Clear sensitive memory without getting optimized out (revival of #636) #1579

theStack · 2024-08-06T21:10:30Z

This PR picks up #636 (which in turn picked up #448, so this is take number three) and is essentially a rebase on master.

Some changes to the original PR:

the clearing function now has the secp256k1_ prefix again, since the related helper _memczero got it as well (see PR Don't use reserved identifiers memczero and benchmark_verify_t #835 / commit e89278f)
the original commit b17a7df ("Make _set_fe_int( . , 0 ) set magnitude to 0") is not needed anymore, since it was already applied in PR VERIFY_CHECK precondition for secp256k1_fe_set_int. #943 (commit d49011f)
clearing of stack memory with secp256k1_memclear is now also done on modules that have been newly introduced since then, i.e. schnorr and ellswift (of course, there is still no guarantee that all places where clearing is necessary are covered)

So far I haven't looked at any disassembly and possible performance implications yet (there were some concerns expressed in #636 (comment)), happy to go deeper there if this gets Concept ACKed.

The proposed method of using a memory barrier to prevent optimizating away the memset is still used in BoringSSL (where it was originally picked up from) and in the Linux Kernel, see e.g. https://github.com/google/boringssl/blob/5af122c3dfc163b5d1859f1f450756e8e320a142/crypto/mem.c#L335 and https://github.com/torvalds/linux/blob/d4560686726f7a357922f300fc81f5964be8df04/include/linux/string.h#L348 / https://github.com/torvalds/linux/blob/d4560686726f7a357922f300fc81f5964be8df04/include/linux/compiler.h#L102

Fixes #185.

real-or-random

Concept ACK (obviously)

Thanks for reviving this, I never had the time/motivation to come back to this PR, but it's important.

We should call SECP256K1_CHECKMEM_UNDEFINE (

secp256k1/src/checkmem.h

Line 27 in b307614

* - SECP256K1_CHECKMEM_UNDEFINE(p, len):

) in secp256k1_memclear after clearing the memory. Reading cleared memory would clearly be a bug.

theStack · 2024-08-20T10:23:52Z

We should call SECP256K1_CHECKMEM_UNDEFINE (

secp256k1/src/checkmem.h

Line 27 in b307614

* - SECP256K1_CHECKMEM_UNDEFINE(p, len):

) in secp256k1_memclear after clearing the memory. Reading cleared memory would clearly be a bug.

Thanks, added that, and rebased on master.

real-or-random · 2024-10-08T12:10:54Z

@theStack Can you rebase this on top of musig which has introduced a few more code locations that need clearing?

Personally, I'd love to have this in the next release.

theStack · 2024-10-08T22:51:17Z

@theStack Can you rebase this on top of musig which has introduced a few more code locations that need clearing?

Sure, done. With only five lines changed in the musig module, this needed less effort than expected, hope I didn't miss any instances (many of them are handled indirectly via the ..._{fe,scalar}_clear functions though).

Relevant excerpt of the range-diff (uncolored here)

$ git range-diff ac0e41...0b01d2
5:  6fcbae9 ! 15:  02ee811 Use secp256k1_memclear() to clear stack memory instead of memset()
    @@ src/modules/ellswift/main_impl.h: int secp256k1_ellswift_xdh(const secp256k1_con
          secp256k1_scalar_clear(&s);
      
     
    + ## src/modules/musig/session_impl.h ##
    +@@ src/modules/musig/session_impl.h: static void secp256k1_nonce_function_musig(secp256k1_scalar *k, const unsigned c
    +         secp256k1_scalar_set_b32(&k[i], buf, NULL);
    + 
    +         /* Attempt to erase secret data */
    +-        memset(buf, 0, sizeof(buf));
    +-        memset(&sha_tmp, 0, sizeof(sha_tmp));
    ++        secp256k1_memclear(buf, sizeof(buf));
    ++        secp256k1_memclear(&sha_tmp, sizeof(sha_tmp));
    +     }
    +-    memset(rand, 0, sizeof(rand));
    +-    memset(&sha, 0, sizeof(sha));
    ++    secp256k1_memclear(rand, sizeof(rand));
    ++    secp256k1_memclear(&sha, sizeof(sha));
    + }
    + 
    + int secp256k1_musig_nonce_gen_internal(const secp256k1_context* ctx, secp256k1_musig_secnonce *secnonce, secp256k1_musig_pubnonce *pubnonce, const unsigned char *input_nonce, const unsigned char *seckey, const secp256k1_pubkey *pubkey, const unsigned char *msg32, const secp256k1_musig_keyagg_cache *keyagg_cache, const unsigned char *extra_input32) {
    +@@ src/modules/musig/session_impl.h: int secp256k1_musig_nonce_gen_counter(const secp256k1_context* ctx, secp256k1_mu
    +     if (!secp256k1_musig_nonce_gen_internal(ctx, secnonce, pubnonce, buf, seckey, &pubkey, msg32, keyagg_cache, extra_input32)) {
    +         return 0;
    +     }
    +-    memset(seckey, 0, sizeof(seckey));
    ++    secp256k1_memclear(seckey, sizeof(seckey));
    +     return 1;
    + }
    + 
    +

