The bulk of RSA_check_key is spent in bn_div_consttime, which is a naive
but constant-time long-division algorithm for the few places that divide
by a secret even divisor: RSA keygen and RSA import. RSA import is
somewhat performance-sensitive, so pick some low-hanging fruit:
The main observation is that, in all but one call site, the bit width of
the divisor is public. That means, for an N-bit divisor, we can skip the
first N-1 iterations of long division because an N-1-bit remainder
cannot exceed the N-bit divisor.
One minor nuisance is bn_lcm_consttime, used in RSA keygen has a case
that does *not* have a public bit width. Apply the optimization there
would leak information. I've implemented this as an optional public
lower bound on num_bits(divisor), which all but that call fills in.
Before:
Did 5060 RSA 2048 private key parse operations in 1058526us (4780.2 ops/sec)
Did 1551 RSA 4096 private key parse operations in 1082343us (1433.0 ops/sec)
After:
Did 11532 RSA 2048 private key parse operations in 1084145us (10637.0 ops/sec) [+122.5%]
Did 3542 RSA 4096 private key parse operations in 1036374us (3417.7 ops/sec) [+138.5%]
Bug: b/192484677
Change-Id: I893ebb8886aeb8200a1a365673b56c49774221a2
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49106
Reviewed-by: Adam Langley <agl@google.com>
See also f8fc0e35e0b1813af15887d42e17b7d5537bb86c from upstream, though
our BN_divs have diverged slightly.
Change-Id: I49fa4f0a5c730d34e6f41f724f1afe3685470712
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48426
Reviewed-by: Adam Langley <agl@google.com>
This comment dates to SSLeay. It appears to be describing the
incremental trial division strategy where they would pick a starting
candidate, compute moduli by small primes, and then update by
incrementing the candidate and saved moduli instead of dividing from
scratch. We use a simpler rejection sampling strategy.
Change-Id: If2203d616f2b1f632bcd7033ceb60a83d1b75674
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48047
Reviewed-by: Adam Langley <agl@google.com>
Because file names are not enclosed in quotation marks in the open call.
https://bugs.chromium.org/p/boringssl/issues/detail?id=415
```
cmake --build "C:\Projects\ Extern\Visual C++ 2015\x64 Debug\Build\BoringSSL\."
[9/439] Generating rdrand-x86_64.asm
FAILED: crypto/fipsmodule/rdrand-x86_64.asm
cmd.exe /C "cd /D "C:\Projects\ Extern\Visual C++ 2015\x64 Debug\Build\BoringSSL\crypto\fipsmodule" && "C:\Program Files\CMake\bin\cmake.exe" -E make_directory . && C:\Perl64\bin\perl.exe "C:/Projects/ Extern/Source/BoringSSL/crypto/fipsmodule/rand/asm/rdrand-x86_64.pl" nasm rdrand-x86_64.asm"
Can't open perl script "C:/Projects/": No such file or directory
error closing STDOUT at C:/Projects/ Extern/Source/BoringSSL/crypto/fipsmodule/rand/asm/rdrand-x86_64.pl line 87.
ninja: build stopped: subcommand failed.
```
Bug: 415
Change-Id: I83c4a460689b9adeb439425ad390322ae8b2002a
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/47884
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
This invovles a |2048|^|225| modexp, which is far from ideal, but is now
required in FIPS mode.
Change-Id: Id7384b4ba92aa74e971231bc44fa0f10434d18e2
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/45085
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
We clear all heap memory on free now, thus the difference between these
functions is quite small. There are some differences though:
Firstly, BN_clear_free will attempt to zero out static limb data. But
static data is probably read-only and thus trying to zero it will crash.
Secondly it will try to zero out the BIGNUM structure itself. But either
it's on the heap, and will be zeroed anyway, or else it's on the stack,
and we don't try and clear the stack in general because the compiler is
duplicating bits of it at will anyway.
Change-Id: I8a07385a102cfd308b555432942225c25eb7c12d
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/45084
Reviewed-by: David Benjamin <davidben@google.com>
Windows on Arm (WoA) builds are currently using the C implementations
of the various functions within BoringSSL. This patch enables feature
detection for the Neon and hardware crypto optimizations, and updates
the perl script to generate AArch64 .S files for WoA.
Note these files use GNU assembler syntax (specifically tested with
Clang assembler), not armasm.
Change-Id: Id8841f4db0498ec16215095a4e6bd60d427cd54b
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/43304
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
If using precompiled headers then this is needed otherwise bn/internal.h
doesn't have a definition for BN_ULONG etc.
Change-Id: I41b331465abae7108f255722a156d2ffb3016ba3
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/44604
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
This change adds optional support for
- Armv8.3-A Pointer Authentication (PAuth) and
- Armv8.5-A Branch Target Identification (BTI)
features to the perl scripts.
Both features can be enabled with additional compiler flags.
Unless any of these are enabled explicitly there is no code change at
all.
The extensions are briefly described below. Please read the appropriate
chapters of the Arm Architecture Reference Manual for the complete
specification.
Scope
-----
This change only affects generated assembly code.
Armv8.3-A Pointer Authentication
--------------------------------
Pointer Authentication extension supports the authentication of the
contents of registers before they are used for indirect branching
or load.
