1 files changed, 134 insertions, 79 deletions

diff --git a/crypto/asymmetric_keys/rsa.c b/crypto/asymmetric_keys/rsa.c
index 8b08ffcdb809..508b57b77474 100644
--- a/crypto/asymmetric_keys/rsa.c
+++ b/crypto/asymmetric_keys/rsa.c
@@ -11,10 +11,10 @@
 
 #define pr_fmt(fmt) "RSA: "fmt
 #include <linux/module.h>
+#include <linux/kernel.h>
 #include <linux/slab.h>
-#include <crypto/akcipher.h>
-#include <crypto/public_key.h>
 #include <crypto/algapi.h>
+#include "public_key.h"
 
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("RSA Public Key Algorithm");
@@ -84,10 +84,72 @@ static const struct {
 #undef _
 };
 
-struct rsa_completion {
-	struct completion completion;
-	int err;
-};
+/*
+ * RSAVP1() function [RFC3447 sec 5.2.2]
+ */
+static int RSAVP1(const struct public_key *key, MPI s, MPI *_m)
+{
+	MPI m;
+	int ret;
+
+	/* (1) Validate 0 <= s < n */
+	if (mpi_cmp_ui(s, 0) < 0) {
+		kleave(" = -EBADMSG [s < 0]");
+		return -EBADMSG;
+	}
+	if (mpi_cmp(s, key->rsa.n) >= 0) {
+		kleave(" = -EBADMSG [s >= n]");
+		return -EBADMSG;
+	}
+
+	m = mpi_alloc(0);
+	if (!m)
+		return -ENOMEM;
+
+	/* (2) m = s^e mod n */
+	ret = mpi_powm(m, s, key->rsa.e, key->rsa.n);
+	if (ret < 0) {
+		mpi_free(m);
+		return ret;
+	}
+
+	*_m = m;
+	return 0;
+}
+
+/*
+ * Integer to Octet String conversion [RFC3447 sec 4.1]
+ */
+static int RSA_I2OSP(MPI x, size_t xLen, u8 **pX)
+{
+	unsigned X_size, x_size;
+	int X_sign;
+	u8 *X;
+
+	/* Make sure the string is the right length.  The number should begin
+	 * with { 0x00, 0x01, ... } so we have to account for 15 leading zero
+	 * bits not being reported by MPI.
+	 */
+	x_size = mpi_get_nbits(x);
+	pr_devel("size(x)=%u xLen*8=%zu\n", x_size, xLen * 8);
+	if (x_size != xLen * 8 - 15)
+		return -ERANGE;
+
+	X = mpi_get_buffer(x, &X_size, &X_sign);
+	if (!X)
+		return -ENOMEM;
+	if (X_sign < 0) {
+		kfree(X);
+		return -EBADMSG;
+	}
+	if (X_size != xLen - 1) {
+		kfree(X);
+		return -EBADMSG;
+	}
+
+	*pX = X;
+	return 0;
+}
 
 /*
  * Perform the RSA signature verification.
@@ -98,7 +160,7 @@ struct rsa_completion {
  * @asn1_template: The DigestInfo ASN.1 template
  * @asn1_size: Size of asm1_template[]
  */
-static int rsa_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size,
+static int RSA_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size,
 		      const u8 *asn1_template, size_t asn1_size)
 {
 	unsigned PS_end, T_offset, i;
@@ -107,10 +169,10 @@ static int rsa_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size,
 
 	if (k < 2 + 1 + asn1_size + hash_size)
 		return -EBADMSG;
-	/* Decode the EMSA-PKCS1-v1_5
-	 * note: leading zeros are stirpped by the RSA implementation */
-	if (EM[0] != 0x01) {
-		kleave(" = -EBADMSG [EM[0] == %02u]", EM[0]);
+
+	/* Decode the EMSA-PKCS1-v1_5 */
+	if (EM[1] != 0x01) {
+		kleave(" = -EBADMSG [EM[1] == %02u]", EM[1]);
 		return -EBADMSG;
 	}
 
@@ -121,7 +183,7 @@ static int rsa_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size,
 		return -EBADMSG;
 	}
 
-	for (i = 1; i < PS_end; i++) {
+	for (i = 2; i < PS_end; i++) {
 		if (EM[i] != 0xff) {
 			kleave(" = -EBADMSG [EM[PS%x] == %02u]", i - 2, EM[i]);
 			return -EBADMSG;
@@ -142,82 +204,75 @@ static int rsa_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size,
 	return 0;
 }
 
-static void public_key_verify_done(struct crypto_async_request *req, int err)
+/*
+ * Perform the verification step [RFC3447 sec 8.2.2].
+ */
+static int RSA_verify_signature(const struct public_key *key,
+				const struct public_key_signature *sig)
 {
-	struct rsa_completion *compl = req->data;
+	size_t tsize;
+	int ret;
 