real-or-random · 2024-10-08T22:59:45Z

This one comes to my mind, too:

secp256k1/src/util.h

Lines 253 to 254 in a88aa93

    
           /* acc may contain secret values. Try to explicitly clear it. */ 
        
           acc = 0;

theStack · 2024-10-08T23:16:40Z

This one comes to my mind, too:

secp256k1/src/util.h

Lines 253 to 254 in a88aa93

/* acc may contain secret values. Try to explicitly clear it. */

acc = 0;

Ah good catch, missed that (only grepped for memset calls). Tackled now as well.

real-or-random

If you want motivated, you could look at git grep secp256k1_ge_set_gej.*(. @sipa's recent comment in the MuSig PR really caught my attention. When I worked on the previous PR, I really didn't consider the possibility that a gej could leak secret data.

I wonder if it makes sense to have the _finalize functions in the hash module clear the state automatically. And then have "unsafe" funtions like _finalize_keep if the callers knows that data is public or if the caller wants to reuse the midstate. It sounds like a neat idea, but I'm not really convinced because it special-cases the hash module somewhat: we'll need to manually clear everything else including scalars, etc... So we have to be careful with this anyway when writing and reviewing code, and perhaps having yet another safety mechanism that works only for the hash module. (This could perhaps be a nice follow-up if we add the same mechanism to more modules, e.g., ge_set_gej could clear the gejs, unless you use a _keep variant.)

src/util.h

src/secp256k1.c

theStack · 2024-10-10T17:38:47Z

If you want motivated, you could look at git grep secp256k1_ge_set_gej.*(. @sipa's recent comment in the MuSig PR really caught my attention. When I worked on the previous PR, I really didn't consider the possibility that a gej could leak secret data.

I found the following functions containing _gej instances resulting from point multiplication (secp256k1_ecmult_{gen,const}) with secret scalars:

ECDH module: secp256k1_ecdh (res, resulting from the ECDH point multiplication; I think this should be cleared not only to avoid leaking the scalar, but even more so as it's a representation of the resulting shared secret)
MuSig2 module: secp256k1_musig_nonce_gen_internal (public nonce nonce_ptj in the for loop)
Schnorr module: secp256k1_schnorrsig_sign_internal (nonce commitment rj)
main library: secp256k1_ec_pubkey_create_helper (public point pj)

Taking care of those could be probably go into an own PR, as its trivial to fix and review and hence has a significantly higher chance to land in the next release than this one? (and having a version where the compiler still might optimize it out seems still much better than not doing it at all)

Interestingly, the ECDSA signing function does clear out the nonce commitment for both the jacobi and affine points (though the latter wouldn't be needed according to #1479 (comment)).

I wonder if it makes sense to have the _finalize functions in the hash module clear the state automatically. And then have "unsafe" funtions like _finalize_keep if the callers knows that data is public or if the caller wants to reuse the midstate. It sounds like a neat idea, but I'm not really convinced because it special-cases the hash module somewhat: we'll need to manually clear everything else including scalars, etc... So we have to be careful with this anyway when writing and reviewing code, and perhaps having yet another safety mechanism that works only for the hash module. (This could perhaps be a nice follow-up if we add the same mechanism to more modules, e.g., ge_set_gej could clear the gejs, unless you use a _keep variant.)

Sounds like a good idea to me for a follow-up.

real-or-random · 2024-10-10T20:55:15Z

Taking care of those could be probably go into an own PR, as its trivial to fix and review and hence has a significantly higher chance to land in the next release than this one? (and having a version where the compiler still might optimize it out seems still much better than not doing it at all)

My guess is that what we do currently is useless on any modern compiler. I admit that I haven't looked at the compiler output, but I'd rather spend the time on resolving the problem.

I don't think that fixing these additional cases here will make it much more difficult to review the PR. And to be honest, while this is a great for defense in depth, we haven't deeply cared about this so far. It's not the end of the world if we need to wait a few more months. So I think it's good to add these cases to this PR here.

theStack · 2024-10-11T16:29:59Z

My guess is that what we do currently is useless on any modern compiler. I admit that I haven't looked at the compiler output, but I'd rather spend the time on resolving the problem.

I don't think that fixing these additional cases here will make it much more difficult to review the PR. And to be honest, while this is a great for defense in depth, we haven't deeply cared about this so far. It's not the end of the world if we need to wait a few more months. So I think it's good to add these cases to this PR here.

