integrity: IMA as an integrity service provider

IMA provides hardware (TPM) based measurement and attestation for
file measurements. As the Trusted Computing (TPM) model requires,
IMA measures all files before they are accessed in any way (on the
integrity_bprm_check, integrity_path_check and integrity_file_mmap
hooks), and commits the measurements to the TPM. Once added to the
TPM, measurements can not be removed.

In addition, IMA maintains a list of these file measurements, which
can be used to validate the aggregate value stored in the TPM.  The
TPM can sign these measurements, and thus the system can prove, to
itself and to a third party, the system's integrity in a way that
cannot be circumvented by malicious or compromised software.

- alloc ima_template_entry before calling ima_store_template()
- log ima_add_boot_aggregate() failure
- removed unused IMA_TEMPLATE_NAME_LEN
- replaced hard coded string length with #define name

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 140 insertions, 0 deletions

diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
new file mode 100644
index 00000000000..c2a46e40999
--- /dev/null
+++ b/security/integrity/ima/ima_crypto.c
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2005,2006,2007,2008 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ * Kylene Hall <kjhall@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * File: ima_crypto.c
+ * 	Calculates md5/sha1 file hash, template hash, boot-aggreate hash
+ */
+
+#include <linux/kernel.h>
+#include <linux/file.h>
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+#include <linux/err.h>
+#include "ima.h"
+
+static int init_desc(struct hash_desc *desc)
+{
+	int rc;
+
+	desc->tfm = crypto_alloc_hash(ima_hash, 0, CRYPTO_ALG_ASYNC);
+	if (IS_ERR(desc->tfm)) {
+		pr_info("failed to load %s transform: %ld\n",
+			ima_hash, PTR_ERR(desc->tfm));
+		rc = PTR_ERR(desc->tfm);
+		return rc;
+	}
+	desc->flags = 0;
+	rc = crypto_hash_init(desc);
+	if (rc)
+		crypto_free_hash(desc->tfm);
+	return rc;
+}
+
+/*
+ * Calculate the MD5/SHA1 file digest
+ */
+int ima_calc_hash(struct file *file, char *digest)
+{
+	struct hash_desc desc;
+	struct scatterlist sg[1];
+	loff_t i_size;
+	char *rbuf;
+	int rc, offset = 0;
+
+	rc = init_desc(&desc);
+	if (rc != 0)
+		return rc;
+
+	rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!rbuf) {
+		rc = -ENOMEM;
+		goto out;
+	}
+	i_size = i_size_read(file->f_dentry->d_inode);
+	while (offset < i_size) {
+		int rbuf_len;
+
+		rbuf_len = kernel_read(file, offset, rbuf, PAGE_SIZE);
+		if (rbuf_len < 0) {
+			rc = rbuf_len;
+			break;
+		}
+		offset += rbuf_len;
+		sg_set_buf(sg, rbuf, rbuf_len);
+
+		rc = crypto_hash_update(&desc, sg, rbuf_len);
+		if (rc)
+			break;
+	}
+	kfree(rbuf);
+	if (!rc)
+		rc = crypto_hash_final(&desc, digest);
+out:
+	crypto_free_hash(desc.tfm);
+	return rc;
+}
+
+/*
+ * Calculate the hash of a given template
+ */
+int ima_calc_template_hash(int template_len, void *template, char *digest)
+{
+	struct hash_desc desc;
+	struct scatterlist sg[1];
+	int rc;
+
+	rc = init_desc(&desc);
+	if (rc != 0)
+		return rc;
+
+	sg_set_buf(sg, template, template_len);
+	rc = crypto_hash_update(&desc, sg, template_len);
+	if (!rc)
+		rc = crypto_hash_final(&desc, digest);
+	crypto_free_hash(desc.tfm);
+	return rc;
+}
+
+static void ima_pcrread(int idx, u8 *pcr)
+{
+	if (!ima_used_chip)
+		return;
+
+	if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
+		pr_err("Error Communicating to TPM chip\n");
+}
+
+/*
+ * Calculate the boot aggregate hash
+ */
+int ima_calc_boot_aggregate(char *digest)
+{
+	struct hash_desc desc;
+	struct scatterlist sg;
+	u8 pcr_i[IMA_DIGEST_SIZE];
+	int rc, i;
+
+	rc = init_desc(&desc);
+	if (rc != 0)
+		return rc;
+
+	/* cumulative sha1 over tpm registers 0-7 */
+	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
+		ima_pcrread(i, pcr_i);
+		/* now accumulate with current aggregate */
+		sg_init_one(&sg, pcr_i, IMA_DIGEST_SIZE);
+		rc = crypto_hash_update(&desc, &sg, IMA_DIGEST_SIZE);
+	}
+	if (!rc)
+		crypto_hash_final(&desc, digest);
+	crypto_free_hash(desc.tfm);
+	return rc;
+}