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| author | Damien Miller <djm@mindrot.org> | 2019-08-23 10:08:48 +1000 |
|---|---|---|
| committer | Damien Miller <djm@mindrot.org> | 2019-08-23 10:10:03 +1000 |
| commit | f6906f9bf12c968debec3671bbf19926ff8a235b (patch) | |
| tree | 0e540b08f4bc1246a1ee910224767aa67acc3a19 /sandbox-seccomp-filter.c | |
| parent | e3b6c966b79c3ea5d51b923c3bbdc41e13b96ea0 (diff) | |
| download | openssh-git-f6906f9bf12c968debec3671bbf19926ff8a235b.tar.gz | |
allow mprotect(2) with PROT_(READ|WRITE|NONE) only
Used by some hardened heap allocators. Requested by Yegor
Timoshenko in https://github.com/openssh/openssh-portable/pull/142
Diffstat (limited to 'sandbox-seccomp-filter.c')
| -rw-r--r-- | sandbox-seccomp-filter.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/sandbox-seccomp-filter.c b/sandbox-seccomp-filter.c index 56eb9317..7b44755c 100644 --- a/sandbox-seccomp-filter.c +++ b/sandbox-seccomp-filter.c @@ -42,6 +42,7 @@ #include <sys/types.h> #include <sys/resource.h> #include <sys/prctl.h> +#include <sys/mman.h> #include <linux/net.h> #include <linux/audit.h> @@ -95,12 +96,12 @@ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW) #define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 6), \ - /* load and test first syscall argument, low word */ \ + /* load and test syscall argument, low word */ \ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \ ((_arg_val) & 0xFFFFFFFF), 0, 3), \ - /* load and test first syscall argument, high word */ \ + /* load and test syscall argument, high word */ \ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \ @@ -109,6 +110,24 @@ /* reload syscall number; all rules expect it in accumulator */ \ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ offsetof(struct seccomp_data, nr)) +/* Allow if syscall argument contains only values in mask */ +#define SC_ALLOW_ARG_MASK(_nr, _arg_nr, _arg_mask) \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 8), \ + /* load, mask and test syscall argument, low word */ \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ + offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \ + BPF_STMT(BPF_ALU+BPF_AND+BPF_K, ~((_arg_mask) & 0xFFFFFFFF)), \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 4), \ + /* load, mask and test syscall argument, high word */ \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ + offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \ + BPF_STMT(BPF_ALU+BPF_AND+BPF_K, \ + ~(((uint32_t)((uint64_t)(_arg_mask) >> 32)) & 0xFFFFFFFF)), \ + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 1), \ + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \ + /* reload syscall number; all rules expect it in accumulator */ \ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ + offsetof(struct seccomp_data, nr)) /* Syscall filtering set for preauth. */ static const struct sock_filter preauth_insns[] = { @@ -202,6 +221,9 @@ static const struct sock_filter preauth_insns[] = { #ifdef __NR_mmap2 SC_ALLOW(__NR_mmap2), #endif +#ifdef __NR_mprotect + SC_ALLOW_ARG_MASK(__NR_mprotect, 2, PROT_READ|PROT_WRITE|PROT_NONE), +#endif #ifdef __NR_mremap SC_ALLOW(__NR_mremap), #endif |