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Guard from undefined behaviour in case of an INT_MAX max_pathlen

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When parsing a certificate with the basic constraints extension
the max_pathlen that was read from it was incremented regardless
of its value. However, if the max_pathlen is equal to INT_MAX (which
is highly unlikely), an undefined behaviour would occur.
This commit adds a check to ensure that such value is not accepted
as valid. Relevant tests for INT_MAX and INT_MAX-1 are also introduced.
Certificates added in this commit were generated using the
test_suite_x509write, function test_x509_crt_check. Input data taken 
from the "Certificate write check Server1 SHA1" test case, so the generated
files are like the "server1.crt", but with the "is_ca" field set to 1 and
max_pathlen as described by the file name.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
This commit is contained in:
Andrzej Kurek 2020-04-14 09:49:52 -04:00
parent 8ea6872889
commit 1605074f97
No known key found for this signature in database
GPG key ID: 89A90840DC388527
4 changed files with 54 additions and 0 deletions
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6
library/x509_crt.c
View file

@ -524,6 +524,12 @@ static int x509_get_basic_constraints( unsigned char **p,
return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
/* Do not accept max_pathlen equal to INT_MAX to avoid a signed integer
* overflow, which is an undefined behavior. */
if( *max_pathlen == INT_MAX )
return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
MBEDTLS_ERR_ASN1_INVALID_LENGTH );
(*max_pathlen)++;
return( 0 );

20
tests/data_files/server1_pathlen_int_max-1.crt Normal file
View file

@ -0,0 +1,20 @@
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

20
tests/data_files/server1_pathlen_int_max.crt Normal file
View file

@ -0,0 +1,20 @@
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

8
tests/suites/test_suite_x509parse.data
View file

@ -1798,6 +1798,14 @@ X509 CRT ASN1 (TBS, inv extBasicConstraint, no pathlen length)
depends_on:MBEDTLS_RSA_C:MBEDTLS_SHA256_C
x509parse_crt:"3081b030819aa0030201028204deadbeef300d06092a864886f70d01010b0500300c310a30080600130454657374301c170c303930313031303030303030170c303931323331323335393539300c310a30080600130454657374302a300d06092A864886F70D010101050003190030160210ffffffffffffffffffffffffffffffff0202ffffa100a200a314301230100603551d130101010406300402010102300d06092a864886f70d01010b0500030200ff":"":MBEDTLS_ERR_X509_INVALID_EXTENSIONS + MBEDTLS_ERR_ASN1_OUT_OF_DATA
X509 CRT ASN1 (inv extBasicConstraint, pathlen is INT_MAX)
depends_on:MBEDTLS_RSA_C:MBEDTLS_SHA256_C:MBEDTLS_SHA1_C
x509parse_crt_file:"data_files/server1_pathlen_int_max.crt":MBEDTLS_ERR_X509_INVALID_EXTENSIONS + MBEDTLS_ERR_ASN1_INVALID_LENGTH
X509 CRT ASN1 (pathlen is INT_MAX-1)
depends_on:MBEDTLS_RSA_C:MBEDTLS_SHA256_C:MBEDTLS_SHA1_C
x509parse_crt_file:"data_files/server1_pathlen_int_max-1.crt":0
X509 CRT ASN1 (TBS, inv extBasicConstraint, pathlen inv length encoding)
depends_on:MBEDTLS_RSA_C:MBEDTLS_SHA256_C
x509parse_crt:"3081b130819ba0030201028204deadbeef300d06092a864886f70d01010b0500300c310a30080600130454657374301c170c303930313031303030303030170c303931323331323335393539300c310a30080600130454657374302a300d06092A864886F70D010101050003190030160210ffffffffffffffffffffffffffffffff0202ffffa100a200a315301330110603551d13010101040730050201010285300d06092a864886f70d01010b0500030200ff":"":MBEDTLS_ERR_X509_INVALID_EXTENSIONS + MBEDTLS_ERR_ASN1_INVALID_LENGTH