// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Mimi Zohar <zohar@us.ibm.com>
 * Kylene Hall <kjhall@us.ibm.com>
 *
 * File: ima_crypto.c
 *      Calculates md5/sha1 file hash, template hash, boot-aggreate hash
 */

#include <linux/kernel.h>
#include <linux/moduleparam.h>
#include <linux/ratelimit.h>
#include <linux/file.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <crypto/hash.h>

#include "ima.h"

/* minimum file size for ahash use */
static unsigned long ima_ahash_minsize;
module_param_named(ahash_minsize, ima_ahash_minsize, ulong, 0644);
MODULE_PARM_DESC(ahash_minsize, "Minimum file size for ahash use");

/* default is 0 - 1 page. */
static int ima_maxorder;
static unsigned int ima_bufsize = PAGE_SIZE;

static int param_set_bufsize(const char *val, const struct kernel_param *kp)
{
        unsigned long long size;
        int order;

        size = memparse(val, NULL);
        order = get_order(size);
        if (order >= MAX_ORDER)
                return -EINVAL;
        ima_maxorder = order;
        ima_bufsize = PAGE_SIZE << order;
        return 0;
}

static const struct kernel_param_ops param_ops_bufsize = {
        .set = param_set_bufsize,
        .get = param_get_uint,
};
#define param_check_bufsize(name, p) __param_check(name, p, unsigned int)

module_param_named(ahash_bufsize, ima_bufsize, bufsize, 0644);
MODULE_PARM_DESC(ahash_bufsize, "Maximum ahash buffer size");

static struct crypto_shash *ima_shash_tfm;
static struct crypto_ahash *ima_ahash_tfm;

struct ima_algo_desc {
        struct crypto_shash *tfm;
        enum hash_algo algo;
};

int ima_sha1_idx __ro_after_init;
int ima_hash_algo_idx __ro_after_init;
/*
 * Additional number of slots reserved, as needed, for SHA1
 * and IMA default algo.
 */
int ima_extra_slots __ro_after_init;

static struct ima_algo_desc *ima_algo_array;

static int __init ima_init_ima_crypto(void)
{
        long rc;

        ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
        if (IS_ERR(ima_shash_tfm)) {
                rc = PTR_ERR(ima_shash_tfm);
                pr_err("Can not allocate %s (reason: %ld)\n",
                       hash_algo_name[ima_hash_algo], rc);
                return rc;
        }
        pr_info("Allocated hash algorithm: %s\n",
                hash_algo_name[ima_hash_algo]);
        return 0;
}

static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
{
        struct crypto_shash *tfm = ima_shash_tfm;
        int rc, i;

        if (algo < 0 || algo >= HASH_ALGO__LAST)
                algo = ima_hash_algo;

        if (algo == ima_hash_algo)
                return tfm;

        for (i = 0; i < NR_BANKS(ima_tpm_chip) + ima_extra_slots; i++)
                if (ima_algo_array[i].tfm && ima_algo_array[i].algo == algo)
                        return ima_algo_array[i].tfm;

        tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
        if (IS_ERR(tfm)) {
                rc = PTR_ERR(tfm);
                pr_err("Can not allocate %s (reason: %d)\n",
                       hash_algo_name[algo], rc);
        }
        return tfm;
}

int __init ima_init_crypto(void)
{
        enum hash_algo algo;
        long rc;
        int i;

        rc = ima_init_ima_crypto();
        if (rc)
                return rc;

        ima_sha1_idx = -1;
        ima_hash_algo_idx = -1;

        for (i = 0; i < NR_BANKS(ima_tpm_chip); i++) {
                algo = ima_tpm_chip->allocated_banks[i].crypto_id;
                if (algo == HASH_ALGO_SHA1)
                        ima_sha1_idx = i;

                if (algo == ima_hash_algo)
                        ima_hash_algo_idx = i;
        }

