCRYPTO_CIPHER_MODE_CBC:
-                drv = &qcrypto_nettle_des_rfb_driver_cbc;
+                drv = &qcrypto_nettle_des_driver_cbc;
                 break;
             case QCRYPTO_CIPHER_MODE_CTR:
-                drv = &qcrypto_nettle_des_rfb_driver_ctr;
+                drv = &qcrypto_nettle_des_driver_ctr;
                 break;
             default:
                 goto bad_cipher_mode;
             }
 
-            ctx = g_new0(QCryptoNettleDESRFB, 1);
+            ctx = g_new0(QCryptoNettleDES, 1);
             ctx->base.driver = drv;
-
-            rfbkey = qcrypto_cipher_munge_des_rfb_key(key, nkey);
-            des_set_key(&ctx->key, rfbkey);
-            g_free(rfbkey);
+            des_set_key(&ctx->key, key);
 
             return &ctx->base;
         }

crypto/cipher.c

@@ -29,7 +29,7 @@ static const size_t alg_key_len[QCRYPTO_CIPHER_ALG__MAX] = {
     [QCRYPTO_CIPHER_ALG_AES_128] = 16,
     [QCRYPTO_CIPHER_ALG_AES_192] = 24,
     [QCRYPTO_CIPHER_ALG_AES_256] = 32,
-    [QCRYPTO_CIPHER_ALG_DES_RFB] = 8,
+    [QCRYPTO_CIPHER_ALG_DES] = 8,
     [QCRYPTO_CIPHER_ALG_3DES] = 24,
     [QCRYPTO_CIPHER_ALG_CAST5_128] = 16,
     [QCRYPTO_CIPHER_ALG_SERPENT_128] = 16,
@@ -44,7 +44,7 @@ static const size_t alg_block_len[QCRYPTO_CIPHER_ALG__MAX] = {
     [QCRYPTO_CIPHER_ALG_AES_128] = 16,
     [QCRYPTO_CIPHER_ALG_AES_192] = 16,
     [QCRYPTO_CIPHER_ALG_AES_256] = 16,
-    [QCRYPTO_CIPHER_ALG_DES_RFB] = 8,
+    [QCRYPTO_CIPHER_ALG_DES] = 8,
     [QCRYPTO_CIPHER_ALG_3DES] = 8,
     [QCRYPTO_CIPHER_ALG_CAST5_128] = 8,
     [QCRYPTO_CIPHER_ALG_SERPENT_128] = 16,
@@ -107,9 +107,9 @@ qcrypto_cipher_validate_key_length(QCryptoCipherAlgorithm alg,
     }
 
     if (mode == QCRYPTO_CIPHER_MODE_XTS) {
-        if (alg == QCRYPTO_CIPHER_ALG_DES_RFB
-                || alg == QCRYPTO_CIPHER_ALG_3DES) {
-            error_setg(errp, "XTS mode not compatible with DES-RFB/3DES");
+        if (alg == QCRYPTO_CIPHER_ALG_DES ||
+            alg == QCRYPTO_CIPHER_ALG_3DES) {
+            error_setg(errp, "XTS mode not compatible with DES/3DES");
             return false;
         }
         if (nkey % 2) {
@@ -132,24 +132,6 @@ qcrypto_cipher_validate_key_length(QCryptoCipherAlgorithm alg,
     return true;
 }
 
-#if defined(CONFIG_GCRYPT) || defined(CONFIG_NETTLE)
-static uint8_t *
-qcrypto_cipher_munge_des_rfb_key(const uint8_t *key,
-                                 size_t nkey)
-{
-    uint8_t *ret = g_new0(uint8_t, nkey);
-    size_t i;
-    for (i = 0; i < nkey; i++) {
-        uint8_t r = key[i];
-        r = (r & 0xf0) >> 4 | (r & 0x0f) << 4;
-        r = (r & 0xcc) >> 2 | (r & 0x33) << 2;
-        r = (r & 0xaa) >> 1 | (r & 0x55) << 1;
-        ret[i] = r;
-    }
-    return ret;
-}
-#endif /* CONFIG_GCRYPT || CONFIG_NETTLE */
-
 #ifdef CONFIG_GCRYPT
 #include "cipher-gcrypt.c.inc"
 #elif defined CONFIG_NETTLE

