supply callback to PEM_read_bio_PrivateKey

OpenSSL 1.1.0i has changed the behaviour of their PEM APIs,
so that empty passphrases are interpreted differently. This
probabalistically breaks loading some keys, because the PEM format
is terrible and doesn't include a proper MAC.

Avoid this by providing a basic callback to avoid passing empty
passphrases to OpenSSL in cases where one is required.

Based on patch from Jakub Jelen in bz#2913; ok dtucker@

1 files changed, 15 insertions, 1 deletions

diff --git a/sshkey.c b/sshkey.c
index e1e882b7..4a656f84 100644
--- a/sshkey.c
+++ b/sshkey.c
@@ -3914,6 +3914,20 @@ convert_libcrypto_error(void)
 }
 
 static int
+pem_passphrase_cb(char *buf, int size, int rwflag, void *u)
+{
+	char *p = (char *)u;
+	size_t len;
+
+	if (p == NULL || (len = strlen(p)) == 0)
+		return -1;
+	if (size < 0 || len > (size_t)size)
+		return -1;
+	memcpy(buf, p, len);
+	return (int)len;
+}
+
+static int
 sshkey_parse_private_pem_fileblob(struct sshbuf *blob, int type,
     const char *passphrase, struct sshkey **keyp)
 {
@@ -3934,7 +3948,7 @@ sshkey_parse_private_pem_fileblob(struct sshbuf *blob, int type,
 	}
 
 	clear_libcrypto_errors();
-	if ((pk = PEM_read_bio_PrivateKey(bio, NULL, NULL,
+	if ((pk = PEM_read_bio_PrivateKey(bio, NULL, pem_passphrase_cb,
 	    (char *)passphrase)) == NULL) {
 	       /*
 		* libcrypto may return various ASN.1 errors when attempting