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gh-134531: simplify code for computing HMAC digests (#138046)

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Bénédikt Tran 2025-08-22 11:19:04 +02:00 • committed by GitHub
parent 531fc3a7a3
commit e545bae55a
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1 changed files with 45 additions and 35 deletions
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80
Modules/_hashopenssl.c
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@ -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 *