152 lines
3.6 KiB
C
152 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* IMA support for appraising module-style appended signatures.
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*
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* Copyright (C) 2019 IBM Corporation
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*
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* Author:
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* Thiago Jung Bauermann <bauerman@linux.ibm.com>
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*/
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#include <linux/types.h>
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#include <linux/module_signature.h>
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#include <keys/asymmetric-type.h>
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#include <crypto/pkcs7.h>
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#include "ima.h"
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struct modsig {
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struct pkcs7_message *pkcs7_msg;
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enum hash_algo hash_algo;
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/* This digest will go in the 'd-modsig' field of the IMA template. */
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const u8 *digest;
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u32 digest_size;
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/*
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* This is what will go to the measurement list if the template requires
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* storing the signature.
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*/
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int raw_pkcs7_len;
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u8 raw_pkcs7[];
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};
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/*
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* ima_read_modsig - Read modsig from buf.
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*
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* Return: 0 on success, error code otherwise.
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*/
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int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
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struct modsig **modsig)
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{
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const size_t marker_len = strlen(MODULE_SIG_STRING);
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const struct module_signature *sig;
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struct modsig *hdr;
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size_t sig_len;
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const void *p;
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int rc;
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if (buf_len <= marker_len + sizeof(*sig))
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return -ENOENT;
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p = buf + buf_len - marker_len;
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if (memcmp(p, MODULE_SIG_STRING, marker_len))
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return -ENOENT;
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buf_len -= marker_len;
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sig = (const struct module_signature *)(p - sizeof(*sig));
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rc = mod_check_sig(sig, buf_len, func_tokens[func]);
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if (rc)
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return rc;
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sig_len = be32_to_cpu(sig->sig_len);
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buf_len -= sig_len + sizeof(*sig);
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/* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */
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hdr = kzalloc(sizeof(*hdr) + sig_len, GFP_KERNEL);
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if (!hdr)
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return -ENOMEM;
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hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
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if (IS_ERR(hdr->pkcs7_msg)) {
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rc = PTR_ERR(hdr->pkcs7_msg);
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kfree(hdr);
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return rc;
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}
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memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
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hdr->raw_pkcs7_len = sig_len;
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/* We don't know the hash algorithm yet. */
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hdr->hash_algo = HASH_ALGO__LAST;
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*modsig = hdr;
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return 0;
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}
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/**
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* ima_collect_modsig - Calculate the file hash without the appended signature.
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* @modsig: parsed module signature
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* @buf: data to verify the signature on
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* @size: data size
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*
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* Since the modsig is part of the file contents, the hash used in its signature
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* isn't the same one ordinarily calculated by IMA. Therefore PKCS7 code
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* calculates a separate one for signature verification.
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*/
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void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size)
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{
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int rc;
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/*
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* Provide the file contents (minus the appended sig) so that the PKCS7
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* code can calculate the file hash.
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*/
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size -= modsig->raw_pkcs7_len + strlen(MODULE_SIG_STRING) +
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sizeof(struct module_signature);
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rc = pkcs7_supply_detached_data(modsig->pkcs7_msg, buf, size);
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if (rc)
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return;
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/* Ask the PKCS7 code to calculate the file hash. */
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rc = pkcs7_get_digest(modsig->pkcs7_msg, &modsig->digest,
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&modsig->digest_size, &modsig->hash_algo);
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}
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int ima_modsig_verify(struct key *keyring, const struct modsig *modsig)
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{
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return verify_pkcs7_message_sig(NULL, 0, modsig->pkcs7_msg, keyring,
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VERIFYING_MODULE_SIGNATURE, NULL, NULL);
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}
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int ima_get_modsig_digest(const struct modsig *modsig, enum hash_algo *algo,
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const u8 **digest, u32 *digest_size)
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{
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*algo = modsig->hash_algo;
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*digest = modsig->digest;
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*digest_size = modsig->digest_size;
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return 0;
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}
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int ima_get_raw_modsig(const struct modsig *modsig, const void **data,
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u32 *data_len)
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{
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*data = &modsig->raw_pkcs7;
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*data_len = modsig->raw_pkcs7_len;
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return 0;
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}
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void ima_free_modsig(struct modsig *modsig)
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{
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if (!modsig)
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return;
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pkcs7_free_message(modsig->pkcs7_msg);
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kfree(modsig);
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}
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