Thanks for the feedback! Makes sense, added an extra commit at the end for the gej clearing after point multiplications, it's only four lines of code anyway. Also went over the necessary hash clearing places and made a few small changes (see #1579 (comment)).

sipa · 2024-10-21T17:50:46Z

utACK c921078. I have not reviewed this for exhaustiveness (as in, are there more places where clearing is useful/necessary), but the code changes look good.

theStack · 2024-10-22T00:56:59Z

src/util.h

+    void *(*volatile const volatile_memset)(void *, int, size_t) = memset;
+    volatile_memset(ptr, 0, len);
+#endif
+    SECP256K1_CHECKMEM_UNDEFINE(ptr, len);


Hm, it seems that in production code, we usually don't call any of the _CHECKMEM_{DEFINE,UNDEFINE} macros. There is one reachable code-path in secp256k1_declassify, but it would only hit if the context was created with the SECP256K1_CONTEXT_DECLASSIFY flag, where the API documentation explicitly says "Do not use". Should that _CHECKMEM_UNDEFINE call here be conditional by a preprocessor #if(def) or something alike, so it only applies to tests and can't slow down (and bloat) release builds?

I noticed that while looking at the disassembly of the .so file and wondering why there was so much extra code after the memory clearing, until I realized this must be valgrind's VALGRIND_MAKE_MEM_UNDEFINED. I'm building now explicitly with -DSECP256K1_VALGRIND=OFF -DSECP256K1_BUILD_CTIME_TESTS=OFF to avoid that.

Hm, great point! The reason why secp256k1_declassify uses a run-time flag (instead of compile-time flag) is that we want to run the constant-time tests on the real binary.

I don't know what the performance impact of these additional instructions is, but I doubt that having a compile-time flag is a concern in this case. That means that we could just wrap the SECP256K1_CHECKMEM_UNDEFINE in an #ifdef VERIFY. @sipa What do you think?

I think the reasoning is that we want the release binaries to be as close as possible to what we actually test in the ctime test, but disable the effect at runtime using SECP256K1_CONTEXT_DECLASSIFY to avoid a performance impact.

It wouldn't surprise me that that is overkill; the conditional to determine whether or not to declassify operations at runtime may have a higher cost than actually executing the nop instructions that declassification actually correspond to when not running instrumented by valgrind.

Oh, sorry, I think we're talking past each other. My suggestion, for which I'd like to have your opinion on, is to wrap SECP256K1_CHECKMEM_UNDEFINE in an #ifdef VERIFY block here in this particular case of clearing memory, i.e., inside secp256k1_memclear (and not in secp256k1_declassify. Do you think that's a reasonable thing to do?

But regarding what you said:

I think the reasoning is that we want the release binaries to be as close as possible to what we actually test in the ctime test, but disable the effect at runtime using SECP256K1_CONTEXT_DECLASSIFY to avoid a performance impact.

Yes, I agree. Perhaps an additional reason is to avoid any shenanigans that the valgrind syscalls may have. They should be noops, but it's certainly a bit safer not to run them at all.

It wouldn't surprise me that that is overkill; the conditional to determine whether or not to declassify operations at runtime may have a higher cost than actually executing the nop instructions that declassification actually correspond to when not running instrumented by valgrind.

I can imagine that the overhead of the noops is negligible, but at least checking the conditional should be negligible as well because we use EXCEPT to help the compiler predict the branch:

secp256k1/src/secp256k1.c

Lines 236 to 238 in 68b5520

static SECP256K1_INLINE void secp256k1_declassify(const secp256k1_context* ctx, const void *p, size_t len) {

if (EXPECT(ctx->declassify, 0)) SECP256K1_CHECKMEM_DEFINE(p, len);

}

What bothered me in general (independent on how lightweight the code generated by the valgrind macros might be) is that when users build with the default CMake settings, they could currently end up with different release binaries, depending on whether valgrind is installed or not. Unrelated to this PR, but maybe the SECP256K1_VALGRIND build setting should only be auto-detected in the "dev-mode" preset, and OFF by default? (I only looked at the CMake build, don't know if the valgrind setting is also auto-detected on autotools).

I see. That's a valid point, which has been brought up before, see #813 (comment). (This thread is also very helpful to understand why we have run-time flag etc.) The conclusion was that the benefits outweigh the drawback that the build outputs depends on the availability of valgrind, but yeah, there's no perfect solution here. And yes, it's also auto-detected in autotools.

I see, so the idea is to have

... #ifndef VERIFY SECP256K1_CHECKMEM_UNDEFINE(ptr, len); #endif }

in secp256k1_memclear()?

That would mean tests_noverify wouldn't detect violations of use-after-clear, nor would applications linking against the production library when running in valgrind. The upside would be that the production library definitely does not have its behavior affected by being compiled with valgrind present.

Indeed.

