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fix: don't enable custom random for openssl fips #5093

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fix: don't enable custom random for openssl fips #5093

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8bd6cdf
fix: don't enable custom random for openssl fips
jmayclin Feb 5, 2025
08bc283
add helper for openssl fips
jmayclin Feb 5, 2025
27e021c
restrict engine support to openssl
jmayclin Feb 5, 2025
3b25b22
Update crypto/s2n_libcrypto.c
jmayclin Feb 5, 2025
b9e35f6
Update crypto/s2n_libcrypto.c
jmayclin Feb 5, 2025
579571c
remove duplicated logic comment
jmayclin Feb 5, 2025
0202407
Merge branch 'main' into openssl-fips-no-custom
jmayclin Feb 8, 2025
e57ef7d
address pr feedback
jmayclin Feb 8, 2025
4d7ace0
remove unnecessary include
jmayclin Feb 8, 2025
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13 changes: 13 additions & 0 deletions crypto/s2n_libcrypto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,19 @@ bool s2n_libcrypto_is_openssl(void)
return !is_other_libcrypto_variant;
}

/* Check if the linked libcrypto is an fips-capable openssl variant.
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*
* This method does check whether the linked libcrypto has fips mode enabled.
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*/
bool s2n_libcrypto_is_openssl_fips(void)
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@goatgoose goatgoose Feb 5, 2025 •
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This was also added in #5081, but with a different meaning.

This also won't return true for openssl3-fips (and we probably wouldn't want it to for this use case). To avoid having two similar APIs here, would it maybe make sense to just add a #elif to s2n_supports_custom_rand and return false specifically for OpenSSL 1.0.2-fips (OPENSSL_FIPS is defined)? I'm not sure it's going to be that useful anywhere else anyway.

{
#if defined(OPENSSL_FIPS)
return true;
#else
return false;
#endif
}

bool s2n_libcrypto_is_awslc()
{
#if defined(OPENSSL_IS_AWSLC)
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1 change: 1 addition & 0 deletions crypto/s2n_libcrypto.h
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Expand Up @@ -21,3 +21,4 @@ uint64_t s2n_libcrypto_awslc_api_version(void);
S2N_RESULT s2n_libcrypto_validate_runtime(void);
const char *s2n_libcrypto_get_version_name(void);
bool s2n_libcrypto_supports_flag_no_check_time();
bool s2n_libcrypto_is_openssl_fips(void);
2 changes: 1 addition & 1 deletion tests/unit/s2n_random_test.c
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Expand Up @@ -796,7 +796,7 @@ static int s2n_random_rand_bytes_after_cleanup_cb(struct random_test_case *test_
static int s2n_random_rand_bytes_before_init(struct random_test_case *test_case)
{
/* s2n_libcrypto_is_fips() is used since we are testing `s2n_init()` */
if (s2n_supports_custom_rand() && !s2n_libcrypto_is_fips()) {
if (s2n_supports_custom_rand()) {
/* Calling RAND_bytes will set a global random method */
unsigned char rndbytes[16] = { 0 };
EXPECT_EQUAL(RAND_bytes(rndbytes, sizeof(rndbytes)), 1);
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9 changes: 8 additions & 1 deletion utils/s2n_random.c
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Expand Up @@ -71,6 +71,7 @@
#include "api/s2n.h"
#include "crypto/s2n_drbg.h"
#include "crypto/s2n_fips.h"
#include "crypto/s2n_libcrypto.h"
#include "error/s2n_errno.h"
#include "s2n_io.h"
#include "stuffer/s2n_stuffer.h"
Expand Down Expand Up @@ -557,7 +558,13 @@ bool s2n_supports_custom_rand(void)
#if !defined(S2N_LIBCRYPTO_SUPPORTS_ENGINE)
return false;
#else
return s2n_libcrypto_is_openssl() && !s2n_is_in_fips_mode();
/* AWS-LC-FIPS supports custom rand unless s2n-tls is in FIPS mode */
/* OpenSSL-FIPS never supports custom rand, regardless of mode */
/* OpenSSL non-fips always supports custom rand */
/* other libcryptos never support custom rand */
bool awslc_fips_with_fips_enabled = s2n_libcrypto_is_awslc() && s2n_is_in_fips_mode();
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Is the AWS-LC check necessary? The custom RAND is never used with aws-lc anyway, right?

bool disable_for_fips = s2n_libcrypto_is_openssl_fips() || awslc_fips_with_fips_enabled;
return s2n_libcrypto_is_openssl() && !disable_for_fips;
#endif
}

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