Sort-of-working, large (4096-bit) RSA keys broken.

Snapshot of mostly but not entirely working code to include the extra
ModExpA7 key components in the keystore.  Need to investigate whether
a more compact representation is practical for these components, as
the current one bloats the key object so much that a bare 4096-bit key
won't fit in a single hash block, and there may not be enough room for
PKCS #11 attributes even for smaller keys.

If more compact representation not possible or insufficient, the other
option is to double the size of a keystore object, making it two flash
subsectors for a total of 8192 octets.  Which would of course halve
the number of keys we can store and require a bunch of little tweaks
all through the ks code (particularly flash erase), so definitely
worth trying for a more compact representation first.

5 files changed, 197 insertions, 47 deletions

diff --git a/hal.h b/hal.h
index b7eae72..f7a7522 100644
--- a/hal.h
+++ b/hal.h
@@ -479,8 +479,6 @@ extern hal_error_t hal_rsa_private_key_to_der(const hal_rsa_key_t * const key,
 extern hal_error_t hal_rsa_private_key_to_der_extra(const hal_rsa_key_t * const key,
                                                     uint8_t *der, size_t *der_len, const size_t der_max);
 
-extern size_t hal_rsa_private_key_to_der_len(const hal_rsa_key_t * const key);
-
 extern hal_error_t hal_rsa_private_key_from_der(hal_rsa_key_t **key,
                                                 void *keybuf, const size_t keybuf_len,
                                                 const uint8_t * const der, const size_t der_len);
@@ -496,6 +494,18 @@ extern hal_error_t hal_rsa_public_key_from_der(hal_rsa_key_t **key,
 
 extern int hal_rsa_key_needs_saving(const hal_rsa_key_t * const key);
 
+static inline size_t hal_rsa_private_key_to_der_len(const hal_rsa_key_t * const key)
+{
+  size_t len = 0;
+  return hal_rsa_private_key_to_der(key, NULL, &len, 0) == HAL_OK ? len : 0;
+}
+
+static inline size_t hal_rsa_private_key_to_der_extra_len(const hal_rsa_key_t * const key)
+{
+  size_t len = 0;
+  return hal_rsa_private_key_to_der_extra(key, NULL, &len, 0) == HAL_OK ? len : 0;
+}
+
 /*
  * ECDSA.
  */
diff --git a/hal_internal.h b/hal_internal.h
index 7ab300d..a60d0b5 100644
--- a/hal_internal.h
+++ b/hal_internal.h
@@ -405,7 +405,19 @@ static inline hal_crc32_t hal_crc32_finalize(hal_crc32_t crc)
  * moment we take the easy way out and cap this at 4096-bit RSA.
  */
 
+#if 0
 #define HAL_KS_WRAPPED_KEYSIZE  ((2373 + 15) & ~7)
+#else
+#warning Temporary test hack to HAL_KS_WRAPPED_KEYSIZE, clean this up
+//
+// See how much of the problem we're having with pkey support for the
+// new modexpa7 components is just this buffer size being too small.
+//
+#define HAL_KS_WRAPPED_KEYSIZE  ((2373 + 6 * 4096 / 8 + 6 * 4 + 15) & ~7)
+#if HAL_KS_WRAPPED_KEYSIZE + 8 > 4096
+#warning HAL_KS_WRAPPED_KEYSIZE is too big for a single 4096-octet block
+#endif
+#endif
 
 /*
  * PINs.
@@ -566,6 +578,10 @@ extern hal_error_t hal_ks_get_attributes(hal_ks_t *ks,
 extern hal_error_t hal_ks_logout(hal_ks_t *ks,
                                  const hal_client_handle_t client);
 
+extern hal_error_t hal_ks_rewrite_der(hal_ks_t *ks,
+                                      hal_pkey_slot_t *slot,
+                                      const uint8_t * const der, const size_t der_len);
+
 /*
  * RPC lowest-level send and receive routines. These are blocking, and
  * transport-specific (sockets, USB).
diff --git a/ks.c b/ks.c
index a4e7498..2401a34 100644
--- a/ks.c
+++ b/ks.c
@@ -518,6 +518,46 @@ static inline int acceptable_key_type(const hal_key_type_t type)
   }
 }
 