That would mean tests_noverify wouldn't detect violations of use-after-clear

Fwiw, I had this downside in mind, and I don't think it's a big deal because we still have the normal tests.

nor would applications linking against the production library when running in valgrind.

Okay, I had not considered this one... I still think that's acceptable, but yeah, it's a good point...

ACK. I guess it makes sense that if the primary goal is making sure no runtime impact for production code, this should be guarded by a compile-time check, as the runtime check isn't available here (being just for ctime testing).

theStack · 2024-10-22T15:13:34Z

For a first check on whether this PR fulfills its promise, I looked at the generated assembler code of secp256k1_ec_seckey_verify, as this function is particularly short and should clear out the secret scalar at the end. The following commands were used to generate the disassembled output:

$ cmake --build build && objdump --no-addresses --no-show-raw-insn --disassemble=secp256k1_ec_seckey_verify ./build/lib/libsecp256k1.so > seckey_verify_disasm.txt

compiler output diff of `secp256k1_ec_seckey_verify` (master vs. PR branch)

running on Debian 12 stable (Bookworm) and gcc 12.2.0 on a x86-64 machine

--- master.txt  2024-10-22 16:09:38.985554751 +0200
+++ pr1579.txt  2024-10-22 16:12:37.324112394 +0200
@@ -11,31 +11,38 @@
 Disassembly of section .text:
 
 <secp256k1_ec_seckey_verify>:
-       sub    $0x38,%rsp
+       push   %rbx
+       sub    $0x30,%rsp
        test   %rsi,%rsi
-       je     <secp256k1_ec_seckey_verify+0x48>
+       je     <secp256k1_ec_seckey_verify+0x58>
+       lea    0x10(%rsp),%rbx
        lea    0xc(%rsp),%rdx
-       lea    0x10(%rsp),%rdi
+       pxor   %xmm0,%xmm0
+       mov    %rbx,%rdi
        call   <secp256k1_scalar_set_b32>
        mov    0xc(%rsp),%ecx
        mov    0x10(%rsp),%rax
        or     0x18(%rsp),%rax
        or     0x20(%rsp),%rax
+       movaps %xmm0,0x10(%rsp)
        or     0x28(%rsp),%rax
+       movaps %xmm0,0x20(%rsp)
        setne  %dl
        xor    %eax,%eax
        test   %ecx,%ecx
        sete   %al
-       add    $0x38,%rsp
        and    %edx,%eax
+       add    $0x30,%rsp
+       pop    %rbx
        ret
        nopl   0x0(%rax)
        mov    %rdi,%rax
        mov    0xb0(%rdi),%rsi
-       lea    0x63b9(%rip),%rdi        # <_fini+0x1196>
+       lea    0x6199(%rip),%rdi        # <_fini+0xf46>
        call   *0xa8(%rax)
+       add    $0x30,%rsp
        xor    %eax,%eax
-       add    $0x38,%rsp
+       pop    %rbx
        ret

There is a little noise in the diff due to different register allocations and jump offsets, but in the middle one can see quite clearly that the memory clearing happens using the 16-byte SSE register xmm0: it is earlier zeroed with a `pxor` instruction and then written with `movaps` instruction twice to memory locations `0x10(%rsp)` and `0x20(%rsp)`, which correspond to the 32-byte `secp256k1_scalar` instance (interestingly, the clearing is interleaved with the `mov`/`or` instructions of the `_scalar_is_zero` check). So this seems to work as expected. Might be interesting to also try it with a variety of other compiler versions (especially newer ones) and different architectures, like arm64.

real-or-random

ACK mod my review comments

src/util.h

This code is not supposed to handle secret data.

theStack · 2024-10-22T16:46:17Z

Fixed #1579 (comment) and rebased on master for easier comparison of branches (since #1553, the output location of the .so file changed from ./build/src to ./build/lib; not being aware of that, I was unintentionally comparing the library file generated from master with itself for quite some time, wondering why the PR doesn't change anything 🤦‍♂️ ).

theStack · 2024-10-25T15:55:07Z

Regarding the open question of whether or not to include the _CHECKMEM_UNDEFINE macro in secp256k1_memclear in non-verify binaries or not, I compared the valgrind-builds on the pr branch with the macro commented out vs. with the macro included. This is what the assembler diff looks like (created for the same function and using the same methodology as in #1579 (comment)):

disassemble of secp256k1_ec_seckey_verify, without and with the SECP256K1_CHECKMEM_UNDEFINE in a valgrind build

--- pr1579_without_checkmem_undefine.txt	2024-10-25 17:34:50.639344958 +0200
+++ pr1579_with_checkmem_undefine.txt	2024-10-25 17:33:35.632626088 +0200
@@ -11,38 +11,59 @@
 Disassembly of section .text:
 
