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![Roberto Sassu](/assets/img/avatar_default.png)
With the new template mechanism introduced in IMA since kernel 3.13, the format of data sent through the binary_runtime_measurements interface is slightly changed. Now, for a generic measurement, the format of template data (after the template name) is: template_len | field1_len | field1 | ... | fieldN_len | fieldN In addition, fields containing a string now include the '\0' termination character. Instead, the format for the 'ima' template should be: SHA1 digest | event name length | event name It must be noted that while in the IMA 3.13 code 'event name length' is 'IMA_EVENT_NAME_LEN_MAX + 1' (256 bytes), so that the template digest is calculated correctly, and 'event name' contains '\0', in the pre 3.13 code 'event name length' is exactly the string length and 'event name' does not contain the termination character. The patch restores the behavior of the IMA code pre 3.13 for the 'ima' template so that legacy userspace tools obtain a consistent behavior when receiving data from the binary_runtime_measurements interface regardless of which kernel version is used. Signed-off-by: Roberto Sassu <roberto.sassu@polito.it> Cc: <stable@vger.kernel.org> # 3.3.13: 3ce1217 ima: define template fields library Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
353 lines
9.2 KiB
C
353 lines
9.2 KiB
C
/*
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* Copyright (C) 2013 Politecnico di Torino, Italy
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* TORSEC group -- http://security.polito.it
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*
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* Author: Roberto Sassu <roberto.sassu@polito.it>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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* File: ima_template_lib.c
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* Library of supported template fields.
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*/
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#include <crypto/hash_info.h>
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#include "ima_template_lib.h"
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static bool ima_template_hash_algo_allowed(u8 algo)
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{
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if (algo == HASH_ALGO_SHA1 || algo == HASH_ALGO_MD5)
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return true;
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return false;
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}
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enum data_formats {
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DATA_FMT_DIGEST = 0,
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DATA_FMT_DIGEST_WITH_ALGO,
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DATA_FMT_EVENT_NAME,
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DATA_FMT_STRING,
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DATA_FMT_HEX
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};
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static int ima_write_template_field_data(const void *data, const u32 datalen,
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enum data_formats datafmt,
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struct ima_field_data *field_data)
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{
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u8 *buf, *buf_ptr;
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u32 buflen;
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switch (datafmt) {
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case DATA_FMT_EVENT_NAME:
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buflen = IMA_EVENT_NAME_LEN_MAX + 1;
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break;
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case DATA_FMT_STRING:
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buflen = datalen + 1;
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break;
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default:
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buflen = datalen;
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}
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buf = kzalloc(buflen, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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memcpy(buf, data, datalen);
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/*
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* Replace all space characters with underscore for event names and
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* strings. This avoid that, during the parsing of a measurements list,
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* filenames with spaces or that end with the suffix ' (deleted)' are
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* split into multiple template fields (the space is the delimitator
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* character for measurements lists in ASCII format).
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*/
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if (datafmt == DATA_FMT_EVENT_NAME || datafmt == DATA_FMT_STRING) {
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for (buf_ptr = buf; buf_ptr - buf < datalen; buf_ptr++)
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if (*buf_ptr == ' ')
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*buf_ptr = '_';
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}
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field_data->data = buf;
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field_data->len = buflen;
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return 0;
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}
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static void ima_show_template_data_ascii(struct seq_file *m,
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enum ima_show_type show,
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enum data_formats datafmt,
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struct ima_field_data *field_data)
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{
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u8 *buf_ptr = field_data->data, buflen = field_data->len;
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switch (datafmt) {
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case DATA_FMT_DIGEST_WITH_ALGO:
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buf_ptr = strnchr(field_data->data, buflen, ':');
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if (buf_ptr != field_data->data)
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seq_printf(m, "%s", field_data->data);
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/* skip ':' and '\0' */
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buf_ptr += 2;
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buflen -= buf_ptr - field_data->data;
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case DATA_FMT_DIGEST:
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case DATA_FMT_HEX:
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if (!buflen)
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break;
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ima_print_digest(m, buf_ptr, buflen);
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break;
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case DATA_FMT_STRING:
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seq_printf(m, "%s", buf_ptr);
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break;
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default:
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break;
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}
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}
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static void ima_show_template_data_binary(struct seq_file *m,
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enum ima_show_type show,
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enum data_formats datafmt,
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struct ima_field_data *field_data)
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{
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u32 len = (show == IMA_SHOW_BINARY_OLD_STRING_FMT) ?