+/*
+ * Internal bits of constructing a new key block.
+ */
+
+static hal_error_t construct_key_block(hal_ks_block_t *block,
+                                       hal_pkey_slot_t *slot,
+                                       const uint8_t * const der, const size_t der_len)
+{
+  if (block == NULL || slot == NULL || der == NULL || der_len == 0)
+    return HAL_ERROR_IMPOSSIBLE;
+
+  hal_ks_key_block_t *k = &block->key;
+  hal_error_t err = HAL_OK;
+  uint8_t kek[KEK_LENGTH];
+  size_t kek_len;
+
+  memset(block, 0xFF, sizeof(*block));
+
+  block->header.block_type   = HAL_KS_BLOCK_TYPE_KEY;
+  block->header.block_status = HAL_KS_BLOCK_STATUS_LIVE;
+
+  k->name    = slot->name;
+  k->type    = slot->type;
+  k->curve   = slot->curve;
+  k->flags   = slot->flags;
+  k->der_len = SIZEOF_KS_KEY_BLOCK_DER;
+  k->attributes_len = 0;
+
+  if ((err = hal_mkm_get_kek(kek, &kek_len, sizeof(kek))) == HAL_OK)
+    err = hal_aes_keywrap(NULL, kek, kek_len, der, der_len, k->der, &k->der_len);
+
+  memset(kek, 0, sizeof(kek));
+
+  return err;
+}
+
+/*
+ * Store a key block.
+ */
+
 hal_error_t hal_ks_store(hal_ks_t *ks,
                          hal_pkey_slot_t *slot,
                          const uint8_t * const der, const size_t der_len)
@@ -527,9 +567,6 @@ hal_error_t hal_ks_store(hal_ks_t *ks,
 
   hal_error_t err = HAL_OK;
   hal_ks_block_t *block;
-  hal_ks_key_block_t *k;
-  uint8_t kek[KEK_LENGTH];
-  size_t kek_len;
   unsigned b;
 
   hal_ks_lock();
@@ -539,35 +576,16 @@ hal_error_t hal_ks_store(hal_ks_t *ks,
     goto done;
   }
 
-  k = &block->key;
-
   if ((err = hal_ks_index_add(ks, &slot->name, &b, &slot->hint)) != HAL_OK)
     goto done;
 
   hal_ks_cache_mark_used(ks, block, b);
 
-  memset(block, 0xFF, sizeof(*block));
-
-  block->header.block_type   = HAL_KS_BLOCK_TYPE_KEY;
-  block->header.block_status = HAL_KS_BLOCK_STATUS_LIVE;
-
-  k->name    = slot->name;
-  k->type    = slot->type;
-  k->curve   = slot->curve;
-  k->flags   = slot->flags;
-  k->der_len = SIZEOF_KS_KEY_BLOCK_DER;
-  k->attributes_len = 0;
-
   if (ks->used < ks->size)
     err = hal_ks_block_erase_maybe(ks, ks->index[ks->used]);
 
   if (err == HAL_OK)
-    err = hal_mkm_get_kek(kek, &kek_len, sizeof(kek));
-
-  if (err == HAL_OK)
-    err = hal_aes_keywrap(NULL, kek, kek_len, der, der_len, k->der, &k->der_len);
-
-  memset(kek, 0, sizeof(kek));
+    err = construct_key_block(block, slot, der, der_len);
 
   if (err == HAL_OK)
     err = hal_ks_block_write(ks, b, block);
@@ -931,6 +949,65 @@ hal_error_t hal_ks_get_attributes(hal_ks_t *ks,
   return err;
 }
 
