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Daniel De Graaf
5c3705c900
This is a complete rewrite of the disk format and key hierarchy for the TPM Manager. The new format supports multiple groups of vTPMs which define the permitted configurations where a given vTPM's keys are available, allowing upgrades of critical components while retaining the secrecy of cryptographic keys. New features of the TPM Manager are explained in the README and in the definitions of the management commands in vtpm_manager.h. New features for vTPMs: 1. The size of the state blob for a vTPM is expanded from 52 to 64 bytes in order to support future vTPMs using SHA-2/3 instead of SHA-1. 2. vTPMs can obtain a quote from the physical TPM with certain resettable PCRs set to include information about the vTPM. This can be used by a vTPM to provide evidence of its integrity, including the secrecy of its EK, and for deep quotes. Some additional changes made by this rewrite that may impact existing users: 1. The value of WELLKNOWN_OWNER_AUTH was incorrect for the physical TPM; the convention is to use all zero bits for well-known authentication values, not all one bits. 2. Randomly generating the owner auth value for the physical TPM is no longer supported, as it prevents later creation or certification of AIKs (which the old manager did not support). 3. The vTPM Manager needs to be provisioned with a PCR composite and an upgrade authority's public key before it will save data across boots. The current implementation still has some limitations: * 5 valid system PCR selections per group * The vTPM Manager's disk can use at most 2MB of space * The vTPM domain's build hash is always set to null/zero Most of the code relating to upgrade and rollback protection is currently stubbed out, but future versions can add: * Support for using the TPM's monotonic counter to prevent rollback of vTPM data by taking and restoring disk snapshots * Masking the master disk encryption key using a value stored in the TPM's NVRAM so that revocation of old data is possible without relying on all previously authorized software stacks to respect the monotonic counter's value Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov> Acked-by: Ian Campbell <ian.campbell@citrix.com>
126 lines
2.6 KiB
C
126 lines
2.6 KiB
C
#include <blkfront.h>
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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#include <inttypes.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include <mini-os/byteorder.h>
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#include "vtpm_manager.h"
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#include "log.h"
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#include "uuid.h"
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#include "vtpmmgr.h"
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#include "vtpm_disk.h"
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#include "disk_tpm.h"
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#include "disk_io.h"
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static uint8_t disk_staging_buf[4096] __attribute__((aligned(4096)));
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static struct blkfront_dev* blkdev;
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static int blkfront_fd = -1;
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int vtpm_storage_init(void) {
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struct blkfront_info info;
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blkdev = init_blkfront(NULL, &info);
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if (blkdev == NULL)
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return -1;
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blkfront_fd = blkfront_open(blkdev);
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if (blkfront_fd < 0)
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return -1;
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return 0;
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}
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void* disk_read_sector(sector_t sector)
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{
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uint32_t pos = be32_native(sector);
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int rc;
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vtpmloginfo(VTPM_LOG_VTPM, "disk_read_sector %x\n", pos);
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lseek(blkfront_fd, pos * 4096, SEEK_SET);
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rc = read(blkfront_fd, disk_staging_buf, 4096);
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if (rc != 4096)
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abort();
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return disk_staging_buf;
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}
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void* disk_write_buf(void) { return disk_staging_buf; }
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void disk_write_sector(sector_t sector, void* buf, size_t siz)
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{
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int rc;
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uint32_t pos = be32_native(sector);
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lseek(blkfront_fd, pos * 4096, SEEK_SET);
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if (siz < 4096) {
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if (buf != disk_staging_buf)
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memcpy(disk_staging_buf, buf, siz);
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memset(disk_staging_buf + siz, 0, 4096 - siz);
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buf = disk_staging_buf;
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} else if (siz > 4096)
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abort();
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rc = write(blkfront_fd, buf, 4096);
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if (rc != 4096)
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abort();
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}
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void disk_write_barrier(void)
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{
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blkfront_sync(blkdev);
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}
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enum inuse_value {
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UNUSED,
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SLOT_1,
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SLOT_2,
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SHARED
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};
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/* TODO make this dynamic to support using more than 2MB of disk */
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#define DISK_MAX_SECTOR 0x200
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/* The first 4 sectors are statically allocated:
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* 0 - disk header (copy 1)
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* 1 - disk header (copy 2)
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* 2 - root sector (copy 1)
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* 3 - root sector (copy 2)
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*/
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#define FIRST_DYNAMIC_SECTOR 4
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static uint8_t sector_inuse_map[DISK_MAX_SECTOR];
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static int active_slot(const struct mem_tpm_mgr *mgr)
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{
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return 1 + mgr->active_root;
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}
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void disk_set_used(sector_t loc, const struct mem_tpm_mgr *mgr)
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{
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uint32_t s = be32_native(loc);
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if (s > DISK_MAX_SECTOR) {
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printk("Attempted disk_set_used %x\n", s);
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return;
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}
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sector_inuse_map[s] |= active_slot(mgr);
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}
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void disk_flush_slot(const struct mem_tpm_mgr *mgr)
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{
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int i;
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for(i = FIRST_DYNAMIC_SECTOR; i < DISK_MAX_SECTOR; i++)
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sector_inuse_map[i] &= ~active_slot(mgr);
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}
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sector_t disk_find_free(const struct mem_tpm_mgr *mgr)
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{
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int i;
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for(i = FIRST_DYNAMIC_SECTOR; i < DISK_MAX_SECTOR; i++) {
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if (sector_inuse_map[i])
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continue;
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sector_inuse_map[i] = active_slot(mgr);
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return native_be32(i);
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}
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// TODO more graceful error handling (in callers)
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abort();
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}
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