From cc048ca536d6bed6f2285b07040b0d57cd559ba5 Mon Sep 17 00:00:00 2001 From: "djm@openbsd.org" Date: Tue, 20 Aug 2024 03:48:30 +0000 Subject: upstream: place shielded keys (i.e. keys at rest in RAM) into memory allocated using mmap(3) with MAP_CONCEAL set. This prevents exposure of the key material in coredumps, etc (this is in addition to other measures we take in this area). ok deraadt@ OpenBSD-Commit-ID: cbbae59f337a00c9858d6358bc65f74e62261369 --- sshkey.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) diff --git a/sshkey.c b/sshkey.c index cc04f94de..6207cfc1d 100644 --- a/sshkey.c +++ b/sshkey.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sshkey.c,v 1.143 2024/08/15 00:51:51 djm Exp $ */ +/* $OpenBSD: sshkey.c,v 1.144 2024/08/20 03:48:30 djm Exp $ */ /* * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. * Copyright (c) 2008 Alexander von Gernler. All rights reserved. @@ -28,6 +28,7 @@ #include "includes.h" #include +#include #include #ifdef WITH_OPENSSL @@ -739,6 +740,27 @@ sshkey_sk_cleanup(struct sshkey *k) k->sk_key_handle = k->sk_reserved = NULL; } +static int +sshkey_prekey_alloc(u_char **prekeyp, size_t len) +{ + u_char *prekey; + + *prekeyp = NULL; + if ((prekey = mmap(NULL, SSHKEY_SHIELD_PREKEY_LEN, PROT_READ|PROT_WRITE, + MAP_ANON|MAP_PRIVATE|MAP_CONCEAL, -1, 0)) == MAP_FAILED) + return SSH_ERR_SYSTEM_ERROR; + *prekeyp = prekey; + return 0; +} + +static void +sshkey_prekey_free(void *prekey, size_t len) +{ + if (prekey == NULL) + return; + munmap(prekey, len); +} + static void sshkey_free_contents(struct sshkey *k) { @@ -752,7 +774,7 @@ sshkey_free_contents(struct sshkey *k) if (sshkey_is_cert(k)) cert_free(k->cert); freezero(k->shielded_private, k->shielded_len); - freezero(k->shield_prekey, k->shield_prekey_len); + sshkey_prekey_free(k->shield_prekey, k->shield_prekey_len); } void @@ -1620,10 +1642,8 @@ sshkey_shield_private(struct sshkey *k) } /* Prepare a random pre-key, and from it an ephemeral key */ - if ((prekey = malloc(SSHKEY_SHIELD_PREKEY_LEN)) == NULL) { - r = SSH_ERR_ALLOC_FAIL; + if ((r = sshkey_prekey_alloc(&prekey, SSHKEY_SHIELD_PREKEY_LEN)) != 0) goto out; - } arc4random_buf(prekey, SSHKEY_SHIELD_PREKEY_LEN); if ((r = ssh_digest_memory(SSHKEY_SHIELD_PREKEY_HASH, prekey, SSHKEY_SHIELD_PREKEY_LEN, @@ -1701,7 +1721,7 @@ sshkey_shield_private(struct sshkey *k) explicit_bzero(keyiv, sizeof(keyiv)); explicit_bzero(&tmp, sizeof(tmp)); freezero(enc, enclen); - freezero(prekey, SSHKEY_SHIELD_PREKEY_LEN); + sshkey_prekey_free(prekey, SSHKEY_SHIELD_PREKEY_LEN); sshkey_free(kswap); sshbuf_free(prvbuf); return r; -- cgit v1.2.3