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Move SID-getting code into a separate function so it can be shared by

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make_private_security_descriptor and a new function protectprocess().

protectprocess() opens the running PuTTY process and adjusts the
Everyone and user access control entries in its ACL to deny a
selection of permissions which malicious processes running as the same
user could use to hijack PuTTY.

(cherry picked from commit aba7234bc1)
This commit is contained in:
Owen Dunn 2015-11-22 12:04:04 +00:00 committed by Simon Tatham
parent 906f8ed262
commit e80b1b8a34
1 changed files with 122 additions and 33 deletions
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155
windows/winsecur.c
View File

@ -12,6 +12,10 @@
#define WINSECUR_GLOBAL
#include "winsecur.h"
/* Initialised once, then kept around to reuse forever */
static PSID worldsid, networksid, usersid;
int got_advapi(void)
{
static int attempted = FALSE;
@ -99,6 +103,52 @@ PSID get_user_sid(void)
return ret;
}
int getsids(char *error)
{
SID_IDENTIFIER_AUTHORITY world_auth = SECURITY_WORLD_SID_AUTHORITY;
SID_IDENTIFIER_AUTHORITY nt_auth = SECURITY_NT_AUTHORITY;
int ret;
error=NULL;
if (!usersid) {
if ((usersid = get_user_sid()) == NULL) {
error = dupprintf("unable to construct SID for current user: %s",
win_strerror(GetLastError()));
goto cleanup;
}
}
if (!worldsid) {
if (!AllocateAndInitializeSid(&world_auth, 1, SECURITY_WORLD_RID,
0, 0, 0, 0, 0, 0, 0, &worldsid)) {
error = dupprintf("unable to construct SID for world: %s",
win_strerror(GetLastError()));
goto cleanup;
}
}
if (!networksid) {
if (!AllocateAndInitializeSid(&nt_auth, 1, SECURITY_NETWORK_RID,
0, 0, 0, 0, 0, 0, 0, &networksid)) {
error = dupprintf("unable to construct SID for "
"local same-user access only: %s",
win_strerror(GetLastError()));
goto cleanup;
}
}
ret=TRUE;
cleanup:
if (ret) {
sfree(error);
error = NULL;
}
return ret;
}
int make_private_security_descriptor(DWORD permissions,
PSECURITY_DESCRIPTOR *psd,
PACL *acl,
@ -110,44 +160,13 @@ int make_private_security_descriptor(DWORD permissions,
int acl_err;
int ret = FALSE;
/* Initialised once, then kept around to reuse forever */
static PSID worldsid, networksid, usersid;
*psd = NULL;
*acl = NULL;
*error = NULL;
if (!got_advapi()) {
*error = dupprintf("unable to load advapi32.dll");
goto cleanup;
}
if (!usersid) {
if ((usersid = get_user_sid()) == NULL) {
*error = dupprintf("unable to construct SID for current user: %s",
win_strerror(GetLastError()));
goto cleanup;
}
}
if (!worldsid) {
if (!AllocateAndInitializeSid(&world_auth, 1, SECURITY_WORLD_RID,
0, 0, 0, 0, 0, 0, 0, &worldsid)) {
*error = dupprintf("unable to construct SID for world: %s",
win_strerror(GetLastError()));
goto cleanup;
}
}
if (!networksid) {
if (!AllocateAndInitializeSid(&nt_auth, 1, SECURITY_NETWORK_RID,
0, 0, 0, 0, 0, 0, 0, &networksid)) {
*error = dupprintf("unable to construct SID for "
"local same-user access only: %s",
win_strerror(GetLastError()));
goto cleanup;
}
}
if (!getsids(*error))
goto cleanup;
memset(ea, 0, sizeof(ea));
ea[0].grfAccessPermissions = permissions;
@ -218,4 +237,74 @@ int make_private_security_descriptor(DWORD permissions,
return ret;
}
int protectprocess(char *error)
{
SID_IDENTIFIER_AUTHORITY world_auth = SECURITY_WORLD_SID_AUTHORITY;
SID_IDENTIFIER_AUTHORITY nt_auth = SECURITY_NT_AUTHORITY;
EXPLICIT_ACCESS ea[2];
int acl_err;
int ret=FALSE;
PACL acl = NULL;
static const nastyace=WRITE_DAC | WRITE_OWNER |
PROCESS_CREATE_PROCESS | PROCESS_CREATE_THREAD |
PROCESS_DUP_HANDLE | PROCESS_QUERY_INFORMATION |
PROCESS_SET_QUOTA | PROCESS_SET_INFORMATION |
PROCESS_VM_OPERATION | PROCESS_VM_READ | PROCESS_VM_WRITE |
PROCESS_SUSPEND_RESUME;
if (!getsids(error))
goto cleanup;
memset(ea, 0, sizeof(ea));
/* Everyone: deny */
ea[0].grfAccessPermissions = nastyace;
ea[0].grfAccessMode = DENY_ACCESS;
ea[0].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
ea[0].Trustee.TrusteeForm = TRUSTEE_IS_SID;
ea[0].Trustee.ptstrName = (LPTSTR)worldsid;
/* User: user ace */
ea[1].grfAccessPermissions = ~nastyace & 0x1fff;
ea[1].grfAccessMode = GRANT_ACCESS;
ea[1].grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
ea[1].Trustee.TrusteeForm = TRUSTEE_IS_SID;
ea[1].Trustee.ptstrName = (LPTSTR)usersid;
acl_err = p_SetEntriesInAclA(2, ea, NULL, &acl);
if (acl_err != ERROR_SUCCESS || acl == NULL) {
error = dupprintf("unable to construct ACL: %s",
win_strerror(acl_err));
goto cleanup;
}
if (ERROR_SUCCESS !=
SetSecurityInfo(
GetCurrentProcess(),
SE_KERNEL_OBJECT,
OWNER_SECURITY_INFORMATION | DACL_SECURITY_INFORMATION,
usersid,
NULL,
acl,
NULL
)) {
error=dupprintf("Unable to set process ACL: %s",
win_strerror(GetLastError()));
goto cleanup;
}
ret=TRUE;
cleanup:
if (!ret) {
if (acl) {
LocalFree(acl);
acl = NULL;
}
}
return ret;
}
#endif /* !defined NO_SECURITY */