Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
new file mode 100644
index 0000000..d106885
--- /dev/null
+++ b/security/integrity/ima/ima_modsig.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * IMA support for appraising module-style appended signatures.
+ *
+ * Copyright (C) 2019 IBM Corporation
+ *
+ * Author:
+ * Thiago Jung Bauermann <bauerman@linux.ibm.com>
+ */
+
+#include <linux/types.h>
+#include <linux/module_signature.h>
+#include <keys/asymmetric-type.h>
+#include <crypto/pkcs7.h>
+
+#include "ima.h"
+
+struct modsig {
+ struct pkcs7_message *pkcs7_msg;
+
+ enum hash_algo hash_algo;
+
+ /* This digest will go in the 'd-modsig' field of the IMA template. */
+ const u8 *digest;
+ u32 digest_size;
+
+ /*
+ * This is what will go to the measurement list if the template requires
+ * storing the signature.
+ */
+ int raw_pkcs7_len;
+ u8 raw_pkcs7[];
+};
+
+/**
+ * ima_hook_supports_modsig - can the policy allow modsig for this hook?
+ *
+ * modsig is only supported by hooks using ima_post_read_file(), because only
+ * they preload the contents of the file in a buffer. FILE_CHECK does that in
+ * some cases, but not when reached from vfs_open(). POLICY_CHECK can support
+ * it, but it's not useful in practice because it's a text file so deny.
+ */
+bool ima_hook_supports_modsig(enum ima_hooks func)
+{
+ switch (func) {
+ case KEXEC_KERNEL_CHECK:
+ case KEXEC_INITRAMFS_CHECK:
+ case MODULE_CHECK:
+ return true;
+ default:
+ return false;
+ }
+}
+
+/*
+ * ima_read_modsig - Read modsig from buf.
+ *
+ * Return: 0 on success, error code otherwise.
+ */
+int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
+ struct modsig **modsig)
+{
+ const size_t marker_len = strlen(MODULE_SIG_STRING);
+ const struct module_signature *sig;
+ struct modsig *hdr;
+ size_t sig_len;
+ const void *p;
+ int rc;
+
+ if (buf_len <= marker_len + sizeof(*sig))
+ return -ENOENT;
+
+ p = buf + buf_len - marker_len;
+ if (memcmp(p, MODULE_SIG_STRING, marker_len))
+ return -ENOENT;
+
+ buf_len -= marker_len;
+ sig = (const struct module_signature *)(p - sizeof(*sig));
+
+ rc = mod_check_sig(sig, buf_len, func_tokens[func]);
+ if (rc)
+ return rc;
+
+ sig_len = be32_to_cpu(sig->sig_len);
+ buf_len -= sig_len + sizeof(*sig);
+
+ /* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */
+ hdr = kzalloc(sizeof(*hdr) + sig_len, GFP_KERNEL);
+ if (!hdr)
+ return -ENOMEM;
+
+ hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
+ if (IS_ERR(hdr->pkcs7_msg)) {
+ rc = PTR_ERR(hdr->pkcs7_msg);
+ kfree(hdr);
+ return rc;
+ }
+
+ memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
+ hdr->raw_pkcs7_len = sig_len;
+
+ /* We don't know the hash algorithm yet. */
+ hdr->hash_algo = HASH_ALGO__LAST;
+
+ *modsig = hdr;
+
+ return 0;
+}
+
+/**
+ * ima_collect_modsig - Calculate the file hash without the appended signature.
+ *
+ * Since the modsig is part of the file contents, the hash used in its signature
+ * isn't the same one ordinarily calculated by IMA. Therefore PKCS7 code
+ * calculates a separate one for signature verification.
+ */
+void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size)
+{
+ int rc;
+
+ /*
+ * Provide the file contents (minus the appended sig) so that the PKCS7
+ * code can calculate the file hash.
+ */
+ size -= modsig->raw_pkcs7_len + strlen(MODULE_SIG_STRING) +
+ sizeof(struct module_signature);
+ rc = pkcs7_supply_detached_data(modsig->pkcs7_msg, buf, size);
+ if (rc)
+ return;
+
+ /* Ask the PKCS7 code to calculate the file hash. */
+ rc = pkcs7_get_digest(modsig->pkcs7_msg, &modsig->digest,
+ &modsig->digest_size, &modsig->hash_algo);
+}
+
+int ima_modsig_verify(struct key *keyring, const struct modsig *modsig)
+{
+ return verify_pkcs7_message_sig(NULL, 0, modsig->pkcs7_msg, keyring,
+ VERIFYING_MODULE_SIGNATURE, NULL, NULL);
+}
+
+int ima_get_modsig_digest(const struct modsig *modsig, enum hash_algo *algo,
+ const u8 **digest, u32 *digest_size)
+{
+ *algo = modsig->hash_algo;
+ *digest = modsig->digest;
+ *digest_size = modsig->digest_size;
+
+ return 0;
+}
+
+int ima_get_raw_modsig(const struct modsig *modsig, const void **data,
+ u32 *data_len)
+{
+ *data = &modsig->raw_pkcs7;
+ *data_len = modsig->raw_pkcs7_len;
+
+ return 0;
+}
+
+void ima_free_modsig(struct modsig *modsig)
+{
+ if (!modsig)
+ return;
+
+ pkcs7_free_message(modsig->pkcs7_msg);
+ kfree(modsig);
+}