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strlen(field_data->data) : field_data->len;
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if (show != IMA_SHOW_BINARY_NO_FIELD_LEN)
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ima_putc(m, &len, sizeof(len));
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if (!len)
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return;
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ima_putc(m, field_data->data, len);
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}
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static void ima_show_template_field_data(struct seq_file *m,
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enum ima_show_type show,
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enum data_formats datafmt,
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struct ima_field_data *field_data)
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{
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switch (show) {
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case IMA_SHOW_ASCII:
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ima_show_template_data_ascii(m, show, datafmt, field_data);
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break;
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case IMA_SHOW_BINARY:
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case IMA_SHOW_BINARY_NO_FIELD_LEN:
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case IMA_SHOW_BINARY_OLD_STRING_FMT:
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ima_show_template_data_binary(m, show, datafmt, field_data);
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break;
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default:
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break;
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}
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}
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void ima_show_template_digest(struct seq_file *m, enum ima_show_type show,
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struct ima_field_data *field_data)
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{
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ima_show_template_field_data(m, show, DATA_FMT_DIGEST, field_data);
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}
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void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
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struct ima_field_data *field_data)
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{
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ima_show_template_field_data(m, show, DATA_FMT_DIGEST_WITH_ALGO,
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field_data);
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}
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void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
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struct ima_field_data *field_data)
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{
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ima_show_template_field_data(m, show, DATA_FMT_STRING, field_data);
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}
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void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
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struct ima_field_data *field_data)
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{
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ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
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}
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static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
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struct ima_field_data *field_data)
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{
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/*
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* digest formats:
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* - DATA_FMT_DIGEST: digest
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* - DATA_FMT_DIGEST_WITH_ALGO: [<hash algo>] + ':' + '\0' + digest,
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* where <hash algo> is provided if the hash algoritm is not
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* SHA1 or MD5
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*/
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u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
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enum data_formats fmt = DATA_FMT_DIGEST;
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u32 offset = 0;
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if (hash_algo < HASH_ALGO__LAST) {
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fmt = DATA_FMT_DIGEST_WITH_ALGO;
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offset += snprintf(buffer, CRYPTO_MAX_ALG_NAME + 1, "%s",
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hash_algo_name[hash_algo]);
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buffer[offset] = ':';
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offset += 2;
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}
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if (digest)
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memcpy(buffer + offset, digest, digestsize);
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else
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/*
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* If digest is NULL, the event being recorded is a violation.
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* Make room for the digest by increasing the offset of
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* IMA_DIGEST_SIZE.
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*/
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offset += IMA_DIGEST_SIZE;
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return ima_write_template_field_data(buffer, offset + digestsize,
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fmt, field_data);
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}
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/*
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* This function writes the digest of an event (with size limit).
