--- /dev/null
+/*-
+ * Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License"). You may not use
+ * this file except in compliance with the License. You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+#include <string.h>
+#include <openssl/decoder.h>
+#include <openssl/encoder.h>
+#include <openssl/evp.h>
+
+/*
+ * Example showing the encoding and decoding of EC public and private keys. A
+ * PEM-encoded EC key is read in from stdin, decoded, and then re-encoded and
+ * output for demonstration purposes. Both public and private keys are accepted.
+ *
+ * This can be used to load EC keys from a file or save EC keys to a file.
+ */
+
+/* A property query used for selecting algorithm implementations. */
+static const char *propq = NULL;
+
+/*
+ * Load a PEM-encoded EC key from a file, optionally decrypting it with a
+ * supplied passphrase.
+ */
+static EVP_PKEY *load_key(OSSL_LIB_CTX *libctx, FILE *f, const char *passphrase)
+{
+ int rv = 0;
+ EVP_PKEY *pkey = NULL;
+ OSSL_DECODER_CTX *dctx = NULL;
+ int selection = 0;
+
+ /*
+ * Create PEM decoder context expecting an EC key.
+ *
+ * For raw (non-PEM-encoded) keys, change "PEM" to "DER".
+ *
+ * The selection argument here specifies whether we are willing to accept a
+ * public key, private key, or either. If it is set to zero, either will be
+ * accepted. If set to EVP_PKEY_KEYPAIR, a private key will be required, and
+ * if set to EVP_PKEY_PUBLIC_KEY, a public key will be required.
+ */
+ dctx = OSSL_DECODER_CTX_new_for_pkey(&pkey, "PEM", NULL, "EC",
+ selection,
+ libctx, propq);
+ if (dctx == NULL) {
+ fprintf(stderr, "OSSL_DECODER_CTX_new_for_pkey() failed\n");
+ goto cleanup;
+ }
+
+ /*
+ * Set passphrase if provided; needed to decrypt encrypted PEM files.
+ * If the input is not encrypted, any passphrase provided is ignored.
+ *
+ * Alternative methods for specifying passphrases exist, such as a callback
+ * (see OSSL_DECODER_CTX_set_passphrase_cb(3)), which may be more useful for
+ * interactive applications which do not know if a passphrase should be
+ * prompted for in advance, or for GUI applications.
+ */
+ if (passphrase != NULL) {
+ if (OSSL_DECODER_CTX_set_passphrase(dctx,
+ (const unsigned char *)passphrase,
+ strlen(passphrase)) == 0) {
+ fprintf(stderr, "OSSL_DECODER_CTX_set_passphrase() failed\n");
+ goto cleanup;
+ }
+ }
+
+ /* Do the decode, reading from file. */
+ if (OSSL_DECODER_from_fp(dctx, f) == 0) {
+ fprintf(stderr, "OSSL_DECODER_from_fp() failed\n");
+ goto cleanup;
+ }
+
+ rv = 1;
+cleanup:
+ OSSL_DECODER_CTX_free(dctx);
+
+ /*
+ * pkey is created by OSSL_DECODER_CTX_new_for_pkey, but we
+ * might fail subsequently, so ensure it's properly freed
+ * in this case.
+ */
+ if (rv == 0) {
+ EVP_PKEY_free(pkey);
+ pkey = NULL;
+ }
+
+ return pkey;
+}
+
+/*
+ * Store a EC public or private key to a file using PEM encoding.
+ *
+ * If a passphrase is supplied, the file is encrypted, otherwise
+ * it is unencrypted.
+ */
+static int store_key(EVP_PKEY *pkey, FILE *f, const char *passphrase)
+{
+ int rv = 0;
+ int selection;
+ OSSL_ENCODER_CTX *ectx = NULL;
+
+ /*
+ * Create a PEM encoder context.
+ *
+ * For raw (non-PEM-encoded) output, change "PEM" to "DER".
+ *
+ * The selection argument controls whether the private key is exported
+ * (EVP_PKEY_KEYPAIR), or only the public key (EVP_PKEY_PUBLIC_KEY). The
+ * former will fail if we only have a public key.
+ *
+ * Note that unlike the decode API, you cannot specify zero here.
+ *
+ * Purely for the sake of demonstration, here we choose to export the whole
+ * key if a passphrase is provided and the public key otherwise.
+ */
+ selection = (passphrase != NULL)
+ ? EVP_PKEY_KEYPAIR
+ : EVP_PKEY_PUBLIC_KEY;
+
+ ectx = OSSL_ENCODER_CTX_new_for_pkey(pkey, selection, "PEM", NULL, propq);
+ if (ectx == NULL) {
+ fprintf(stderr, "OSSL_ENCODER_CTX_new_for_pkey() failed\n");
+ goto cleanup;
+ }
+
+ /*
+ * Set passphrase if provided; the encoded output will then be encrypted
+ * using the passphrase.
+ *
+ * Alternative methods for specifying passphrases exist, such as a callback
+ * (see OSSL_ENCODER_CTX_set_passphrase_cb(3), just as for OSSL_DECODER_CTX;
+ * however you are less likely to need them as you presumably know whether
+ * encryption is desired in advance.
+ *
+ * Note that specifying a passphrase alone is not enough to cause the
+ * key to be encrypted. You must set both a cipher and a passphrase.
+ */
+ if (passphrase != NULL) {
+ /*
+ * Set cipher. Let's use AES-256-CBC, because it is
+ * more quantum resistant.
+ */
+ if (OSSL_ENCODER_CTX_set_cipher(ectx, "AES-256-CBC", propq) == 0) {
+ fprintf(stderr, "OSSL_ENCODER_CTX_set_cipher() failed\n");
+ goto cleanup;
+ }
+
+ /* Set passphrase. */
+ if (OSSL_ENCODER_CTX_set_passphrase(ectx,
+ (const unsigned char *)passphrase,
+ strlen(passphrase)) == 0) {
+ fprintf(stderr, "OSSL_ENCODER_CTX_set_passphrase() failed\n");
+ goto cleanup;
+ }
+ }
+
+ /* Do the encode, writing to the given file. */
+ if (OSSL_ENCODER_to_fp(ectx, f) == 0) {
+ fprintf(stderr, "OSSL_ENCODER_to_fp() failed\n");
+ goto cleanup;
+ }
+
+ rv = 1;
+cleanup:
+ OSSL_ENCODER_CTX_free(ectx);
+ return rv;
+}
+
+int main(int argc, char **argv)
+{
+ int rv = 1;
+ OSSL_LIB_CTX *libctx = NULL;
+ EVP_PKEY *pkey = NULL;
+ const char *passphrase_in = NULL, *passphrase_out = NULL;
+
+ /* usage: ec_encode <passphrase-in> <passphrase-out> */
+ if (argc > 1 && argv[1][0])
+ passphrase_in = argv[1];
+
+ if (argc > 2 && argv[2][0])
+ passphrase_out = argv[2];
+
+ /* Decode PEM key from stdin and then PEM encode it to stdout. */
+ pkey = load_key(libctx, stdin, passphrase_in);
+ if (pkey == NULL) {
+ fprintf(stderr, "Failed to decode key\n");
+ goto cleanup;
+ }
+
+ if (store_key(pkey, stdout, passphrase_out) == 0) {
+ fprintf(stderr, "Failed to encode key\n");
+ goto cleanup;
+ }
+
+ rv = 0;
+cleanup:
+ EVP_PKEY_free(pkey);
+ OSSL_LIB_CTX_free(libctx);
+ return rv;
+}
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