        if (ima_sha1_idx < 0) {
                ima_sha1_idx = NR_BANKS(ima_tpm_chip) + ima_extra_slots++;
                if (ima_hash_algo == HASH_ALGO_SHA1)
                        ima_hash_algo_idx = ima_sha1_idx;
        }

        if (ima_hash_algo_idx < 0)
                ima_hash_algo_idx = NR_BANKS(ima_tpm_chip) + ima_extra_slots++;

        ima_algo_array = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
                                 sizeof(*ima_algo_array), GFP_KERNEL);
        if (!ima_algo_array) {
                rc = -ENOMEM;
                goto out;
        }

        for (i = 0; i < NR_BANKS(ima_tpm_chip); i++) {
                algo = ima_tpm_chip->allocated_banks[i].crypto_id;
                ima_algo_array[i].algo = algo;

                /* unknown TPM algorithm */
                if (algo == HASH_ALGO__LAST)
                        continue;

                if (algo == ima_hash_algo) {
                        ima_algo_array[i].tfm = ima_shash_tfm;
                        continue;
                }

                ima_algo_array[i].tfm = ima_alloc_tfm(algo);
                if (IS_ERR(ima_algo_array[i].tfm)) {
                        if (algo == HASH_ALGO_SHA1) {
                                rc = PTR_ERR(ima_algo_array[i].tfm);
                                ima_algo_array[i].tfm = NULL;
                                goto out_array;
                        }

                        ima_algo_array[i].tfm = NULL;
                }
        }

        if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip)) {
                if (ima_hash_algo == HASH_ALGO_SHA1) {
                        ima_algo_array[ima_sha1_idx].tfm = ima_shash_tfm;
                } else {
                        ima_algo_array[ima_sha1_idx].tfm =
                                                ima_alloc_tfm(HASH_ALGO_SHA1);
                        if (IS_ERR(ima_algo_array[ima_sha1_idx].tfm)) {
                                rc = PTR_ERR(ima_algo_array[ima_sha1_idx].tfm);
                                goto out_array;
                        }
                }

                ima_algo_array[ima_sha1_idx].algo = HASH_ALGO_SHA1;
        }

        if (ima_hash_algo_idx >= NR_BANKS(ima_tpm_chip) &&
            ima_hash_algo_idx != ima_sha1_idx) {
                ima_algo_array[ima_hash_algo_idx].tfm = ima_shash_tfm;
                ima_algo_array[ima_hash_algo_idx].algo = ima_hash_algo;
        }

        return 0;
out_array:
        for (i = 0; i < NR_BANKS(ima_tpm_chip) + ima_extra_slots; i++) {
                if (!ima_algo_array[i].tfm ||
                    ima_algo_array[i].tfm == ima_shash_tfm)
                        continue;

                crypto_free_shash(ima_algo_array[i].tfm);
        }
out:
        crypto_free_shash(ima_shash_tfm);
        return rc;
}

static void ima_free_tfm(struct crypto_shash *tfm)
{
        int i;

        if (tfm == ima_shash_tfm)
                return;

        for (i = 0; i < NR_BANKS(ima_tpm_chip) + ima_extra_slots; i++)
                if (ima_algo_array[i].tfm == tfm)
                        return;

        crypto_free_shash(tfm);
}

/**
 * ima_alloc_pages() - Allocate contiguous pages.
 * @max_size:       Maximum amount of memory to allocate.
 * @allocated_size: Returned size of actual allocation.
 * @last_warn:      Should the min_size allocation warn or not.
 *
 * Tries to do opportunistic allocation for memory first trying to allocate
 * max_size amount of memory and then splitting that until zero order is
 * reached. Allocation is tried without generating allocation warnings unless
 * last_warn is set. Last_warn set affects only last allocation of zero order.
 *
 * By default, ima_maxorder is 0 and it is equivalent to kmalloc(GFP_KERNEL)
 *
 * Return pointer to allocated memory, or NULL on failure.
 */
static void *ima_alloc_pages(loff_t max_size, size_t *allocated_size,
                             int last_warn)
{
        void *ptr;
        int order = ima_maxorder;
        gfp_t gfp_mask = __GFP_RECLAIM | __GFP_NOWARN | __GFP_NORETRY;

