ima_inode_setxattr() can be called with no value. Function does not check the length so that following command can be used to produce kernel oops: setfattr -n security.ima FOO. This patch fixes it. Changes in v3: * for stable reverted "allow setting hash only in fix or log mode" It will be a separate patch. Changes in v2: * testing validity of xattr type * allow setting hash only in fix or log mode (Mimi) [ 261.562522] BUG: unable to handle kernel NULL pointer dereference at (null) [ 261.564109] IP: [<ffffffff812af272>] ima_inode_setxattr+0x3e/0x5a [ 261.564109] PGD 3112f067 PUD 42965067 PMD 0 [ 261.564109] Oops: 0000 [#1] SMP [ 261.564109] Modules linked in: bridge stp llc evdev serio_raw i2c_piix4 button fuse [ 261.564109] CPU: 0 PID: 3299 Comm: setxattr Not tainted 3.16.0-kds+ #2924 [ 261.564109] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 261.564109] task: ffff8800428c2430 ti: ffff880042be0000 task.ti: ffff880042be0000 [ 261.564109] RIP: 0010:[<ffffffff812af272>] [<ffffffff812af272>] ima_inode_setxattr+0x3e/0x5a [ 261.564109] RSP: 0018:ffff880042be3d50 EFLAGS: 00010246 [ 261.564109] RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000015 [ 261.564109] RDX: 0000001500000000 RSI: 0000000000000000 RDI: ffff8800375cc600 [ 261.564109] RBP: ffff880042be3d68 R08: 0000000000000000 R09: 00000000004d6256 [ 261.564109] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88002149ba00 [ 261.564109] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 261.564109] FS: 00007f6c1e219740(0000) GS:ffff88005da00000(0000) knlGS:0000000000000000 [ 261.564109] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 261.564109] CR2: 0000000000000000 CR3: 000000003b35a000 CR4: 00000000000006f0 [ 261.564109] Stack: [ 261.564109] ffff88002149ba00 ffff880042be3df8 0000000000000000 ffff880042be3d98 [ 261.564109] ffffffff812a101b ffff88002149ba00 ffff880042be3df8 0000000000000000 [ 261.564109] 0000000000000000 ffff880042be3de0 ffffffff8116d08a ffff880042be3dc8 [ 261.564109] Call Trace: [ 261.564109] [<ffffffff812a101b>] security_inode_setxattr+0x48/0x6a [ 261.564109] [<ffffffff8116d08a>] vfs_setxattr+0x6b/0x9f [ 261.564109] [<ffffffff8116d1e0>] setxattr+0x122/0x16c [ 261.564109] [<ffffffff811687e8>] ? mnt_want_write+0x21/0x45 [ 261.564109] [<ffffffff8114d011>] ? __sb_start_write+0x10f/0x143 [ 261.564109] [<ffffffff811687e8>] ? mnt_want_write+0x21/0x45 [ 261.564109] [<ffffffff811687c0>] ? __mnt_want_write+0x48/0x4f [ 261.564109] [<ffffffff8116d3e6>] SyS_setxattr+0x6e/0xb0 [ 261.564109] [<ffffffff81529da9>] system_call_fastpath+0x16/0x1b [ 261.564109] Code: 48 89 f7 48 c7 c6 58 36 81 81 53 31 db e8 73 27 04 00 85 c0 75 28 bf 15 00 00 00 e8 8a a5 d9 ff 84 c0 75 05 83 cb ff eb 15 31 f6 <41> 80 7d 00 03 49 8b 7c 24 68 40 0f 94 c6 e8 e1 f9 ff ff 89 d8 [ 261.564109] RIP [<ffffffff812af272>] ima_inode_setxattr+0x3e/0x5a [ 261.564109] RSP <ffff880042be3d50> [ 261.564109] CR2: 0000000000000000 [ 261.599998] ---[ end trace 39a89a3fc267e652 ]--- Reported-by: Jan Kara <jack@suse.cz> Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com> Cc: stable@vger.kernel.org Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
401 lines
9.7 KiB
C
401 lines
9.7 KiB
C
/*
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* Copyright (C) 2011 IBM Corporation
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*
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* Author:
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* Mimi Zohar <zohar@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*/
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#include <linux/module.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/xattr.h>
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#include <linux/magic.h>
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#include <linux/ima.h>
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#include <linux/evm.h>
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#include <crypto/hash_info.h>
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#include "ima.h"
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static int __init default_appraise_setup(char *str)
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{
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if (strncmp(str, "off", 3) == 0)
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ima_appraise = 0;
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else if (strncmp(str, "log", 3) == 0)
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ima_appraise = IMA_APPRAISE_LOG;
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else if (strncmp(str, "fix", 3) == 0)
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ima_appraise = IMA_APPRAISE_FIX;
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return 1;
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}
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__setup("ima_appraise=", default_appraise_setup);
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/*
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* ima_must_appraise - set appraise flag
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*
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* Return 1 to appraise
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*/
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int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
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{
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if (!ima_appraise)
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return 0;
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return ima_match_policy(inode, func, mask, IMA_APPRAISE);
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}
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static int ima_fix_xattr(struct dentry *dentry,
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struct integrity_iint_cache *iint)
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{
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int rc, offset;
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u8 algo = iint->ima_hash->algo;
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if (algo <= HASH_ALGO_SHA1) {
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offset = 1;
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iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
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} else {
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offset = 0;
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iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
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iint->ima_hash->xattr.ng.algo = algo;
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}
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rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
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&iint->ima_hash->xattr.data[offset],
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(sizeof(iint->ima_hash->xattr) - offset) +
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iint->ima_hash->length, 0);
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return rc;
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}
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/* Return specific func appraised cached result */
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enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
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int func)
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{
