SHA1 is considered obsolete. It is no longer considered to be
collision resistant and, in general, it should not be used for new
applications. Change the new-in-4.10 BPF digest to SHA-256. This
means that potential future applications of the digest that need
collision resistance will be able to use the BPF digest. Applications
that just want a short identifier for a BPF program are welcome to
truncate the digest.
This is also a cleanup IMO -- the new sha256_*_direct() API is much
nicer than the old SHA1 library helpers. It will also enable
incremental hashing so the BPF code can avoid calling vmalloc().
I moved the digest field to keep all of the bpf program metadata in
the same cache line.
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Alexei Starovoitov <a...@kernel.org>
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
include/linux/filter.h | 11 +++--------
init/Kconfig | 1 +
kernel/bpf/core.c | 42 ++++++++----------------------------------
3 files changed, 12 insertions(+), 42 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 702314253797..23df2574e30c 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -14,7 +14,8 @@
#include <linux/workqueue.h>
#include <linux/sched.h>
#include <linux/capability.h>
-#include <linux/cryptohash.h>
+
+#include <crypto/sha.h>
#include <net/sch_generic.h>
@@ -408,11 +409,11 @@ struct bpf_prog {
kmemcheck_bitfield_end(meta);
enum bpf_prog_type type; /* Type of BPF program */
u32 len; /* Number of filter blocks */
- u32 digest[SHA_DIGEST_WORDS]; /* Program digest */
struct bpf_prog_aux *aux; /* Auxiliary fields */
struct sock_fprog_kern *orig_prog; /* Original BPF program */
unsigned int (*bpf_func)(const void *ctx,
const struct bpf_insn *insn);
+ u8 digest[SHA256_DIGEST_SIZE]; /* Program digest */
/* Instructions for interpreter */
union {
struct sock_filter insns[0];
@@ -519,12 +520,6 @@ static inline u32 bpf_prog_insn_size(const struct bpf_prog
*prog)
return prog->len * sizeof(struct bpf_insn);
}
-static inline u32 bpf_prog_digest_scratch_size(const struct bpf_prog *prog)
-{
- return round_up(bpf_prog_insn_size(prog) +
- sizeof(__be64) + 1, SHA_MESSAGE_BYTES);
-}
-
static inline unsigned int bpf_prog_size(unsigned int proglen)
{
return max(sizeof(struct bpf_prog),
diff --git a/init/Kconfig b/init/Kconfig
index 223b734abccd..f1ea6d023f8c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1389,6 +1389,7 @@ config HAVE_PCSPKR_PLATFORM
# interpreter that classic socket filters depend on
config BPF
bool
+ select CRYPTO_SHA256_DIRECT
menuconfig EXPERT
bool "Configure standard kernel features (expert users)"
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 1eb4f1303756..668b92f6ab58 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -148,22 +148,18 @@ void __bpf_prog_free(struct bpf_prog *fp)
int bpf_prog_calc_digest(struct bpf_prog *fp)
{
- const u32 bits_offset = SHA_MESSAGE_BYTES - sizeof(__be64);
- u32 raw_size = bpf_prog_digest_scratch_size(fp);
- u32 ws[SHA_WORKSPACE_WORDS];
- u32 i, bsize, psize, blocks;
+ struct sha256_state sha;
+ u32 i, psize;
struct bpf_insn *dst;
bool was_ld_map;
- u8 *raw, *todo;
- __be32 *result;
- __be64 *bits;
+ u8 *raw;
- raw = vmalloc(raw_size);
+ psize = bpf_prog_insn_size(fp);
+ raw = vmalloc(psize);
if (!raw)
return -ENOMEM;
- sha_init(fp->digest);
- memset(ws, 0, sizeof(ws));
+ sha256_init_direct(&sha);
/* We need to take out the map fd for the digest calculation
* since they are unstable from user space side.
@@ -188,30 +184,8 @@ int bpf_prog_calc_digest(struct bpf_prog *fp)
}
}
- psize = bpf_prog_insn_size(fp);
- memset(&raw[psize], 0, raw_size - psize);
- raw[psize++] = 0x80;
-
- bsize = round_up(psize, SHA_MESSAGE_BYTES);
- blocks = bsize / SHA_MESSAGE_BYTES;
- todo = raw;
- if (bsize - psize >= sizeof(__be64)) {
- bits = (__be64 *)(todo + bsize - sizeof(__be64));
- } else {
- bits = (__be64 *)(todo + bsize + bits_offset);
- blocks++;
- }
- *bits = cpu_to_be64((psize - 1) << 3);
-
- while (blocks--) {
- sha_transform(fp->digest, todo, ws);
- todo += SHA_MESSAGE_BYTES;
- }
-
- result = (__force __be32 *)fp->digest;
- for (i = 0; i < SHA_DIGEST_WORDS; i++)
- result[i] = cpu_to_be32(fp->digest[i]);
-
+ sha256_update_direct(&sha, raw, psize);
+ sha256_final_direct(&sha, fp->digest);
vfree(raw);
return 0;
}
--
2.9.3
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