algif_hash bug?

AF_ALG hash supports the accept() call to allow for partial hash states to be cloned. If an accept() is issued against a socket before ever doing a send(), crypto_ahash_init() will never have been called for the original socket. The hash_accept function in algif_hash will call crypto_ahash_export() which will return an uninitialized request context and then use that for import into the new socket. A problem arises here because hash_accept sets the 'more' bit of the new context to 1 (ctx2->more = 1). This will cause the first send() call for the new socket to skip calling crypto_ahash_init() which can result in an error or oops because the request context for the cloned socket was never initialized.

Is it assumed that the accept() call should only ever be made after having issued at least one send()? Should the ctx2->more value be the value from the original context so that crypto_ahash_init() is called when needed?

Quoted 13 lines · Tom Lendacky

AF_ALG hash supports the accept() call to allow for partial hash states to be cloned. If an accept() is issued against a socket before ever doing a send(), crypto_ahash_init() will never have been called for the original socket. The hash_accept function in algif_hash will call crypto_ahash_export() which will return an uninitialized request context and then use that for import into the new socket. A problem arises here because hash_accept sets the 'more' bit of the new context to 1 (ctx2->more = 1). This will cause the first send() call for the new socket to skip calling crypto_ahash_init() which can result in an error or oops because the request context for the cloned socket was never initialized.

Quoted 4 lines

Is it assumed that the accept() call should only ever be made after having issued at least one send()? Should the ctx2->more value be the value from the original context so that crypto_ahash_init() is called when needed?

I thought we've already fixed this bug with

commit 4afa5f9617927453ac04b24b584f6c718dfb4f45

Author: Herbert Xu <[email protected]>
Date:   Sun Nov 1 17:11:19 2015 +0800

crypto: algif_hash - Only export and import on sockets with data

Cheers,