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Prevent Make from talking to public Internet

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This change introduces the nointernet() function which may be called to
prevent a process and its descendants from communicating with publicly
routable Internet addresses. GNU Make has been modified to always call
this function. In the future Landlock Make will have a way to whitelist
subnets to override this behavior, or disable it entirely. Support is
available for Linux only. Our firewall does not require root access.

Calling nointernet() will return control to the caller inside a new
process that has a SECCOMP BPF filter installed, which traps network
related system calls. Your original process then becomes a permanent
ptrace() supervisor that monitors all processes and threads descending
from the returned child. Whenever a networking system call happens the
kernel will stop the process and wakes up the monitor, which then peeks
into the child memory to read the sockaddr_in to determine if it's ok.

The downside to doing this is that there can be only one supervisor at a
time using ptrace() on a process. So this firewall won't be enabled if
you run make under strace or inside gdb. It also makes testing tricky.
This commit is contained in:
Justine Tunney 2022-08-12 05:17:06 -07:00
parent 8a0a2c0c36
commit 7cf66bc161
48 changed files with 4924 additions and 2046 deletions
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12
libc/calls/calls.h
View file

@ -35,10 +35,11 @@
#define WIFCONTINUED(s) ((s) == 0xffff)
#define WIFEXITED(s) (!WTERMSIG(s))
#define WIFSIGNALED(s) ((0xffff & (s)) - 1u < 0xffu)
#define WIFSTOPPED(s) ((short)(((0xffff & (s)) * 0x10001) >> 8) > 0x7f00)
#define WSTOPSIG(s) WEXITSTATUS(s)
#define WTERMSIG(s) (127 & (s))
#define W_STOPCODE(s) ((s) << 8 | 0177)
#define WIFSTOPPED(s) \
((short)(((0xffff & (unsigned)(s)) * 0x10001) >> 8) > 0x7f00)
#define WSTOPSIG(s) WEXITSTATUS(s)
#define WTERMSIG(s) (127 & (s))
#define W_STOPCODE(s) ((s) << 8 | 0177)
#if !(__ASSEMBLER__ + __LINKER__ + 0)
COSMOPOLITAN_C_START_
@ -115,6 +116,7 @@ int getresuid(uint32_t *, uint32_t *, uint32_t *);
int getsid(int) nosideeffect libcesque;
int gettid(void) libcesque;
int getuid(void) libcesque;
int iopl(int);
int ioprio_get(int, int);
int ioprio_set(int, int, int);
int issetugid(void);
@ -178,6 +180,7 @@ int siginterrupt(int, int);
int symlink(const char *, const char *);
int symlinkat(const char *, int, const char *);
int sync_file_range(int, int64_t, int64_t, unsigned);
int sys_ptrace(int, ...);
int sysctl(const int *, unsigned, void *, size_t *, void *, size_t);
int tgkill(int, int, int);
int tkill(int, int);
@ -194,7 +197,6 @@ int wait(int *);
int waitpid(int, int *, int);
intptr_t syscall(int, ...);
long ptrace(int, ...);
size_t GetFileSize(const char *);
ssize_t copy_file_range(int, long *, int, long *, size_t, uint32_t);
ssize_t copyfd(int, int64_t *, int, int64_t *, size_t, uint32_t);
ssize_t getfiledescriptorsize(int);