crypto: add sanity checking of plaintext/ciphertext length

When encrypting/decrypting data, the plaintext/ciphertext
buffers are required to be a multiple of the cipher block
size. If this is not done, nettle will abort and gcrypt
will report an error. To get consistent behaviour add
explicit checks upfront for the buffer sizes.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 45 insertions, 16 deletions

diff --git a/crypto/cipher-gcrypt.c b/crypto/cipher-gcrypt.c
index 8cfc562..c4f8114 100644
--- a/crypto/cipher-gcrypt.c
+++ b/crypto/cipher-gcrypt.c
@@ -34,6 +34,11 @@ bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg)
     }
 }
 
+typedef struct QCryptoCipherGcrypt QCryptoCipherGcrypt;
+struct QCryptoCipherGcrypt {
+    gcry_cipher_hd_t handle;
+    size_t blocksize;
+};
 
 QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
                                   QCryptoCipherMode mode,
@@ -41,7 +46,7 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
                                   Error **errp)
 {
     QCryptoCipher *cipher;
-    gcry_cipher_hd_t handle;
+    QCryptoCipherGcrypt *ctx;
     gcry_error_t err;
     int gcryalg, gcrymode;
 
@@ -87,7 +92,9 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
     cipher->alg = alg;
     cipher->mode = mode;
 
-    err = gcry_cipher_open(&handle, gcryalg, gcrymode, 0);
+    ctx = g_new0(QCryptoCipherGcrypt, 1);
+
+    err = gcry_cipher_open(&ctx->handle, gcryalg, gcrymode, 0);
     if (err != 0) {
         error_setg(errp, "Cannot initialize cipher: %s",
                    gcry_strerror(err));
@@ -100,10 +107,12 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
          * bizarre RFB variant of DES :-)
          */
         uint8_t *rfbkey = qcrypto_cipher_munge_des_rfb_key(key, nkey);
-        err = gcry_cipher_setkey(handle, rfbkey, nkey);
+        err = gcry_cipher_setkey(ctx->handle, rfbkey, nkey);
         g_free(rfbkey);
+        ctx->blocksize = 8;
     } else {
-        err = gcry_cipher_setkey(handle, key, nkey);
+        err = gcry_cipher_setkey(ctx->handle, key, nkey);
+        ctx->blocksize = 16;
     }
     if (err != 0) {
         error_setg(errp, "Cannot set key: %s",
@@ -111,11 +120,12 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
         goto error;
     }
 
-    cipher->opaque = handle;
+    cipher->opaque = ctx;
     return cipher;
 
  error:
-    gcry_cipher_close(handle);
+    gcry_cipher_close(ctx->handle);
+    g_free(ctx);
     g_free(cipher);
     return NULL;
 }
@@ -123,12 +133,13 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
 
 void qcrypto_cipher_free(QCryptoCipher *cipher)
 {
-    gcry_cipher_hd_t handle;
+    QCryptoCipherGcrypt *ctx;
     if (!cipher) {
         return;
     }
-    handle = cipher->opaque;
-    gcry_cipher_close(handle);
+    ctx = cipher->opaque;
+    gcry_cipher_close(ctx->handle);
+    g_free(ctx);
     g_free(cipher);
 }
 
@@ -139,10 +150,16 @@ int qcrypto_cipher_encrypt(QCryptoCipher *cipher,
                            size_t len,
                            Error **errp)
 {
-    gcry_cipher_hd_t handle = cipher->opaque;
+    QCryptoCipherGcrypt *ctx = cipher->opaque;
     gcry_error_t err;
 
-    err = gcry_cipher_encrypt(handle,
+    if (len % ctx->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctx->blocksize);
+        return -1;
+    }
+
+    err = gcry_cipher_encrypt(ctx->handle,
                               out, len,
                               in, len);
     if (err != 0) {
@@ -161,10 +178,16 @@ int qcrypto_cipher_decrypt(QCryptoCipher *cipher,
                            size_t len,
                            Error **errp)
 {
-    gcry_cipher_hd_t handle = cipher->opaque;
+    QCryptoCipherGcrypt *ctx = cipher->opaque;
     gcry_error_t err;
 
-    err = gcry_cipher_decrypt(handle,
+    if (len % ctx->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctx->blocksize);
+        return -1;
+    }
+
+    err = gcry_cipher_decrypt(ctx->handle,
                               out, len,
                               in, len);
     if (err != 0) {
@@ -180,11 +203,17 @@ int qcrypto_cipher_setiv(QCryptoCipher *cipher,
                          const uint8_t *iv, size_t niv,
                          Error **errp)
 {
-    gcry_cipher_hd_t handle = cipher->opaque;
+    QCryptoCipherGcrypt *ctx = cipher->opaque;
     gcry_error_t err;
 
-    gcry_cipher_reset(handle);
-    err = gcry_cipher_setiv(handle, iv, niv);
+    if (niv != ctx->blocksize) {
+        error_setg(errp, "Expected IV size %zu not %zu",
+                   ctx->blocksize, niv);
+        return -1;
+    }
+
+    gcry_cipher_reset(ctx->handle);
+    err = gcry_cipher_setiv(ctx->handle, iv, niv);
     if (err != 0) {
         error_setg(errp, "Cannot set IV: %s",
                    gcry_strerror(err));