 <secp256k1_ec_seckey_verify>:
+	push   %rbp
 	push   %rbx
-	sub    $0x30,%rsp
+	sub    $0x68,%rsp
 	test   %rsi,%rsi
-	je     <secp256k1_ec_seckey_verify+0x58>
+	je     <secp256k1_ec_seckey_verify+0xb8>
+	lea    0x30(%rsp),%rbp
 	lea    0x10(%rsp),%rbx
-	lea    0xc(%rsp),%rdx
 	pxor   %xmm0,%xmm0
+	mov    %rbp,%rdx
 	mov    %rbx,%rdi
 	call   <secp256k1_scalar_set_b32>
-	mov    0xc(%rsp),%ecx
-	mov    0x10(%rsp),%rax
-	or     0x18(%rsp),%rax
-	or     0x20(%rsp),%rax
+	mov    0x10(%rsp),%rdx
+	or     0x18(%rsp),%rdx
 	movaps %xmm0,0x10(%rsp)
-	or     0x28(%rsp),%rax
+	or     0x20(%rsp),%rdx
+	or     0x28(%rsp),%rdx
 	movaps %xmm0,0x20(%rsp)
-	setne  %dl
-	xor    %eax,%eax
-	test   %ecx,%ecx
-	sete   %al
-	and    %edx,%eax
-	add    $0x30,%rsp
+	mov    0x30(%rsp),%edx
+	setne  %al
+	xor    %ecx,%ecx
+	test   %edx,%edx
+	sete   %cl
+	and    %eax,%ecx
+	movq   $0x4d430001,0x30(%rsp)
+	xor    %edx,%edx
+	mov    %rbp,%rax
+	mov    %rbx,0x38(%rsp)
+	movq   $0x20,0x40(%rsp)
+	movq   $0x0,0x48(%rsp)
+	movq   $0x0,0x50(%rsp)
+	movq   $0x0,0x58(%rsp)
+	rol    $0x3,%rdi
+	rol    $0xd,%rdi
+	rol    $0x3d,%rdi
+	rol    $0x33,%rdi
+	xchg   %rbx,%rbx
+	mov    %rdx,0x8(%rsp)
+	mov    0x8(%rsp),%rax
+	add    $0x68,%rsp
+	mov    %ecx,%eax
 	pop    %rbx
+	pop    %rbp
 	ret
-	nopl   0x0(%rax)
+	nopl   0x0(%rax,%rax,1)
 	mov    %rdi,%rax
 	mov    0xb0(%rdi),%rsi
-	lea    0x5d09(%rip),%rdi        # <_fini+0x766>
+	lea    0x7b99(%rip),%rdi        # <_fini+0x14e6>
 	call   *0xa8(%rax)
-	add    $0x30,%rsp
-	xor    %eax,%eax
+	add    $0x68,%rsp
+	xor    %ecx,%ecx
+	mov    %ecx,%eax
 	pop    %rbx
+	pop    %rbp
 	ret
 
 Disassembly of section .fini:

Seems like at least in this function, it causes at least 15 extra (no-op like) instructions to be emitted. Considering that previously, these valgrind placeholders were not reachable (unless explicitly specified in the context object) and these extra instructions are added at multiple places spread all over the code, it might be better to not include them in the release binaries? OTOH, "ctime-tests should run with the same binary as in the release" then doesn't hold anymore. So really not sure what's better 🤔

real-or-random · 2024-10-25T16:28:21Z

OTOH, "ctime-tests should run with the same binary as in the release" then doesn't hold anymore.

I don't think so. If we wrap the new _CHECKMEM_UNDEFINE within _memclear in #ifdef VERIFY, I don't see how this affects the ctimetests at all. We'd still include the _CHECKMEM_UNDEFINE in declassify in the release builds. And the ctimetests executable will still link against the (release) binary of the library. (Note that the ctimetests test executable uses the public API, it's really just an application that consumes the library by linking against it, as opposed to the other test binaries, which essentially #include all the library code.)

We rely on memset() and an __asm__ memory barrier where it's available or on SecureZeroMemory() on Windows. The fallback implementation uses a volatile function pointer to memset which the compiler is not clever enough to optimize.

There are two uses of the secp256k1_fe_clear() function that are now separated into these two functions in order to reflect the intent: 1) initializing the memory prior to being used -> converted to fe_set_int( . , 0 ) 2) zeroing the memory after being used such that no sensitive data remains. -> remains as fe_clear() In the latter case, 'magnitude' and 'normalized' need to be overwritten when VERIFY is enabled. Co-Authored-By: isle2983 <[email protected]>

Co-Authored-By: isle2983 <[email protected]> Co-Authored-By: Pieter Wuille <[email protected]>

All of the invocations of secp256k1_memclear() operate on stack memory and happen after the function is done with the memory object. This commit replaces existing memset() invocations and also adds secp256k1_memclear() to code locations where clearing was missing; there is no guarantee that this commit covers all code locations where clearing is necessary. Co-Authored-By: isle2983 <[email protected]>

This gives the caller more control about whether the state should be cleaned (= should be considered secret). Moreover, it gives the caller the possibility to clean a hash struct without finalizing it.

