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Merge pull request #297 from gilles-peskine-arm/asn1_get_int-undefined_shift
Fix int overflow in mbedtls_asn1_get_int
This commit is contained in:
Gilles Peskine
GitHub
commit
3cdb3da3a0
@ -149,16 +149,26 @@ int mbedtls_asn1_get_int( unsigned char **p,
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if( ( ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_INTEGER ) ) != 0 )
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return( ret );
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if( len == 0 || ( **p & 0x80 ) != 0 )
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/* len==0 is malformed (0 must be represented as 020100). */
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if( len == 0 )
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return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
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/* This is a cryptography library. Reject negative integers. */
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if( ( **p & 0x80 ) != 0 )
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return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
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/* Skip leading zeros. */
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while( len > 0 && **p == 0 )
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{
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++( *p );
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--len;
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}
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/* Reject integers that don't fit in an int. This code assumes that
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* the int type has no padding bit. */
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if( len > sizeof( int ) )
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return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
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if( len == sizeof( int ) && ( **p & 0x80 ) != 0 )
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return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
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*val = 0;
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while( len-- > 0 )
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@ -164,8 +164,7 @@ Not BOOLEAN
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get_boolean:"020101":0:MBEDTLS_ERR_ASN1_UNEXPECTED_TAG
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Empty INTEGER
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depends_on:SUPPORT_NEGATIVE_INTEGERS
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get_integer:"0200":"":MBEDTLS_ERR_ASN1_INVALID_LENGTH
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empty_integer:"0200"
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INTEGER 0
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get_integer:"020100":"0":0
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@ -173,27 +172,15 @@ get_integer:"020100":"0":0
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INTEGER 0, extra leading 0
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get_integer:"02020000":"0":0
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INTEGER -0
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depends_on:SUPPORT_NEGATIVE_INTEGERS
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get_integer:"020180":"0":0
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INTEGER 1
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get_integer:"020101":"1":0:
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INTEGER 1, extra leading 0
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get_integer:"02020001":"1":0:
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INTEGER -1
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depends_on:SUPPORT_NEGATIVE_INTEGERS
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get_integer:"020181":"-1":0
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INTEGER 0x7f
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get_integer:"02017f":"7f":0
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INTEGER -0x7f
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depends_on:SUPPORT_NEGATIVE_INTEGERS
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get_integer:"0201ff":"-7f":0
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INTEGER 0x80
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get_integer:"02020080":"80":0
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@ -212,9 +199,30 @@ get_integer:"020412345678":"12345678":0
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INTEGER 0x12345678, extra leading 0
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get_integer:"02050012345678":"12345678":0
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INTEGER 0x7fffffff
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get_integer:"02047fffffff":"7fffffff":0
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INTEGER 0x7fffffff, extra leading 0
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get_integer:"0205007fffffff":"7fffffff":0
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INTEGER 0x80000000
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get_integer:"02050080000000":"80000000":0
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INTEGER 0xffffffff
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get_integer:"020500ffffffff":"ffffffff":0
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INTEGER 0x100000000
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get_integer:"02050100000000":"0100000000":0
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INTEGER 0x123456789abcdef0
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get_integer:"0208123456789abcdef0":"123456789abcdef0":0
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INTEGER 0xfedcab9876543210
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get_integer:"020900fedcab9876543210":"fedcab9876543210":0
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INTEGER 0x1fedcab9876543210
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get_integer:"020901fedcab9876543210":"1fedcab9876543210":0
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INTEGER with 127 value octets
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get_integer:"027f0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcd":"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcd":0
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@ -227,6 +235,51 @@ get_integer:"0281800123456789abcdef0123456789abcdef0123456789abcdef0123456789abc
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INTEGER with 128 value octets (leading 0 in length)
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get_integer:"028200800123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef":"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef":0
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INTEGER -1
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get_integer:"0201ff":"-1":0
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INTEGER -1, extra leading ff
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get_integer:"0202ffff":"-1":0
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INTEGER -0x7f
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get_integer:"020181":"-7f":0
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INTEGER -0x80
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get_integer:"020180":"-80":0
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INTEGER -0x81
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get_integer:"0202ff7f":"-81":0
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INTEGER -0xff
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get_integer:"0202ff01":"-ff":0
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INTEGER -0x100
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get_integer:"0202ff00":"-100":0
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INTEGER -0x7fffffff
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get_integer:"020480000001":"-7fffffff":0
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INTEGER -0x80000000
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get_integer:"020480000000":"-80000000":0
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INTEGER -0x80000001
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get_integer:"0205ff7fffffff":"-80000001":0
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INTEGER -0xffffffff
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get_integer:"0205ff00000001":"-ffffffff":0
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INTEGER -0x100000000
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get_integer:"0205ff00000000":"-100000000":0
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INTEGER -0x123456789abcdef0
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get_integer:"0208edcba98765432110":"-123456789abcdef0":0
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INTEGER -0xfedcba9876543210
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get_integer:"0209ff0123456789abcdf0":"-fedcba9876543210":0
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INTEGER -0x1fedcab9876543210
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get_integer:"0209fe0123546789abcdf0":"-1fedcab9876543210":0
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Not INTEGER
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get_integer:"010101":"":MBEDTLS_ERR_ASN1_UNEXPECTED_TAG
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@ -59,6 +59,10 @@ static int nested_parse( unsigned char **const p,
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*p = start;
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ret = mbedtls_asn1_get_mpi( p, end, &mpi );
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mbedtls_mpi_free( &mpi );
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#else
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*p = start + 1;
