[PATCH v8 03/10] crypto: akcipher - new verify API for public key algorithms

Vitaly Chikunov
2019-03-26T12:59:19Z

Previous akcipher .verify() just `decrypts' (using RSA encrypt which is
using public key) signature to uncover message hash, which was then
compared in upper level public_key_verify_signature() with the expected
hash value, which itself was never passed into verify().

This approach was incompatible with EC-DSA family of algorithms,
because, to verify a signature EC-DSA algorithm also needs a hash value
as input; then it's used (together with a signature divided into halves
`r||s') to produce a witness value, which is then compared with `r' to
determine if the signature is correct. Thus, for EC-DSA, nor
requirements of .verify() itself, nor its output expectations in
public_key_verify_signature() wasn't sufficient.

Make improved .verify() call which gets hash value as input and produce
complete signature check without any output besides status.

Now for the top level verification only crypto_akcipher_verify() needs
to be called and its return value inspected.

Make sure that `digest' is in kmalloc'd memory (in place of `output`) in
{public,tpm}_key_verify_signature() as insisted by Herbert Xu, and will
be changed in the following commit.

Cc: David Howells <dhowells@redhat.com>
Cc: keyrings@vger.kernel.org
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
---
crypto/asymmetric_keys/asym_tpm.c | 34 ++++++++-----------------
crypto/asymmetric_keys/public_key.c | 34 ++++++++-----------------
crypto/rsa-pkcs1pad.c | 29 +++++++++++++--------
crypto/testmgr.c | 50 ++++++++++++++++++++++---------------
include/crypto/akcipher.h | 36 ++++++++++++++++----------
5 files changed, 92 insertions(+), 91 deletions(-)

diff --git a/crypto/asymmetric_keys/asym_tpm.c b/crypto/asymmetric_keys/asym_tpm.c
index 5d4c270463f6..4e5b6fb57a94 100644
--- a/crypto/asymmetric_keys/asym_tpm.c
+++ b/crypto/asymmetric_keys/asym_tpm.c
@@ -744,12 +744,11 @@ static int tpm_key_verify_signature(const struct key *key,
struct crypto_wait cwait;
struct crypto_akcipher *tfm;
struct akcipher_request *req;
- struct scatterlist sig_sg, digest_sg;
+ struct scatterlist src_sg[2];
char alg_name[CRYPTO_MAX_ALG_NAME];
uint8_t der_pub_key[PUB_KEY_BUF_SIZE];
uint32_t der_pub_key_len;
- void *output;
- unsigned int outlen;
+ void *digest;
int ret;

pr_devel("==>%s()\n", __func__);
@@ -782,35 +781,22 @@ static int tpm_key_verify_signature(const struct key *key,
goto error_free_tfm;

ret = -ENOMEM;
- outlen = crypto_akcipher_maxsize(tfm);
- output = kmalloc(outlen, GFP_KERNEL);
- if (!output)
+ digest = kmemdup(sig->digest, sig->digest_size, GFP_KERNEL);
+ if (!digest)
goto error_free_req;

- sg_init_one(&sig_sg, sig->s, sig->s_size);
- sg_init_one(&digest_sg, output, outlen);
- akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
- outlen);
+ sg_init_table(src_sg, 2);
+ sg_set_buf(&src_sg[0], sig->s, sig->s_size);
+ sg_set_buf(&src_sg[1], digest, sig->digest_size);
+ akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
+ sig->digest_size);
crypto_init_wait(&cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
-
- /* Perform the verification calculation. This doesn't actually do the
- * verification, but rather calculates the hash expected by the
- * signature and returns that to us.
- */
ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
- if (ret)
- goto out_free_output;
-
- /* Do the actual verification step. */
- if (req->dst_len != sig->digest_size ||
- memcmp(sig->digest, output, sig->digest_size) != 0)
- ret = -EKEYREJECTED;

-out_free_output:
- kfree(output);
+ kfree(digest);
error_free_req:
akcipher_request_free(req);
error_free_tfm:
diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index f5d85b47fcc6..0c069fe8a59c 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -227,10 +227,9 @@ int public_key_verify_signature(const struct public_key *pkey,
struct crypto_wait cwait;
struct crypto_akcipher *tfm;
struct akcipher_request *req;
- struct scatterlist sig_sg, digest_sg;
+ struct scatterlist src_sg[2];
char alg_name[CRYPTO_MAX_ALG_NAME];
- void *output;
- unsigned int outlen;
+ void *digest;
int ret;

pr_devel("==>%s()\n", __func__);
@@ -264,35 +263,22 @@ int public_key_verify_signature(const struct public_key *pkey,
goto error_free_req;

ret = -ENOMEM;
- outlen = crypto_akcipher_maxsize(tfm);
- output = kmalloc(outlen, GFP_KERNEL);
- if (!output)
+ digest = kmemdup(sig->digest, sig->digest_size, GFP_KERNEL);
+ if (!digest)
goto error_free_req;