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*/
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int ima_eventdigest_init(struct integrity_iint_cache *iint, struct file *file,
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const unsigned char *filename,
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struct evm_ima_xattr_data *xattr_value, int xattr_len,
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struct ima_field_data *field_data)
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{
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struct {
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struct ima_digest_data hdr;
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char digest[IMA_MAX_DIGEST_SIZE];
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} hash;
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u8 *cur_digest = NULL;
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u32 cur_digestsize = 0;
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struct inode *inode;
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int result;
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memset(&hash, 0, sizeof(hash));
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if (!iint) /* recording a violation. */
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goto out;
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if (ima_template_hash_algo_allowed(iint->ima_hash->algo)) {
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cur_digest = iint->ima_hash->digest;
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cur_digestsize = iint->ima_hash->length;
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goto out;
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}
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if (!file) /* missing info to re-calculate the digest */
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return -EINVAL;
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inode = file_inode(file);
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hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
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ima_hash_algo : HASH_ALGO_SHA1;
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result = ima_calc_file_hash(file, &hash.hdr);
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if (result) {
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
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filename, "collect_data",
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"failed", result, 0);
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return result;
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}
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cur_digest = hash.hdr.digest;
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cur_digestsize = hash.hdr.length;
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out:
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return ima_eventdigest_init_common(cur_digest, cur_digestsize,
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HASH_ALGO__LAST, field_data);
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}
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/*
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* This function writes the digest of an event (without size limit).
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*/
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int ima_eventdigest_ng_init(struct integrity_iint_cache *iint,
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struct file *file, const unsigned char *filename,
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struct evm_ima_xattr_data *xattr_value,
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int xattr_len, struct ima_field_data *field_data)
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{
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u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
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u32 cur_digestsize = 0;
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/* If iint is NULL, we are recording a violation. */
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if (!iint)
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goto out;
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cur_digest = iint->ima_hash->digest;
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cur_digestsize = iint->ima_hash->length;
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hash_algo = iint->ima_hash->algo;
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out:
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return ima_eventdigest_init_common(cur_digest, cur_digestsize,
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hash_algo, field_data);
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}
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static int ima_eventname_init_common(struct integrity_iint_cache *iint,
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struct file *file,
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const unsigned char *filename,
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struct ima_field_data *field_data,
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bool size_limit)
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{
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const char *cur_filename = NULL;
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u32 cur_filename_len = 0;
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enum data_formats fmt = size_limit ?
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DATA_FMT_EVENT_NAME : DATA_FMT_STRING;
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BUG_ON(filename == NULL && file == NULL);
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if (filename) {
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cur_filename = filename;
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cur_filename_len = strlen(filename);
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if (!size_limit || cur_filename_len <= IMA_EVENT_NAME_LEN_MAX)
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goto out;
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}
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if (file) {
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cur_filename = file->f_dentry->d_name.name;
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cur_filename_len = strlen(cur_filename);
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} else
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/*
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* Truncate filename if the latter is too long and
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* the file descriptor is not available.
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*/
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cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
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out:
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return ima_write_template_field_data(cur_filename, cur_filename_len,
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fmt, field_data);
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}
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/*
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* This function writes the name of an event (with size limit).
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*/
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int ima_eventname_init(struct integrity_iint_cache *iint, struct file *file,
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const unsigned char *filename,
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struct evm_ima_xattr_data *xattr_value, int xattr_len,
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struct ima_field_data *field_data)
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{
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return ima_eventname_init_common(iint, file, filename,
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field_data, true);
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}
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/*
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* This function writes the name of an event (without size limit).
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*/
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int ima_eventname_ng_init(struct integrity_iint_cache *iint, struct file *file,
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const unsigned char *filename,
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struct evm_ima_xattr_data *xattr_value, int xattr_len,
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struct ima_field_data *field_data)
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{
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return ima_eventname_init_common(iint, file, filename,
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field_data, false);
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}
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/*
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* ima_eventsig_init - include the file signature as part of the template data
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*/
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int ima_eventsig_init(struct integrity_iint_cache *iint, struct file *file,
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const unsigned char *filename,
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struct evm_ima_xattr_data *xattr_value, int xattr_len,
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struct ima_field_data *field_data)
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{
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enum data_formats fmt = DATA_FMT_HEX;
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int rc = 0;
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if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
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goto out;
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rc = ima_write_template_field_data(xattr_value, xattr_len, fmt,
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field_data);
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out:
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return rc;
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}
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