        if (order)
                order = min(get_order(max_size), order);

        for (; order; order--) {
                ptr = (void *)__get_free_pages(gfp_mask, order);
                if (ptr) {
                        *allocated_size = PAGE_SIZE << order;
                        return ptr;
                }
        }

        /* order is zero - one page */

        gfp_mask = GFP_KERNEL;

        if (!last_warn)
                gfp_mask |= __GFP_NOWARN;

        ptr = (void *)__get_free_pages(gfp_mask, 0);
        if (ptr) {
                *allocated_size = PAGE_SIZE;
                return ptr;
        }

        *allocated_size = 0;
        return NULL;
}

/**
 * ima_free_pages() - Free pages allocated by ima_alloc_pages().
 * @ptr:  Pointer to allocated pages.
 * @size: Size of allocated buffer.
 */
static void ima_free_pages(void *ptr, size_t size)
{
        if (!ptr)
                return;
        free_pages((unsigned long)ptr, get_order(size));
}

static struct crypto_ahash *ima_alloc_atfm(enum hash_algo algo)
{
        struct crypto_ahash *tfm = ima_ahash_tfm;
        int rc;

        if (algo < 0 || algo >= HASH_ALGO__LAST)
                algo = ima_hash_algo;

        if (algo != ima_hash_algo || !tfm) {
                tfm = crypto_alloc_ahash(hash_algo_name[algo], 0, 0);
                if (!IS_ERR(tfm)) {
                        if (algo == ima_hash_algo)
                                ima_ahash_tfm = tfm;
                } else {
                        rc = PTR_ERR(tfm);
                        pr_err("Can not allocate %s (reason: %d)\n",
                               hash_algo_name[algo], rc);
                }
        }
        return tfm;
}

static void ima_free_atfm(struct crypto_ahash *tfm)
{
        if (tfm != ima_ahash_tfm)
                crypto_free_ahash(tfm);
}

static inline int ahash_wait(int err, struct crypto_wait *wait)
{

        err = crypto_wait_req(err, wait);

        if (err)
                pr_crit_ratelimited("ahash calculation failed: err: %d\n", err);

        return err;
}

static int ima_calc_file_hash_atfm(struct file *file,
                                   struct ima_digest_data *hash,
                                   struct crypto_ahash *tfm)
{
        loff_t i_size, offset;
        char *rbuf[2] = { NULL, };
        int rc, rbuf_len, active = 0, ahash_rc = 0;
        struct ahash_request *req;
        struct scatterlist sg[1];
        struct crypto_wait wait;
        size_t rbuf_size[2];

        hash->length = crypto_ahash_digestsize(tfm);

        req = ahash_request_alloc(tfm, GFP_KERNEL);
        if (!req)
                return -ENOMEM;

        crypto_init_wait(&wait);
        ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
                                   CRYPTO_TFM_REQ_MAY_SLEEP,
                                   crypto_req_done, &wait);

        rc = ahash_wait(crypto_ahash_init(req), &wait);
        if (rc)
                goto out1;

        i_size = i_size_read(file_inode(file));

        if (i_size == 0)
                goto out2;

        /*
         * Try to allocate maximum size of memory.
         * Fail if even a single page cannot be allocated.
         */
        rbuf[0] = ima_alloc_pages(i_size, &rbuf_size[0], 1);
        if (!rbuf[0]) {
                rc = -ENOMEM;
                goto out1;
        }