-	if (err == -EINPROGRESS)
-		return;
+	/* Variables as per RFC3447 sec 8.2.2 */
+	const u8 *H = sig->digest;
+	u8 *EM = NULL;
+	MPI m = NULL;
+	size_t k;
 
-	compl->err = err;
-	complete(&compl->completion);
-}
+	kenter("");
 
-int rsa_verify_signature(const struct public_key *pkey,
-			 const struct public_key_signature *sig)
-{
-	struct crypto_akcipher *tfm;
-	struct akcipher_request *req;
-	struct rsa_completion compl;
-	struct scatterlist sig_sg, sg_out;
-	void *outbuf = NULL;
-	unsigned int outlen = 0;
-	int ret = -ENOMEM;
-
-	tfm = crypto_alloc_akcipher("rsa", 0, 0);
-	if (IS_ERR(tfm))
-		goto error_out;
-
-	req = akcipher_request_alloc(tfm, GFP_KERNEL);
-	if (!req)
-		goto error_free_tfm;
-
-	ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
-	if (ret)
-		goto error_free_req;
-
-	ret = -EINVAL;
-	outlen = crypto_akcipher_maxsize(tfm);
-	if (!outlen)
-		goto error_free_req;
-
-	/* initlialzie out buf */
-	ret = -ENOMEM;
-	outbuf = kmalloc(outlen, GFP_KERNEL);
-	if (!outbuf)
-		goto error_free_req;
-
-	sg_init_one(&sig_sg, sig->s, sig->s_size);
-	sg_init_one(&sg_out, outbuf, outlen);
-	akcipher_request_set_crypt(req, &sig_sg, &sg_out, sig->s_size, outlen);
-	init_completion(&compl.completion);
-	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
-				      CRYPTO_TFM_REQ_MAY_SLEEP,
-				      public_key_verify_done, &compl);
-
-	ret = crypto_akcipher_verify(req);
-	if (ret == -EINPROGRESS) {
-		wait_for_completion(&compl.completion);
-		ret = compl.err;
+	if (!RSA_ASN1_templates[sig->pkey_hash_algo].data)
+		return -ENOTSUPP;
+
+	/* (1) Check the signature size against the public key modulus size */
+	k = mpi_get_nbits(key->rsa.n);
+	tsize = mpi_get_nbits(sig->rsa.s);
+
+	/* According to RFC 4880 sec 3.2, length of MPI is computed starting
+	 * from most significant bit.  So the RFC 3447 sec 8.2.2 size check
+	 * must be relaxed to conform with shorter signatures - so we fail here
+	 * only if signature length is longer than modulus size.
+	 */
+	pr_devel("step 1: k=%zu size(S)=%zu\n", k, tsize);
+	if (k < tsize) {
+		ret = -EBADMSG;
+		goto error;
 	}
 
-	if (ret)
-		goto error_free_req;
+	/* Round up and convert to octets */
+	k = (k + 7) / 8;
 
-	/*
-	 * Output from the operation is an encoded message (EM) of
-	 * length k octets.
+	/* (2b) Apply the RSAVP1 verification primitive to the public key */
+	ret = RSAVP1(key, sig->rsa.s, &m);
+	if (ret < 0)
+		goto error;
+
+	/* (2c) Convert the message representative (m) to an encoded message
+	 *      (EM) of length k octets.
+	 *
+	 *      NOTE!  The leading zero byte is suppressed by MPI, so we pass a
+	 *      pointer to the _preceding_ byte to RSA_verify()!
 	 */
-	outlen = req->dst_len;
-	ret = rsa_verify(sig->digest, outbuf, outlen, sig->digest_size,
+	ret = RSA_I2OSP(m, k, &EM);
+	if (ret < 0)
+		goto error;
+
+	ret = RSA_verify(H, EM - 1, k, sig->digest_size,
 			 RSA_ASN1_templates[sig->pkey_hash_algo].data,
 			 RSA_ASN1_templates[sig->pkey_hash_algo].size);
-error_free_req:
-	akcipher_request_free(req);
-error_free_tfm:
-	crypto_free_akcipher(tfm);
-error_out:
-	kfree(outbuf);
+
+error:
+	kfree(EM);
+	mpi_free(m);
+	kleave(" = %d", ret);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(rsa_verify_signature);
+
+const struct public_key_algorithm RSA_public_key_algorithm = {
+	.name		= "RSA",
+	.n_pub_mpi	= 2,
+	.n_sec_mpi	= 3,
+	.n_sig_mpi	= 1,
+	.verify_signature = RSA_verify_signature,
+};
+EXPORT_SYMBOL_GPL(RSA_public_key_algorithm);