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upstream: Ensure FIDO/PKCS11 libraries contain expected symbols

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This checks via nlist(3) that candidate provider libraries contain one
of the symbols that we will require prior to dlopen(), which can cause
a number of side effects, including execution of constructors.

Feedback deraadt; ok markus

OpenBSD-Commit-ID: 1508a5fbd74e329e69a55b56c453c292029aefbe
This commit is contained in:
djm@openbsd.org 2023-07-19 14:02:27 +00:00 committed by Damien Miller
parent 1f2731f5d7
commit 29ef8a0486
No known key found for this signature in database
4 changed files with 89 additions and 6 deletions
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78
misc.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: misc.c,v 1.183 2023/07/14 07:44:21 dtucker Exp $ */
/* $OpenBSD: misc.c,v 1.184 2023/07/19 14:02:27 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2005-2020 Damien Miller. All rights reserved.
@ -22,6 +22,7 @@
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
@ -35,6 +36,9 @@
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#ifdef HAVE_NLIST_H
#include <nlist.h>
#endif
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
@ -2920,3 +2924,75 @@ ptimeout_isset(struct timespec *pt)
{
return pt->tv_sec != -1;
}
/*
* Returns zero if the library at 'path' contains symbol 's', nonzero
* otherwise.
*/
int
lib_contains_symbol(const char *path, const char *s)
{
#ifdef HAVE_NLIST_H
struct nlist nl[2];
int ret = -1, r;
memset(nl, 0, sizeof(nl));
nl[0].n_name = xstrdup(s);
nl[1].n_name = NULL;
if ((r = nlist(path, nl)) == -1) {
error_f("nlist failed for %s", path);
goto out;
}
if (r != 0 || nl[0].n_value == 0 || nl[0].n_type == 0) {
error_f("library %s does not contain symbol %s", path, s);
goto out;
}
/* success */
ret = 0;
out:
free(nl[0].n_name);
return ret;
#else /* HAVE_NLIST_H */
int fd, ret = -1;
struct stat st;
void *m = NULL;
size_t sz = 0;
memset(&st, 0, sizeof(st));
if ((fd = open(path, O_RDONLY)) < 0) {
error_f("open %s: %s", path, strerror(errno));
return -1;
}
if (fstat(fd, &st) != 0) {
error_f("fstat %s: %s", path, strerror(errno));
goto out;
}
if (!S_ISREG(st.st_mode)) {
error_f("%s is not a regular file", path);
goto out;
}
if (st.st_size < 0 ||
(size_t)st.st_size < strlen(s) ||
st.st_size >= INT_MAX/2) {
error_f("%s bad size %lld", path, (long long)st.st_size);
goto out;
}
sz = (size_t)st.st_size;
if ((m = mmap(NULL, sz, PROT_READ, MAP_PRIVATE, fd, 0)) == MAP_FAILED ||
m == NULL) {
error_f("mmap %s: %s", path, strerror(errno));
goto out;
}
if (memmem(m, sz, s, strlen(s)) == NULL) {
error_f("%s does not contain expected string %s", path, s);
goto out;
}
/* success */
ret = 0;
out:
if (m != NULL && m != MAP_FAILED)
munmap(m, sz);
close(fd);
return ret;
#endif /* HAVE_NLIST_H */
}

3
misc.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: misc.h,v 1.102 2023/03/03 02:37:58 dtucker Exp $ */
/* $OpenBSD: misc.h,v 1.103 2023/07/19 14:02:27 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@ -96,6 +96,7 @@ int parse_absolute_time(const char *, uint64_t *);
void format_absolute_time(uint64_t, char *, size_t);
int path_absolute(const char *);
int stdfd_devnull(int, int, int);
int lib_contains_symbol(const char *, const char *);
void sock_set_v6only(int);

6
ssh-pkcs11.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-pkcs11.c,v 1.57 2023/07/19 13:55:53 djm Exp $ */
/* $OpenBSD: ssh-pkcs11.c,v 1.58 2023/07/19 14:02:27 djm Exp $ */
/*
* Copyright (c) 2010 Markus Friedl. All rights reserved.
* Copyright (c) 2014 Pedro Martelletto. All rights reserved.
@ -1532,6 +1532,10 @@ pkcs11_register_provider(char *provider_id, char *pin,
debug_f("provider already registered: %s", provider_id);
goto fail;
}
if (lib_contains_symbol(provider_id, "C_GetFunctionList") != 0) {
error("provider %s is not a PKCS11 library", provider_id);
goto fail;
}
/* open shared pkcs11-library */
if ((handle = dlopen(provider_id, RTLD_NOW)) == NULL) {
error("dlopen %s failed: %s", provider_id, dlerror());

8
ssh-sk.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-sk.c,v 1.39 2022/07/20 03:29:14 djm Exp $ */
/* $OpenBSD: ssh-sk.c,v 1.40 2023/07/19 14:02:27 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
@ -133,10 +133,12 @@ sshsk_open(const char *path)
goto fail;
#endif
}
if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL) {
error("Provider \"%s\" dlopen failed: %s", path, dlerror());
if (lib_contains_symbol(path, "sk_api_version") != 0) {
error("provider %s is not an OpenSSH FIDO library", path);
goto fail;
}
if ((ret->dlhandle = dlopen(path, RTLD_NOW)) == NULL)
fatal("Provider \"%s\" dlopen failed: %s", path, dlerror());
if ((ret->sk_api_version = dlsym(ret->dlhandle,
"sk_api_version")) == NULL) {
error("Provider \"%s\" dlsym(sk_api_version) failed: %s",