From 2baa4fc6a37106233fb49985d0a3d6951edba482 Mon Sep 17 00:00:00 2001
From: Johannes Roth <johannes.roth@mtg.de>
Date: Fri, 22 Sep 2023 16:41:38 +0200
Subject: [PATCH] fix not signing with mandated hash algorithm when using PQC

---
 src/lib/crypto/dilithium.cpp   |  6 +++++
 src/lib/crypto/dilithium.h     |  2 ++
 src/lib/crypto/sphincsplus.cpp | 41 +++++++++++++++++++++++++++++++++-
 src/lib/crypto/sphincsplus.h   |  3 +++
 src/lib/pgp-key.cpp            | 22 ++++++++++++++++++
 5 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/src/lib/crypto/dilithium.cpp b/src/lib/crypto/dilithium.cpp
index 2c061518..bd7f112b 100644
--- a/src/lib/crypto/dilithium.cpp
+++ b/src/lib/crypto/dilithium.cpp
@@ -128,4 +128,10 @@ dilithium_hash_allowed(pgp_hash_alg_t hash_alg)
     default:
         return false;
     }
+}
+
+pgp_hash_alg_t
+dilithium_default_hash_alg()
+{
+    return PGP_HASH_SHA3_256;
 }
\ No newline at end of file
diff --git a/src/lib/crypto/dilithium.h b/src/lib/crypto/dilithium.h
index 678cf372..18035ce0 100644
--- a/src/lib/crypto/dilithium.h
+++ b/src/lib/crypto/dilithium.h
@@ -111,4 +111,6 @@ std::pair<pgp_dilithium_public_key_t, pgp_dilithium_private_key_t> dilithium_gen
 
 bool dilithium_hash_allowed(pgp_hash_alg_t hash_alg);
 
+pgp_hash_alg_t dilithium_default_hash_alg();
+
 #endif
diff --git a/src/lib/crypto/sphincsplus.cpp b/src/lib/crypto/sphincsplus.cpp
index 5589212e..d948ddbe 100644
--- a/src/lib/crypto/sphincsplus.cpp
+++ b/src/lib/crypto/sphincsplus.cpp
@@ -383,4 +383,43 @@ sphincsplus_hash_allowed(pgp_pubkey_alg_t        pk_alg,
         break;
     }
     return true;
-}
\ No newline at end of file
+}
+
+pgp_hash_alg_t
+sphincsplus_default_hash_alg(pgp_pubkey_alg_t        pk_alg,
+                             sphincsplus_parameter_t sphincsplus_param)
+{
+    switch (sphincsplus_param) {
+    case sphincsplus_simple_128s:
+        FALLTHROUGH_STATEMENT;
+    case sphincsplus_simple_128f:
+        switch (pk_alg) {
+        case PGP_PKA_SPHINCSPLUS_SHA2:
+            return PGP_HASH_SHA256;
+        case PGP_PKA_SPHINCSPLUS_SHAKE:
+            return PGP_HASH_SHA3_256;
+        default:
+            RNP_LOG("invalid parameter given");
+            throw rnp::rnp_exception(RNP_ERROR_BAD_PARAMETERS);
+        }
+    case sphincsplus_simple_192s:
+        FALLTHROUGH_STATEMENT;
+    case sphincsplus_simple_192f:
+        FALLTHROUGH_STATEMENT;
+    case sphincsplus_simple_256s:
+        FALLTHROUGH_STATEMENT;
+    case sphincsplus_simple_256f:
+        switch (pk_alg) {
+        case PGP_PKA_SPHINCSPLUS_SHA2:
+            return PGP_HASH_SHA512;
+        case PGP_PKA_SPHINCSPLUS_SHAKE:
+            return PGP_HASH_SHA3_512;
+        default:
+            RNP_LOG("invalid parameter given");
+            throw rnp::rnp_exception(RNP_ERROR_BAD_PARAMETERS);
+        }
+    default:
+        RNP_LOG("invalid parameter given");
+        throw rnp::rnp_exception(RNP_ERROR_BAD_PARAMETERS);
+    }
+}
diff --git a/src/lib/crypto/sphincsplus.h b/src/lib/crypto/sphincsplus.h
index c709bb89..17d61c8e 100644
--- a/src/lib/crypto/sphincsplus.h
+++ b/src/lib/crypto/sphincsplus.h
@@ -199,4 +199,7 @@ bool sphincsplus_hash_allowed(pgp_pubkey_alg_t        pk_alg,
                               sphincsplus_parameter_t sphincsplus_param,
                               pgp_hash_alg_t          hash_alg);
 
+pgp_hash_alg_t sphincsplus_default_hash_alg(pgp_pubkey_alg_t        pk_alg,
+                                            sphincsplus_parameter_t sphincsplus_param);
+
 #endif
\ No newline at end of file
diff --git a/src/lib/pgp-key.cpp b/src/lib/pgp-key.cpp
index 99f21ab9..aadd1054 100644
--- a/src/lib/pgp-key.cpp
+++ b/src/lib/pgp-key.cpp
@@ -520,6 +520,28 @@ find_suitable_key(pgp_op_t            op,
 pgp_hash_alg_t
 pgp_hash_adjust_alg_to_key(pgp_hash_alg_t hash, const pgp_key_pkt_t *pubkey)
 {
+#if defined(ENABLE_PQC)
+    switch (pubkey->alg) {
+    case PGP_PKA_SPHINCSPLUS_SHA2:
+        FALLTHROUGH_STATEMENT;
+    case PGP_PKA_SPHINCSPLUS_SHAKE:
+        return sphincsplus_default_hash_alg(pubkey->alg,
+                                            pubkey->material.sphincsplus.pub.param());
+    case PGP_PKA_DILITHIUM3_ED25519:
+        FALLTHROUGH_STATEMENT;
+    case PGP_PKA_DILITHIUM3_P256:
+        FALLTHROUGH_STATEMENT;
+    case PGP_PKA_DILITHIUM5_P384:
+        FALLTHROUGH_STATEMENT;
+    case PGP_PKA_DILITHIUM3_BP256:
+        FALLTHROUGH_STATEMENT;
+    case PGP_PKA_DILITHIUM5_BP384:
+        return dilithium_default_hash_alg();
+    default:
+        break;
+    }
+#endif
+
     if ((pubkey->alg != PGP_PKA_DSA) && (pubkey->alg != PGP_PKA_ECDSA)) {
         return hash;
     }