        /* Only allocate one buffer if that is enough. */
        if (i_size > rbuf_size[0]) {
                /*
                 * Try to allocate secondary buffer. If that fails fallback to
                 * using single buffering. Use previous memory allocation size
                 * as baseline for possible allocation size.
                 */
                rbuf[1] = ima_alloc_pages(i_size - rbuf_size[0],
                                          &rbuf_size[1], 0);
        }

        for (offset = 0; offset < i_size; offset += rbuf_len) {
                if (!rbuf[1] && offset) {
                        /* Not using two buffers, and it is not the first
                         * read/request, wait for the completion of the
                         * previous ahash_update() request.
                         */
                        rc = ahash_wait(ahash_rc, &wait);
                        if (rc)
                                goto out3;
                }
                /* read buffer */
                rbuf_len = min_t(loff_t, i_size - offset, rbuf_size[active]);
                rc = integrity_kernel_read(file, offset, rbuf[active],
                                           rbuf_len);
                if (rc != rbuf_len) {
                        if (rc >= 0)
                                rc = -EINVAL;
                        /*
                         * Forward current rc, do not overwrite with return value
                         * from ahash_wait()
                         */
                        ahash_wait(ahash_rc, &wait);
                        goto out3;
                }

                if (rbuf[1] && offset) {
                        /* Using two buffers, and it is not the first
                         * read/request, wait for the completion of the
                         * previous ahash_update() request.
                         */
                        rc = ahash_wait(ahash_rc, &wait);
                        if (rc)
                                goto out3;
                }

                sg_init_one(&sg[0], rbuf[active], rbuf_len);
                ahash_request_set_crypt(req, sg, NULL, rbuf_len);

                ahash_rc = crypto_ahash_update(req);

                if (rbuf[1])
                        active = !active; /* swap buffers, if we use two */
        }
        /* wait for the last update request to complete */
        rc = ahash_wait(ahash_rc, &wait);
out3:
        ima_free_pages(rbuf[0], rbuf_size[0]);
        ima_free_pages(rbuf[1], rbuf_size[1]);
out2:
        if (!rc) {
                ahash_request_set_crypt(req, NULL, hash->digest, 0);
                rc = ahash_wait(crypto_ahash_final(req), &wait);
        }
out1:
        ahash_request_free(req);
        return rc;
}

static int ima_calc_file_ahash(struct file *file, struct ima_digest_data *hash)
{
        struct crypto_ahash *tfm;
        int rc;

        tfm = ima_alloc_atfm(hash->algo);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        rc = ima_calc_file_hash_atfm(file, hash, tfm);

        ima_free_atfm(tfm);

        return rc;
}

static int ima_calc_file_hash_tfm(struct file *file,
                                  struct ima_digest_data *hash,
                                  struct crypto_shash *tfm)
{
        loff_t i_size, offset = 0;
        char *rbuf;
        int rc;
        SHASH_DESC_ON_STACK(shash, tfm);

        shash->tfm = tfm;

        hash->length = crypto_shash_digestsize(tfm);

        rc = crypto_shash_init(shash);
        if (rc != 0)
                return rc;

        i_size = i_size_read(file_inode(file));

        if (i_size == 0)
                goto out;

        rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!rbuf)
                return -ENOMEM;

        while (offset < i_size) {
                int rbuf_len;

                rbuf_len = integrity_kernel_read(file, offset, rbuf, PAGE_SIZE);
                if (rbuf_len < 0) {
                        rc = rbuf_len;
                        break;
                }
                if (rbuf_len == 0) {    /* unexpected EOF */
                        rc = -EINVAL;
                        break;
                }
                offset += rbuf_len;

                rc = crypto_shash_update(shash, rbuf, rbuf_len);
                if (rc)
                        break;
        }
        kfree(rbuf);
out:
        if (!rc)
                rc = crypto_shash_final(shash, hash->digest);
        return rc;
}

static int ima_calc_file_shash(struct file *file, struct ima_digest_data *hash)
{
        struct crypto_shash *tfm;
        int rc;

