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upstream: place shielded keys (i.e. keys at rest in RAM) into memory

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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
This commit is contained in:
djm@openbsd.org 2024-08-20 03:48:30 +00:00 committed by Damien Miller
parent a0b35c791c
commit cc048ca536
No known key found for this signature in database
1 changed files with 26 additions and 6 deletions
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32
sshkey.c
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@ -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 <sys/types.h>
#include <sys/mman.h>
#include <netinet/in.h>
#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;