ima: on soft reboot, restore the measurement list

The TPM PCRs are only reset on a hard reboot.  In order to validate a
TPM's quote after a soft reboot (eg.  kexec -e), the IMA measurement
list of the running kernel must be saved and restored on boot.  This
patch restores the measurement list.

Link: http://lkml.kernel.org/r/1480554346-29071-3-git-send-email-zohar@linux.vnet.ibm.com
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andreas Steffen <andreas.steffen@strongswan.org>
Cc: Josh Sklar <sklar@linux.vnet.ibm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 9aeaeda..29f198b 100644 (file)
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -8,4 +8,5 @@ obj-$(CONFIG_IMA) += ima.o
 ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
         ima_policy.o ima_template.o ima_template_lib.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
+ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index db25f54..51dc8d5 100644 (file)
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -28,6 +28,10 @@
 
 #include "../integrity.h"
 
+#ifdef CONFIG_HAVE_IMA_KEXEC
+#include <asm/ima.h>
+#endif
+
 enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_BINARY_NO_FIELD_LEN,
                     IMA_SHOW_BINARY_OLD_STRING_FMT, IMA_SHOW_ASCII };
 enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
@@ -102,6 +106,21 @@ struct ima_queue_entry {
 };
 extern struct list_head ima_measurements;      /* list of all measurements */
 
+/* Some details preceding the binary serialized measurement list */
+struct ima_kexec_hdr {
+       u16 version;
+       u16 _reserved0;
+       u32 _reserved1;
+       u64 buffer_size;
+       u64 count;
+};
+
+#ifdef CONFIG_HAVE_IMA_KEXEC
+void ima_load_kexec_buffer(void);
+#else
+static inline void ima_load_kexec_buffer(void) {}
+#endif /* CONFIG_HAVE_IMA_KEXEC */
+
 /* Internal IMA function definitions */
 int ima_init(void);
 int ima_fs_init(void);
@@ -122,6 +141,8 @@ int ima_init_crypto(void);
 void ima_putc(struct seq_file *m, void *data, int datalen);
 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
 struct ima_template_desc *ima_template_desc_current(void);
+int ima_restore_measurement_entry(struct ima_template_entry *entry);
+int ima_restore_measurement_list(loff_t bufsize, void *buf);
 int ima_init_template(void);
 
 /*

diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 2ac1f41..2967d49 100644 (file)
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -129,6 +129,8 @@ int __init ima_init(void)
        if (rc != 0)
                return rc;
 
+       ima_load_kexec_buffer();
+
        rc = ima_add_boot_aggregate();  /* boot aggregate must be first entry */
        if (rc != 0)
                return rc;

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
new file mode 100644 (file)
index 0000000..36afd0f
--- /dev/null
+++ b/security/integrity/ima/ima_kexec.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016 IBM Corporation
+ *
+ * Authors:
+ * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
+ * Mimi Zohar <zohar@linux.vnet.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; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+#include "ima.h"
+
+/*
+ * Restore the measurement list from the previous kernel.
+ */
+void ima_load_kexec_buffer(void)
+{
+       void *kexec_buffer = NULL;
+       size_t kexec_buffer_size = 0;
+       int rc;
+
+       rc = ima_get_kexec_buffer(&kexec_buffer, &kexec_buffer_size);
+       switch (rc) {
+       case 0:
+               rc = ima_restore_measurement_list(kexec_buffer_size,
+                                                 kexec_buffer);
+               if (rc != 0)
+                       pr_err("Failed to restore the measurement list: %d\n",
+                               rc);
+
+               ima_free_kexec_buffer();
+               break;
+       case -ENOTSUPP:
+               pr_debug("Restoring the measurement list not supported\n");
+               break;
+       case -ENOENT:
+               pr_debug("No measurement list to restore\n");
+               break;
+       default:
+               pr_debug("Error restoring the measurement list: %d\n", rc);
+       }
+}

diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 32f6ac0..4b1bb77 100644 (file)
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -149,3 +149,13 @@ out:
                            op, audit_cause, result, audit_info);
        return result;
 }
+
+int ima_restore_measurement_entry(struct ima_template_entry *entry)
+{
+       int result = 0;
+
+       mutex_lock(&ima_extend_list_mutex);
+       result = ima_add_digest_entry(entry);
+       mutex_unlock(&ima_extend_list_mutex);
+       return result;
+}

diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index febd12e..03803de 100644 (file)
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -37,6 +37,7 @@ static struct ima_template_field supported_fields[] = {
        {.field_id = "sig", .field_init = ima_eventsig_init,
         .field_show = ima_show_template_sig},
 };
+#define MAX_TEMPLATE_NAME_LEN 15
 
 static struct ima_template_desc *ima_template;
 static struct ima_template_desc *lookup_template_desc(const char *name);
@@ -205,3 +206,179 @@ int __init ima_init_template(void)
 
