/*
 * Copyright (C) 2013 Politecnico di Torino, Italy
 *                    TORSEC group -- http://security.polito.it
 *
 * Author: Roberto Sassu <roberto.sassu@polito.it>
 *
 * 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, version 2 of the
 * License.
 *
 * File: ima_template_lib.c
 *      Library of supported template fields.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include "ima_template_lib.h"

static bool ima_template_hash_algo_allowed(u8 algo)
{
        if (algo == HASH_ALGO_SHA1 || algo == HASH_ALGO_MD5)
                return true;

        return false;
}

enum data_formats {
        DATA_FMT_DIGEST = 0,
        DATA_FMT_DIGEST_WITH_ALGO,
        DATA_FMT_STRING,
        DATA_FMT_HEX
};

static int ima_write_template_field_data(const void *data, const u32 datalen,
                                         enum data_formats datafmt,
                                         struct ima_field_data *field_data)
{
        u8 *buf, *buf_ptr;
        u32 buflen = datalen;

        if (datafmt == DATA_FMT_STRING)
                buflen = datalen + 1;

        buf = kzalloc(buflen, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        memcpy(buf, data, datalen);

        /*
         * Replace all space characters with underscore for event names and
         * strings. This avoid that, during the parsing of a measurements list,
         * filenames with spaces or that end with the suffix ' (deleted)' are
         * split into multiple template fields (the space is the delimitator
         * character for measurements lists in ASCII format).
         */
        if (datafmt == DATA_FMT_STRING) {
                for (buf_ptr = buf; buf_ptr - buf < datalen; buf_ptr++)
                        if (*buf_ptr == ' ')
                                *buf_ptr = '_';
        }

        field_data->data = buf;
        field_data->len = buflen;
        return 0;
}

static void ima_show_template_data_ascii(struct seq_file *m,
                                         enum ima_show_type show,
                                         enum data_formats datafmt,
                                         struct ima_field_data *field_data)
{
        u8 *buf_ptr = field_data->data;
        u32 buflen = field_data->len;

        switch (datafmt) {
        case DATA_FMT_DIGEST_WITH_ALGO:
                buf_ptr = strnchr(field_data->data, buflen, ':');
                if (buf_ptr != field_data->data)
                        seq_printf(m, "%s", field_data->data);

                /* skip ':' and '\0' */
                buf_ptr += 2;
                buflen -= buf_ptr - field_data->data;
        case DATA_FMT_DIGEST:
        case DATA_FMT_HEX:
                if (!buflen)
                        break;
                ima_print_digest(m, buf_ptr, buflen);
                break;
        case DATA_FMT_STRING:
                seq_printf(m, "%s", buf_ptr);
                break;
        default:
                break;
        }
}

static void ima_show_template_data_binary(struct seq_file *m,
                                          enum ima_show_type show,
                                          enum data_formats datafmt,
                                          struct ima_field_data *field_data)
{
        u32 len = (show == IMA_SHOW_BINARY_OLD_STRING_FMT) ?
            strlen(field_data->data) : field_data->len;

        if (show != IMA_SHOW_BINARY_NO_FIELD_LEN) {
                u32 field_len = !ima_canonical_fmt ? len : cpu_to_le32(len);

                ima_putc(m, &field_len, sizeof(field_len));
        }

        if (!len)
                return;

        ima_putc(m, field_data->data, len);
}

static void ima_show_template_field_data(struct seq_file *m,
                                         enum ima_show_type show,
                                         enum data_formats datafmt,
                                         struct ima_field_data *field_data)
{
        switch (show) {
        case IMA_SHOW_ASCII:
                ima_show_template_data_ascii(m, show, datafmt, field_data);
                break;
        case IMA_SHOW_BINARY:
        case IMA_SHOW_BINARY_NO_FIELD_LEN:
        case IMA_SHOW_BINARY_OLD_STRING_FMT:
                ima_show_template_data_binary(m, show, datafmt, field_data);
                break;
        default:
                break;
        }
}