- sg_init_one(&sig_sg, sig->s, sig->s_size);
- sg_init_one(&digest_sg, output, outlen);
- akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
- outlen);
+ sg_init_table(src_sg, 2);
+ sg_set_buf(&src_sg[0], sig->s, sig->s_size);
+ sg_set_buf(&src_sg[1], digest, sig->digest_size);
+ akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
+ sig->digest_size);
crypto_init_wait(&cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
-
- /* Perform the verification calculation. This doesn't actually do the
- * verification, but rather calculates the hash expected by the
- * signature and returns that to us.
- */
ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
- if (ret)
- goto out_free_output;
-
- /* Do the actual verification step. */
- if (req->dst_len != sig->digest_size ||
- memcmp(sig->digest, output, sig->digest_size) != 0)
- ret = -EKEYREJECTED;

-out_free_output:
- kfree(output);
+ kfree(digest);
error_free_req:
akcipher_request_free(req);
error_free_tfm:
diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c
index 94382fa2c6ac..29c336068dc0 100644
--- a/crypto/rsa-pkcs1pad.c
+++ b/crypto/rsa-pkcs1pad.c
@@ -488,14 +488,21 @@ static int pkcs1pad_verify_complete(struct akcipher_request *req, int err)

err = 0;

- if (req->dst_len < dst_len - pos)
- err = -EOVERFLOW;
- req->dst_len = dst_len - pos;
-
- if (!err)
- sg_copy_from_buffer(req->dst,
- sg_nents_for_len(req->dst, req->dst_len),
- out_buf + pos, req->dst_len);
+ if (req->dst_len != dst_len - pos) {
+ err = -EKEYREJECTED;
+ req->dst_len = dst_len - pos;
+ goto done;
+ }
+ /* Extract appended digest. */
+ sg_pcopy_to_buffer(req->src,
+ sg_nents_for_len(req->src,
+ req->src_len + req->dst_len),
+ req_ctx->out_buf + ctx->key_size,
+ req->dst_len, ctx->key_size);
+ /* Do the actual verification step. */
+ if (memcmp(req_ctx->out_buf + ctx->key_size, out_buf + pos,
+ req->dst_len) != 0)
+ err = -EKEYREJECTED;
done:
kzfree(req_ctx->out_buf);

@@ -532,10 +539,12 @@ static int pkcs1pad_verify(struct akcipher_request *req)
struct pkcs1pad_request *req_ctx = akcipher_request_ctx(req);
int err;

- if (!ctx->key_size || req->src_len < ctx->key_size)
+ if (WARN_ON(req->dst) ||
+ WARN_ON(!req->dst_len) ||
+ !ctx->key_size || req->src_len < ctx->key_size)
return -EINVAL;

- req_ctx->out_buf = kmalloc(ctx->key_size, GFP_KERNEL);
+ req_ctx->out_buf = kmalloc(ctx->key_size + req->dst_len, GFP_KERNEL);
if (!req_ctx->out_buf)
return -ENOMEM;

diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index 2c2ddebb48d3..0013cc398b1f 100644
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -2592,7 +2592,7 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
struct crypto_wait wait;
unsigned int out_len_max, out_len = 0;
int err = -ENOMEM;
- struct scatterlist src, dst, src_tab[2];
+ struct scatterlist src, dst, src_tab[3];
const char *m, *c;
unsigned int m_size, c_size;
const char *op;
@@ -2615,13 +2615,12 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
if (err)
goto free_req;

- err = -ENOMEM;
- out_len_max = crypto_akcipher_maxsize(tfm);
-
/*
* First run test which do not require a private key, such as
* encrypt or verify.
*/
+ err = -ENOMEM;
+ out_len_max = crypto_akcipher_maxsize(tfm);
outbuf_enc = kzalloc(out_len_max, GFP_KERNEL);
if (!outbuf_enc)
goto free_req;
@@ -2647,12 +2646,20 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
goto free_all;
memcpy(xbuf[0], m, m_size);

- sg_init_table(src_tab, 2);
+ sg_init_table(src_tab, 3);
sg_set_buf(&src_tab[0], xbuf[0], 8);
sg_set_buf(&src_tab[1], xbuf[0] + 8, m_size - 8);
- sg_init_one(&dst, outbuf_enc, out_len_max);
- akcipher_request_set_crypt(req, src_tab, &dst, m_size,
- out_len_max);
+ if (vecs->siggen_sigver_test) {
+ if (WARN_ON(c_size > PAGE_SIZE))
+ goto free_all;
+ memcpy(xbuf[1], c, c_size);
+ sg_set_buf(&src_tab[2], xbuf[1], c_size);
+ akcipher_request_set_crypt(req, src_tab, NULL, m_size, c_size);
+ } else {
+ sg_init_one(&dst, outbuf_enc, out_len_max);
+ akcipher_request_set_crypt(req, src_tab, &dst, m_size,
+ out_len_max);
+ }
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
crypto_req_done, &wait);