Quoting sipa (see bitcoin-core#1479 (comment)): "When performing an EC multiplication A = aG for secret a, the resulting _affine_ coordinates of A are presumed to not leak information about a (ECDLP), but the same is not necessarily true for the Jacobian coordinates that come out of our multiplication algorithm." For the ECDH point multiplication result, the result in Jacobi coordinates should be cleared not only to avoid leaking the scalar, but even more so as it's a representation of the resulting shared secret.

theStack · 2024-10-25T16:57:23Z

OTOH, "ctime-tests should run with the same binary as in the release" then doesn't hold anymore.

I don't think so. If we wrap the new _CHECKMEM_UNDEFINE within _memclear in #ifdef VERIFY, I don't see how this affects the ctimetests at all. We'd still include the _CHECKMEM_UNDEFINE in declassify in the release builds. And the ctimetests executable will still link against the (release) binary of the library. (Note that the ctimetests test executable uses the public API, it's really just an application that consumes the library by linking against it, as opposed to the other test binaries, which essentially #include all the library code.)

Oh right, for some reason I assumed that the ctimetests binary is also compiled with VERIFY defined, which is of course nonsensical. Added the "#ifdef VERIFY" block around _CHECKMEM_UNDEFINE now, as it looks we have consensus on doing that (#1579 (comment)).

real-or-random

ACK 765ef53

sipa · 2024-11-04T15:15:59Z

reACK 765ef53

0cdc758a563 Merge bitcoin-core/secp256k1#1631: release: prepare for 0.6.0 39d5dfd542a release: prepare for 0.6.0 df2eceb2790 build: add ellswift.md and musig.md to release tarball a306bb7e903 tools: fix check-abi.sh after cmake out locations were changed 145868a84d2 Do not export `secp256k1_musig_nonce_gen_internal` b161bffb8bf Merge bitcoin-core/secp256k1#1579: Clear sensitive memory without getting optimized out (revival of bitcoin#636) a38d879a1a6 Merge bitcoin-core/secp256k1#1628: Name public API structs 7d48f5ed02e Merge bitcoin-core/secp256k1#1581: test, ci: Lower default iteration count to 16 694342fdb71 Name public API structs 0f73caf7c62 test, ci: Lower default iteration count to 16 9a8db52f4e9 Merge bitcoin-core/secp256k1#1582: cmake, test: Add `secp256k1_` prefix to test names 765ef53335a Clear _gej instances after point multiplication to avoid potential leaks 349e6ab916b Introduce separate _clear functions for hash module 99cc9fd6d01 Don't rely on memset to set signed integers to 0 97c57f42ba8 Implement various _clear() functions with secp256k1_memclear() 9bb368d1466 Use secp256k1_memclear() to clear stack memory instead of memset() e3497bbf001 Separate between clearing memory and setting to zero in tests d79a6ccd43a Separate secp256k1_fe_set_int( . , 0 ) from secp256k1_fe_clear() 1c081262227 Add secp256k1_memclear() for clearing secret data 1464f15c812 Merge bitcoin-core/secp256k1#1625: util: Remove unused (u)int64_t formatting macros 980c08df80a util: Remove unused (u)int64_t formatting macros 9b7c59cbb90 Merge bitcoin-core/secp256k1#1624: ci: Update macOS image 096e3e23f63 ci: Update macOS image e7d384488e8 Don't clear secrets in pippenger implementation 68b55209f1b Merge bitcoin-core/secp256k1#1619: musig: ctimetests: fix _declassify range for generated nonce points f0868a9b3d8 Merge bitcoin-core/secp256k1#1595: build: 45839th attempt to fix symbol visibility on Windows 1fae76f50c0 Merge bitcoin-core/secp256k1#1620: Remove unused scratch space from API 8be3839fb2e Remove unused scratch space from API 57eda3ba300 musig: ctimetests: fix _declassify range for generated nonce points 87384f5c0f2 cmake, test: Add `secp256k1_` prefix to test names e59158b6eb7 Merge bitcoin-core/secp256k1#1553: cmake: Set top-level target output locations 18f9b967c25 Merge bitcoin-core/secp256k1#1616: examples: do not retry generating seckey randomness in musig 5bab8f6d3c4 examples: make key generation doc consistent e8908221a45 examples: do not retry generating seckey randomness in musig 70b6be1834e extrakeys: improve doc of keypair_create (don't suggest retry) 01b5893389e Merge bitcoin-core/secp256k1#1599: bitcoin#1570 improve examples: remove key generation loop cd4f84f3ba8 Improve examples/documentation: remove key generation loops a88aa935063 Merge bitcoin-core/secp256k1#1603: f can never equal -m 3660fe5e2a9 Merge bitcoin-core/secp256k1#1479: Add module "musig" that implements MuSig2 multi-signatures (BIP 327) 168c92011f5 build: allow enabling the musig module in cmake f411841a46b Add module "musig" that implements MuSig2 multi-signatures (BIP 327) 0be79660f38 util: add constant-time is_zero_array function c8fbdb1b972 group: add ge_to_bytes_ext and ge_from_bytes_ext ef7ff03407f f can never equal -m c232486d84e Revert "cmake: Set `ENVIRONMENT` property for examples on Windows" 26e4a7c2146 cmake: Set top-level target output locations 4c57c7a5a95 Merge bitcoin-core/secp256k1#1554: cmake: Clean up testing code 447334cb06d include: Avoid visibility("default") on Windows 472faaa8ee6 Merge bitcoin-core/secp256k1#1604: doc: fix typos in `secp256k1_ecdsa_{recoverable_,}signature` API description 292310fbb24 doc: fix typos in `secp256k1_ecdsa_{recoverable_,}signature` API description 85e224dd97f group: add ge_to_bytes and ge_from_bytes 7c987ec89e6 cmake: Call `enable_testing()` unconditionally 6aa576515ef cmake: Delete `CTest` module git-subtree-dir: src/secp256k1 git-subtree-split: 0cdc758a56360bf58a851fe91085a327ec97685a