        tfm = ima_alloc_tfm(hash->algo);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        rc = ima_calc_file_hash_tfm(file, hash, tfm);

        ima_free_tfm(tfm);

        return rc;
}

/*
 * ima_calc_file_hash - calculate file hash
 *
 * Asynchronous hash (ahash) allows using HW acceleration for calculating
 * a hash. ahash performance varies for different data sizes on different
 * crypto accelerators. shash performance might be better for smaller files.
 * The 'ima.ahash_minsize' module parameter allows specifying the best
 * minimum file size for using ahash on the system.
 *
 * If the ima.ahash_minsize parameter is not specified, this function uses
 * shash for the hash calculation.  If ahash fails, it falls back to using
 * shash.
 */
int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
{
        loff_t i_size;
        int rc;
        struct file *f = file;
        bool new_file_instance = false, modified_mode = false;

        /*
         * For consistency, fail file's opened with the O_DIRECT flag on
         * filesystems mounted with/without DAX option.
         */
        if (file->f_flags & O_DIRECT) {
                hash->length = hash_digest_size[ima_hash_algo];
                hash->algo = ima_hash_algo;
                return -EINVAL;
        }

        /* Open a new file instance in O_RDONLY if we cannot read */
        if (!(file->f_mode & FMODE_READ)) {
                int flags = file->f_flags & ~(O_WRONLY | O_APPEND |
                                O_TRUNC | O_CREAT | O_NOCTTY | O_EXCL);
                flags |= O_RDONLY;
                f = dentry_open(&file->f_path, flags, file->f_cred);
                if (IS_ERR(f)) {
                        /*
                         * Cannot open the file again, lets modify f_mode
                         * of original and continue
                         */
                        pr_info_ratelimited("Unable to reopen file for reading.\n");
                        f = file;
                        f->f_mode |= FMODE_READ;
                        modified_mode = true;
                } else {
                        new_file_instance = true;
                }
        }

        i_size = i_size_read(file_inode(f));

        if (ima_ahash_minsize && i_size >= ima_ahash_minsize) {
                rc = ima_calc_file_ahash(f, hash);
                if (!rc)
                        goto out;
        }

        rc = ima_calc_file_shash(f, hash);
out:
        if (new_file_instance)
                fput(f);
        else if (modified_mode)
                f->f_mode &= ~FMODE_READ;
        return rc;
}

/*
 * Calculate the hash of template data
 */
static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
                                         struct ima_template_entry *entry,
                                         int tfm_idx)
{
        SHASH_DESC_ON_STACK(shash, ima_algo_array[tfm_idx].tfm);
        struct ima_template_desc *td = entry->template_desc;
        int num_fields = entry->template_desc->num_fields;
        int rc, i;

        shash->tfm = ima_algo_array[tfm_idx].tfm;

        rc = crypto_shash_init(shash);
        if (rc != 0)
                return rc;

        for (i = 0; i < num_fields; i++) {
                u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 };
                u8 *data_to_hash = field_data[i].data;
                u32 datalen = field_data[i].len;
                u32 datalen_to_hash =
                    !ima_canonical_fmt ? datalen : cpu_to_le32(datalen);

                if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) {
                        rc = crypto_shash_update(shash,
                                                (const u8 *) &datalen_to_hash,
                                                sizeof(datalen_to_hash));
                        if (rc)
                                break;
                } else if (strcmp(td->fields[i]->field_id, "n") == 0) {
                        memcpy(buffer, data_to_hash, datalen);
                        data_to_hash = buffer;
                        datalen = IMA_EVENT_NAME_LEN_MAX + 1;
                }
                rc = crypto_shash_update(shash, data_to_hash, datalen);
                if (rc)
                        break;
        }

        if (!rc)
                rc = crypto_shash_final(shash, entry->digests[tfm_idx].digest);