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switch (func) {
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case MMAP_CHECK:
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return iint->ima_mmap_status;
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case BPRM_CHECK:
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return iint->ima_bprm_status;
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case MODULE_CHECK:
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return iint->ima_module_status;
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case FIRMWARE_CHECK:
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return iint->ima_firmware_status;
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case FILE_CHECK:
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default:
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return iint->ima_file_status;
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}
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}
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static void ima_set_cache_status(struct integrity_iint_cache *iint,
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int func, enum integrity_status status)
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{
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switch (func) {
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case MMAP_CHECK:
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iint->ima_mmap_status = status;
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break;
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case BPRM_CHECK:
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iint->ima_bprm_status = status;
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break;
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case MODULE_CHECK:
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iint->ima_module_status = status;
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break;
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case FIRMWARE_CHECK:
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iint->ima_firmware_status = status;
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break;
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case FILE_CHECK:
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default:
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iint->ima_file_status = status;
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break;
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}
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}
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static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
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{
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switch (func) {
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case MMAP_CHECK:
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iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
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break;
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case BPRM_CHECK:
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iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
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break;
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case MODULE_CHECK:
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iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED);
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break;
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case FIRMWARE_CHECK:
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iint->flags |= (IMA_FIRMWARE_APPRAISED | IMA_APPRAISED);
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break;
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case FILE_CHECK:
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default:
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iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
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break;
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}
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}
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void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
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struct ima_digest_data *hash)
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{
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struct signature_v2_hdr *sig;
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if (!xattr_value || xattr_len < 2)
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return;
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switch (xattr_value->type) {
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case EVM_IMA_XATTR_DIGSIG:
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sig = (typeof(sig))xattr_value;
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if (sig->version != 2 || xattr_len <= sizeof(*sig))
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return;
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hash->algo = sig->hash_algo;
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break;
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case IMA_XATTR_DIGEST_NG:
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hash->algo = xattr_value->digest[0];
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break;
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case IMA_XATTR_DIGEST:
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/* this is for backward compatibility */
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if (xattr_len == 21) {
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unsigned int zero = 0;
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if (!memcmp(&xattr_value->digest[16], &zero, 4))
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hash->algo = HASH_ALGO_MD5;
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else
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hash->algo = HASH_ALGO_SHA1;
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} else if (xattr_len == 17)
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hash->algo = HASH_ALGO_MD5;
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break;
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}
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}
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int ima_read_xattr(struct dentry *dentry,
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struct evm_ima_xattr_data **xattr_value)
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{
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struct inode *inode = dentry->d_inode;
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if (!inode->i_op->getxattr)
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return 0;
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return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
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0, GFP_NOFS);
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}
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/*
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* ima_appraise_measurement - appraise file measurement
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*
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* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
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* Assuming success, compare the xattr hash with the collected measurement.
