generic curve25519 encode/decode API

doc/dox_comments/header_files/asn_public.h

@@ -1557,6 +1557,137 @@ int wc_EccPublicKeyToDer(ecc_key* key, byte* output,
 int wc_EccPublicKeyToDer_ex(ecc_key* key, byte* output,
                                      word32 inLen, int with_AlgCurve, int comp);
 
+
+/*!
+    \ingroup ASN
+
+    \brief This function decodes a Curve25519 private key (only) from a DER
+    encoded buffer
+
+    \return 0 Success
+    \return BAD_FUNC_ARG Returns if input, inOutIdx or key is null
+    \return ASN_PARSE_E Returns if there is an error parsing the DER encoded
+    data
+    \return ECC_BAD_ARG_E Returns if the key length is not CURVE25519_KEYSIZE or
+    the DER key contains other issues despite being properly formatted.
+    \return BUFFER_E Returns if the input buffer is too small to contain a
+    valid DER encoded key.
+
+    \param input Pointer to buffer containing DER encoded private key
+    \param inOutIdx Index to start reading input buffer from.  On output,
+    index is set to last position parsed of input buffer.
+    \param key Pointer to curve25519_key structure to store decoded key
+    \param inSz Size of input DER buffer
+*/
+int wc_Curve25519PrivateKeyDecode(const byte* input, word32* inOutIdx,
+                                  curve25519_key* key, word32 inSz);
+
+/*!
+    \ingroup ASN
+
+    \brief This function decodes a Curve25519 public key (only) from a DER
+    encoded buffer.
+
+    \return 0 Success
+    \return BAD_FUNC_ARG Returns if input, inOutIdx or key is null
+    \return ASN_PARSE_E Returns if there is an error parsing the DER encoded
+    data
+    \return ECC_BAD_ARG_E Returns if the key length is not CURVE25519_KEYSIZE or
+    the DER key contains other issues despite being properly formatted.
+    \return BUFFER_E Returns if the input buffer is too small to contain a
+    valid DER encoded key.
+
+    \param input Pointer to buffer containing DER encoded public key
+    \param inOutIdx Index to start reading input buffer from.  On output,
+    index is set to last position parsed of input buffer.
+    \param key Pointer to curve25519_key structure to store decoded key
+    \param inSz Size of input DER buffer
+*/
+int wc_Curve25519PublicKeyDecode(const byte* input, word32* inOutIdx,
+                                 curve25519_key* key, word32 inSz);
+
+/*!
+    \ingroup ASN
+
+    \brief This function decodes a Curve25519 key from a DER encoded buffer. It
+    can decode either a private key, a public key, or both.
+
+    \return 0 Success
+    \return BAD_FUNC_ARG Returns if input, inOutIdx or key is null
+    \return ASN_PARSE_E Returns if there is an error parsing the DER encoded
+    data
+    \return ECC_BAD_ARG_E Returns if the key length is not CURVE25519_KEYSIZE or
+    the DER key contains other issues despite being properly formatted.
+    \return BUFFER_E Returns if the input buffer is too small to contain a
+    valid DER encoded key.
+
+    \param input Pointer to buffer containing DER encoded key
+    \param inOutIdx Index to start reading input buffer from.  On output,
+    index is set to last position parsed of input buffer.
+    \param key Pointer to curve25519_key structure to store decoded key
+    \param inSz Size of input DER buffer
+*/
+int wc_Curve25519KeyDecode(const byte* input, word32* inOutIdx,
+                           curve25519_key* key, word32 inSz);
+
+/*!
+    \ingroup ASN
+
+    \brief This function encodes a Curve25519 private key to DER format. If the
+    input key structure contains a public key, it will be ignored.
+
+    \return >0 Success, length of DER encoding
+    \return BAD_FUNC_ARG Returns if key or output is null
+    \return MEMORY_E Returns if there is an allocation failure
+    \return BUFFER_E Returns if output buffer is too small
+
+    \param key Pointer to curve25519_key structure containing private key to
+    encode
+    \param output Buffer to hold DER encoding
+    \param inLen Size of output buffer
+*/
+int wc_Curve25519PrivateKeyToDer(curve25519_key* key, byte* output,
+                                 word32 inLen);
+
+/*!
+    \ingroup ASN
+
+    \brief This function encodes a Curve25519 public key to DER format. If the
+    input key structure contains a private key, it will be ignored.
+
+    \return >0 Success, length of DER encoding
+    \return BAD_FUNC_ARG Returns if key or output is null
+    \return MEMORY_E Returns if there is an allocation failure
+    \return BUFFER_E Returns if output buffer is too small
+
+    \param key Pointer to curve25519_key structure containing public key to
+    encode
+    \param output Buffer to hold DER encoding
+    \param inLen Size of output buffer
+    \param withAlg Whether to include algorithm identifier
+*/
+int wc_Curve25519PublicKeyToDer(curve25519_key* key, byte* output, word32 inLen,
+                                int withAlg);
+
+/*!
+    \ingroup ASN
+
+    \brief This function encodes a Curve25519 key to DER format. It can encode
+    either a private key, a public key, or both.
+
+    \return >0 Success, length of DER encoding
+    \return BAD_FUNC_ARG Returns if key or output is null
+    \return MEMORY_E Returns if there is an allocation failure
+    \return BUFFER_E Returns if output buffer is too small
+
+    \param key Pointer to curve25519_key structure containing key to encode
+    \param output Buffer to hold DER encoding
+    \param inLen Size of output buffer
+    \param withAlg Whether to include algorithm identifier
+*/
+int wc_Curve25519KeyToDer(curve25519_key* key, byte* output, word32 inLen,
+                          int withAlg);
+
 /*!
     \ingroup ASN
 