void ima_show_template_digest(struct seq_file *m, enum ima_show_type show,
                              struct ima_field_data *field_data)
{
        ima_show_template_field_data(m, show, DATA_FMT_DIGEST, field_data);
}

void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
                                 struct ima_field_data *field_data)
{
        ima_show_template_field_data(m, show, DATA_FMT_DIGEST_WITH_ALGO,
                                     field_data);
}

void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
                              struct ima_field_data *field_data)
{
        ima_show_template_field_data(m, show, DATA_FMT_STRING, field_data);
}

void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
                           struct ima_field_data *field_data)
{
        ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
}

/**
 * ima_parse_buf() - Parses lengths and data from an input buffer
 * @bufstartp:       Buffer start address.
 * @bufendp:         Buffer end address.
 * @bufcurp:         Pointer to remaining (non-parsed) data.
 * @maxfields:       Length of fields array.
 * @fields:          Array containing lengths and pointers of parsed data.
 * @curfields:       Number of array items containing parsed data.
 * @len_mask:        Bitmap (if bit is set, data length should not be parsed).
 * @enforce_mask:    Check if curfields == maxfields and/or bufcurp == bufendp.
 * @bufname:         String identifier of the input buffer.
 *
 * Return: 0 on success, -EINVAL on error.
 */
int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
                  int maxfields, struct ima_field_data *fields, int *curfields,
                  unsigned long *len_mask, int enforce_mask, char *bufname)
{
        void *bufp = bufstartp;
        int i;

        for (i = 0; i < maxfields; i++) {
                if (len_mask == NULL || !test_bit(i, len_mask)) {
                        if (bufp > (bufendp - sizeof(u32)))
                                break;

                        fields[i].len = *(u32 *)bufp;
                        if (ima_canonical_fmt)
                                fields[i].len = le32_to_cpu(fields[i].len);

                        bufp += sizeof(u32);
                }

                if (bufp > (bufendp - fields[i].len))
                        break;

                fields[i].data = bufp;
                bufp += fields[i].len;
        }

        if ((enforce_mask & ENFORCE_FIELDS) && i != maxfields) {
                pr_err("%s: nr of fields mismatch: expected: %d, current: %d\n",
                       bufname, maxfields, i);
                return -EINVAL;
        }

        if ((enforce_mask & ENFORCE_BUFEND) && bufp != bufendp) {
                pr_err("%s: buf end mismatch: expected: %p, current: %p\n",
                       bufname, bufendp, bufp);
                return -EINVAL;
        }

        if (curfields)
                *curfields = i;

        if (bufcurp)
                *bufcurp = bufp;

        return 0;
}

static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
                                       struct ima_field_data *field_data)
{
        /*
         * digest formats:
         *  - DATA_FMT_DIGEST: digest
         *  - DATA_FMT_DIGEST_WITH_ALGO: [<hash algo>] + ':' + '\0' + digest,
         *    where <hash algo> is provided if the hash algoritm is not
         *    SHA1 or MD5
         */
        u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
        enum data_formats fmt = DATA_FMT_DIGEST;
        u32 offset = 0;

        if (hash_algo < HASH_ALGO__LAST) {
                fmt = DATA_FMT_DIGEST_WITH_ALGO;
                offset += snprintf(buffer, CRYPTO_MAX_ALG_NAME + 1, "%s",
                                   hash_algo_name[hash_algo]);
                buffer[offset] = ':';
                offset += 2;
        }

        if (digest)
                memcpy(buffer + offset, digest, digestsize);
        else
                /*
                 * If digest is NULL, the event being recorded is a violation.
                 * Make room for the digest by increasing the offset of
                 * IMA_DIGEST_SIZE.
                 */
                offset += IMA_DIGEST_SIZE;

        return ima_write_template_field_data(buffer, offset + digestsize,
                                             fmt, field_data);
}