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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_appraise_measurement(int func, 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, int opened)
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{
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static const char op[] = "appraise_data";
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char *cause = "unknown";
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struct dentry *dentry = file->f_dentry;
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struct inode *inode = dentry->d_inode;
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enum integrity_status status = INTEGRITY_UNKNOWN;
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int rc = xattr_len, hash_start = 0;
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if (!inode->i_op->getxattr)
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return INTEGRITY_UNKNOWN;
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if (rc <= 0) {
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if (rc && rc != -ENODATA)
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goto out;
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cause = "missing-hash";
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status = INTEGRITY_NOLABEL;
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if (opened & FILE_CREATED) {
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iint->flags |= IMA_NEW_FILE;
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status = INTEGRITY_PASS;
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}
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goto out;
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}
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status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
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if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
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if ((status == INTEGRITY_NOLABEL)
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|| (status == INTEGRITY_NOXATTRS))
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cause = "missing-HMAC";
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else if (status == INTEGRITY_FAIL)
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cause = "invalid-HMAC";
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goto out;
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}
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switch (xattr_value->type) {
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case IMA_XATTR_DIGEST_NG:
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/* first byte contains algorithm id */
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hash_start = 1;
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case IMA_XATTR_DIGEST:
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if (iint->flags & IMA_DIGSIG_REQUIRED) {
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cause = "IMA-signature-required";
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status = INTEGRITY_FAIL;
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break;
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}
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if (xattr_len - sizeof(xattr_value->type) - hash_start >=
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iint->ima_hash->length)
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/* xattr length may be longer. md5 hash in previous
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version occupied 20 bytes in xattr, instead of 16
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*/
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rc = memcmp(&xattr_value->digest[hash_start],
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iint->ima_hash->digest,
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iint->ima_hash->length);
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else
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rc = -EINVAL;
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if (rc) {
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cause = "invalid-hash";
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status = INTEGRITY_FAIL;
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break;
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}
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status = INTEGRITY_PASS;
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break;
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case EVM_IMA_XATTR_DIGSIG:
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iint->flags |= IMA_DIGSIG;
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rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
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(const char *)xattr_value, rc,
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iint->ima_hash->digest,
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iint->ima_hash->length);
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if (rc == -EOPNOTSUPP) {
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status = INTEGRITY_UNKNOWN;
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} else if (rc) {
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cause = "invalid-signature";
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status = INTEGRITY_FAIL;
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} else {
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status = INTEGRITY_PASS;
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}
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break;
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default:
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status = INTEGRITY_UNKNOWN;
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cause = "unknown-ima-data";
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break;
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}
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out:
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if (status != INTEGRITY_PASS) {
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if ((ima_appraise & IMA_APPRAISE_FIX) &&
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(!xattr_value ||
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xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
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if (!ima_fix_xattr(dentry, iint))
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status = INTEGRITY_PASS;
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}
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
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op, cause, rc, 0);
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} else {
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ima_cache_flags(iint, func);
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}
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ima_set_cache_status(iint, func, status);
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return status;
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}
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/*
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* ima_update_xattr - update 'security.ima' hash value
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*/
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void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
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{
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struct dentry *dentry = file->f_dentry;
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int rc = 0;
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/* do not collect and update hash for digital signatures */
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if (iint->flags & IMA_DIGSIG)
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return;
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rc = ima_collect_measurement(iint, file, NULL, NULL);
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if (rc < 0)
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return;
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ima_fix_xattr(dentry, iint);
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}
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/**
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* ima_inode_post_setattr - reflect file metadata changes
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* @dentry: pointer to the affected dentry
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*
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* Changes to a dentry's metadata might result in needing to appraise.
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*
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* This function is called from notify_change(), which expects the caller
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* to lock the inode's i_mutex.
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*/
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void ima_inode_post_setattr(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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struct integrity_iint_cache *iint;
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int must_appraise, rc;
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if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
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|| !inode->i_op->removexattr)
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return;
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must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
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iint = integrity_iint_find(inode);
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if (iint) {
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iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
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IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
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IMA_ACTION_FLAGS);
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if (must_appraise)
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iint->flags |= IMA_APPRAISE;
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}
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if (!must_appraise)
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rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
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return;
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}
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/*
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* ima_protect_xattr - protect 'security.ima'
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*
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* Ensure that not just anyone can modify or remove 'security.ima'.
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*/
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static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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{
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if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return 1;
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}
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return 0;
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}
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static void ima_reset_appraise_flags(struct inode *inode, int digsig)
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{
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struct integrity_iint_cache *iint;
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if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
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return;
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iint = integrity_iint_find(inode);
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if (!iint)
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return;
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iint->flags &= ~IMA_DONE_MASK;
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if (digsig)
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iint->flags |= IMA_DIGSIG;
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return;
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}
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int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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{
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const struct evm_ima_xattr_data *xvalue = xattr_value;
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int result;
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result = ima_protect_xattr(dentry, xattr_name, xattr_value,
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xattr_value_len);
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if (result == 1) {
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if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
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return -EINVAL;
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ima_reset_appraise_flags(dentry->d_inode,
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(xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0);
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result = 0;
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}
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return result;
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}
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int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
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{
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int result;
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result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
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if (result == 1) {
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ima_reset_appraise_flags(dentry->d_inode, 0);
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result = 0;
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}
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return result;
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}
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