SLH-DSA Update private key getter to also return public components.

The private key is defined in FIPS 205 as containing the public key,
so we return this also. This also matches what happens in fromdata.

Updated Documentation for SLH_DSA.

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/26839)

diff --git a/doc/man7/EVP_PKEY-SLH-DSA.pod b/doc/man7/EVP_PKEY-SLH-DSA.pod
index 31709ec600fc2a68a43f5076e2e464d5916a529c..bf17d689b3b89acebdd3486a87a6c949ddb96f71 100644 (file)
--- a/doc/man7/EVP_PKEY-SLH-DSA.pod
+++ b/doc/man7/EVP_PKEY-SLH-DSA.pod
@@ -23,13 +23,38 @@ implemented in OpenSSL's default and FIPS providers.  These implementations
 support the associated key, containing the public key I<pub> and the
 private key I<priv>.
 
+SLH-DSA (Stateless Hash-based Digital Signature Standard) uses small keys,
+but has relatively large signatures and is relatively slow performing all
+operations compared to B<ML-DSA>. It does however have proven security proofs,
+since it relies only on hash functions.
+
 Each of the different key types has an associated security parameter B<n>.
 This value is one of 16, 24 or 32 for key types B<SLH-DSA*128*>, B<SLH-DSA*192*>
 and B<SLH-DSA*256*>, respectively.
 
-Both the public and private key contain 2 elements of size B<n>.
+Both the public and private key components contain 2 elements of size B<n>.
 Key generation generates the private key elements and one of the public key
-elements randomly, the final public key element is computed from these values.
+elements randomly, and the final public key element is computed from these values.
+
+The public key has relatively small sizes of 32, 48 or 64 bytes,
+corresponding to the algorithm names of 128, 192 and 256 respectively.
+
+The algorithms ending with B<s> produce smaller signatures, but are much slower
+than the faster B<f> variants.
+
+The signature sizes for the B<s> algorithm variants are 7856, 16224 and 29792
+which correspond to the algorithm names of 128s, 192s and 256s respectively.
+The signature sizes for the B<f> algorithm variants are 17088, 35664 and 49856
+which correspond to the algorithm names containing 128f, 192f and 256f respectively.
+
+Internally there are 7 hash related functions that are used for each algorithm.
+For algorithms containing B<SHAKE> in their name B<SHAKE-256> is used for all
+functions.
+For the <SHA2-128> algorithms the functions use <MGF1-SHA-256>, <HMAC-SHA-256>
+and <SHA-256>.
+The remaining <SHA2> algorithms use <MGF1-SHA-512>, <HMAC-SHA-512>, <SHA-256> and
+<SHA-512>.
+See FIPS 205 Section 11.1 and 11.2 for more information.
 
 =head2 Keygen Parameters
 
@@ -63,11 +88,19 @@ and settable when using EVP_PKEY_fromdata().
 
 =item "pub" (B<OSSL_PKEY_PARAM_PUB_KEY>) <octet string>
 
-The public key value of size 2 * B<n>
+The public key has a size of 2 * B<n> bytes.
+i.e. It consists of the concatenation of PK.seed and PK.root
+as defined by FIPS 205 Figure 16.
 
 =item "priv" (B<OSSL_PKEY_PARAM_PRIV_KEY>) <octet string>
 
-The private key value of size 2 * B<n>.
+The private key has a size of 4 * B<n> bytes, which includes the public key components.
+i.e. It consists of the concatenation of SK.seed, SK.prf, PK.seed and PF.root
+as defined by FIPS 205 Figure 15.
+
+=item "mandatory-digest" (B<OSSL_PKEY_PARAM_MANDATORY_DIGEST>) <UTF8 string>
+
+The empty string, signifying that no digest may be specified.
 
 =back
 
@@ -84,15 +117,15 @@ The private key value of size 2 * B<n>.
 An B<EVP_PKEY> context can be obtained by calling:
 
     EVP_PKEY_CTX *pctx =
-        EVP_PKEY_CTX_new_from_name(NULL, "SLH-DSA-SHA2-128s", NULL);
+        EVP_PKEY_CTX_new_from_name(NULL, "SLH-DSA-SHA2-128f", NULL);
 
 An B<SLH-DSA> key can be generated like this:
 
-    pkey = EVP_PKEY_Q_keygen(NULL, NULL, "SLH-DSA-SHA2-128s");
+    pkey = EVP_PKEY_Q_keygen(NULL, NULL, "SLH-DSA-SHA2-128f");
 
 The key pair components can be extracted from a key by calling:
 
-    uint8_t priv[64], pub[64];
+    uint8_t priv[64], pub[32];
     size_t priv_len, pub_len;
 
     EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PRIV_KEY,

diff --git a/providers/implementations/keymgmt/slh_dsa_kmgmt.c b/providers/implementations/keymgmt/slh_dsa_kmgmt.c
index f4df2e8813cef37a2f1dedbf37473ce54acdddf5..04fe5d9485af643cc6c9880f9fdec443945fc8f0 100644 (file)
--- a/providers/implementations/keymgmt/slh_dsa_kmgmt.c
+++ b/providers/implementations/keymgmt/slh_dsa_kmgmt.c
@@ -185,13 +185,10 @@ static int slh_dsa_get_params(void *keydata, OSSL_PARAM params[])
     priv = ossl_slh_dsa_key_get_priv(key);
     if (priv != NULL) {
         p = OSSL_PARAM_locate(params, OSSL_PKEY_PARAM_PRIV_KEY);
-        /*
-         * ossl_slh_dsa_key_get_priv_len() includes the public key also
-         * so dividing by 2 returns only the private component.
-         */
+        /* Note: ossl_slh_dsa_key_get_priv_len() includes the public key */
         if (p != NULL
             && !OSSL_PARAM_set_octet_string(p, priv,
-                                            ossl_slh_dsa_key_get_priv_len(key) / 2))
+                                            ossl_slh_dsa_key_get_priv_len(key)))
             return 0;
     }
     pub = ossl_slh_dsa_key_get_pub(key);