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First implementation of Copy-On-Write
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,196 @@ | ||
| /* | ||
| * This file is part of PRoot. | ||
| * | ||
| * Copyright (C) 2016 Alejandro Liu | ||
| * | ||
| * 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; either version 2 of the | ||
| * License, or (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, but | ||
| * WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| * General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program; if not, write to the Free Software | ||
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA | ||
| * 02110-1301 USA. | ||
| */ | ||
|
|
||
| #include <stdint.h> /* intptr_t, */ | ||
| #include <stdlib.h> /* strtoul(3), */ | ||
| #include <linux/version.h> /* KERNEL_VERSION, */ | ||
| #include <assert.h> /* assert(3), */ | ||
| #include <sys/utsname.h> /* uname(2), utsname, */ | ||
| #include <string.h> /* str*(3), memcpy(3), */ | ||
| #include <talloc.h> /* talloc_*, */ | ||
| #include <fcntl.h> /* AT_*, */ | ||
| #include <sys/ptrace.h> /* linux.git:c0a3a20b */ | ||
| #include <errno.h> /* errno, */ | ||
| #include <linux/auxvec.h> /* AT_, */ | ||
| #include <linux/futex.h> /* FUTEX_PRIVATE_FLAG */ | ||
| #include <sys/param.h> /* MIN, */ | ||
| #include <sys/mman.h> /* mmap, munmap */ | ||
| #include <unistd.h> /* unlink, close, write, fchown */ | ||
|
|
||
| #include "extension/extension.h" | ||
| #include "syscall/seccomp.h" | ||
| #include "syscall/sysnum.h" | ||
| #include "syscall/syscall.h" | ||
| #include "syscall/chain.h" | ||
| #include "tracee/tracee.h" | ||
| #include "tracee/reg.h" | ||
| #include "tracee/abi.h" | ||
| #include "tracee/mem.h" | ||
| #include "execve/auxv.h" | ||
| #include "cli/note.h" | ||
| #include "arch.h" | ||
|
|
||
| typedef int Config; | ||
|
|
||
| /* List of syscalls handled by this extensions. */ | ||
| static FilteredSysnum filtered_sysnums[] = { | ||
| { PR_open, FILTER_SYSEXIT }, | ||
| { PR_openat, FILTER_SYSEXIT }, | ||
| FILTERED_SYSNUM_END, | ||
| }; | ||
|
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||
|
|
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| static int check_flags(Tracee *tracee, Reg reg) { | ||
| int flags; | ||
| flags = peek_reg(tracee,CURRENT, reg); | ||
| switch (flags & O_ACCMODE) { | ||
| case O_WRONLY: | ||
| case O_RDWR: | ||
| return 1; | ||
| } | ||
| return 0; | ||
| } | ||
|
|
||
| static void check_inode_and_copy(Tracee *tracee,char const *name) { | ||
| struct stat stb; | ||
| int sfd, nfd; | ||
| if (stat(name,&stb) == -1) return; | ||
| if (stb.st_nlink < 2) return; | ||
| if (-1 == (sfd = open(name,O_RDONLY))) return; | ||
| if (unlink(name) == -1) { | ||
| close(sfd); | ||
| return; | ||
| } | ||
| if (-1 == (nfd = open(name,O_CREAT|O_EXCL|O_WRONLY,stb.st_mode))) { | ||
| note(tracee, ERROR, USER, "Error opening %s",name); | ||
| close(sfd); | ||
| return; | ||
| } | ||
| void *addr; | ||
| if ((addr=mmap(NULL,stb.st_size,PROT_READ,MAP_PRIVATE, sfd,0))==MAP_FAILED) { | ||
| note(tracee, ERROR, USER, "Error mmaping %s",name); | ||
| close(nfd); | ||
| close(sfd); | ||
| return; | ||
| } | ||
| if (write(nfd,addr,stb.st_size) != stb.st_size) { | ||
| note(tracee, ERROR, USER, "Error writing %s",name); | ||
| } | ||
| munmap(addr,stb.st_size); | ||
| close(sfd); | ||
| fchown(nfd,stb.st_uid,stb.st_gid); | ||
| close(nfd); | ||
| } | ||
|
|
||
| /** | ||