PAuth provides a probabilistic method to detect corruption of register
values. PAuth signing instructions generate a Pointer Authentication
Code (PAC) based on the value of a register, a seed and a key.
The generated PAC is inserted into the original value in the register.
A PAuth authentication instruction recomputes the PAC, and if it matches
the PAC in the register, restores its original value. In case of a
mismatch, an architecturally unmapped address is generated instead.
With PAuth, mitigation against ROP (Return-oriented Programming) attacks
can be implemented. This is achieved by signing the contents of the
link-register (LR) before it is pushed to stack. Once LR is popped,
it is authenticated. This way a stack corruption which overwrites the
LR on the stack is detectable.
The PAuth extension adds several new instructions, some of which are not
recognized by older hardware. To support a single codebase for both pre
Armv8.3-A targets and newer ones, only NOP-space instructions are added
by this patch. These instructions are treated as NOPs on hardware
which does not support Armv8.3-A. Furthermore, this patch only considers
cases where LR is saved to the stack and then restored before branching
to its content. There are cases in the code where LR is pushed to stack
but it is not used later. We do not address these cases as they are not
affected by PAuth.
There are two keys available to sign an instruction address: A and B.
PACIASP and PACIBSP only differ in the used keys: A and B, respectively.
The keys are typically managed by the operating system.
To enable generating code for PAuth compile with
-mbranch-protection=<mode>:
- standard or pac-ret: add PACIASP and AUTIASP, also enables BTI
(read below)
- pac-ret+b-key: add PACIBSP and AUTIBSP
Armv8.5-A Branch Target Identification
--------------------------------------
Branch Target Identification features some new instructions which
protect the execution of instructions on guarded pages which are not
intended branch targets.
If Armv8.5-A is supported by the hardware, execution of an instruction
changes the value of PSTATE.BTYPE field. If an indirect branch
lands on a guarded page the target instruction must be one of the
BTI <jc> flavors, or in case of a direct call or jump it can be any
other instruction. If the target instruction is not compatible with the
value of PSTATE.BTYPE a Branch Target Exception is generated.
In short, indirect jumps are compatible with BTI <j> and <jc> while
indirect calls are compatible with BTI <c> and <jc>. Please refer to the
specification for the details.
Armv8.3-A PACIASP and PACIBSP are implicit branch target
identification instructions which are equivalent with BTI c or BTI jc
depending on system register configuration.
BTI is used to mitigate JOP (Jump-oriented Programming) attacks by
limiting the set of instructions which can be jumped to.
BTI requires active linker support to mark the pages with BTI-enabled
code as guarded. For ELF64 files BTI compatibility is recorded in the
.note.gnu.property section. For a shared object or static binary it is
required that all linked units support BTI. This means that even a
single assembly file without the required note section turns-off BTI
for the whole binary or shared object.
The new BTI instructions are treated as NOPs on hardware which does
not support Armv8.5-A or on pages which are not guarded.
To insert this new and optional instruction compile with
-mbranch-protection=standard (also enables PAuth) or +bti.
When targeting a guarded page from a non-guarded page, weaker
compatibility restrictions apply to maintain compatibility between
legacy and new code. For detailed rules please refer to the Arm ARM.
Compiler support
----------------
Compiler support requires understanding '-mbranch-protection=<mode>'
and emitting the appropriate feature macros (__ARM_FEATURE_BTI_DEFAULT
and __ARM_FEATURE_PAC_DEFAULT). The current state is the following:
-------------------------------------------------------
| Compiler | -mbranch-protection | Feature macros |
+----------+---------------------+--------------------+
| clang | 9.0.0 | 11.0.0 |
+----------+---------------------+--------------------+
| gcc | 9 | expected in 10.1+ |
-------------------------------------------------------
Available Platforms
------------------
Arm Fast Model and QEMU support both extensions.
https://developer.arm.com/tools-and-software/simulation-models/fast-modelshttps://www.qemu.org/
Implementation Notes
--------------------
This change adds BTI landing pads even to assembly functions which are
likely to be directly called only. In these cases, landing pads might
be superfluous depending on what code the linker generates.
Code size and performance impact for these cases would be negligble.
Interaction with C code
-----------------------
Pointer Authentication is a per-frame protection while Branch Target
Identification can be turned on and off only for all code pages of a
whole shared object or static binary. Because of these properties if
C/C++ code is compiled without any of the above features but assembly
files support any of them unconditionally there is no incompatibility
between the two.
Useful Links
------------
To fully understand the details of both PAuth and BTI it is advised to
read the related chapters of the Arm Architecture Reference Manual
(Arm ARM):
https://developer.arm.com/documentation/ddi0487/latest/
Additional materials:
"Providing protection for complex software"
https://developer.arm.com/architectures/learn-the-architecture/providing-protection-for-complex-software
Arm Compiler Reference Guide Version 6.14: -mbranch-protection
https://developer.arm.com/documentation/101754/0614/armclang-Reference/armclang-Command-line-Options/-mbranch-protection?lang=en
Arm C Language Extensions (ACLE)
https://developer.arm.com/docs/101028/latest
Change-Id: I4335f92e2ccc8e209c7d68a0a79f1acdf3aeb791
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/42084
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
David Benjamin
Florin Crișan
Adam Langley
Anthony Roberts
Adam Langley
Tamas Petz