[gnunet] branch master updated: - Add KEM validation error handling

[gnunet]

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martin-schanzenbach pushed a commit to branch master
in repository gnunet.

The following commit(s) were added to refs/heads/master by this push:
     new 0e9d6af26 - Add KEM validation error handling
0e9d6af26 is described below

commit 0e9d6af260c8bfd5293ce6dc084325f6fabdd9ea
Author: Martin Schanzenbach <schanzen@gnunet.org>
AuthorDate: Wed Jul 17 09:09:54 2024 +0200

    - Add KEM validation error handling
---
 src/lib/util/crypto_ecc.c | 12 ++++++++++--
 src/lib/util/crypto_kem.c | 15 +++++++++------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/lib/util/crypto_ecc.c b/src/lib/util/crypto_ecc.c
index a1f6d5c74..ee5c42417 100644
--- a/src/lib/util/crypto_ecc.c
+++ b/src/lib/util/crypto_ecc.c
@@ -768,9 +768,13 @@ GNUNET_CRYPTO_x25519_ecdh (const struct 
GNUNET_CRYPTO_EcdhePrivateKey *sk,
                            const struct GNUNET_CRYPTO_EcdhePublicKey *pub,
                            struct GNUNET_CRYPTO_EcdhePublicKey *dh)
 {
+  uint8_t checkbyte = 0;
   if (0 != crypto_scalarmult_curve25519 (dh->q_y, sk->d, pub->q_y))
     return GNUNET_SYSERR;
-  return GNUNET_OK;
+  // We need to check if this is the all-zero value
+  for (int i = 0; i < sizeof *dh; i++)
+    checkbyte ^= ((uint8_t*)dh)[i];
+  return (0 == checkbyte) ? GNUNET_SYSERR : GNUNET_OK;
 }
 
 
@@ -779,9 +783,13 @@ GNUNET_CRYPTO_ecdh_x25519 (const struct 
GNUNET_CRYPTO_EcdhePrivateKey *sk,
                            const struct GNUNET_CRYPTO_EcdhePublicKey *pk,
                            struct GNUNET_CRYPTO_EcdhePublicKey *dh)
 {
+  uint8_t checkbyte = 0;
   if (0 != crypto_scalarmult_curve25519 (dh->q_y, sk->d, pk->q_y))
     return GNUNET_SYSERR;
-  return GNUNET_OK;
+  // We need to check if this is the all-zero value
+  for (int i = 0; i < sizeof *dh; i++)
+    checkbyte ^= ((uint8_t*)dh)[i];
+  return (0 == checkbyte) ? GNUNET_SYSERR : GNUNET_OK;
 }
 
 
diff --git a/src/lib/util/crypto_kem.c b/src/lib/util/crypto_kem.c
index 5a6ff8d3d..fd7fc4575 100644
--- a/src/lib/util/crypto_kem.c
+++ b/src/lib/util/crypto_kem.c
@@ -54,8 +54,8 @@ labeled_extract (const char *ctx_str,
                  const uint8_t *suite_id, size_t suite_id_len,
                  struct GNUNET_ShortHashCode *prk)
 {
-  size_t labeled_ikm_len = strlen (ctx_str) + suite_id_len +
-    label_len + ikm_len;
+  size_t labeled_ikm_len = strlen (ctx_str) + suite_id_len
+                           + label_len + ikm_len;
   uint8_t labeled_ikm[labeled_ikm_len];
   uint8_t *tmp = labeled_ikm;
 
@@ -218,8 +218,9 @@ GNUNET_CRYPTO_kem_encaps_norand (const struct 
GNUNET_CRYPTO_EcdhePublicKey *pub,
   GNUNET_CRYPTO_ecdhe_key_get_public (skE, c);
 
   // dh = DH(skE, pkR)
-  GNUNET_assert (GNUNET_OK == GNUNET_CRYPTO_ecdh_x25519 (skE, pub,
-                                                         &dh));
+  if (GNUNET_OK != GNUNET_CRYPTO_ecdh_x25519 (skE, pub,
+                                              &dh))
+    return GNUNET_SYSERR; // ValidationError
   // enc = SerializePublicKey(pkE) is a NOP, see Section 7.1.1
   // pkRm = SerializePublicKey(pkR) is a NOP, see Section 7.1.1
   // kem_context = concat(enc, pkRm)
@@ -279,8 +280,10 @@ GNUNET_CRYPTO_kem_decaps (const struct 
GNUNET_CRYPTO_EcdhePrivateKey *skR,
 
   // pkE = DeserializePublicKey(enc) is a NOP, see Section 7.1.1
   // dh = DH(skR, pkE)
-  GNUNET_assert (GNUNET_OK == GNUNET_CRYPTO_x25519_ecdh (skR, c,
-                                                         &dh));
+  if (GNUNET_OK != GNUNET_CRYPTO_x25519_ecdh (skR, c,
+                                              &dh))
+    return GNUNET_SYSERR; // ValidationError
+
   // pkRm = DeserializePublicKey(pk(skR)) is a NOP, see Section 7.1.1
   crypto_scalarmult_curve25519_base (pkR, skR->d);
   // kem_context = concat(enc, pkRm)

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