@@ -2665,18 +2672,21 @@ static int test_akcipher_one(struct crypto_akcipher *tfm,
pr_err("alg: akcipher: %s test failed. err %d\n", op, err);
goto free_all;
}
- if (req->dst_len != c_size) {
- pr_err("alg: akcipher: %s test failed. Invalid output len\n",
- op);
- err = -EINVAL;
- goto free_all;
- }
- /* verify that encrypted message is equal to expected */
- if (memcmp(c, outbuf_enc, c_size)) {
- pr_err("alg: akcipher: %s test failed. Invalid output\n", op);
- hexdump(outbuf_enc, c_size);
- err = -EINVAL;
- goto free_all;
+ if (!vecs->siggen_sigver_test) {
+ if (req->dst_len != c_size) {
+ pr_err("alg: akcipher: %s test failed. Invalid output len\n",
+ op);
+ err = -EINVAL;
+ goto free_all;
+ }
+ /* verify that encrypted message is equal to expected */
+ if (memcmp(c, outbuf_enc, c_size) != 0) {
+ pr_err("alg: akcipher: %s test failed. Invalid output\n",
+ op);
+ hexdump(outbuf_enc, c_size);
+ err = -EINVAL;
+ goto free_all;
+ }
}

/*
diff --git a/include/crypto/akcipher.h b/include/crypto/akcipher.h
index 2d690494568c..2d26939fff51 100644
--- a/include/crypto/akcipher.h
+++ b/include/crypto/akcipher.h
@@ -19,14 +19,20 @@
*
* @base: Common attributes for async crypto requests
* @src: Source data
- * @dst: Destination data
+ * For verify op this is signature + digest, in that case
+ * total size of @src is @src_len + @dst_len.
+ * @dst: Destination data (Should be NULL for verify op)
* @src_len: Size of the input buffer
- * @dst_len: Size of the output buffer. It needs to be at least
- * as big as the expected result depending on the operation
+ * For verify op it's size of signature part of @src, this part
+ * is supposed to be operated by cipher.
+ * @dst_len: Size of @dst buffer (for all ops except verify).
+ * It needs to be at least as big as the expected result
+ * depending on the operation.
* After operation it will be updated with the actual size of the
* result.
* In case of error where the dst sgl size was insufficient,
* it will be updated to the size required for the operation.
+ * For verify op this is size of digest part in @src.
* @__ctx: Start of private context data
*/
struct akcipher_request {
@@ -55,10 +61,9 @@ struct crypto_akcipher {
* algorithm. In case of error, where the dst_len was insufficient,
* the req->dst_len will be updated to the size required for the
* operation
- * @verify: Function performs a sign operation as defined by public key
- * algorithm. In case of error, where the dst_len was insufficient,
- * the req->dst_len will be updated to the size required for the
- * operation
+ * @verify: Function performs a complete verify operation as defined by
+ * public key algorithm, returning verification status. Requires
+ * digest value as input parameter.
* @encrypt: Function performs an encrypt operation as defined by public key
* algorithm. In case of error, where the dst_len was insufficient,
* the req->dst_len will be updated to the size required for the
@@ -238,9 +243,10 @@ static inline void akcipher_request_set_callback(struct akcipher_request *req,
*
* @req: public key request
* @src: ptr to input scatter list
- * @dst: ptr to output scatter list
+ * @dst: ptr to output scatter list or NULL for verify op
* @src_len: size of the src input scatter list to be processed
- * @dst_len: size of the dst output scatter list
+ * @dst_len: size of the dst output scatter list or size of signature
+ * portion in @src for verify op
*/
static inline void akcipher_request_set_crypt(struct akcipher_request *req,
struct scatterlist *src,
@@ -343,14 +349,18 @@ static inline int crypto_akcipher_sign(struct akcipher_request *req)
}

/**
- * crypto_akcipher_verify() - Invoke public key verify operation
+ * crypto_akcipher_verify() - Invoke public key signature verification
*
- * Function invokes the specific public key verify operation for a given
- * public key algorithm
+ * Function invokes the specific public key signature verification operation
+ * for a given public key algorithm.
*
* @req: asymmetric key request
*
- * Return: zero on success; error code in case of error
+ * Note: req->dst should be NULL, req->src should point to SG of size
+ * (req->src_size + req->dst_size), containing signature (of req->src_size
+ * length) with appended digest (of req->dst_size length).
+ *
+ * Return: zero on verification success; error code in case of error.
*/
static inline int crypto_akcipher_verify(struct akcipher_request *req)
{
--
2.11.0