bpo-18407: win32_urandom() uses PY_DWORD_MAX (pythonGH-10656)

vstinner · jkloth · web-flow · commit c48ff73dd60b · 2018-11-22T14:43:07.000+01:00
CryptGenRandom() maximum size is PY_DWORD_MAX, not INT_MAX.
Use DWORD type for the 'chunk' variable

Co-Authored-By: Jeremy Kloth &lt;jeremy.kloth@gmail.com&gt;
diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
@@ -55,8 +55,6 @@ win32_urandom_init(int raise)
 static int
 win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
 {
-    Py_ssize_t chunk;
-
     if (hCryptProv == 0)
     {
         if (win32_urandom_init(raise) == -1) {
@@ -66,8 +64,8 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
 
     while (size > 0)
     {
-        chunk = size > INT_MAX ? INT_MAX : size;
-        if (!CryptGenRandom(hCryptProv, (DWORD)chunk, buffer))
+        DWORD chunk = (DWORD)Py_MIN(size, PY_DWORD_MAX);
+        if (!CryptGenRandom(hCryptProv, chunk, buffer))
         {
             /* CryptGenRandom() failed */
             if (raise) {

Original file line number	Diff line number	Diff line change
`@@ -55,8 +55,6 @@ win32_urandom_init(int raise)`
`55`	`55`	`static int`
`56`	`56`	`win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)`
`57`	`57`	`{`
`58`		`- Py_ssize_t chunk;`
`59`		`-`
`60`	`58`	`if (hCryptProv == 0)`
`61`	`59`	`{`
`62`	`60`	`if (win32_urandom_init(raise) == -1) {`
`@@ -66,8 +64,8 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)`
`66`	`64`
`67`	`65`	`while (size > 0)`
`68`	`66`	`{`
`69`		`- chunk = size > INT_MAX ? INT_MAX : size;`
`70`		`- if (!CryptGenRandom(hCryptProv, (DWORD)chunk, buffer))`
	`67`	`+ DWORD chunk = (DWORD)Py_MIN(size, PY_DWORD_MAX);`
	`68`	`+ if (!CryptGenRandom(hCryptProv, chunk, buffer))`
`71`	`69`	`{`
`72`	`70`	`/* CryptGenRandom() failed */`
`73`	`71`	`if (raise) {`