/*
 * This function writes the digest of an event (with size limit).
 */
int ima_eventdigest_init(struct ima_event_data *event_data,
                         struct ima_field_data *field_data)
{
        struct {
                struct ima_digest_data hdr;
                char digest[IMA_MAX_DIGEST_SIZE];
        } hash;
        u8 *cur_digest = NULL;
        u32 cur_digestsize = 0;
        struct inode *inode;
        int result;

        memset(&hash, 0, sizeof(hash));

        if (event_data->violation)      /* recording a violation. */
                goto out;

        if (ima_template_hash_algo_allowed(event_data->iint->ima_hash->algo)) {
                cur_digest = event_data->iint->ima_hash->digest;
                cur_digestsize = event_data->iint->ima_hash->length;
                goto out;
        }

        if (!event_data->file)  /* missing info to re-calculate the digest */
                return -EINVAL;

        inode = file_inode(event_data->file);
        hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
            ima_hash_algo : HASH_ALGO_SHA1;
        result = ima_calc_file_hash(event_data->file, &hash.hdr);
        if (result) {
                integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
                                    event_data->filename, "collect_data",
                                    "failed", result, 0);
                return result;
        }
        cur_digest = hash.hdr.digest;
        cur_digestsize = hash.hdr.length;
out:
        return ima_eventdigest_init_common(cur_digest, cur_digestsize,
                                           HASH_ALGO__LAST, field_data);
}

/*
 * This function writes the digest of an event (without size limit).
 */
int ima_eventdigest_ng_init(struct ima_event_data *event_data,
                            struct ima_field_data *field_data)
{
        u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
        u32 cur_digestsize = 0;

        if (event_data->violation)      /* recording a violation. */
                goto out;

        cur_digest = event_data->iint->ima_hash->digest;
        cur_digestsize = event_data->iint->ima_hash->length;

        hash_algo = event_data->iint->ima_hash->algo;
out:
        return ima_eventdigest_init_common(cur_digest, cur_digestsize,
                                           hash_algo, field_data);
}

static int ima_eventname_init_common(struct ima_event_data *event_data,
                                     struct ima_field_data *field_data,
                                     bool size_limit)
{
        const char *cur_filename = NULL;
        u32 cur_filename_len = 0;

        BUG_ON(event_data->filename == NULL && event_data->file == NULL);

        if (event_data->filename) {
                cur_filename = event_data->filename;
                cur_filename_len = strlen(event_data->filename);

                if (!size_limit || cur_filename_len <= IMA_EVENT_NAME_LEN_MAX)
                        goto out;
        }

        if (event_data->file) {
                cur_filename = event_data->file->f_path.dentry->d_name.name;
                cur_filename_len = strlen(cur_filename);
        } else
                /*
                 * Truncate filename if the latter is too long and
                 * the file descriptor is not available.
                 */
                cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
out:
        return ima_write_template_field_data(cur_filename, cur_filename_len,
                                             DATA_FMT_STRING, field_data);
}

/*
 * This function writes the name of an event (with size limit).
 */
int ima_eventname_init(struct ima_event_data *event_data,
                       struct ima_field_data *field_data)
{
        return ima_eventname_init_common(event_data, field_data, true);
}

/*
 * This function writes the name of an event (without size limit).
 */
int ima_eventname_ng_init(struct ima_event_data *event_data,
                          struct ima_field_data *field_data)
{
        return ima_eventname_init_common(event_data, field_data, false);
}

/*
 *  ima_eventsig_init - include the file signature as part of the template data
 */
int ima_eventsig_init(struct ima_event_data *event_data,
                      struct ima_field_data *field_data)
{
        struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;

        if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
                return 0;

        return ima_write_template_field_data(xattr_value, event_data->xattr_len,
                                             DATA_FMT_HEX, field_data);
}