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Been meaning to get round to this for a while: use CryptGenRandom to

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gather extra entropy at Windows PuTTY startup time. (It's only used as
one of the inputs to PuTTY's internal entropy pool, so nobody is
required to trust it.)

[originally from svn r9941]
This commit is contained in:
Simon Tatham 2013-07-20 08:34:54 +00:00
parent b426872219
commit 8902fef445
1 changed files with 30 additions and 3 deletions
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33
windows/winnoise.c
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@ -9,10 +9,18 @@
#include "ssh.h" #include "ssh.h"
#include "storage.h" #include "storage.h"
#include <wincrypt.h>
DECL_WINDOWS_FUNCTION(static, BOOL, CryptAcquireContextA,
(HCRYPTPROV *, LPCTSTR, LPCTSTR, DWORD, DWORD));
DECL_WINDOWS_FUNCTION(static, BOOL, CryptGenRandom,
(HCRYPTPROV, DWORD, BYTE *));
DECL_WINDOWS_FUNCTION(static, BOOL, CryptReleaseContext,
(HCRYPTPROV, DWORD));
static HMODULE wincrypt_module = NULL;
/* /*
* This function is called once, at PuTTY startup, and will do some * This function is called once, at PuTTY startup.
* seriously silly things like listing directories and getting disk
* free space and a process snapshot.
*/ */
void noise_get_heavy(void (*func) (void *, int)) void noise_get_heavy(void (*func) (void *, int))
@ -20,6 +28,7 @@ void noise_get_heavy(void (*func) (void *, int))
HANDLE srch; HANDLE srch;
WIN32_FIND_DATA finddata; WIN32_FIND_DATA finddata;
DWORD pid; DWORD pid;
HCRYPTPROV crypt_provider;
char winpath[MAX_PATH + 3]; char winpath[MAX_PATH + 3];
GetWindowsDirectory(winpath, sizeof(winpath)); GetWindowsDirectory(winpath, sizeof(winpath));
@ -35,6 +44,24 @@ void noise_get_heavy(void (*func) (void *, int))
pid = GetCurrentProcessId(); pid = GetCurrentProcessId();
func(&pid, sizeof(pid)); func(&pid, sizeof(pid));
if (!wincrypt_module) {
wincrypt_module = load_system32_dll("advapi32.dll");
GET_WINDOWS_FUNCTION(wincrypt_module, CryptAcquireContextA);
GET_WINDOWS_FUNCTION(wincrypt_module, CryptGenRandom);
GET_WINDOWS_FUNCTION(wincrypt_module, CryptReleaseContext);
}
if (wincrypt_module && p_CryptAcquireContextA &&
p_CryptGenRandom && p_CryptReleaseContext &&
p_CryptAcquireContextA(&crypt_provider, NULL, NULL, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT)) {
BYTE buf[32];
if (p_CryptGenRandom(crypt_provider, 32, buf)) {
func(buf, sizeof(buf));
}
p_CryptReleaseContext(crypt_provider, 0);
}
read_random_seed(func); read_random_seed(func);
/* Update the seed immediately, in case another instance uses it. */ /* Update the seed immediately, in case another instance uses it. */
random_save_seed(); random_save_seed();