| * Adjust current @tracee's syscall parameters according to @config. | ||
| * This function always returns 0. | ||
| */ | ||
| static int handle_sysenter_end(Tracee *tracee, const Config *config UNUSED) | ||
| { | ||
| word_t sysnum; | ||
| char old_path[PATH_MAX]; | ||
| int status; | ||
|
|
||
| sysnum = get_sysnum(tracee, ORIGINAL); | ||
| switch (sysnum) { | ||
| case PR_open: | ||
| if (!check_flags(tracee, SYSARG_2)) return 0; | ||
| /* Extract the currrent path. */ | ||
| status = get_sysarg_path(tracee, old_path, SYSARG_1); | ||
| if (status < 0) return status; | ||
| //note(tracee, INFO, USER, "PR_open(%s)",old_path); | ||
| check_inode_and_copy(tracee,old_path); | ||
| return 0; | ||
| case PR_openat: | ||
| if (!check_flags(tracee, SYSARG_3)) return 0; | ||
| /* Extract the currrent path. */ | ||
| status = get_sysarg_path(tracee, old_path, SYSARG_2); | ||
| if (status < 0) return status; | ||
| //note(tracee, INFO, USER, "PR_openat(%s)",old_path); | ||
| check_inode_and_copy(tracee,old_path); | ||
| return 0; | ||
| default: | ||
| return 0; | ||
| } | ||
|
|
||
| /* Never reached */ | ||
| assert(0); | ||
| return 0; | ||
|
|
||
| } | ||
|
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||
| /** | ||
| * Handler for this @extension. It is triggered each time an @event | ||
| * occurred. See ExtensionEvent for the meaning of @data1 and @data2. | ||
| */ | ||
| int cow_callback(Extension *extension, ExtensionEvent event, intptr_t data1, intptr_t data2 UNUSED) | ||
| { | ||
| switch (event) { | ||
| case INITIALIZATION: { | ||
| Config *config; | ||
| extension->config = talloc(extension, Config); | ||
| if (extension->config == NULL) | ||
| return -1; | ||
|
|
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| config = talloc_get_type_abort(extension->config, Config); | ||
| *config = 0; | ||
| extension->filtered_sysnums = filtered_sysnums; | ||
| return 0; | ||
| } | ||
|
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| case INHERIT_PARENT: /* Inheritable for sub reconfiguration ... */ | ||
| return 1; | ||
|
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| case INHERIT_CHILD: { | ||
| /* Copy the parent configuration to the child. The | ||
| * structure should not be shared as uid/gid changes | ||
| * in one process should not affect other processes. | ||
| * This assertion is not true for POSIX threads | ||
| * sharing the same group, however Linux threads never | ||
| * share uid/gid information. As a consequence, the | ||
| * GlibC emulates the POSIX behavior on Linux by | ||
| * sending a signal to all group threads to cause them | ||
| * to invoke the system call too. Finally, PRoot | ||
| * doesn't have to worry about clone flags. | ||
| */ | ||
|
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| Extension *parent = (Extension *) data1; | ||
| extension->config = talloc_zero(extension, Config); | ||
| if (extension->config == NULL) | ||
| return -1; | ||
|
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| memcpy(extension->config, parent->config, sizeof(Config)); | ||
| return 0; | ||
| } | ||
|
|
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| case SYSCALL_ENTER_END: { | ||
| Tracee *tracee = TRACEE(extension); | ||
| Config *config = talloc_get_type_abort(extension->config, Config); | ||
|
|
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| return handle_sysenter_end(tracee, config); | ||
| } | ||
|
|
||
|
|
||
| default: | ||
| return 0; | ||
| } | ||
| } |
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