        return result;
 }
+
+static int ima_restore_template_data(struct ima_template_desc *template_desc,
+                                    void *template_data,
+                                    int template_data_size,
+                                    struct ima_template_entry **entry)
+{
+       struct binary_field_data {
+               u32 len;
+               u8 data[0];
+       } __packed;
+
+       struct binary_field_data *field_data;
+       int offset = 0;
+       int ret = 0;
+       int i;
+
+       *entry = kzalloc(sizeof(**entry) +
+                   template_desc->num_fields * sizeof(struct ima_field_data),
+                   GFP_NOFS);
+       if (!*entry)
+               return -ENOMEM;
+
+       (*entry)->template_desc = template_desc;
+       for (i = 0; i < template_desc->num_fields; i++) {
+               field_data = template_data + offset;
+
+               /* Each field of the template data is prefixed with a length. */
+               if (offset > (template_data_size - sizeof(*field_data))) {
+                       pr_err("Restoring the template field failed\n");
+                       ret = -EINVAL;
+                       break;
+               }
+               offset += sizeof(*field_data);
+
+               if (offset > (template_data_size - field_data->len)) {
+                       pr_err("Restoring the template field data failed\n");
+                       ret = -EINVAL;
+                       break;
+               }
+               offset += field_data->len;
+
+               (*entry)->template_data[i].len = field_data->len;
+               (*entry)->template_data_len += sizeof(field_data->len);
+
+               (*entry)->template_data[i].data =
+                       kzalloc(field_data->len + 1, GFP_KERNEL);
+               if (!(*entry)->template_data[i].data) {
+                       ret = -ENOMEM;
+                       break;
+               }
+               memcpy((*entry)->template_data[i].data, field_data->data,
+                       field_data->len);
+               (*entry)->template_data_len += field_data->len;
+       }
+
+       if (ret < 0) {
+               ima_free_template_entry(*entry);
+               *entry = NULL;
+       }
+
+       return ret;
+}
+
+/* Restore the serialized binary measurement list without extending PCRs. */
+int ima_restore_measurement_list(loff_t size, void *buf)
+{
+       struct binary_hdr_v1 {
+               u32 pcr;
+               u8 digest[TPM_DIGEST_SIZE];
+               u32 template_name_len;
+               char template_name[0];
+       } __packed;
+       char template_name[MAX_TEMPLATE_NAME_LEN];
+
+       struct binary_data_v1 {
+               u32 template_data_size;
+               char template_data[0];
+       } __packed;
+
+       struct ima_kexec_hdr *khdr = buf;
+       struct binary_hdr_v1 *hdr_v1;
+       struct binary_data_v1 *data_v1;
+
+       void *bufp = buf + sizeof(*khdr);
+       void *bufendp = buf + khdr->buffer_size;
+       struct ima_template_entry *entry;
+       struct ima_template_desc *template_desc;
+       unsigned long count = 0;
+       int ret = 0;
+
+       if (!buf || size < sizeof(*khdr))
+               return 0;
+
+       if (khdr->version != 1) {
+               pr_err("attempting to restore a incompatible measurement list");
+               return -EINVAL;
+       }
+
+       if (khdr->count > ULONG_MAX - 1) {
+               pr_err("attempting to restore too many measurements");
+               return -EINVAL;
+       }
+
+       /*
+        * ima kexec buffer prefix: version, buffer size, count
+        * v1 format: pcr, digest, template-name-len, template-name,
+        *            template-data-size, template-data
+        */
+       while ((bufp < bufendp) && (count++ < khdr->count)) {
+               hdr_v1 = bufp;
+               if (bufp > (bufendp - sizeof(*hdr_v1))) {
+                       pr_err("attempting to restore partial measurement\n");
+                       ret = -EINVAL;
+                       break;
+               }
+               bufp += sizeof(*hdr_v1);
+
+               if ((hdr_v1->template_name_len >= MAX_TEMPLATE_NAME_LEN) ||
+                   (bufp > (bufendp - hdr_v1->template_name_len))) {
+                       pr_err("attempting to restore a template name \
+                               that is too long\n");
+                       ret = -EINVAL;
+                       break;
+               }
+               data_v1 = bufp += (u_int8_t)hdr_v1->template_name_len;
+
+               /* template name is not null terminated */
+               memcpy(template_name, hdr_v1->template_name,
+                      hdr_v1->template_name_len);
+               template_name[hdr_v1->template_name_len] = 0;
+
+               if (strcmp(template_name, "ima") == 0) {
+                       pr_err("attempting to restore an unsupported \
+                               template \"%s\" failed\n", template_name);
+                       ret = -EINVAL;
+                       break;
+               }
+
+               /* get template format */
+               template_desc = lookup_template_desc(template_name);
+               if (!template_desc) {
+                       pr_err("template \"%s\" not found\n", template_name);
+                       ret = -EINVAL;
+                       break;
+               }
+
+               if (bufp > (bufendp - sizeof(data_v1->template_data_size))) {
+                       pr_err("restoring the template data size failed\n");
+                       ret = -EINVAL;
+                       break;
+               }
+               bufp += (u_int8_t) sizeof(data_v1->template_data_size);
+
+               if (bufp > (bufendp - data_v1->template_data_size)) {
+                       pr_err("restoring the template data failed\n");
+                       ret = -EINVAL;
+                       break;
+               }
+               bufp += data_v1->template_data_size;
+
+               ret = ima_restore_template_data(template_desc,
+                                               data_v1->template_data,
+                                               data_v1->template_data_size,
+                                               &entry);
+               if (ret < 0)
+                       break;
+
+               memcpy(entry->digest, hdr_v1->digest, TPM_DIGEST_SIZE);
+               entry->pcr = hdr_v1->pcr;
+               ret = ima_restore_measurement_entry(entry);
+               if (ret < 0)
+                       break;
+
+       }
+       return ret;
+}