X.509: Embed public_key_signature struct and create filler function

Embed a public_key_signature struct in struct x509_certificate, eliminating
now unnecessary fields, and split x509_check_signature() to create a filler
function for it that attaches a digest of the signed data and an MPI that
represents the signature data.  x509_free_certificate() is then modified to
deal with these.

Whilst we're at it, export both x509_check_signature() and the new
x509_get_sig_params().

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Josh Boyer <jwboyer@redhat.com>

3 files changed, 74 insertions, 55 deletions

diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
index 8cc253d2dc92..144201ccba0c 100644
--- a/crypto/asymmetric_keys/x509_cert_parser.c
+++ b/crypto/asymmetric_keys/x509_cert_parser.c
@@ -47,6 +47,8 @@ void x509_free_certificate(struct x509_certificate *cert)
                 kfree(cert->subject);
                 kfree(cert->fingerprint);
                 kfree(cert->authority);
+                kfree(cert->sig.digest);
+                mpi_free(cert->sig.rsa.s);
                 kfree(cert);
         }
 }
@@ -152,33 +154,33 @@ int x509_note_pkey_algo(void *context, size_t hdrlen,
                 return -ENOPKG; /* Unsupported combination */
 
         case OID_md4WithRSAEncryption:
-                ctx->cert->sig_hash_algo = PKEY_HASH_MD5;
-                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
+                ctx->cert->sig.pkey_hash_algo = PKEY_HASH_MD5;
+                ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
                 break;
 
         case OID_sha1WithRSAEncryption:
-                ctx->cert->sig_hash_algo = PKEY_HASH_SHA1;
-                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
+                ctx->cert->sig.pkey_hash_algo = PKEY_HASH_SHA1;
+                ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
                 break;
 
         case OID_sha256WithRSAEncryption:
-                ctx->cert->sig_hash_algo = PKEY_HASH_SHA256;
-                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
+                ctx->cert->sig.pkey_hash_algo = PKEY_HASH_SHA256;
+                ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
                 break;
 
         case OID_sha384WithRSAEncryption:
-                ctx->cert->sig_hash_algo = PKEY_HASH_SHA384;
-                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
+                ctx->cert->sig.pkey_hash_algo = PKEY_HASH_SHA384;
+                ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
                 break;
 
         case OID_sha512WithRSAEncryption:
-                ctx->cert->sig_hash_algo = PKEY_HASH_SHA512;
-                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
+                ctx->cert->sig.pkey_hash_algo = PKEY_HASH_SHA512;
+                ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
                 break;
 
         case OID_sha224WithRSAEncryption:
-                ctx->cert->sig_hash_algo = PKEY_HASH_SHA224;
-                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
+                ctx->cert->sig.pkey_hash_algo = PKEY_HASH_SHA224;
+                ctx->cert->sig.pkey_algo = PKEY_ALGO_RSA;
                 break;
         }
 
@@ -203,8 +205,8 @@ int x509_note_signature(void *context, size_t hdrlen,
                 return -EINVAL;
         }
 
-        ctx->cert->sig = value;
-        ctx->cert->sig_size = vlen;
+        ctx->cert->raw_sig = value;
+        ctx->cert->raw_sig_size = vlen;
         return 0;
 }
 
diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h
index 2d0118214770..87d9cc26f630 100644
--- a/crypto/asymmetric_keys/x509_parser.h
+++ b/crypto/asymmetric_keys/x509_parser.h
@@ -21,12 +21,11 @@ struct x509_certificate {
         char            *authority;             /* Authority key fingerprint as hex */
         struct tm       valid_from;
         struct tm       valid_to;
-        enum pkey_algo  sig_pkey_algo : 8;      /* Signature public key algorithm */
-        enum pkey_hash_algo sig_hash_algo : 8;  /* Signature hash algorithm */
         const void      *tbs;                   /* Signed data */
-        size_t          tbs_size;               /* Size of signed data */
-        const void      *sig;                   /* Signature data */
-        size_t          sig_size;               /* Size of sigature */
+        unsigned        tbs_size;               /* Size of signed data */
+        unsigned        raw_sig_size;           /* Size of sigature */
+        const void      *raw_sig;               /* Signature data */
+        struct public_key_signature sig;        /* Signature parameters */
 };
 
 /*
@@ -34,3 +33,10 @@ struct x509_certificate {
  */
 extern void x509_free_certificate(struct x509_certificate *cert);
 extern struct x509_certificate *x509_cert_parse(const void *data, size_t datalen);
+
+/*
+ * x509_public_key.c
+ */
+extern int x509_get_sig_params(struct x509_certificate *cert);
+extern int x509_check_signature(const struct public_key *pub,
+                                struct x509_certificate *cert);
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 8cb2f7075479..b7c81d8df08b 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -24,72 +24,83 @@
 #include "x509_parser.h"
 
