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EVP: Take care of locks when downgrading an EVP_PKEY

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The temporary copy that's made didn't have a lock, which could end up
with a crash.  We now handle locks a bit better, and take extra care to
lock it and keep track of which lock is used where and which lock is
thrown away.

Fixes #12876

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/12978)
This commit is contained in:
Richard Levitte 2020-09-25 09:28:14 +02:00
parent 9f7505ab6a
commit a8154452e5
1 changed files with 48 additions and 13 deletions
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61
crypto/evp/p_lib.c
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@ -1379,6 +1379,13 @@ size_t EVP_PKEY_get1_tls_encodedpoint(EVP_PKEY *pkey, unsigned char **ppt)
/*- All methods below can also be used in FIPS_MODULE */
/*
* This reset function must be used very carefully, as it literally throws
* away everything in an EVP_PKEY without freeing them, and may cause leaks
* of memory, locks, what have you.
* The only reason we have this is to have the same code for EVP_PKEY_new()
* and evp_pkey_downgrade().
*/
static int evp_pkey_reset_unlocked(EVP_PKEY *pk)
{
if (pk == NULL)
@ -1389,6 +1396,12 @@ static int evp_pkey_reset_unlocked(EVP_PKEY *pk)
pk->save_type = EVP_PKEY_NONE;
pk->references = 1;
pk->save_parameters = 1;
pk->lock = CRYPTO_THREAD_lock_new();
if (pk->lock == NULL) {
EVPerr(0, ERR_R_MALLOC_FAILURE);
return 0;
}
return 1;
}
@ -1404,11 +1417,6 @@ EVP_PKEY *EVP_PKEY_new(void)
if (!evp_pkey_reset_unlocked(ret))
goto err;
ret->lock = CRYPTO_THREAD_lock_new();
if (ret->lock == NULL) {
EVPerr(EVP_F_EVP_PKEY_NEW, ERR_R_MALLOC_FAILURE);
goto err;
}
#ifndef FIPS_MODULE
if (!CRYPTO_new_ex_data(CRYPTO_EX_INDEX_EVP_PKEY, ret, &ret->ex_data)) {
EVPerr(EVP_F_EVP_PKEY_NEW, ERR_R_MALLOC_FAILURE);
@ -1908,24 +1916,41 @@ int evp_pkey_copy_downgraded(EVP_PKEY **dest, const EVP_PKEY *src)
int evp_pkey_downgrade(EVP_PKEY *pk)
{
EVP_PKEY tmp_copy; /* Stack allocated! */
EVP_PKEY tmp_copy; /* Stack allocated! */
CRYPTO_RWLOCK *tmp_lock = NULL; /* Temporary lock */
int rv = 0;
if (!ossl_assert(pk != NULL))
return 0;
/*
* Throughout this whole function, we must ensure that we lock / unlock
* the exact same lock. Note that we do pass it around a bit.
*/
if (!CRYPTO_THREAD_write_lock(pk->lock))
return 0;
/* If this isn't an assigned provider side key, we're done */
if (!evp_pkey_is_assigned(pk) || !evp_pkey_is_provided(pk))
return 1;
if (!evp_pkey_is_assigned(pk) || !evp_pkey_is_provided(pk)) {
rv = 1;
goto end;
}
/*
* To be able to downgrade, we steal the contents of |pk|, then reset
* it, and finally try to make it a downgraded copy. If any of that
* fails, we restore the copied contents into |pk|.
*/
tmp_copy = *pk;
tmp_copy = *pk; /* |tmp_copy| now owns THE lock */
if (evp_pkey_reset_unlocked(pk)
&& evp_pkey_copy_downgraded(&pk, &tmp_copy)) {
/* Grab the temporary lock to avoid lock leak */
tmp_lock = pk->lock;
/* Restore the common attributes, then empty |tmp_copy| */
pk->references = tmp_copy.references;
pk->lock = tmp_copy.lock;
pk->lock = tmp_copy.lock; /* |pk| now owns THE lock */
pk->attributes = tmp_copy.attributes;
pk->save_parameters = tmp_copy.save_parameters;
pk->ex_data = tmp_copy.ex_data;
@ -1955,12 +1980,22 @@ int evp_pkey_downgrade(EVP_PKEY *pk)
tmp_copy.keydata = NULL;
evp_pkey_free_it(&tmp_copy);
rv = 1;
} else {
/* Grab the temporary lock to avoid lock leak */
tmp_lock = pk->lock;
return 1;
/* Restore the original key */
*pk = tmp_copy; /* |pk| now owns THE lock */
}
*pk = tmp_copy;
return 0;
/* Free the temporary lock. It should never be NULL */
CRYPTO_THREAD_lock_free(tmp_lock);
end:
if (!CRYPTO_THREAD_unlock(pk->lock))
return 0;
return rv;
}
#endif /* FIPS_MODULE */