+hal_error_t hal_ks_rewrite_der(hal_ks_t *ks,
+                               hal_pkey_slot_t *slot,
+                               const uint8_t * const der, const size_t der_len)
+{
+  if (ks == NULL || slot == NULL || der == NULL || der_len == 0 || !acceptable_key_type(slot->type))
+    return HAL_ERROR_BAD_ARGUMENTS;
+
+  hal_ks_block_t *block = NULL;
+  hal_error_t err = HAL_OK;
+  unsigned b;
+
+  hal_ks_lock();
+
+  {
+    if ((err = hal_ks_index_find(ks, &slot->name, &b, &slot->hint))         != HAL_OK ||
+        (err = hal_ks_block_test_owner(ks, b, slot->client, slot->session)) != HAL_OK ||
+        (err = hal_ks_block_read_cached(ks, b, &block))                     != HAL_OK)
+      goto done;
+
+    hal_ks_cache_mark_used(ks, block, b);
+
+    size_t bytes_len = 0, attributes_len = 0;
+    unsigned *count = NULL;
+    uint8_t *bytes = NULL;
+
+    if ((err = locate_attributes(block, &bytes, &bytes_len,  &count))                  != HAL_OK ||
+        (err = hal_ks_attribute_scan(bytes, bytes_len, NULL, *count, &attributes_len)) != HAL_OK)
+      goto done;
+
+    if (der_len + attributes_len > SIZEOF_KS_KEY_BLOCK_DER) {
+      err = HAL_ERROR_RESULT_TOO_LONG;
+      goto done;
+    }
+
+    uint8_t attributes[attributes_len > 0 ? attributes_len : 1];
+    hal_ks_key_block_t *k = &block->key;
+    unsigned attributes_count = *count;
+
+    memcpy(attributes, bytes, attributes_len);
+
+    if ((err = construct_key_block(block, slot, der, der_len)) != HAL_OK)
+      goto done;
+
+    if (k->der_len + attributes_len > SIZEOF_KS_KEY_BLOCK_DER) {
+      err = HAL_ERROR_IMPOSSIBLE;
+      goto done;
+    }
+
+    memcpy(k->der + k->der_len, attributes, attributes_len);
+    k->attributes_len = attributes_count;
+
+    err = hal_ks_block_update(ks, b, block, &slot->name, &slot->hint);
+  }
+
+ done:
+  hal_ks_unlock();
+  return err;
+}
+
 /*
  * Local variables:
  * indent-tabs-mode: nil
diff --git a/rpc_pkey.c b/rpc_pkey.c
index 3d4a379..53d3214 100644
--- a/rpc_pkey.c
+++ b/rpc_pkey.c
@@ -734,7 +734,8 @@ static hal_error_t pkey_local_get_public_key(const hal_pkey_handle_t pkey,
  * algorithm-specific functions.
  */
 
-static hal_error_t pkey_local_sign_rsa(uint8_t *keybuf, const size_t keybuf_len,
+static hal_error_t pkey_local_sign_rsa(hal_pkey_slot_t *slot,
+                                       uint8_t *keybuf, const size_t keybuf_len,
                                        const uint8_t * const der, const size_t der_len,
                                        const hal_hash_handle_t hash,
                                        const uint8_t * input, size_t input_len,
@@ -763,10 +764,21 @@ static hal_error_t pkey_local_sign_rsa(uint8_t *keybuf, const size_t keybuf_len,
       (err = hal_rsa_decrypt(NULL, key, signature, *signature_len, signature, *signature_len)) != HAL_OK)
     return err;
 
+  if (hal_rsa_key_needs_saving(key)) {
+    uint8_t pkcs8[hal_rsa_private_key_to_der_extra_len(key)];
+    size_t pkcs8_len = 0;
+    if ((err = hal_rsa_private_key_to_der_extra(key, pkcs8, &pkcs8_len, sizeof(pkcs8))) == HAL_OK)
+      err = hal_ks_rewrite_der(ks_from_flags(slot->flags), slot, pkcs8, pkcs8_len);
+    memset(pkcs8, 0, sizeof(pkcs8));
+    if (err != HAL_OK)
+      return err;
+  }
+
   return HAL_OK;
 }
 
-static hal_error_t pkey_local_sign_ecdsa(uint8_t *keybuf, const size_t keybuf_len,
+static hal_error_t pkey_local_sign_ecdsa(hal_pkey_slot_t *slot,
+                                         uint8_t *keybuf, const size_t keybuf_len,
                                          const uint8_t * const der, const size_t der_len,
                                          const hal_hash_handle_t hash,
                                          const uint8_t * input, size_t input_len,
@@ -813,7 +825,8 @@ static hal_error_t pkey_local_sign(const hal_pkey_handle_t pkey,
   if (slot == NULL)
     return HAL_ERROR_KEY_NOT_FOUND;
 