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ret = mbedtls_asn1_get_len( p, end, &len );
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*p += len;
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#endif
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/* If we're sure that the number fits in an int, also
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* call mbedtls_asn1_get_int(). */
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@ -246,6 +250,41 @@ void get_boolean( const data_t *input,
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}
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/* END_CASE */
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/* BEGIN_CASE */
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void empty_integer( const data_t *input )
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{
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unsigned char *p;
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#if defined(MBEDTLS_BIGNUM_C)
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mbedtls_mpi actual_mpi;
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#endif
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int val;
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#if defined(MBEDTLS_BIGNUM_C)
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mbedtls_mpi_init( & actual_mpi );
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#endif
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/* An INTEGER with no content is not valid. */
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p = input->x;
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TEST_EQUAL( mbedtls_asn1_get_int( &p, input->x + input->len, &val ),
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MBEDTLS_ERR_ASN1_INVALID_LENGTH );
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#if defined(MBEDTLS_BIGNUM_C)
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/* INTEGERs are sometimes abused as bitstrings, so the library accepts
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* an INTEGER with empty content and gives it the value 0. */
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p = input->x;
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TEST_EQUAL( mbedtls_asn1_get_mpi( &p, input->x + input->len, &actual_mpi ),
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0 );
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TEST_EQUAL( mbedtls_mpi_cmp_int( &actual_mpi, 0 ), 0 );
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#endif
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exit:
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#if defined(MBEDTLS_BIGNUM_C)
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mbedtls_mpi_free( &actual_mpi );
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#endif
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/*empty cleanup in some configurations*/ ;
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}
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/* END_CASE */
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/* BEGIN_CASE */
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void get_integer( const data_t *input,
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const char *expected_hex, int expected_result )
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@ -254,16 +293,18 @@ void get_integer( const data_t *input,
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#if defined(MBEDTLS_BIGNUM_C)
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mbedtls_mpi expected_mpi;
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mbedtls_mpi actual_mpi;
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mbedtls_mpi complement;
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int expected_result_for_mpi = expected_result;
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#endif
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long expected_value;
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int expected_result_for_int = expected_result;
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int expected_result_for_mpi = expected_result;
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int val;
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int ret;
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#if defined(MBEDTLS_BIGNUM_C)
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mbedtls_mpi_init( &expected_mpi );
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mbedtls_mpi_init( &actual_mpi );
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mbedtls_mpi_init( &complement );
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#endif
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errno = 0;
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@ -275,6 +316,16 @@ void get_integer( const data_t *input,
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#endif
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) )
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{
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/* The library returns the dubious error code INVALID_LENGTH
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* for integers that are out of range. */
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expected_result_for_int = MBEDTLS_ERR_ASN1_INVALID_LENGTH;
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}
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if( expected_result == 0 && expected_value < 0 )
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{
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/* The library does not support negative INTEGERs and
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* returns the dubious error code INVALID_LENGTH.
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* Test that we preserve the historical behavior. If we
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* decide to change the behavior, we'll also change this test. */
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expected_result_for_int = MBEDTLS_ERR_ASN1_INVALID_LENGTH;
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}
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@ -300,7 +351,34 @@ void get_integer( const data_t *input,
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TEST_EQUAL( ret, expected_result_for_mpi );
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if( ret == 0 )
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{
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TEST_ASSERT( mbedtls_mpi_cmp_mpi( &actual_mpi , &expected_mpi ) == 0 );
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if( expected_value >= 0 )
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{
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TEST_ASSERT( mbedtls_mpi_cmp_mpi( &actual_mpi,
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&expected_mpi ) == 0 );
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}
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else
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{
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/* The library ignores the sign bit in ASN.1 INTEGERs
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* (which makes sense insofar as INTEGERs are sometimes
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* abused as bit strings), so the result of parsing them
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* is a positive integer such that expected_mpi +
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* actual_mpi = 2^n where n is the length of the content
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* of the INTEGER. (Leading ff octets don't matter for the
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* expected value, but they matter for the actual value.)
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* Test that we don't change from this behavior. If we
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* decide to fix the library to change the behavior on
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* negative INTEGERs, we'll fix this test code. */
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unsigned char *q = input->x + 1;
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size_t len;
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TEST_ASSERT( mbedtls_asn1_get_len( &q, input->x + input->len,
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&len ) == 0 );
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TEST_ASSERT( mbedtls_mpi_lset( &complement, 1 ) == 0 );
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TEST_ASSERT( mbedtls_mpi_shift_l( &complement, len * 8 ) == 0 );
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TEST_ASSERT( mbedtls_mpi_add_mpi( &complement, &complement,
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&expected_mpi ) == 0 );
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TEST_ASSERT( mbedtls_mpi_cmp_mpi( &complement,
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&actual_mpi ) == 0 );
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}
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TEST_ASSERT( p == input->x + input->len );
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}
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#endif
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@ -309,7 +387,9 @@ exit:
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#if defined(MBEDTLS_BIGNUM_C)
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mbedtls_mpi_free( &expected_mpi );
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mbedtls_mpi_free( &actual_mpi );
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mbedtls_mpi_free( &complement );
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#endif
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/*empty cleanup in some configurations*/ ;
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}
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/* END_CASE */
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