| Message ID | 44569470.FQKUtYhtg6@tachyon.chronox.de (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Herbert Xu |
| Headers | show |
On Thu, Mar 12, 2015 at 09:17:51AM +0100, Stephan Mueller wrote: > The kernel crypto API logic requires the caller to provide the > length of (ciphertext || authentication tag) as cryptlen for the > AEAD decryption operation. Thus, the cipher implementation must > calculate the size of the plaintext output itself and cannot simply use > cryptlen. > > The RFC4106 GCM decryption operation tries to overwrite cryptlen memory > in req->dst. As the destination buffer for decryption only needs to hold > the plaintext memory but cryptlen references the input buffer holding > (ciphertext || authentication tag), the assumption of the destination > buffer length in RFC4106 GCM operation leads to a too large size. This > patch simply uses the already calculated plaintext size. > > In addition, this patch fixes the offset calculation of the AAD buffer > pointer: as mentioned before, cryptlen already includes the size of the > tag. Thus, the tag does not need to be added. With the addition, the AAD > will be written beyond the already allocated buffer. > > Note, this fixes a kernel crash that can be triggered from user space > via AF_ALG(aead) -- simply use the libkcapi test application > from [1] and update it to use rfc4106-gcm-aes. > > Using [1], the changes were tested using CAVS vectors to demonstrate > that the crypto operation still delivers the right results. > > [1] http://www.chronox.de/libkcapi.html > > CC: Tadeusz Struk <tadeusz.struk@intel.com> > Signed-off-by: Stephan Mueller <smueller@chronox.de> Patch applied. Thanks!
diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c index 6893f49..d71eb9d 100644 --- a/arch/x86/crypto/aesni-intel_glue.c +++ b/arch/x86/crypto/aesni-intel_glue.c @@ -1135,7 +1135,7 @@ static int __driver_rfc4106_decrypt(struct aead_request *req) src = kmalloc(req->cryptlen + req->assoclen, GFP_ATOMIC); if (!src) return -ENOMEM; - assoc = (src + req->cryptlen + auth_tag_len); + assoc = (src + req->cryptlen); scatterwalk_map_and_copy(src, req->src, 0, req->cryptlen, 0); scatterwalk_map_and_copy(assoc, req->assoc, 0, req->assoclen, 0); @@ -1160,7 +1160,7 @@ static int __driver_rfc4106_decrypt(struct aead_request *req) scatterwalk_done(&src_sg_walk, 0, 0); scatterwalk_done(&assoc_sg_walk, 0, 0); } else { - scatterwalk_map_and_copy(dst, req->dst, 0, req->cryptlen, 1); + scatterwalk_map_and_copy(dst, req->dst, 0, tempCipherLen, 1); kfree(src); } return retval;
The kernel crypto API logic requires the caller to provide the length of (ciphertext || authentication tag) as cryptlen for the AEAD decryption operation. Thus, the cipher implementation must calculate the size of the plaintext output itself and cannot simply use cryptlen. The RFC4106 GCM decryption operation tries to overwrite cryptlen memory in req->dst. As the destination buffer for decryption only needs to hold the plaintext memory but cryptlen references the input buffer holding (ciphertext || authentication tag), the assumption of the destination buffer length in RFC4106 GCM operation leads to a too large size. This patch simply uses the already calculated plaintext size. In addition, this patch fixes the offset calculation of the AAD buffer pointer: as mentioned before, cryptlen already includes the size of the tag. Thus, the tag does not need to be added. With the addition, the AAD will be written beyond the already allocated buffer. Note, this fixes a kernel crash that can be triggered from user space via AF_ALG(aead) -- simply use the libkcapi test application from [1] and update it to use rfc4106-gcm-aes. Using [1], the changes were tested using CAVS vectors to demonstrate that the crypto operation still delivers the right results. [1] http://www.chronox.de/libkcapi.html CC: Tadeusz Struk <tadeusz.struk@intel.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> --- arch/x86/crypto/aesni-intel_glue.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)