https://github.com/python/cpython/commit/e545bae55a608e39d84fb3577f5b266ccab480cc
commit: e545bae55a608e39d84fb3577f5b266ccab480cc
branch: main
author: Bénédikt Tran <[email protected]>
committer: picnixz <[email protected]>
date: 2025-08-22T09:19:04Z
summary:
gh-134531: simplify code for computing HMAC digests (#138046)
files:
M Modules/_hashopenssl.c
diff --git a/Modules/_hashopenssl.c b/Modules/_hashopenssl.c
index 9deafb5253056c..a6496d0f04f2d0 100644
--- a/Modules/_hashopenssl.c
+++ b/Modules/_hashopenssl.c
@@ -1939,20 +1939,30 @@ locked_HMAC_CTX_copy(HMAC_CTX *new_ctx_p, HMACobject
*self)
return 0;
}
-/* returning 0 means that an error occurred and an exception is set */
+#define BAD_DIGEST_SIZE 0
+
+/*
+ * Return the digest size in bytes.
+ *
+ * On error, set an exception and return BAD_DIGEST_SIZE.
+ */
static unsigned int
_hashlib_hmac_digest_size(HMACobject *self)
{
const EVP_MD *md = _hashlib_hmac_get_md(self);
if (md == NULL) {
- return 0;
+ return BAD_DIGEST_SIZE;
}
- unsigned int digest_size = EVP_MD_size(md);
- assert(digest_size <= EVP_MAX_MD_SIZE);
+ int digest_size = EVP_MD_size(md);
+ /* digest_size < 0 iff EVP_MD context is NULL (which is impossible here) */
+ assert(digest_size >= 0);
+ assert(digest_size <= (int)EVP_MAX_MD_SIZE);
+ /* digest_size == 0 means that the context is not entirely initialized */
if (digest_size == 0) {
- notify_ssl_error_occurred("invalid digest size");
+ raise_ssl_error(PyExc_ValueError, "missing digest size");
+ return BAD_DIGEST_SIZE;
}
- return digest_size;
+ return (unsigned int)digest_size;
}
static int
@@ -2053,24 +2063,38 @@ _hashlib_HMAC_update_impl(HMACobject *self, PyObject
*msg)
Py_RETURN_NONE;
}
-static int
-_hmac_digest(HMACobject *self, unsigned char *buf, unsigned int len)
+/*
+ * Extract the MAC value to 'buf' and return the digest size.
+ *
+ * The buffer 'buf' must have at least hashlib_openssl_HMAC_digest_size(self)
+ * bytes. Smaller buffers lead to undefined behaviors.
+ *
+ * On error, set an exception and return -1.
+ */
+static Py_ssize_t
+_hmac_digest(HMACobject *self, unsigned char *buf)
{
+ unsigned int digest_size = _hashlib_hmac_digest_size(self);
+ assert(digest_size <= EVP_MAX_MD_SIZE);
+ if (digest_size == BAD_DIGEST_SIZE) {
+ assert(PyErr_Occurred());
+ return -1;
+ }
HMAC_CTX *temp_ctx = py_openssl_wrapper_HMAC_CTX_new();
if (temp_ctx == NULL) {
- return 0;
+ return -1;
}
if (locked_HMAC_CTX_copy(temp_ctx, self) < 0) {
HMAC_CTX_free(temp_ctx);
- return 0;
+ return -1;
}
- int r = HMAC_Final(temp_ctx, buf, &len);
+ int r = HMAC_Final(temp_ctx, buf, NULL);
HMAC_CTX_free(temp_ctx);
if (r == 0) {
notify_ssl_error_occurred_in(Py_STRINGIFY(HMAC_Final));
- return 0;
+ return -1;
}
- return 1;
+ return digest_size;
}
/*[clinic input]
@@ -2082,16 +2106,9 @@ static PyObject *
_hashlib_HMAC_digest_impl(HMACobject *self)
/*[clinic end generated code: output=1b1424355af7a41e input=bff07f74da318fb4]*/
{
- unsigned char digest[EVP_MAX_MD_SIZE];
- unsigned int digest_size = _hashlib_hmac_digest_size(self);
- if (digest_size == 0) {
- return NULL;
- }
- int r = _hmac_digest(self, digest, digest_size);
- if (r == 0) {
- return NULL;
- }
- return PyBytes_FromStringAndSize((const char *)digest, digest_size);
+ unsigned char buf[EVP_MAX_MD_SIZE];
+ Py_ssize_t n = _hmac_digest(self, buf);
+ return n < 0 ? NULL : PyBytes_FromStringAndSize((const char *)buf, n);
}
/*[clinic input]
@@ -2109,24 +2126,17 @@ static PyObject *
_hashlib_HMAC_hexdigest_impl(HMACobject *self)
/*[clinic end generated code: output=80d825be1eaae6a7 input=5e48db83ab1a4d19]*/
{
- unsigned char digest[EVP_MAX_MD_SIZE];
- unsigned int digest_size = _hashlib_hmac_digest_size(self);
- if (digest_size == 0) {
- return NULL;
- }
- int r = _hmac_digest(self, digest, digest_size);
- if (r == 0) {
- return NULL;
- }
- return _Py_strhex((const char *)digest, digest_size);
+ unsigned char buf[EVP_MAX_MD_SIZE];
+ Py_ssize_t n = _hmac_digest(self, buf);
+ return n < 0 ? NULL : _Py_strhex((const char *)buf, n);
}
static PyObject *
_hashlib_hmac_get_digest_size(PyObject *op, void *Py_UNUSED(closure))
{
HMACobject *self = HMACobject_CAST(op);
- unsigned int digest_size = _hashlib_hmac_digest_size(self);
- return digest_size == 0 ? NULL : PyLong_FromLong(digest_size);
+ unsigned int size = _hashlib_hmac_digest_size(self);
+ return size == BAD_DIGEST_SIZE ? NULL : PyLong_FromLong(size);
}
static PyObject *
_______________________________________________
Python-checkins mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3//lists/python-checkins.python.org
Member address: [email protected]