 /*
- * Check the signature on a certificate using the provided public key
+ * Set up the signature parameters in an X.509 certificate.  This involves
+ * digesting the signed data and extracting the signature.
  */
-static int x509_check_signature(const struct public_key *pub,
-                                const struct x509_certificate *cert)
+int x509_get_sig_params(struct x509_certificate *cert)
 {
-        struct public_key_signature *sig;
         struct crypto_shash *tfm;
         struct shash_desc *desc;
         size_t digest_size, desc_size;
+        void *digest;
         int ret;
 
         pr_devel("==>%s()\n", __func__);
-        
+
+        if (cert->sig.rsa.s)
+                return 0;
+
+        cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
+        if (!cert->sig.rsa.s)
+                return -ENOMEM;
+        cert->sig.nr_mpi = 1;
+
         /* Allocate the hashing algorithm we're going to need and find out how
          * big the hash operational data will be.
          */
-        tfm = crypto_alloc_shash(pkey_hash_algo_name[cert->sig_hash_algo], 0, 0);
+        tfm = crypto_alloc_shash(pkey_hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
         if (IS_ERR(tfm))
                 return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
 
         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
         digest_size = crypto_shash_digestsize(tfm);
 
-        /* We allocate the hash operational data storage on the end of our
-         * context data.
+        /* We allocate the hash operational data storage on the end of the
+         * digest storage space.
          */
         ret = -ENOMEM;
-        sig = kzalloc(sizeof(*sig) + desc_size + digest_size, GFP_KERNEL);
-        if (!sig)
-                goto error_no_sig;
+        digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
+        if (!digest)
+                goto error;
 
-        sig->pkey_hash_algo     = cert->sig_hash_algo;
-        sig->digest             = (u8 *)sig + sizeof(*sig) + desc_size;
-        sig->digest_size        = digest_size;
+        cert->sig.digest = digest;
+        cert->sig.digest_size = digest_size;
 
-        desc = (void *)sig + sizeof(*sig);
-        desc->tfm       = tfm;
-        desc->flags     = CRYPTO_TFM_REQ_MAY_SLEEP;
+        desc = digest + digest_size;
+        desc->tfm = tfm;
+        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
 
         ret = crypto_shash_init(desc);
         if (ret < 0)
                 goto error;
+        might_sleep();
+        ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
+error:
+        crypto_free_shash(tfm);
+        pr_devel("<==%s() = %d\n", __func__, ret);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(x509_get_sig_params);
 
-        ret = -ENOMEM;
-        sig->rsa.s = mpi_read_raw_data(cert->sig, cert->sig_size);
-        if (!sig->rsa.s)
-                goto error;
+/*
+ * Check the signature on a certificate using the provided public key
+ */
+int x509_check_signature(const struct public_key *pub,
+                         struct x509_certificate *cert)
+{
+        int ret;
 
-        ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest);
-        if (ret < 0)
-                goto error_mpi;
+        pr_devel("==>%s()\n", __func__);
 
-        ret = public_key_verify_signature(pub, sig);
+        ret = x509_get_sig_params(cert);
+        if (ret < 0)
+                return ret;
 
+        ret = public_key_verify_signature(pub, &cert->sig);
         pr_debug("Cert Verification: %d\n", ret);
-
-error_mpi:
-        mpi_free(sig->rsa.s);
-error:
-        kfree(sig);
-error_no_sig:
-        crypto_free_shash(tfm);
-
-        pr_devel("<==%s() = %d\n", __func__, ret);
         return ret;
 }
+EXPORT_SYMBOL_GPL(x509_check_signature);
 
 /*
  * Attempt to parse a data blob for a key as an X509 certificate.
@@ -118,8 +129,8 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
                  cert->valid_to.tm_mday, cert->valid_to.tm_hour,
                  cert->valid_to.tm_min,  cert->valid_to.tm_sec);
         pr_devel("Cert Signature: %s + %s\n",
-                 pkey_algo_name[cert->sig_pkey_algo],
-                 pkey_hash_algo_name[cert->sig_hash_algo]);
+                 pkey_algo_name[cert->sig.pkey_algo],
+                 pkey_hash_algo_name[cert->sig.pkey_hash_algo]);
 
         if (!cert->fingerprint || !cert->authority) {
                 pr_warn("Cert for '%s' must have SubjKeyId and AuthKeyId extensions\n",