libceph: introduce ceph_crypt() for in-place en/decryption

Starting with 4.9, kernel stacks may be vmalloced and therefore not
guaranteed to be physically contiguous; the new CONFIG_VMAP_STACK
option is enabled by default on x86.  This makes it invalid to use
on-stack buffers with the crypto scatterlist API, as sg_set_buf()
expects a logical address and won't work with vmalloced addresses.

There isn't a different (e.g. kvec-based) crypto API we could switch
net/ceph/crypto.c to and the current scatterlist.h API isn't getting
updated to accommodate this use case.  Allocating a new header and
padding for each operation is a non-starter, so do the en/decryption
in-place on a single pre-assembled (header + data + padding) heap
buffer.  This is explicitly supported by the crypto API:

    "... the caller may provide the same scatter/gather list for the
     plaintext and cipher text. After the completion of the cipher
     operation, the plaintext data is replaced with the ciphertext data
     in case of an encryption and vice versa for a decryption."

Change-Id: I554cae76340899bb6f00e2e06230f3a27da186a1
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>

2 files changed, 89 insertions, 0 deletions

diff --git a/net/ceph/crypto.c b/net/ceph/crypto.c
index 06f19b9e1..7eb1b89d5 100644
--- a/net/ceph/crypto.c
+++ b/net/ceph/crypto.c
@@ -496,6 +496,93 @@ int ceph_encrypt(struct ceph_crypto_key *secret, void *dst, size_t *dst_len,
 	}
 }
 
+static int ceph_aes_crypt(const struct ceph_crypto_key *key, bool encrypt,
+			  void *buf, int buf_len, int in_len, int *pout_len)
+{
+	struct crypto_skcipher *tfm = ceph_crypto_alloc_cipher();
+	SKCIPHER_REQUEST_ON_STACK(req, tfm);
+	struct sg_table sgt;
+	struct scatterlist prealloc_sg;
+	char iv[AES_BLOCK_SIZE];
+	int pad_byte = AES_BLOCK_SIZE - (in_len & (AES_BLOCK_SIZE - 1));
+	int crypt_len = encrypt ? in_len + pad_byte : in_len;
+	int ret;
+
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	WARN_ON(crypt_len > buf_len);
+	if (encrypt)
+		memset(buf + in_len, pad_byte, pad_byte);
+	ret = setup_sgtable(&sgt, &prealloc_sg, buf, crypt_len);
+	if (ret)
+		goto out_tfm;
+
+	crypto_skcipher_setkey((void *)tfm, key->key, key->len);
+	memcpy(iv, aes_iv, AES_BLOCK_SIZE);
+
+	skcipher_request_set_tfm(req, tfm);
+	skcipher_request_set_callback(req, 0, NULL, NULL);
+	skcipher_request_set_crypt(req, sgt.sgl, sgt.sgl, crypt_len, iv);
+
+	/*
+	print_hex_dump(KERN_ERR, "key: ", DUMP_PREFIX_NONE, 16, 1,
+		       key->key, key->len, 1);
+	print_hex_dump(KERN_ERR, " in: ", DUMP_PREFIX_NONE, 16, 1,
+		       buf, crypt_len, 1);
+	*/
+	if (encrypt)
+		ret = crypto_skcipher_encrypt(req);
+	else
+		ret = crypto_skcipher_decrypt(req);
+	skcipher_request_zero(req);
+	if (ret) {
+		pr_err("%s %scrypt failed: %d\n", __func__,
+		       encrypt ? "en" : "de", ret);
+		goto out_sgt;
+	}
+	/*
+	print_hex_dump(KERN_ERR, "out: ", DUMP_PREFIX_NONE, 16, 1,
+		       buf, crypt_len, 1);
+	*/
+
+	if (encrypt) {
+		*pout_len = crypt_len;
+	} else {
+		pad_byte = *(char *)(buf + in_len - 1);
+		if (pad_byte > 0 && pad_byte <= AES_BLOCK_SIZE &&
+		    in_len >= pad_byte) {
+			*pout_len = in_len - pad_byte;
+		} else {
+			pr_err("%s got bad padding %d on in_len %d\n",
+			       __func__, pad_byte, in_len);
+			ret = -EPERM;
+			goto out_sgt;
+		}
+	}
+
+out_sgt:
+	teardown_sgtable(&sgt);
+out_tfm:
+	crypto_free_skcipher(tfm);
+	return ret;
+}
+
+int ceph_crypt(const struct ceph_crypto_key *key, bool encrypt,
+	       void *buf, int buf_len, int in_len, int *pout_len)
+{
+	switch (key->type) {
+	case CEPH_CRYPTO_NONE:
+		*pout_len = in_len;
+		return 0;
+	case CEPH_CRYPTO_AES:
+		return ceph_aes_crypt(key, encrypt, buf, buf_len, in_len,
+				      pout_len);
+	default:
+		return -ENOTSUPP;
+	}
+}
+
 int ceph_encrypt2(struct ceph_crypto_key *secret, void *dst, size_t *dst_len,
 		  const void *src1, size_t src1_len,
 		  const void *src2, size_t src2_len)
diff --git a/net/ceph/crypto.h b/net/ceph/crypto.h
index 3572dc518..8ef8ae945 100644
--- a/net/ceph/crypto.h
+++ b/net/ceph/crypto.h
@@ -43,6 +43,8 @@ extern int ceph_encrypt2(struct ceph_crypto_key *secret,
 			 void *dst, size_t *dst_len,
 			 const void *src1, size_t src1_len,
 			 const void *src2, size_t src2_len);
+int ceph_crypt(const struct ceph_crypto_key *key, bool encrypt,
+	       void *buf, int buf_len, int in_len, int *pout_len);
 extern int ceph_crypto_init(void);
 extern void ceph_crypto_shutdown(void);