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Remove unnecessary uses of MD2 in X.509 parsing test suite #2430

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merged 13 commits into from Jun 14, 2019

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hanno-becker
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As has been reported in #821, many test cases in the X.509 parsing test suite use MD2 in places where an arbitrary hash algorithm would be supported. This is bad for two reasons: Firstly, it shows bad practice using a weak digest, and secondly, it significantly reduces negative test coverage in the default configuration which doesn't have MD2 enabled.

This PR changes the tests to use SHA-256 in place of MD2 in those instances where a general hash algorithm is allowed (and we're not specifically testing support for MD2).

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(Partial review so far.)

@@ -12,7 +12,7 @@ x509_cert_info:"data_files/test-ca.crt":"cert. version \: 3\nserial number

X509 Certificate information MD2 Digest
depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_MD2_C
x509_cert_info:"data_files/cert_md2.crt":"cert. version \: 3\nserial number \: 09\nissuer name \: C=NL, O=PolarSSL, CN=PolarSSL Test CA\nsubject name \: C=NL, O=PolarSSL, CN=PolarSSL Cert MD2\nissued on \: 2009-07-12 10\:56\:59\nexpires on \: 2011-07-12 10\:56\:59\nsigned using \: RSA with MD2\nRSA key size \: 2048 bits\nbasic constraints \: CA=false\n"
x509_cert_info:"data_files/cert_md2.crt":"cert. version \: 3\nserial number \: 09\nissuer name \: C=NL, O=PolarSSL, CN=PolarSSL Test CA\nsubject name \: C=NL, O=PolarSSL, CN=PolarSSL Cert MD2\nissued on \: 2009-07-12 10\:56\:59\nexpires on \: 2011-07-12 10\:56\:59\nsigned using \: RSA with SHA-256\nRSA key size \: 2048 bits\nbasic constraints \: CA=false\n"
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Do you really mean SHA-256 here? The name of the test case seems pretty explicit about testing MD2. (A few other occurrences below.)

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@mpg No, I'm sorry, that was careless.

@hanno-becker hanno-becker added needs-work and removed needs-review Every commit must be reviewed by at least two team members, labels Feb 12, 2019
@hanno-becker hanno-becker added needs-review Every commit must be reviewed by at least two team members, and removed needs-work labels Feb 12, 2019
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@mpg Could you take another look?

AndrzejKurek
AndrzejKurek previously approved these changes Feb 13, 2019
Patater
Patater previously approved these changes Feb 19, 2019
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LGTM

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Nothing has changed since @AndrzejKurek's approval - I think it got lost when @mpg re-requested it. Was there a particular reason for that, @mpg?

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mpg commented Feb 19, 2019

I don't remember doing that, so probably no particular reason ^^

k-stachowiak
k-stachowiak previously approved these changes Feb 20, 2019
@hanno-becker hanno-becker removed the needs-review Every commit must be reviewed by at least two team members, label Feb 22, 2019
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Ping @Patater for gatekeeping.

@Patater Patater added the approved Design and code approved - may be waiting for CI or backports label Feb 22, 2019
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mpg commented Feb 28, 2019

This fixes #821 which is labeled as a bug, so relabeling this with "bug", and hence needing backports.

@mpg mpg added the bug label Feb 28, 2019
AndrzejKurek
AndrzejKurek previously approved these changes Jun 3, 2019
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The changes to the test data are fine, but we no longer have any test for a certificate that uses an MD2 digest. Please add a “Valid Cert MD2 Digest” test case that's similar to the “Valid Cert MD4 Digest“.

@gilles-peskine-arm gilles-peskine-arm removed the request for review from Patater June 3, 2019 12:29
@gilles-peskine-arm gilles-peskine-arm added needs-work and removed needs-ci Needs to pass CI tests labels Jun 3, 2019
The example programs programs/x509/cert_req and programs/x509/cert_write
(demonstrating the use of X.509 CSR and CRT writing functionality)
previously didn't support MD2 signatures.

For testing purposes, this commit adds support for MD2 to cert_req,
and support for MD2 and MD4 to cert_write.
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@gilles-peskine-arm Thanks for your review.

The PR doesn't make the situation worse, because it only replaces MD2 by SHA-256 in parsing tests, and a MD2-specific parsing test remains ("X509 Certification information MD2 digest").

Nonetheless, you have a point that there's a pre-existing gap in the tests in that we don't exercise verification of an MD2 signed certificate, and I've added an analogue of "Valid Cert MD4 Digest" for MD2.

Also, I noticed that these tests don't expect success because they use a profile which forbids MDx, and I've added three tests which use a test-only profile allowing all MDs, so that we now also cover successful verification of MDx-signed CRTs.

@gilles-peskine-arm @AndrzejKurek Can you please re-review?

@@ -2511,7 +2511,7 @@
* it, and considering stronger message digests instead.
*
*/
//#define MBEDTLS_MD2_C
#define MBEDTLS_MD2_C
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You accidentally committed a modified config.h. Feel free to rebase the offending commit as far as I'm concerned.

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Damn... sorry

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Fixed.

The X.509 parsing test suite test_suite_x509parse contains a test
exercising X.509 verification for a valid MD4/MD5 certificate in a
profile which doesn't allow MD4/MD5. This commit adds an analogous
test for MD2.
@hanno-becker hanno-becker removed the needs-review Every commit must be reviewed by at least two team members, label Jun 4, 2019
@Patater Patater added the approved Design and code approved - may be waiting for CI or backports label Jun 12, 2019
@Patater Patater added this to To do in Mbed TLS PRs via automation Jun 13, 2019
@Patater Patater merged commit 024b53a into Mbed-TLS:development Jun 14, 2019
Mbed TLS PRs automation moved this from To do to Done Jun 14, 2019
@daverodgman daverodgman removed this from Done in Mbed TLS PRs Mar 30, 2022
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8 participants