8deef00b3 Merge bitcoin-core/secp256k1#1634: Fix some misspellings 39705450e Fix some misspellings ec329c250 Merge bitcoin-core/secp256k1#1633: release cleanup: bump version after 0.6.0 c97059f59 release cleanup: bump version after 0.6.0 0cdc758a5 Merge bitcoin-core/secp256k1#1631: release: prepare for 0.6.0 39d5dfd54 release: prepare for 0.6.0 df2eceb27 build: add ellswift.md and musig.md to release tarball a306bb7e9 tools: fix check-abi.sh after cmake out locations were changed 145868a84 Do not export `secp256k1_musig_nonce_gen_internal` b161bffb8 Merge bitcoin-core/secp256k1#1579: Clear sensitive memory without getting optimized out (revival of #636) a38d879a1 Merge bitcoin-core/secp256k1#1628: Name public API structs 7d48f5ed0 Merge bitcoin-core/secp256k1#1581: test, ci: Lower default iteration count to 16 694342fdb Name public API structs 0f73caf7c test, ci: Lower default iteration count to 16 9a8db52f4 Merge bitcoin-core/secp256k1#1582: cmake, test: Add `secp256k1_` prefix to test names 765ef5333 Clear _gej instances after point multiplication to avoid potential leaks 349e6ab91 Introduce separate _clear functions for hash module 99cc9fd6d Don't rely on memset to set signed integers to 0 97c57f42b Implement various _clear() functions with secp256k1_memclear() 9bb368d14 Use secp256k1_memclear() to clear stack memory instead of memset() e3497bbf0 Separate between clearing memory and setting to zero in tests d79a6ccd4 Separate secp256k1_fe_set_int( . , 0 ) from secp256k1_fe_clear() 1c0812622 Add secp256k1_memclear() for clearing secret data e7d384488 Don't clear secrets in pippenger implementation 87384f5c0 cmake, test: Add `secp256k1_` prefix to test names git-subtree-dir: src/secp256k1 git-subtree-split: 8deef00b33ca81202aca80fe0bcd9730f084fbd2

theStack force-pushed the revival_of_pr636_cleanse branch from deebc69 to abb3be2 Compare August 6, 2024 21:19

real-or-random added the side-channel label Aug 17, 2024

real-or-random reviewed Aug 17, 2024

View reviewed changes

theStack force-pushed the revival_of_pr636_cleanse branch from abb3be2 to ac0e41b Compare August 20, 2024 10:13

theStack force-pushed the revival_of_pr636_cleanse branch from ac0e41b to 0b01d2a Compare October 8, 2024 22:51

theStack force-pushed the revival_of_pr636_cleanse branch from 0b01d2a to 05a46b5 Compare October 8, 2024 23:14

real-or-random reviewed Oct 10, 2024

View reviewed changes

src/util.h Outdated Show resolved Hide resolved

src/secp256k1.c Show resolved Hide resolved

real-or-random added the needs-changelog label Oct 10, 2024

theStack force-pushed the revival_of_pr636_cleanse branch from 05a46b5 to c921078 Compare October 11, 2024 16:15

real-or-random mentioned this pull request Oct 21, 2024

Add BIP352 silentpayments module #1519

Open

3 tasks

theStack commented Oct 22, 2024

View reviewed changes

real-or-random mentioned this pull request Oct 22, 2024

cleanse: switch to SecureZeroMemory for Windows cross-compile bitcoin/bitcoin#26950