-  hal_error_t (*signer)(uint8_t *keybuf, const size_t keybuf_len,
+  hal_error_t (*signer)(hal_pkey_slot_t *slot,
+                        uint8_t *keybuf, const size_t keybuf_len,
                         const uint8_t * const der, const size_t der_len,
                         const hal_hash_handle_t hash,
                         const uint8_t * const input,  const size_t input_len,
@@ -840,7 +853,7 @@ static hal_error_t pkey_local_sign(const hal_pkey_handle_t pkey,
   hal_error_t err;
 
   if ((err = ks_fetch_from_flags(slot, der, &der_len, sizeof(der))) == HAL_OK)
-    err = signer(keybuf, sizeof(keybuf), der, der_len, hash, input, input_len,
+    err = signer(slot, keybuf, sizeof(keybuf), der, der_len, hash, input, input_len,
                  signature, signature_len, signature_max);
 
   memset(keybuf, 0, sizeof(keybuf));
diff --git a/rsa.c b/rsa.c
index 24dc66f..dace19b 100644
--- a/rsa.c
+++ b/rsa.c
@@ -871,9 +871,9 @@ int hal_rsa_key_needs_saving(const hal_rsa_key_t * const key)
   _(ASN1_PRIVATE + 4, qC, RSA_FLAG_PRECALC_PQ_DONE);    \
   _(ASN1_PRIVATE + 5, qF, RSA_FLAG_PRECALC_PQ_DONE);
 
-hal_error_t hal_rsa_private_key_to_der_extra_maybe(const hal_rsa_key_t * const key,
-                                                   const int include_extra,
-                                                   uint8_t *der, size_t *der_len, const size_t der_max)
+hal_error_t hal_rsa_private_key_to_der_internal(const hal_rsa_key_t * const key,
+                                                const int include_extra,
+                                                uint8_t *der, size_t *der_len, const size_t der_max)
 {
   hal_error_t err = HAL_OK;
 
@@ -888,7 +888,15 @@ hal_error_t hal_rsa_private_key_to_der_extra_maybe(const hal_rsa_key_t * const k
 
   size_t hlen = 0, vlen = 0;
 
-#define _(x) { size_t n = 0; if ((err = hal_asn1_encode_integer(x, NULL, &n, der_max - vlen)) != HAL_OK) return err; vlen += n; }
+#define _(x)                                                            \
+  {                                                                     \
+    size_t n = 0;                                                       \
+    err = hal_asn1_encode_integer(x, NULL, &n, der_max - vlen);         \
+    if (err != HAL_OK)                                                  \
+      return err;                                                       \
+    vlen += n;                                                          \
+  }
+
   RSAPrivateKey_fields;
 #undef _
 
@@ -926,7 +934,16 @@ hal_error_t hal_rsa_private_key_to_der_extra_maybe(const hal_rsa_key_t * const k
   uint8_t *d = der + hlen;
   memset(d, 0, vlen);
 
-#define _(x) { size_t n = 0; if ((err = hal_asn1_encode_integer(x, d, &n, vlen)) != HAL_OK) return err; d += n; vlen -= n; }
+#define _(x)                                                            \
+  {                                                                     \
+    size_t n = 0;                                                       \
+    err = hal_asn1_encode_integer(x, d, &n, vlen);                      \
+    if (err != HAL_OK)                                                  \
+      return err;                                                       \
+    d += n;                                                             \
+    vlen -= n;                                                          \
+  }
+
   RSAPrivateKey_fields;
 #undef _
 