wolfcrypt/src/asn.c

@@ -35661,6 +35661,55 @@ int wc_Curve25519PublicKeyDecode(const byte* input, word32* inOutIdx,
     }
     return ret;
 }
+
+/* Decode Curve25519 key from DER format - can handle private only,
+ * public only, or private+public key pairs.
+ * return 0 on success, negative on error */
+int wc_Curve25519KeyDecode(const byte* input, word32* inOutIdx,
+                          curve25519_key* key, word32 inSz)
+{
+    int ret;
+    byte privKey[CURVE25519_KEYSIZE];
+    byte pubKey[CURVE25519_KEYSIZE];
+    word32 privKeyLen = CURVE25519_KEYSIZE;
+    word32 pubKeyLen = CURVE25519_KEYSIZE;
+
+    /* sanity check */
+    if (input == NULL || inOutIdx == NULL || key == NULL || inSz == 0) {
+        return BAD_FUNC_ARG;
+    }
+
+    /* Try to decode as private key first (may include public) */
+    ret = DecodeAsymKey(input, inOutIdx, inSz, privKey, &privKeyLen,
+                        pubKey, &pubKeyLen, X25519k);
+
+    if (ret == 0) {
+        /* Successfully decoded private key */
+        if (pubKeyLen > 0) {
+            /* Have both private and public */
+            ret = wc_curve25519_import_private_raw(privKey, privKeyLen,
+                                                   pubKey, pubKeyLen, key);
+        }
+        else {
+            /* Private only */
+            ret = wc_curve25519_import_private(privKey, privKeyLen, key);
+        }
+    }
+    else {
+        /* Try decoding as public key */
+        *inOutIdx = 0; /* Reset index */
+        pubKeyLen = CURVE25519_KEYSIZE;
+        ret = DecodeAsymKeyPublic(input, inOutIdx, inSz,
+                                  pubKey, &pubKeyLen, X25519k);
+        if (ret == 0) {
+            /* Successfully decoded public key */
+            ret = wc_curve25519_import_public(pubKey, pubKeyLen, key);
+        }
+    }
+
+    return ret;
+}
+
 #endif /* HAVE_CURVE25519 && HAVE_ED25519_KEY_IMPORT */
 
 
@@ -35868,6 +35917,63 @@ int wc_Curve25519PublicKeyToDer(curve25519_key* key, byte* output, word32 inLen,
     }
     return ret;
 }
+
+/* Export Curve25519 key to DER format - handles private only, public only,
+ * or private+public key pairs based on what's set in the key structure.
+ * Returns length written on success, negative on error */
+int wc_Curve25519KeyToDer(curve25519_key* key, byte* output, word32 inLen, int withAlg)
+{
+    int ret;
+    byte privKey[CURVE25519_KEYSIZE];
+    byte pubKey[CURVE25519_KEYSIZE];
+    word32 privKeyLen = CURVE25519_KEYSIZE;
+    word32 pubKeyLen = CURVE25519_KEYSIZE;
+
+    if (key == NULL) {
+        return BAD_FUNC_ARG;
+    }
+
+    /* Check what we have in the key structure */
+    if (key->privSet) {
+        /* Export private key to buffer */
+        ret = wc_curve25519_export_private_raw(key, privKey, &privKeyLen);
+        if (ret != 0) {
+            return ret;
+        }
+
+        if (key->pubSet) {
+            /* Export public key if available */
+            ret = wc_curve25519_export_public(key, pubKey, &pubKeyLen);
+            if (ret != 0) {
+                return ret;
+            }
+            /* Export both private and public */
+            ret = SetAsymKeyDer(privKey, privKeyLen,
+                                pubKey, pubKeyLen,
+                                output, inLen, X25519k);
+        }
+        else {
+            /* Export private only */
+            ret = SetAsymKeyDer(privKey, privKeyLen,
+                                NULL, 0,
+                                output, inLen, X25519k);
+        }
+    }
+    else if (key->pubSet) {
+        /* Export public key only */
+        ret = wc_curve25519_export_public(key, pubKey, &pubKeyLen);
+        if (ret == 0) {
+            ret = SetAsymKeyDerPublic(pubKey, pubKeyLen,
+                                      output, inLen, X25519k, withAlg);
+        }
+    }
+    else {
+        /* Neither public nor private key is set */
+        ret = BAD_FUNC_ARG;
+    }
+
+    return ret;
+}
 #endif /* HAVE_CURVE25519 && HAVE_CURVE25519_KEY_EXPORT */
 
 #if defined(HAVE_ED448) && defined(HAVE_ED448_KEY_IMPORT)