Explicit length checks in circuit_init_cpath_crypto().

1 files changed, 18 insertions, 5 deletions

diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c
index fdcf3e7a75..0dd33fc03a 100644
--- a/src/or/circuitbuild.c
+++ b/src/or/circuitbuild.c
@@ -46,6 +46,7 @@
 #include "crypto.h"
 #include "directory.h"
 #include "entrynodes.h"
+#include "hs_ntor.h"
 #include "main.h"
 #include "microdesc.h"
 #include "networkstatus.h"
@@ -1331,7 +1332,7 @@ circuit_extend(cell_t *cell, circuit_t *circ)
  * service circuits and <b>key_data</b> must be at least
  * HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN bytes in length.
  *
- * If <b>is_hs_v3</b> is not set, key_data must contain CPATH_KEY_MATERIAL
+ * If <b>is_hs_v3</b> is not set, key_data must contain CPATH_KEY_MATERIAL_LEN
  * bytes, which are used as follows:
  *   - 20 to initialize f_digest
  *   - 20 to initialize b_digest
@@ -1339,9 +1340,12 @@ circuit_extend(cell_t *cell, circuit_t *circ)
  *   - 16 to key b_crypto
  *
  * (If 'reverse' is true, then f_XX and b_XX are swapped.)
+ *
+ * Return 0 if init was successful, else -1 if it failed.
  */
 int
-circuit_init_cpath_crypto(crypt_path_t *cpath, const char *key_data,
+circuit_init_cpath_crypto(crypt_path_t *cpath,
+                          const char *key_data, size_t key_data_len,
                           int reverse, int is_hs_v3)
 {
   crypto_digest_t *tmp_digest;
@@ -1354,6 +1358,13 @@ circuit_init_cpath_crypto(crypt_path_t *cpath, const char *key_data,
   tor_assert(!(cpath->f_crypto || cpath->b_crypto ||
              cpath->f_digest || cpath->b_digest));
 
+  /* Basic key size validation */
+  if (is_hs_v3 && BUG(key_data_len != HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN)) {
+    return -1;
+  } else if (!is_hs_v3 && BUG(key_data_len != CPATH_KEY_MATERIAL_LEN)) {
+    return -1;
+  }
+
   /* If we are using this cpath for next gen onion services use SHA3-256,
      otherwise use good ol' SHA1 */
   if (is_hs_v3) {
@@ -1450,7 +1461,7 @@ circuit_finish_handshake(origin_circuit_t *circ,
 
   onion_handshake_state_release(&hop->handshake_state);
 
-  if (circuit_init_cpath_crypto(hop, keys, 0, 0)<0) {
+  if (circuit_init_cpath_crypto(hop, keys, sizeof(keys), 0, 0)<0) {
     return -END_CIRC_REASON_TORPROTOCOL;
   }
 
@@ -1517,12 +1528,14 @@ circuit_truncated(origin_circuit_t *circ, crypt_path_t *layer, int reason)
 int
 onionskin_answer(or_circuit_t *circ,
                  const created_cell_t *created_cell,
-                 const char *keys,
+                 const char *keys, size_t keys_len,
                  const uint8_t *rend_circ_nonce)
 {
   cell_t cell;
   crypt_path_t *tmp_cpath;
 
+  tor_assert(keys_len == CPATH_KEY_MATERIAL_LEN);
+
   if (created_cell_format(&cell, created_cell) < 0) {
     log_warn(LD_BUG,"couldn't format created cell (type=%d, len=%d)",
              (int)created_cell->cell_type, (int)created_cell->handshake_len);
@@ -1538,7 +1551,7 @@ onionskin_answer(or_circuit_t *circ,
   log_debug(LD_CIRC,"init digest forward 0x%.8x, backward 0x%.8x.",
             (unsigned int)get_uint32(keys),
             (unsigned int)get_uint32(keys+20));
-  if (circuit_init_cpath_crypto(tmp_cpath, keys, 0, 0)<0) {
+  if (circuit_init_cpath_crypto(tmp_cpath, keys, keys_len, 0, 0)<0) {
     log_warn(LD_BUG,"Circuit initialization failed");
     tor_free(tmp_cpath);
     return -1;