[tor-commits] [tor/master] memwipe interesting unused memory

[nickm at torproject.org]

commit 74981d1f133f0ecb1050715af4ee5d409fcebd41
Author: George Kadianakis <desnacked at riseup.net>
Date:   Thu Aug 3 15:42:30 2017 +0300

    memwipe interesting unused memory
---
 src/or/hs_cell.c   | 15 +++++++++------
 src/or/hs_common.c |  8 ++++++++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/src/or/hs_cell.c b/src/or/hs_cell.c
index 712faa335..922ff7346 100644
--- a/src/or/hs_cell.c
+++ b/src/or/hs_cell.c
@@ -193,18 +193,16 @@ build_legacy_establish_intro(const char *circ_nonce, crypto_pk_t *enc_key,
                              uint8_t *cell_out)
 {
   ssize_t cell_len;
-  char buf[RELAY_PAYLOAD_SIZE] = {0};
 
   tor_assert(circ_nonce);
   tor_assert(enc_key);
   tor_assert(cell_out);
 
-  cell_len = rend_service_encode_establish_intro_cell(buf, sizeof(buf),
+  memwipe(cell_out, 0, RELAY_PAYLOAD_SIZE);
+
+  cell_len = rend_service_encode_establish_intro_cell((char*)cell_out,
+                                                      RELAY_PAYLOAD_SIZE,
                                                       enc_key, circ_nonce);
-  tor_assert(cell_len <= RELAY_PAYLOAD_SIZE);
-  if (cell_len >= 0) {
-    memcpy(cell_out, buf, cell_len);
-  }
   return cell_len;
 }
 
@@ -326,6 +324,9 @@ hs_cell_build_establish_intro(const char *circ_nonce,
                         tmp_cell_enc, tmp_cell_enc_len - tmp_cell_mac_offset);
     handshake_ptr = trn_cell_establish_intro_getarray_handshake_mac(cell);
     memcpy(handshake_ptr, mac, sizeof(mac));
+
+    memwipe(mac, 0, sizeof(mac));
+    memwipe(tmp_cell_enc, 0, sizeof(tmp_cell_enc));
   }
 
   /* Calculate the cell signature SIG. */
@@ -353,6 +354,8 @@ hs_cell_build_establish_intro(const char *circ_nonce,
     /* Copy the signature into the cell. */
     sig_ptr = trn_cell_establish_intro_getarray_sig(cell);
     memcpy(sig_ptr, sig.sig, sig_len);
+
+    memwipe(tmp_cell_enc, 0, sizeof(tmp_cell_enc));
   }
 
   /* Encode the cell. Can't be bigger than a standard cell. */
diff --git a/src/or/hs_common.c b/src/or/hs_common.c
index f3604d67c..f63adf51b 100644
--- a/src/or/hs_common.c
+++ b/src/or/hs_common.c
@@ -582,6 +582,8 @@ build_blinded_key_param(const ed25519_public_key_t *pubkey,
   /* Extract digest and put it in the param. */
   crypto_digest_get_digest(digest, (char *) param_out, DIGEST256_LEN);
   crypto_digest_free(digest);
+
+  memwipe(nonce, 0, sizeof(nonce));
 }
 
 /* Using an ed25519 public key and version to build the checksum of an
@@ -701,6 +703,8 @@ hs_get_subcredential(const ed25519_public_key_t *identity_pk,
                           ED25519_PUBKEY_LEN);
   crypto_digest_get_digest(digest, (char *) subcred_out, DIGEST256_LEN);
   crypto_digest_free(digest);
+
+  memwipe(credential, 0, sizeof(credential));
 }
 
 /* From the given list of hidden service ports, find the matching one from the
@@ -892,6 +896,8 @@ hs_build_blinded_pubkey(const ed25519_public_key_t *pk,
   build_blinded_key_param(pk, secret, secret_len,
                           time_period_num, get_time_period_length(), param);
   ed25519_public_blind(blinded_pk_out, pk, param);
+
+  memwipe(param, 0, sizeof(param));
 }
 
 /* From a given ed25519 keypair kp and an optional secret, compute a blinded
@@ -916,6 +922,8 @@ hs_build_blinded_keypair(const ed25519_keypair_t *kp,
   build_blinded_key_param(&kp->pubkey, secret, secret_len,
                           time_period_num, get_time_period_length(), param);
   ed25519_keypair_blind(blinded_kp_out, kp, param);
+
+  memwipe(param, 0, sizeof(param));
 }
 
 /* Return true if overlap mode is active given the date in consensus. If