@@ -936,8 +953,11 @@ hal_error_t hal_rsa_private_key_to_der_extra_maybe(const hal_rsa_key_t * const k
     if ((err = hal_asn1_encode_header(x, sizeof(key->y), d,             \
                                       &n, vlen)) != HAL_OK)             \
       return err;                                                       \
-    d    += n + sizeof(key->y);                                         \
-    vlen -= n + sizeof(key->y);                                         \
+    d    += n;                                                          \
+    vlen -= n;                                                          \
+    memcpy(d, key->y, sizeof(key->y));                                  \
+    d    += sizeof(key->y);                                             \
+    vlen -= sizeof(key->y);                                             \
   }
 
   if (include_extra) {
@@ -952,19 +972,13 @@ hal_error_t hal_rsa_private_key_to_der_extra_maybe(const hal_rsa_key_t * const k
 hal_error_t hal_rsa_private_key_to_der(const hal_rsa_key_t * const key,
                                        uint8_t *der, size_t *der_len, const size_t der_max)
 {
-  return hal_rsa_private_key_to_der_extra_maybe(key, 0, der, der_len, der_max);
+  return hal_rsa_private_key_to_der_internal(key, 0, der, der_len, der_max);
 }
 
 hal_error_t hal_rsa_private_key_to_der_extra(const hal_rsa_key_t * const key,
                                        uint8_t *der, size_t *der_len, const size_t der_max)
 {
-  return hal_rsa_private_key_to_der_extra_maybe(key, 1, der, der_len, der_max);
-}
-
-size_t hal_rsa_private_key_to_der_len(const hal_rsa_key_t * const key)
-{
-  size_t len = 0;
-  return hal_rsa_private_key_to_der(key, NULL, &len, 0) == HAL_OK ? len : 0;
+  return hal_rsa_private_key_to_der_internal(key, 1, der, der_len, der_max);
 }
 
 hal_error_t hal_rsa_private_key_from_der(hal_rsa_key_t **key_,
@@ -1002,7 +1016,16 @@ hal_error_t hal_rsa_private_key_from_der(hal_rsa_key_t **key_,
 
   fp_int version[1] = INIT_FP_INT;
 
-#define _(x) { size_t n; if ((err = hal_asn1_decode_integer(x, d, &n, vlen)) != HAL_OK) return err; d += n; vlen -= n; }
+#define _(x)                                                            \
+  {                                                                     \
+    size_t n;                                                           \
+    err = hal_asn1_decode_integer(x, d, &n, vlen);                      \
+    if (err != HAL_OK)                                                  \
+      return err;                                                       \
+    d += n;                                                             \
+    vlen -= n;                                                          \
+  }
+
   RSAPrivateKey_fields;
 #undef _
 
@@ -1011,8 +1034,11 @@ hal_error_t hal_rsa_private_key_from_der(hal_rsa_key_t **key_,
     size_t hl = 0, vl = 0;                                              \
     if ((err = hal_asn1_decode_header(x, d, vlen, &hl, &vl)) != HAL_OK) \
       return err;                                                       \
-    if (vl > sizeof(key->y))                                            \
+    if (vl > sizeof(key->y)) {                                          \
+      hal_log(HAL_LOG_DEBUG, "extra factor %s too big (%lu > %lu)",     \
+              #y, (unsigned long) vl, (unsigned long) sizeof(key->y));  \
       return HAL_ERROR_ASN1_PARSE_FAILED;                               \
+    }                                                                   \
     memcpy(key->y, d + hl, vl);                                         \
     key->flags |= z;                                                    \
     d    += hl + vl;                                                    \
@@ -1022,8 +1048,16 @@ hal_error_t hal_rsa_private_key_from_der(hal_rsa_key_t **key_,
   RSAPrivateKey_extra_fields;
 #undef _
 
-  if (d != privkey + privkey_len || !fp_iszero(version))
+  if (d != privkey + privkey_len) {
+    hal_log(HAL_LOG_DEBUG, "not at end of buffer (0x%lx != 0x%lx)",
+            (unsigned long) d, (unsigned long) privkey + privkey_len);
     return HAL_ERROR_ASN1_PARSE_FAILED;
+    }
+
+  if (!fp_iszero(version)) {
+    hal_log(HAL_LOG_DEBUG, "nonzero version");
+    return HAL_ERROR_ASN1_PARSE_FAILED;
+  }
 
   *key_ = key;