qapi/crypto.json

@@ -66,7 +66,7 @@
 # @aes-128: AES with 128 bit / 16 byte keys
 # @aes-192: AES with 192 bit / 24 byte keys
 # @aes-256: AES with 256 bit / 32 byte keys
-# @des-rfb: RFB specific variant of single DES. Do not use except in VNC.
+# @des: DES with 56 bit / 8 byte keys. Do not use except in VNC. (since 6.1)
 # @3des: 3DES(EDE) with 192 bit / 24 byte keys (since 2.9)
 # @cast5-128: Cast5 with 128 bit / 16 byte keys
 # @serpent-128: Serpent with 128 bit / 16 byte keys
@@ -80,7 +80,7 @@
 { 'enum': 'QCryptoCipherAlgorithm',
   'prefix': 'QCRYPTO_CIPHER_ALG',
   'data': ['aes-128', 'aes-192', 'aes-256',
-           'des-rfb', '3des',
+           'des', '3des',
            'cast5-128',
            'serpent-128', 'serpent-192', 'serpent-256',
            'twofish-128', 'twofish-192', 'twofish-256']}

tests/unit/test-crypto-cipher.c

@@ -155,28 +155,28 @@ static QCryptoCipherTestData test_data[] = {
          * in single AES block, and gives identical
          * ciphertext in ECB and CBC modes
          */
-        .path = "/crypto/cipher/des-rfb-ecb-56-one-block",
-        .alg = QCRYPTO_CIPHER_ALG_DES_RFB,
+        .path = "/crypto/cipher/des-ecb-56-one-block",
+        .alg = QCRYPTO_CIPHER_ALG_DES,
         .mode = QCRYPTO_CIPHER_MODE_ECB,
-        .key = "0123456789abcdef",
+        .key = "80c4a2e691d5b3f7",
         .plaintext = "70617373776f7264",
         .ciphertext = "73fa80b66134e403",
     },
     {
         /* See previous comment */
-        .path = "/crypto/cipher/des-rfb-cbc-56-one-block",
-        .alg = QCRYPTO_CIPHER_ALG_DES_RFB,
+        .path = "/crypto/cipher/des-cbc-56-one-block",
+        .alg = QCRYPTO_CIPHER_ALG_DES,
         .mode = QCRYPTO_CIPHER_MODE_CBC,
-        .key = "0123456789abcdef",
+        .key = "80c4a2e691d5b3f7",
         .iv = "0000000000000000",
         .plaintext = "70617373776f7264",
         .ciphertext = "73fa80b66134e403",
     },
     {
-        .path = "/crypto/cipher/des-rfb-ecb-56",
-        .alg = QCRYPTO_CIPHER_ALG_DES_RFB,
+        .path = "/crypto/cipher/des-ecb-56",
+        .alg = QCRYPTO_CIPHER_ALG_DES,
         .mode = QCRYPTO_CIPHER_MODE_ECB,
-        .key = "0123456789abcdef",
+        .key = "80c4a2e691d5b3f7",
         .plaintext =
             "6bc1bee22e409f96e93d7e117393172a"
             "ae2d8a571e03ac9c9eb76fac45af8e51"

ui/vnc.c

@@ -2733,6 +2733,19 @@ static void authentication_failed(VncState *vs)
     vnc_client_error(vs);
 }
 
+static void
+vnc_munge_des_rfb_key(unsigned char *key, size_t nkey)
+{
+    size_t i;
+    for (i = 0; i < nkey; i++) {
+        uint8_t r = key[i];
+        r = (r & 0xf0) >> 4 | (r & 0x0f) << 4;
+        r = (r & 0xcc) >> 2 | (r & 0x33) << 2;
+        r = (r & 0xaa) >> 1 | (r & 0x55) << 1;
+        key[i] = r;
+    }
+}
+
 static int protocol_client_auth_vnc(VncState *vs, uint8_t *data, size_t len)
 {
     unsigned char response[VNC_AUTH_CHALLENGE_SIZE];
@@ -2757,9 +2770,10 @@ static int protocol_client_auth_vnc(VncState *vs, uint8_t *data, size_t len)
     pwlen = strlen(vs->vd->password);
     for (i=0; i<sizeof(key); i++)
         key[i] = i<pwlen ? vs->vd->password[i] : 0;
+    vnc_munge_des_rfb_key(key, sizeof(key));
 
     cipher = qcrypto_cipher_new(
-        QCRYPTO_CIPHER_ALG_DES_RFB,
+        QCRYPTO_CIPHER_ALG_DES,
         QCRYPTO_CIPHER_MODE_ECB,
         key, G_N_ELEMENTS(key),
         &err);
@@ -4045,9 +4059,9 @@ void vnc_display_open(const char *id, Error **errp)
             goto fail;
         }
         if (!qcrypto_cipher_supports(
-                QCRYPTO_CIPHER_ALG_DES_RFB, QCRYPTO_CIPHER_MODE_ECB)) {
+                QCRYPTO_CIPHER_ALG_DES, QCRYPTO_CIPHER_MODE_ECB)) {
             error_setg(errp,
-                       "Cipher backend does not support DES RFB algorithm");
+                       "Cipher backend does not support DES algorithm");
             goto fail;
         }
     }