drivers/char/tpm/eventlog/tpm2.c

   1 /*
   2  * Copyright (C) 2016 IBM Corporation
   3  *
   4  * Authors:
   5  *      Nayna Jain <nayna@linux.vnet.ibm.com>
   6  *
   7  * Access to TPM 2.0 event log as written by Firmware.
   8  * It assumes that writer of event log has followed TCG Specification
   9  * for Family "2.0" and written the event data in little endian.
  10  * With that, it doesn't need any endian conversion for structure
  11  * content.
  12  *
  13  * This program is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU General Public License
  15  * as published by the Free Software Foundation; either version
  16  * 2 of the License, or (at your option) any later version.
  17  */
  18
  19 #include <linux/seq_file.h>
  20 #include <linux/fs.h>
  21 #include <linux/security.h>
  22 #include <linux/module.h>
  23 #include <linux/slab.h>
  24 #include <linux/tpm_eventlog.h>
  25
  26 #include "../tpm.h"
  27 #include "common.h"
  28
  29 /*
  30  * calc_tpm2_event_size() - calculate the event size, where event
  31  * is an entry in the TPM 2.0 event log. The event is of type Crypto
  32  * Agile Log Entry Format as defined in TCG EFI Protocol Specification
  33  * Family "2.0".
  34
  35  * @event: event whose size is to be calculated.
  36  * @event_header: the first event in the event log.
  37  *
  38  * Returns size of the event. If it is an invalid event, returns 0.
  39  */
  40 static int calc_tpm2_event_size(struct tcg_pcr_event2 *event,
  41                                 struct tcg_pcr_event *event_header)
  42 {
  43         struct tcg_efi_specid_event *efispecid;
  44         struct tcg_event_field *event_field;
  45         void *marker;
  46         void *marker_start;
  47         u32 halg_size;
  48         size_t size;
  49         u16 halg;
  50         int i;
  51         int j;
  52
  53         marker = event;
  54         marker_start = marker;
  55         marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
  56                 + sizeof(event->count);
  57
  58         efispecid = (struct tcg_efi_specid_event *)event_header->event;
  59
  60         /* Check if event is malformed. */
  61         if (event->count > efispecid->num_algs)
  62                 return 0;
  63
  64         for (i = 0; i < event->count; i++) {
  65                 halg_size = sizeof(event->digests[i].alg_id);
  66                 memcpy(&halg, marker, halg_size);
  67                 marker = marker + halg_size;
  68                 for (j = 0; j < efispecid->num_algs; j++) {
  69                         if (halg == efispecid->digest_sizes[j].alg_id) {
  70                                 marker +=
  71                                         efispecid->digest_sizes[j].digest_size;
  72                                 break;
  73                         }
  74                 }
  75                 /* Algorithm without known length. Such event is unparseable. */
  76                 if (j == efispecid->num_algs)
  77                         return 0;
  78         }
  79
  80         event_field = (struct tcg_event_field *)marker;
  81         marker = marker + sizeof(event_field->event_size)
  82                 + event_field->event_size;
  83         size = marker - marker_start;
  84
  85         if ((event->event_type == 0) && (event_field->event_size == 0))
  86                 return 0;
  87
  88         return size;
  89 }
  90
  91 static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
  92 {
  93         struct tpm_chip *chip = m->private;
  94         struct tpm_bios_log *log = &chip->log;
  95         void *addr = log->bios_event_log;
  96         void *limit = log->bios_event_log_end;
  97         struct tcg_pcr_event *event_header;
  98         struct tcg_pcr_event2 *event;
  99         size_t size;
 100         int i;
 101
 102         event_header = addr;
 103         size = sizeof(struct tcg_pcr_event) - sizeof(event_header->event)
 104                 + event_header->event_size;
 105
 106         if (*pos == 0) {
 107                 if (addr + size < limit) {
 108                         if ((event_header->event_type == 0) &&
 109                             (event_header->event_size == 0))
 110                                 return NULL;
 111                         return SEQ_START_TOKEN;
 112                 }
 113         }
 114
 115         if (*pos > 0) {
 116                 addr += size;
 117                 event = addr;
 118                 size = calc_tpm2_event_size(event, event_header);
 119                 if ((addr + size >=  limit) || (size == 0))
 120                         return NULL;
 121         }
 122
 123         for (i = 0; i < (*pos - 1); i++) {
 124                 event = addr;
 125                 size = calc_tpm2_event_size(event, event_header);
 126
 127                 if ((addr + size >= limit) || (size == 0))
 128                         return NULL;
 129                 addr += size;
 130         }
 131
 132         return addr;
 133 }
 134
 135 static void *tpm2_bios_measurements_next(struct seq_file *m, void *v,
 136                                          loff_t *pos)
 137 {
 138         struct tcg_pcr_event *event_header;
 139         struct tcg_pcr_event2 *event;
 140         struct tpm_chip *chip = m->private;
 141         struct tpm_bios_log *log = &chip->log;
 142         void *limit = log->bios_event_log_end;
 143         size_t event_size;
 144         void *marker;
 145
 146         event_header = log->bios_event_log;
 147
 148         if (v == SEQ_START_TOKEN) {
 149                 event_size = sizeof(struct tcg_pcr_event) -
 150                         sizeof(event_header->event) + event_header->event_size;
 151                 marker = event_header;
 152         } else {
 153                 event = v;
 154                 event_size = calc_tpm2_event_size(event, event_header);
 155                 if (event_size == 0)
 156                         return NULL;
 157                 marker = event;
 158         }
 159
 160         marker = marker + event_size;
 161         if (marker >= limit)
 162                 return NULL;
 163         v = marker;
 164         event = v;
 165
 166         event_size = calc_tpm2_event_size(event, event_header);
 167         if (((v + event_size) >= limit) || (event_size == 0))
 168                 return NULL;
 169
 170         (*pos)++;
 171         return v;
 172 }
 173
 174 static void tpm2_bios_measurements_stop(struct seq_file *m, void *v)
 175 {
 176 }
 177
 178 static int tpm2_binary_bios_measurements_show(struct seq_file *m, void *v)
 179 {
 180         struct tpm_chip *chip = m->private;
 181         struct tpm_bios_log *log = &chip->log;
 182         struct tcg_pcr_event *event_header = log->bios_event_log;
 183         struct tcg_pcr_event2 *event = v;
 184         void *temp_ptr;
 185         size_t size;
 186
 187         if (v == SEQ_START_TOKEN) {
 188                 size = sizeof(struct tcg_pcr_event) -
 189                         sizeof(event_header->event) + event_header->event_size;
 190
 191                 temp_ptr = event_header;
 192
 193                 if (size > 0)
 194                         seq_write(m, temp_ptr, size);
 195         } else {
 196                 size = calc_tpm2_event_size(event, event_header);
 197                 temp_ptr = event;
 198                 if (size > 0)
 199                         seq_write(m, temp_ptr, size);
 200         }
 201
 202         return 0;
 203 }
 204
 205 const struct seq_operations tpm2_binary_b_measurements_seqops = {
 206         .start = tpm2_bios_measurements_start,
 207         .next = tpm2_bios_measurements_next,
 208         .stop = tpm2_bios_measurements_stop,
 209         .show = tpm2_binary_bios_measurements_show,
 210 };