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Fix remote code execution in ssh-agent PKCS#11 support

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Resolves: CVE-2023-38408
This commit is contained in:
Dmitry Belyavskiy 2023-07-21 17:00:23 +02:00
parent 9fd130d8eb
commit c3494feffe
2 changed files with 137 additions and 1 deletions
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130
openssh-9.3p1-upstream-cve-2023-38408.patch Normal file
View File

@ -0,0 +1,130 @@
diff --git a/ssh-agent.c b/ssh-agent.c
index 618bb198..8ea831f4 100644
diff -up openssh-9.3p1/ssh-agent.c.cve openssh-9.3p1/ssh-agent.c
--- openssh-9.3p1/ssh-agent.c.cve 2023-07-21 15:38:13.237276580 +0200
+++ openssh-9.3p1/ssh-agent.c 2023-07-21 15:41:30.269943569 +0200
@@ -169,6 +169,12 @@ char socket_dir[PATH_MAX];
/* Pattern-list of allowed PKCS#11/Security key paths */
static char *allowed_providers;
+/*
+ * Allows PKCS11 providers or SK keys that use non-internal providers to
+ * be added over a remote connection (identified by session-bind@openssh.com).
+ */
+static int remote_add_provider;
+
/* locking */
#define LOCK_SIZE 32
#define LOCK_SALT_SIZE 16
@@ -1228,6 +1234,12 @@ process_add_identity(SocketEntry *e)
if (strcasecmp(sk_provider, "internal") == 0) {
debug_f("internal provider");
} else {
+ if (e->nsession_ids != 0 && !remote_add_provider) {
+ verbose("failed add of SK provider \"%.100s\": "
+ "remote addition of providers is disabled",
+ sk_provider);
+ goto out;
+ }
if (realpath(sk_provider, canonical_provider) == NULL) {
verbose("failed provider \"%.100s\": "
"realpath: %s", sk_provider,
@@ -1368,7 +1380,7 @@ no_identities(SocketEntry *e)
#ifdef ENABLE_PKCS11
static char *
-sanitize_pkcs11_provider(const char *provider)
+sanitize_pkcs11_provider(SocketEntry *e, const char *provider)
{
struct pkcs11_uri *uri = NULL;
char *sane_uri, *module_path = NULL; /* default path */
@@ -1399,6 +1411,11 @@ sanitize_pkcs11_provider(const char *pro
module_path = strdup(provider); /* simple path */
if (module_path != NULL) { /* do not validate default NULL path in URI */
+ if (e->nsession_ids != 0 && !remote_add_provider) {
+ verbose("failed PKCS#11 add of \"%.100s\": remote addition of "
+ "providers is disabled", provider);
+ return NULL;
+ }
if (realpath(module_path, canonical_provider) == NULL) {
verbose("failed PKCS#11 provider \"%.100s\": realpath: %s",
module_path, strerror(errno));
@@ -1455,7 +1472,7 @@ process_add_smartcard_key(SocketEntry *e
goto send;
}
- sane_uri = sanitize_pkcs11_provider(provider);
+ sane_uri = sanitize_pkcs11_provider(e, provider);
if (sane_uri == NULL)
goto send;
@@ -1516,7 +1533,7 @@ process_remove_smartcard_key(SocketEntry
}
free(pin);
- sane_uri = sanitize_pkcs11_provider(provider);
+ sane_uri = sanitize_pkcs11_provider(e, provider);
if (sane_uri == NULL)
goto send;
@@ -2108,7 +2125,9 @@ main(int ac, char **av)
break;
case 'O':
if (strcmp(optarg, "no-restrict-websafe") == 0)
- restrict_websafe = 0;
+ restrict_websafe = 0;
+ else if (strcmp(optarg, "allow-remote-pkcs11") == 0)
+ remote_add_provider = 1;
else
fatal("Unknown -O option");
break;
diff --git a/ssh-pkcs11.c b/ssh-pkcs11.c
index 6be647ec..ebddf6c3 100644
--- a/ssh-pkcs11.c
+++ b/ssh-pkcs11.c
@@ -1537,10 +1537,8 @@ pkcs11_register_provider(char *provider_id, char *pin,
error("dlopen %s failed: %s", provider_module, dlerror());
goto fail;
}
- if ((getfunctionlist = dlsym(handle, "C_GetFunctionList")) == NULL) {
- error("dlsym(C_GetFunctionList) failed: %s", dlerror());
- goto fail;
- }
+ if ((getfunctionlist = dlsym(handle, "C_GetFunctionList")) == NULL)
+ fatal("dlsym(C_GetFunctionList) failed: %s", dlerror());
p->module->handle = handle;
/* setup the pkcs11 callbacks */
--- a/ssh-agent.1 2023-03-15 22:28:19.000000000 +0100
+++ b/ssh-agent.1 2023-07-19 21:39:17.981406432 +0200
@@ -107,9 +107,27 @@
.It Fl O Ar option
Specify an option when starting
.Nm .
-Currently only one option is supported:
+Currently two options are supported:
+.Cm allow-remote-pkcs11
+and
.Cm no-restrict-websafe .
-This instructs
+.Pp
+The
+.Cm allow-remote-pkcs11
+option allows clients of a forwarded
+.Nm
+to load PKCS#11 or FIDO provider libraries.
+By default only local clients may perform this operation.
+Note that signalling that a
+.Nm
+client remote is performed by
+.Xr ssh 1 ,
+and use of other tools to forward access to the agent socket may circumvent
+this restriction.
+.Pp
+The
+.Cm no-restrict-websafe ,
+instructs
.Nm
to permit signatures using FIDO keys that might be web authentication
requests.

8
openssh.spec
View File

@ -47,7 +47,7 @@
# Do not forget to bump pam_ssh_agent_auth release if you rewind the main package release to 1
%global openssh_ver 9.3p1
%global openssh_rel 3
%global openssh_rel 5
%global pam_ssh_agent_ver 0.10.4
%global pam_ssh_agent_rel 9
@ -228,6 +228,7 @@ Patch1006: openssh-8.7p1-negotiate-supported-algs.patch
Patch1012: openssh-9.0p1-evp-fips-dh.patch
Patch1013: openssh-9.0p1-evp-fips-ecdh.patch
Patch1014: openssh-8.7p1-nohostsha1proof.patch
Patch1015: openssh-9.3p1-upstream-cve-2023-38408.patch
License: BSD
Requires: /sbin/nologin
@ -430,6 +431,7 @@ popd
%patch -P 1012 -p1 -b .evp-fips-dh
%patch -P 1013 -p1 -b .evp-fips-ecdh
%patch -P 1014 -p1 -b .nosha1hostproof
%patch -P 1015 -p1 -b .cve-2023-38408
%patch -P 100 -p1 -b .coverity
@ -737,6 +739,10 @@ test -f %{sysconfig_anaconda} && \
%endif
%changelog
* Fri Jul 21 2023 Dmitry Belyavskiy <dbelyavs@redhat.com> - 9.3p1-5
- Fix remote code execution in ssh-agent PKCS#11 support
Resolves: CVE-2023-38408
* Thu Jul 20 2023 Fedora Release Engineering <releng@fedoraproject.org> - 9.3p1-3.1
- Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild