upstream: support PKCS8 as an optional format for storage of

private keys, enabled via "ssh-keygen -m PKCS8" on operations that save
private keys to disk.

The OpenSSH native key format remains the default, but PKCS8 is a
superior format to PEM if interoperability with non-OpenSSH software
is required, as it may use a less terrible KDF (IIRC PEM uses a single
round of MD5 as a KDF).

adapted from patch by Jakub Jelen via bz3013; ok markus

OpenBSD-Commit-ID: 027824e3bc0b1c243dc5188504526d73a55accb1

1 files changed, 56 insertions, 22 deletions

diff --git a/sshkey.c b/sshkey.c
index 6b5ff0485..a0cea9257 100644
--- a/sshkey.c
+++ b/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.79 2019/07/07 01:05:00 dtucker Exp $ */
+/* $OpenBSD: sshkey.c,v 1.80 2019/07/15 13:16:29 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -3975,10 +3975,10 @@ sshkey_parse_private2(struct sshbuf *blob, int type, const char *passphrase,
 
 
 #ifdef WITH_OPENSSL
-/* convert SSH v2 key in OpenSSL PEM format */
+/* convert SSH v2 key to PEM or PKCS#8 format */
 static int
-sshkey_private_pem_to_blob(struct sshkey *key, struct sshbuf *buf,
-    const char *_passphrase, const char *comment)
+sshkey_private_to_blob_pem_pkcs8(struct sshkey *key, struct sshbuf *buf,
+    int format, const char *_passphrase, const char *comment)
 {
         int was_shielded = sshkey_is_shielded(key);
         int success, r;
@@ -3988,32 +3988,49 @@ sshkey_private_pem_to_blob(struct sshkey *key, struct sshbuf *buf,
         char *bptr;
         BIO *bio = NULL;
         struct sshbuf *blob;
+        EVP_PKEY *pkey = NULL;
 
         if (len > 0 && len <= 4)
                 return SSH_ERR_PASSPHRASE_TOO_SHORT;
         if ((blob = sshbuf_new()) == NULL)
                 return SSH_ERR_ALLOC_FAIL;
-        if ((bio = BIO_new(BIO_s_mem())) == NULL) {
-                sshbuf_free(blob);
-                return SSH_ERR_ALLOC_FAIL;
+        if ((bio = BIO_new(BIO_s_mem())) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
         }
+        if (format == SSHKEY_PRIVATE_PKCS8 && (pkey = EVP_PKEY_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
         if ((r = sshkey_unshield_private(key)) != 0)
                 goto out;
 
         switch (key->type) {
         case KEY_DSA:
-                success = PEM_write_bio_DSAPrivateKey(bio, key->dsa,
-                    cipher, passphrase, len, NULL, NULL);
+                if (format == SSHKEY_PRIVATE_PEM) {
+                        success = PEM_write_bio_DSAPrivateKey(bio, key->dsa,
+                            cipher, passphrase, len, NULL, NULL);
+                } else {
+                        success = EVP_PKEY_set1_DSA(pkey, key->dsa);
+                }
                 break;
 #ifdef OPENSSL_HAS_ECC
         case KEY_ECDSA:
-                success = PEM_write_bio_ECPrivateKey(bio, key->ecdsa,
-                    cipher, passphrase, len, NULL, NULL);
+                if (format == SSHKEY_PRIVATE_PEM) {
+                        success = PEM_write_bio_ECPrivateKey(bio, key->ecdsa,
+                            cipher, passphrase, len, NULL, NULL);
+                } else {
+                        success = EVP_PKEY_set1_EC_KEY(pkey, key->ecdsa);
+                }
                 break;
 #endif
         case KEY_RSA:
-                success = PEM_write_bio_RSAPrivateKey(bio, key->rsa,
-                    cipher, passphrase, len, NULL, NULL);
+                if (format == SSHKEY_PRIVATE_PEM) {
+                        success = PEM_write_bio_RSAPrivateKey(bio, key->rsa,
+                            cipher, passphrase, len, NULL, NULL);
+                } else {
+                        success = EVP_PKEY_set1_RSA(pkey, key->rsa);
+                }
                 break;
         default:
                 success = 0;
@@ -4023,6 +4040,13 @@ sshkey_private_pem_to_blob(struct sshkey *key, struct sshbuf *buf,
                 r = SSH_ERR_LIBCRYPTO_ERROR;
                 goto out;
         }
+        if (format == SSHKEY_PRIVATE_PKCS8) {
+                if ((success = PEM_write_bio_PrivateKey(bio, pkey, cipher,
+                    passphrase, len, NULL, NULL)) == 0) {
+                        r = SSH_ERR_LIBCRYPTO_ERROR;
+                        goto out;
+                }
+        }
         if ((blen = BIO_get_mem_data(bio, &bptr)) <= 0) {
                 r = SSH_ERR_INTERNAL_ERROR;
                 goto out;
@@ -4035,8 +4059,9 @@ sshkey_private_pem_to_blob(struct sshkey *key, struct sshbuf *buf,
                 r = sshkey_shield_private(key);
         if (r == 0)
                 r = sshbuf_putb(buf, blob);
-        sshbuf_free(blob);
 
+        EVP_PKEY_free(pkey);
+        sshbuf_free(blob);
         BIO_free(bio);
         return r;
 }
@@ -4046,29 +4071,38 @@ sshkey_private_pem_to_blob(struct sshkey *key, struct sshbuf *buf,
 int
 sshkey_private_to_fileblob(struct sshkey *key, struct sshbuf *blob,
     const char *passphrase, const char *comment,
-    int force_new_format, const char *new_format_cipher, int new_format_rounds)
+    int format, const char *openssh_format_cipher, int openssh_format_rounds)
 {
         switch (key->type) {
 #ifdef WITH_OPENSSL
         case KEY_DSA:
         case KEY_ECDSA:
         case KEY_RSA:
-                if (force_new_format) {
-                        return sshkey_private_to_blob2(key, blob, passphrase,
-                            comment, new_format_cipher, new_format_rounds);
-                }
-                return sshkey_private_pem_to_blob(key, blob,
-                    passphrase, comment);
+                break; /* see below */
 #endif /* WITH_OPENSSL */
         case KEY_ED25519:
 #ifdef WITH_XMSS
         case KEY_XMSS:
 #endif /* WITH_XMSS */
                 return sshkey_private_to_blob2(key, blob, passphrase,
-                    comment, new_format_cipher, new_format_rounds);
+                    comment, openssh_format_cipher, openssh_format_rounds);
         default:
                 return SSH_ERR_KEY_TYPE_UNKNOWN;
         }
+
+#ifdef WITH_OPENSSL
+        switch (format) {
+        case SSHKEY_PRIVATE_OPENSSH:
+                return sshkey_private_to_blob2(key, blob, passphrase,
+                    comment, openssh_format_cipher, openssh_format_rounds);
+        case SSHKEY_PRIVATE_PEM:
+        case SSHKEY_PRIVATE_PKCS8:
+                return sshkey_private_to_blob_pem_pkcs8(key, blob,
+                    format, passphrase, comment);
+        default:
+                return SSH_ERR_INVALID_ARGUMENT;
+        }
+#endif /* WITH_OPENSSL */
 }