        return rc;
}

int ima_calc_field_array_hash(struct ima_field_data *field_data,
                              struct ima_template_entry *entry)
{
        u16 alg_id;
        int rc, i;

        rc = ima_calc_field_array_hash_tfm(field_data, entry, ima_sha1_idx);
        if (rc)
                return rc;

        entry->digests[ima_sha1_idx].alg_id = TPM_ALG_SHA1;

        for (i = 0; i < NR_BANKS(ima_tpm_chip) + ima_extra_slots; i++) {
                if (i == ima_sha1_idx)
                        continue;

                if (i < NR_BANKS(ima_tpm_chip)) {
                        alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
                        entry->digests[i].alg_id = alg_id;
                }

                /* for unmapped TPM algorithms digest is still a padded SHA1 */
                if (!ima_algo_array[i].tfm) {
                        memcpy(entry->digests[i].digest,
                               entry->digests[ima_sha1_idx].digest,
                               TPM_DIGEST_SIZE);
                        continue;
                }

                rc = ima_calc_field_array_hash_tfm(field_data, entry, i);
                if (rc)
                        return rc;
        }
        return rc;
}

static int calc_buffer_ahash_atfm(const void *buf, loff_t len,
                                  struct ima_digest_data *hash,
                                  struct crypto_ahash *tfm)
{
        struct ahash_request *req;
        struct scatterlist sg;
        struct crypto_wait wait;
        int rc, ahash_rc = 0;

        hash->length = crypto_ahash_digestsize(tfm);

        req = ahash_request_alloc(tfm, GFP_KERNEL);
        if (!req)
                return -ENOMEM;

        crypto_init_wait(&wait);
        ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
                                   CRYPTO_TFM_REQ_MAY_SLEEP,
                                   crypto_req_done, &wait);

        rc = ahash_wait(crypto_ahash_init(req), &wait);
        if (rc)
                goto out;

        sg_init_one(&sg, buf, len);
        ahash_request_set_crypt(req, &sg, NULL, len);

        ahash_rc = crypto_ahash_update(req);

        /* wait for the update request to complete */
        rc = ahash_wait(ahash_rc, &wait);
        if (!rc) {
                ahash_request_set_crypt(req, NULL, hash->digest, 0);
                rc = ahash_wait(crypto_ahash_final(req), &wait);
        }
out:
        ahash_request_free(req);
        return rc;
}

static int calc_buffer_ahash(const void *buf, loff_t len,
                             struct ima_digest_data *hash)
{
        struct crypto_ahash *tfm;
        int rc;

        tfm = ima_alloc_atfm(hash->algo);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        rc = calc_buffer_ahash_atfm(buf, len, hash, tfm);

        ima_free_atfm(tfm);

        return rc;
}

static int calc_buffer_shash_tfm(const void *buf, loff_t size,
                                struct ima_digest_data *hash,
                                struct crypto_shash *tfm)
{
        SHASH_DESC_ON_STACK(shash, tfm);
        unsigned int len;
        int rc;

        shash->tfm = tfm;

        hash->length = crypto_shash_digestsize(tfm);

        rc = crypto_shash_init(shash);
        if (rc != 0)
                return rc;

        while (size) {
                len = size < PAGE_SIZE ? size : PAGE_SIZE;
                rc = crypto_shash_update(shash, buf, len);
                if (rc)
                        break;
                buf += len;
                size -= len;
        }

        if (!rc)
                rc = crypto_shash_final(shash, hash->digest);
        return rc;
}

static int calc_buffer_shash(const void *buf, loff_t len,
                             struct ima_digest_data *hash)
{
        struct crypto_shash *tfm;
        int rc;

        tfm = ima_alloc_tfm(hash->algo);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        rc = calc_buffer_shash_tfm(buf, len, hash, tfm);

        ima_free_tfm(tfm);
        return rc;
}

int ima_calc_buffer_hash(const void *buf, loff_t len,
                         struct ima_digest_data *hash)
{
        int rc;

        if (ima_ahash_minsize && len >= ima_ahash_minsize) {
                rc = calc_buffer_ahash(buf, len, hash);
                if (!rc)
                        return 0;
        }

        return calc_buffer_shash(buf, len, hash);
}

static void ima_pcrread(u32 idx, struct tpm_digest *d)
{
        if (!ima_tpm_chip)
                return;

        if (tpm_pcr_read(ima_tpm_chip, idx, d) != 0)
                pr_err("Error Communicating to TPM chip\n");
}

