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authorDavid Howells <dhowells@redhat.com>2015-07-20 20:16:27 (GMT)
committerDavid Howells <dhowells@redhat.com>2015-08-07 15:26:13 (GMT)
commit3f1e1bea34740069f70c6bc92d0f712345d5c28e (patch)
tree35ceac092ff7591536810cceecdbf22f4132b046 /kernel/module_signing.c
parentbc1c373dd2a5113800360f7152be729c9da996cc (diff)
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MODSIGN: Use PKCS#7 messages as module signatures
Move to using PKCS#7 messages as module signatures because: (1) We have to be able to support the use of X.509 certificates that don't have a subjKeyId set. We're currently relying on this to look up the X.509 certificate in the trusted keyring list. (2) PKCS#7 message signed information blocks have a field that supplies the data required to match with the X.509 certificate that signed it. (3) The PKCS#7 certificate carries fields that specify the digest algorithm used to generate the signature in a standardised way and the X.509 certificates specify the public key algorithm in a standardised way - so we don't need our own methods of specifying these. (4) We now have PKCS#7 message support in the kernel for signed kexec purposes and we can make use of this. To make this work, the old sign-file script has been replaced with a program that needs compiling in a previous patch. The rules to build it are added here. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Vivek Goyal <vgoyal@redhat.com>
Diffstat (limited to 'kernel/module_signing.c')
-rw-r--r--kernel/module_signing.c220
1 files changed, 44 insertions, 176 deletions
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index be5b8fa..8eb20cc 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -11,10 +11,9 @@
#include <linux/kernel.h>
#include <linux/err.h>
-#include <crypto/public_key.h>
-#include <crypto/hash.h>
-#include <keys/asymmetric-type.h>
#include <keys/system_keyring.h>
+#include <crypto/public_key.h>
+#include <crypto/pkcs7.h>
#include "module-internal.h"
/*
@@ -28,157 +27,53 @@
* - Information block
*/
struct module_signature {
- u8 algo; /* Public-key crypto algorithm [enum pkey_algo] */
- u8 hash; /* Digest algorithm [enum hash_algo] */
- u8 id_type; /* Key identifier type [enum pkey_id_type] */
- u8 signer_len; /* Length of signer's name */
- u8 key_id_len; /* Length of key identifier */
+ u8 algo; /* Public-key crypto algorithm [0] */
+ u8 hash; /* Digest algorithm [0] */
+ u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */
+ u8 signer_len; /* Length of signer's name [0] */
+ u8 key_id_len; /* Length of key identifier [0] */
u8 __pad[3];
__be32 sig_len; /* Length of signature data */
};
/*
- * Digest the module contents.
+ * Verify a PKCS#7-based signature on a module.
*/
-static struct public_key_signature *mod_make_digest(enum hash_algo hash,
- const void *mod,
- unsigned long modlen)
+static int mod_verify_pkcs7(const void *mod, unsigned long modlen,
+ const void *raw_pkcs7, size_t pkcs7_len)
{
- struct public_key_signature *pks;
- struct crypto_shash *tfm;
- struct shash_desc *desc;
- size_t digest_size, desc_size;
+ struct pkcs7_message *pkcs7;
+ bool trusted;
int ret;
- pr_devel("==>%s()\n", __func__);
-
- /* Allocate the hashing algorithm we're going to need and find out how
- * big the hash operational data will be.
- */
- tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
- if (IS_ERR(tfm))
- return (PTR_ERR(tfm) == -ENOENT) ? ERR_PTR(-ENOPKG) : ERR_CAST(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 and the digest output buffer on the end of that.
- */
- ret = -ENOMEM;
- pks = kzalloc(digest_size + sizeof(*pks) + desc_size, GFP_KERNEL);
- if (!pks)
- goto error_no_pks;
-
- pks->pkey_hash_algo = hash;
- pks->digest = (u8 *)pks + sizeof(*pks) + desc_size;
- pks->digest_size = digest_size;
-
- desc = (void *)pks + sizeof(*pks);
- desc->tfm = tfm;
- desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
-
- ret = crypto_shash_init(desc);
+ pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
+ if (IS_ERR(pkcs7))
+ return PTR_ERR(pkcs7);
+
+ /* The data should be detached - so we need to supply it. */
+ if (pkcs7_supply_detached_data(pkcs7, mod, modlen) < 0) {
+ pr_err("PKCS#7 signature with non-detached data\n");
+ ret = -EBADMSG;
+ goto error;
+ }
+
+ ret = pkcs7_verify(pkcs7);
if (ret < 0)
goto error;
- ret = crypto_shash_finup(desc, mod, modlen, pks->digest);
+ ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
if (ret < 0)
goto error;
- crypto_free_shash(tfm);
- pr_devel("<==%s() = ok\n", __func__);
- return pks;
+ if (!trusted) {
+ pr_err("PKCS#7 signature not signed with a trusted key\n");
+ ret = -ENOKEY;
+ }
error:
- kfree(pks);
-error_no_pks:
- crypto_free_shash(tfm);
+ pkcs7_free_message(pkcs7);
pr_devel("<==%s() = %d\n", __func__, ret);
- return ERR_PTR(ret);
-}
-
-/*
- * Extract an MPI array from the signature data. This represents the actual
- * signature. Each raw MPI is prefaced by a BE 2-byte value indicating the
- * size of the MPI in bytes.