Merged

real-or-random reviewed Oct 22, 2024

View reviewed changes

src/util.h Outdated Show resolved Hide resolved

src/util.h Show resolved Hide resolved

src/util.h Show resolved Hide resolved

Don't clear secrets in pippenger implementation

e7d3844

This code is not supposed to handle secret data.

theStack mentioned this pull request Oct 22, 2024

[CI test, dontmerge] PR #1579 with secp256k1_memclear using volatile_memset #1622

Closed

theStack force-pushed the revival_of_pr636_cleanse branch from c921078 to b942b9f Compare October 22, 2024 16:43

Add secp256k1_memclear() for clearing secret data

1c08126

We rely on memset() and an __asm__ memory barrier where it's available or on SecureZeroMemory() on Windows. The fallback implementation uses a volatile function pointer to memset which the compiler is not clever enough to optimize.

real-or-random and others added 7 commits October 25, 2024 18:44

Separate between clearing memory and setting to zero in tests

e3497bb

Co-Authored-By: isle2983 <[email protected]> Co-Authored-By: Pieter Wuille <[email protected]>

Implement various _clear() functions with secp256k1_memclear()

97c57f4

Don't rely on memset to set signed integers to 0

99cc9fd

Introduce separate _clear functions for hash module

349e6ab

This gives the caller more control about whether the state should be cleaned (= should be considered secret). Moreover, it gives the caller the possibility to clean a hash struct without finalizing it.

theStack force-pushed the revival_of_pr636_cleanse branch from b942b9f to 765ef53 Compare October 25, 2024 16:45

real-or-random approved these changes Nov 1, 2024

View reviewed changes

real-or-random merged commit b161bff into bitcoin-core:master Nov 4, 2024
116 checks passed

theStack deleted the revival_of_pr636_cleanse branch November 4, 2024 15:53

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Clear sensitive memory without getting optimized out (revival of #636) #1579

Clear sensitive memory without getting optimized out (revival of #636) #1579

theStack commented Aug 6, 2024

real-or-random left a comment •

edited

Loading

theStack commented Aug 20, 2024

real-or-random commented Oct 8, 2024

theStack commented Oct 8, 2024

real-or-random commented Oct 8, 2024

theStack commented Oct 8, 2024

real-or-random left a comment

theStack commented Oct 10, 2024

real-or-random commented Oct 10, 2024 •

edited

Loading

theStack commented Oct 11, 2024

sipa commented Oct 21, 2024

theStack Oct 22, 2024

real-or-random Oct 22, 2024

sipa Oct 22, 2024

real-or-random Oct 22, 2024

theStack Oct 22, 2024 •

edited

Loading

real-or-random Oct 22, 2024

sipa Oct 25, 2024

real-or-random Oct 25, 2024

sipa Oct 25, 2024

theStack commented Oct 22, 2024 •

edited

Loading

real-or-random left a comment

theStack commented Oct 22, 2024

theStack commented Oct 25, 2024 •

edited

Loading

real-or-random commented Oct 25, 2024

theStack commented Oct 25, 2024

real-or-random left a comment

sipa commented Nov 4, 2024

	static SECP256K1_INLINE void secp256k1_declassify(const secp256k1_context* ctx, const void *p, size_t len) {
	if (EXPECT(ctx->declassify, 0)) SECP256K1_CHECKMEM_DEFINE(p, len);
	}

Clear sensitive memory without getting optimized out (revival of #636) #1579

Clear sensitive memory without getting optimized out (revival of #636) #1579

Conversation

theStack commented Aug 6, 2024

real-or-random left a comment • edited Loading

Choose a reason for hiding this comment

theStack commented Aug 20, 2024

real-or-random commented Oct 8, 2024

theStack commented Oct 8, 2024

real-or-random commented Oct 8, 2024

theStack commented Oct 8, 2024

real-or-random left a comment

Choose a reason for hiding this comment

theStack commented Oct 10, 2024

real-or-random commented Oct 10, 2024 • edited Loading

theStack commented Oct 11, 2024

sipa commented Oct 21, 2024

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

theStack Oct 22, 2024 • edited Loading

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

theStack commented Oct 22, 2024 • edited Loading

real-or-random left a comment

Choose a reason for hiding this comment

theStack commented Oct 22, 2024

theStack commented Oct 25, 2024 • edited Loading

real-or-random commented Oct 25, 2024

theStack commented Oct 25, 2024

real-or-random left a comment

Choose a reason for hiding this comment

sipa commented Nov 4, 2024

real-or-random left a comment •

edited

Loading

real-or-random commented Oct 10, 2024 •

edited

Loading

theStack Oct 22, 2024 •

edited

Loading

theStack commented Oct 22, 2024 •

edited

Loading

theStack commented Oct 25, 2024 •

edited

Loading