upstream: Ensure FIDO/PKCS11 libraries contain expected symbols

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

diff --git a/misc.c b/misc.c
index e77b869be4e62aa91515a750d2421e1b46222cfe..253ecd5bd3d0914a69040a116c3149f49842b6cc 100644 (file)
--- a/misc.c
+++ b/misc.c
@@ -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 */
+}

diff --git a/misc.h b/misc.h
index 07408ca13c457077d3fad441ace2ca02ca56110d..fd77a7fd7273d664f28f06fc5601ec6e68a73818 100644 (file)
--- a/misc.h
+++ b/misc.h
@@ -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);
 

diff --git a/ssh-pkcs11.c b/ssh-pkcs11.c
index 0b51e7753882fd6bc747c12171e21db708313b7a..8e2b9cb973109184fd720d2e0c4e7bf6a2042afd 100644 (file)
--- a/ssh-pkcs11.c
+++ b/ssh-pkcs11.c
@@ -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());

diff --git a/ssh-sk.c b/ssh-sk.c
index fbeb39320976f7791f40688fc3f64e748a2dae00..d1c18803ff83ebd1d5de89f27f233992645beed3 100644 (file)
--- a/ssh-sk.c
+++ b/ssh-sk.c
@@ -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",