- *
- * RSA signatures only have one MPI, so currently we only read one.
- */
-static int mod_extract_mpi_array(struct public_key_signature *pks,
- const void *data, size_t len)
-{
- size_t nbytes;
- MPI mpi;
-
- if (len < 3)
- return -EBADMSG;
- nbytes = ((const u8 *)data)[0] << 8 | ((const u8 *)data)[1];
- data += 2;
- len -= 2;
- if (len != nbytes)
- return -EBADMSG;
-
- mpi = mpi_read_raw_data(data, nbytes);
- if (!mpi)
- return -ENOMEM;
- pks->mpi[0] = mpi;
- pks->nr_mpi = 1;
- return 0;
-}
-
-/*
- * Request an asymmetric key.
- */
-static struct key *request_asymmetric_key(const char *signer, size_t signer_len,
- const u8 *key_id, size_t key_id_len)
-{
- key_ref_t key;
- size_t i;
- char *id, *q;
-
- pr_devel("==>%s(,%zu,,%zu)\n", __func__, signer_len, key_id_len);
-
- /* Construct an identifier. */
- id = kmalloc(signer_len + 2 + key_id_len * 2 + 1, GFP_KERNEL);
- if (!id)
- return ERR_PTR(-ENOKEY);
-
- memcpy(id, signer, signer_len);
-
- q = id + signer_len;
- *q++ = ':';
- *q++ = ' ';
- for (i = 0; i < key_id_len; i++) {
- *q++ = hex_asc[*key_id >> 4];
- *q++ = hex_asc[*key_id++ & 0x0f];
- }
-
- *q = 0;
-
- pr_debug("Look up: \"%s\"\n", id);
-
- key = keyring_search(make_key_ref(system_trusted_keyring, 1),
- &key_type_asymmetric, id);
- if (IS_ERR(key))
- pr_warn("Request for unknown module key '%s' err %ld\n",
- id, PTR_ERR(key));
- kfree(id);
-
- if (IS_ERR(key)) {
- switch (PTR_ERR(key)) {
- /* Hide some search errors */
- case -EACCES:
- case -ENOTDIR:
- case -EAGAIN:
- return ERR_PTR(-ENOKEY);
- default:
- return ERR_CAST(key);
- }
- }
-
- pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key_ref_to_ptr(key)));
- return key_ref_to_ptr(key);
+ return ret;
}
/*
@@ -186,12 +81,8 @@ static struct key *request_asymmetric_key(const char *signer, size_t signer_len,
*/
int mod_verify_sig(const void *mod, unsigned long *_modlen)
{
- struct public_key_signature *pks;
struct module_signature ms;
- struct key *key;
- const void *sig;
size_t modlen = *_modlen, sig_len;
- int ret;
pr_devel("==>%s(,%zu)\n", __func__, modlen);
@@ -205,46 +96,23 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen)
if (sig_len >= modlen)
return -EBADMSG;
modlen -= sig_len;
- if ((size_t)ms.signer_len + ms.key_id_len >= modlen)
- return -EBADMSG;
- modlen -= (size_t)ms.signer_len + ms.key_id_len;
-
*_modlen = modlen;
- sig = mod + modlen;
-
- /* For the moment, only support RSA and X.509 identifiers */
- if (ms.algo != PKEY_ALGO_RSA ||
- ms.id_type != PKEY_ID_X509)
- return -ENOPKG;
- if (ms.hash >= PKEY_HASH__LAST ||
- !hash_algo_name[ms.hash])
+ if (ms.id_type != PKEY_ID_PKCS7) {
+ pr_err("Module is not signed with expected PKCS#7 message\n");
return -ENOPKG;
-
- key = request_asymmetric_key(sig, ms.signer_len,
- sig + ms.signer_len, ms.key_id_len);
- if (IS_ERR(key))
- return PTR_ERR(key);
-
- pks = mod_make_digest(ms.hash, mod, modlen);
- if (IS_ERR(pks)) {
- ret = PTR_ERR(pks);
- goto error_put_key;
}
- ret = mod_extract_mpi_array(pks, sig + ms.signer_len + ms.key_id_len,
- sig_len);
- if (ret < 0)
- goto error_free_pks;
-
- ret = verify_signature(key, pks);
- pr_devel("verify_signature() = %d\n", ret);
+ if (ms.algo != 0 ||
+ ms.hash != 0 ||
+ ms.signer_len != 0 ||
+ ms.key_id_len != 0 ||
+ ms.__pad[0] != 0 ||
+ ms.__pad[1] != 0 ||
+ ms.__pad[2] != 0) {
+ pr_err("PKCS#7 signature info has unexpected non-zero params\n");
+ return -EBADMSG;
+ }
-error_free_pks:
- mpi_free(pks->rsa.s);
- kfree(pks);
-error_put_key:
- key_put(key);
- pr_devel("<==%s() = %d\n", __func__, ret);
- return ret;
+ return mod_verify_pkcs7(mod, modlen, mod + modlen, sig_len);
}