/*
 * The boot_aggregate is a cumulative hash over TPM registers 0 - 7.  With
 * TPM 1.2 the boot_aggregate was based on reading the SHA1 PCRs, but with
 * TPM 2.0 hash agility, TPM chips could support multiple TPM PCR banks,
 * allowing firmware to configure and enable different banks.
 *
 * Knowing which TPM bank is read to calculate the boot_aggregate digest
 * needs to be conveyed to a verifier.  For this reason, use the same
 * hash algorithm for reading the TPM PCRs as for calculating the boot
 * aggregate digest as stored in the measurement list.
 */
static int ima_calc_boot_aggregate_tfm(char *digest, u16 alg_id,
                                       struct crypto_shash *tfm)
{
        struct tpm_digest d = { .alg_id = alg_id, .digest = {0} };
        int rc;
        u32 i;
        SHASH_DESC_ON_STACK(shash, tfm);

        shash->tfm = tfm;

        pr_devel("calculating the boot-aggregate based on TPM bank: %04x\n",
                 d.alg_id);

        rc = crypto_shash_init(shash);
        if (rc != 0)
                return rc;

        /* cumulative digest over TPM registers 0-7 */
        for (i = TPM_PCR0; i < TPM_PCR8; i++) {
                ima_pcrread(i, &d);
                /* now accumulate with current aggregate */
                rc = crypto_shash_update(shash, d.digest,
                                         crypto_shash_digestsize(tfm));
        }
        /*
         * Extend cumulative digest over TPM registers 8-9, which contain
         * measurement for the kernel command line (reg. 8) and image (reg. 9)
         * in a typical PCR allocation. Registers 8-9 are only included in
         * non-SHA1 boot_aggregate digests to avoid ambiguity.
         */
        if (alg_id != TPM_ALG_SHA1) {
                for (i = TPM_PCR8; i < TPM_PCR10; i++) {
                        ima_pcrread(i, &d);
                        rc = crypto_shash_update(shash, d.digest,
                                                crypto_shash_digestsize(tfm));
                }
        }
        if (!rc)
                crypto_shash_final(shash, digest);
        return rc;
}

int ima_calc_boot_aggregate(struct ima_digest_data *hash)
{
        struct crypto_shash *tfm;
        u16 crypto_id, alg_id;
        int rc, i, bank_idx = -1;

        for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) {
                crypto_id = ima_tpm_chip->allocated_banks[i].crypto_id;
                if (crypto_id == hash->algo) {
                        bank_idx = i;
                        break;
                }

                if (crypto_id == HASH_ALGO_SHA256)
                        bank_idx = i;

                if (bank_idx == -1 && crypto_id == HASH_ALGO_SHA1)
                        bank_idx = i;
        }

        if (bank_idx == -1) {
                pr_err("No suitable TPM algorithm for boot aggregate\n");
                return 0;
        }

        hash->algo = ima_tpm_chip->allocated_banks[bank_idx].crypto_id;

        tfm = ima_alloc_tfm(hash->algo);
        if (IS_ERR(tfm))
                return PTR_ERR(tfm);

        hash->length = crypto_shash_digestsize(tfm);
        alg_id = ima_tpm_chip->allocated_banks[bank_idx].alg_id;
        rc = ima_calc_boot_aggregate_tfm(hash->digest, alg_id, tfm);

        ima_free_tfm(tfm);

        return rc;
}