drivers/char/tpm/tpm2_eventlog.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
  25 #include "tpm.h"
  26 #include "tpm_eventlog.h"
  27
  28 /*
  29  * calc_tpm2_event_size() - calculate the event size, where event
  30  * is an entry in the TPM 2.0 event log. The event is of type Crypto
  31  * Agile Log Entry Format as defined in TCG EFI Protocol Specification
  32  * Family "2.0".
  33
  34  * @event: event whose size is to be calculated.
  35  * @event_header: the first event in the event log.
  36  *
  37  * Returns size of the event. If it is an invalid event, returns 0.
  38  */
  39 static int calc_tpm2_event_size(struct tcg_pcr_event2 *event,
  40                                 struct tcg_pcr_event *event_header)
  41 {
  42         struct tcg_efi_specid_event *efispecid;
  43         struct tcg_event_field *event_field;
  44         void *marker;
  45         void *marker_start;
  46         u32 halg_size;
  47         size_t size;
  48         u16 halg;
  49         int i;
  50         int j;
  51
  52         marker = event;
  53         marker_start = marker;
  54         marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
  55                 + sizeof(event->count);
  56
  57         efispecid = (struct tcg_efi_specid_event *)event_header->event;
  58
  59         /* Check if event is malformed. */
  60         if (event->count > efispecid->num_algs)
  61                 return 0;
  62
  63         for (i = 0; i < event->count; i++) {
  64                 halg_size = sizeof(event->digests[i].alg_id);
  65                 memcpy(&halg, marker, halg_size);
  66                 marker = marker + halg_size;
  67                 for (j = 0; j < efispecid->num_algs; j++) {
  68                         if (halg == efispecid->digest_sizes[j].alg_id) {
  69                                 marker +=
  70                                         efispecid->digest_sizes[j].digest_size;
  71                                 break;
  72                         }
  73                 }
  74                 /* Algorithm without known length. Such event is unparseable. */
  75                 if (j == efispecid->num_algs)
  76                         return 0;
  77         }
  78
  79         event_field = (struct tcg_event_field *)marker;
  80         marker = marker + sizeof(event_field->event_size)
  81                 + event_field->event_size;
  82         size = marker - marker_start;
  83
  84         if ((event->event_type == 0) && (event_field->event_size == 0))
  85                 return 0;
  86
  87         return size;
  88 }
  89
  90 static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
  91 {
  92         struct tpm_chip *chip = m->private;
  93         struct tpm_bios_log *log = &chip->log;
  94         void *addr = log->bios_event_log;
  95         void *limit = log->bios_event_log_end;
  96         struct tcg_pcr_event *event_header;
  97         struct tcg_pcr_event2 *event;
  98         size_t size;
  99         int i;
 100
 101         event_header = addr;
 102         size = sizeof(struct tcg_pcr_event) - sizeof(event_header->event)
 103                 + event_header->event_size;
 104
 105         if (*pos == 0) {
 106                 if (addr + size < limit) {
 107                         if ((event_header->event_type == 0) &&
 108                             (event_header->event_size == 0))
 109                                 return NULL;
 110                         return SEQ_START_TOKEN;
 111                 }
 112         }
 113
 114         if (*pos > 0) {
 115                 addr += size;
 116                 event = addr;
 117                 size = calc_tpm2_event_size(event, event_header);
 118                 if ((addr + size >=  limit) || (size == 0))
 119                         return NULL;
 120         }
 121
 122         for (i = 0; i < (*pos - 1); i++) {
 123                 event = addr;
 124                 size = calc_tpm2_event_size(event, event_header);
 125
 126                 if ((addr + size >= limit) || (size == 0))
 127                         return NULL;
 128                 addr += size;
 129         }
 130
 131         return addr;
 132 }
 133
 134 static void *tpm2_bios_measurements_next(struct seq_file *m, void *v,
 135                                          loff_t *pos)
 136 {
 137         struct tcg_pcr_event *event_header;
 138         struct tcg_pcr_event2 *event;
 139         struct tpm_chip *chip = m->private;
 140         struct tpm_bios_log *log = &chip->log;
 141         void *limit = log->bios_event_log_end;
 142         size_t event_size;
 143         void *marker;
 144
 145         event_header = log->bios_event_log;
 146
 147         if (v == SEQ_START_TOKEN) {
 148                 event_size = sizeof(struct tcg_pcr_event) -
 149                         sizeof(event_header->event) + event_header->event_size;
 150                 marker = event_header;
 151         } else {
 152                 event = v;
 153                 event_size = calc_tpm2_event_size(event, event_header);
 154                 if (event_size == 0)
 155                         return NULL;
 156                 marker = event;
 157         }
 158
 159         marker = marker + event_size;
 160         if (marker >= limit)
 161                 return NULL;
 162         v = marker;
 163         event = v;
 164
 165         event_size = calc_tpm2_event_size(event, event_header);
 166         if (((v + event_size) >= limit) || (event_size == 0))
 167                 return NULL;
 168
 169         (*pos)++;
 170         return v;
 171 }
 172
 173 static void tpm2_bios_measurements_stop(struct seq_file *m, void *v)
 174 {
 175 }
 176
 177 static int tpm2_binary_bios_measurements_show(struct seq_file *m, void *v)
 178 {
 179         struct tpm_chip *chip = m->private;
 180         struct tpm_bios_log *log = &chip->log;
 181         struct tcg_pcr_event *event_header = log->bios_event_log;
 182         struct tcg_pcr_event2 *event = v;
 183         void *temp_ptr;
 184         size_t size;
 185
 186         if (v == SEQ_START_TOKEN) {
 187                 size = sizeof(struct tcg_pcr_event) -
 188                         sizeof(event_header->event) + event_header->event_size;
 189
 190                 temp_ptr = event_header;
 191
 192                 if (size > 0)
 193                         seq_write(m, temp_ptr, size);
 194         } else {
 195                 size = calc_tpm2_event_size(event, event_header);
 196                 temp_ptr = event;
 197                 if (size > 0)
 198                         seq_write(m, temp_ptr, size);
 199         }
 200
 201         return 0;
 202 }
 203
 204 const struct seq_operations tpm2_binary_b_measurements_seqops = {
 205         .start = tpm2_bios_measurements_start,
 206         .next = tpm2_bios_measurements_next,
 207         .stop = tpm2_bios_measurements_stop,
 208         .show = tpm2_binary_bios_measurements_show,
 209 };