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Merge pull request #838 from gilles-peskine-arm/ecp_max_bits-check-2.16

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Backport 2.16: check MBEDTLS_ECP_MAX_BITS
This commit is contained in:
Ronald Cron
2021-06-15 11:12:52 +02:00
committed by GitHub
parent 1283ed9e3b 5a6549752f
commit 6f4fbb4640
3 changed files with 49 additions and 1 deletions
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4
ChangeLog.d/ecp_max_bits.txt Normal file
View File

@@ -0,0 +1,4 @@
Security
* It was possible to configure MBEDTLS_ECP_MAX_BITS to a value that is
too small, leading to buffer overflows in ECC operations. Fail the build
in such a case.

42
include/mbedtls/ecp.h
View File

@@ -154,6 +154,40 @@ typedef struct mbedtls_ecp_point
}
mbedtls_ecp_point;
/* Determine the minimum safe value of MBEDTLS_ECP_MAX_BITS. */
#if !defined(MBEDTLS_ECP_C)
#define MBEDTLS_ECP_MAX_BITS_MIN 0
/* Note: the curves must be listed in DECREASING size! */
#elif defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 521
#elif defined(MBEDTLS_ECP_DP_BP512R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 512
#elif defined(MBEDTLS_ECP_DP_CURVE448_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 448
#elif defined(MBEDTLS_ECP_DP_BP384R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 384
#elif defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 384
#elif defined(MBEDTLS_ECP_DP_BP256R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 256
#elif defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 256
#elif defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 256
#elif defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 255
#elif defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 225 // n is slightly above 2^224
#elif defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 224
#elif defined(MBEDTLS_ECP_DP_SECP192K1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 192
#elif defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED)
#define MBEDTLS_ECP_MAX_BITS_MIN 192
#else
#error "MBEDTLS_ECP_C enabled, but no curve?"
#endif
#if !defined(MBEDTLS_ECP_ALT)
/*
* default mbed TLS elliptic curve arithmetic implementation
@@ -228,7 +262,13 @@ mbedtls_ecp_group;
* \{
*/
#if !defined(MBEDTLS_ECP_MAX_BITS)
#if defined(MBEDTLS_ECP_MAX_BITS)
#if MBEDTLS_ECP_MAX_BITS < MBEDTLS_ECP_MAX_BITS_MIN
#error "MBEDTLS_ECP_MAX_BITS is smaller than the largest supported curve"
#endif
#else
/**
* The maximum size of the groups, that is, of \c N and \c P.
*/

4
tests/suites/test_suite_ecp.function
View File

@@ -393,6 +393,8 @@ void mbedtls_ecp_curve_info( int id, int tls_id, int size, char * name )
TEST_ASSERT( by_id == by_name );
TEST_ASSERT( by_id->bit_size == size );
TEST_ASSERT( size <= MBEDTLS_ECP_MAX_BITS );
TEST_ASSERT( size <= MBEDTLS_ECP_MAX_BYTES * 8 );
}
/* END_CASE */
@@ -750,6 +752,7 @@ void ecp_muladd( int id,
TEST_EQUAL( 0, mbedtls_ecp_point_write_binary(
&grp, &R, MBEDTLS_ECP_PF_UNCOMPRESSED,
&len, actual_result, sizeof( actual_result ) ) );
TEST_ASSERT( len <= MBEDTLS_ECP_MAX_PT_LEN );
ASSERT_COMPARE( expected_result->x, expected_result->len,
actual_result, len );
@@ -821,6 +824,7 @@ void ecp_write_binary( int id, char * x, char * y, char * z, int format,
if( ret == 0 )
{
TEST_ASSERT( olen <= MBEDTLS_ECP_MAX_PT_LEN );
TEST_ASSERT( mbedtls_test_hexcmp( buf, out->x, olen, out->len ) == 0 );
}