added ubuntu-security to the bug, just for quick review to make sure they don't object to the patch
I can sponsor this to -updates if there's no objection -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssl in Ubuntu. https://bugs.launchpad.net/bugs/1926254 Title: x509 Certificate verification fails when basicConstraints=CA:FALSE,pathlen:0 on self-signed leaf certs Status in openssl package in Ubuntu: Fix Released Status in openssl source package in Focal: In Progress Status in openssl source package in Groovy: In Progress Status in openssl source package in Hirsute: Fix Released Bug description: [Impact] In openssl 1.1.1f, the below commit was merged: commit ba4356ae4002a04e28642da60c551877eea804f7 Author: Bernd Edlinger <bernd.edlin...@hotmail.de> Date: Sat Jan 4 15:54:53 2020 +0100 Subject: Fix error handling in x509v3_cache_extensions and related functions Link: https://github.com/openssl/openssl/commit/ba4356ae4002a04e28642da60c551877eea804f7 This introduced a regression which caused certificate validation to fail when certificates violate RFC 5280 [1], namely, when a certificate has "basicConstraints=CA:FALSE,pathlen:0". This combination is commonly seen by self-signed leaf certificates with an intermediate CA before the root CA. Because of this, openssl 1.1.1f rejects these certificates and they cannot be used in the system certificate store, and ssl connections fail when you try to use them to connect to a ssl endpoint. The error you see when you try verify is: $ openssl verify -CAfile CA/rootCA_cert.pem -untrusted CA/subCA_cert.pem user1_cert.pem error 20 at 0 depth lookup: unable to get local issuer certificate error user1_cert.pem: verification failed The exact same certificates work fine on Xenial, Bionic and Hirsute. [1] https://tools.ietf.org/html/rfc5280.html [Testcase] We will create our own root CA, intermediate CA and leaf server certificate. Create necessary directories: $ mkdir reproducer $ cd reproducer $ mkdir CA Write openssl configuration files to disk for each CA and cert: $ cat << EOF >> rootCA.cnf [ req ] prompt = no distinguished_name = req_distinguished_name x509_extensions = usr_cert [ req_distinguished_name ] C = DE O = Test Org CN = Test RSA PSS Root-CA [ usr_cert ] basicConstraints = critical,CA:TRUE keyUsage = critical,keyCertSign,cRLSign subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always EOF $ cat << EOF >> subCA.cnf [ req ] prompt = no distinguished_name = req_distinguished_name x509_extensions = usr_cert [ req_distinguished_name ] C = DE O = Test Org CN = Test RSA PSS Sub-CA [ usr_cert ] basicConstraints = critical,CA:TRUE,pathlen:0 keyUsage = critical,keyCertSign,cRLSign subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always EOF $ cat << EOF >> user.cnf [ req ] prompt = no distinguished_name = req_distinguished_name x509_extensions = usr_cert [ req_distinguished_name ] C = DE O = Test Org CN = Test User [ usr_cert ] basicConstraints = critical,CA:FALSE,pathlen:0 keyUsage = critical,digitalSignature,keyAgreement extendedKeyUsage = clientAuth,serverAuth subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always EOF Then generate the necessary RSA keys and form certificates: $ openssl genpkey -algorithm RSA-PSS -out rootCA_key.pem -pkeyopt rsa_keygen_bits:2048 $ openssl req -config rootCA.cnf -set_serial 01 -new -batch -sha256 -nodes -x509 -days 9125 -out CA/rootCA_cert.pem -key rootCA_key.pem -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-1 $ openssl genpkey -algorithm RSA-PSS -out subCA_key.pem -pkeyopt rsa_keygen_bits:2048 $ openssl req -config subCA.cnf -new -out subCA_req.pem -key subCA_key.pem -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-1 $ openssl x509 -req -sha256 -in subCA_req.pem -CA CA/rootCA_cert.pem -CAkey rootCA_key.pem -out CA/subCA_cert.pem -CAserial rootCA_serial.txt -CAcreateserial -extfile subCA.cnf -extensions usr_cert -days 4380 -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-1 $ c_rehash CA $ openssl genpkey -algorithm RSA-PSS -out user1_key.pem -pkeyopt rsa_keygen_bits:2048 $ openssl req -config user.cnf -new -out user1_req.pem -key user1_key.pem -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-1 $ openssl x509 -req -sha256 -in user1_req.pem -CA CA/subCA_cert.pem -CAkey subCA_key.pem -out user1_cert.pem -CAserial subCA_serial.txt -CAcreateserial -extfile user.cnf -extensions usr_cert -days 1825 -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-1 Now, let's try verify the generated certificates: $ openssl version OpenSSL 1.1.1f 31 Mar 2020 $ openssl verify -CAfile CA/rootCA_cert.pem -untrusted CA/subCA_cert.pem user1_cert.pem error 20 at 0 depth lookup: unable to get local issuer certificate error user1_cert.pem: verification failed There are test packages available in the following ppa: https://launchpad.net/~mruffell/+archive/ubuntu/sf308725-test If you install these test packages, and attempt to verify, things work as planned. $ openssl verify -CAfile CA/rootCA_cert.pem -untrusted CA/subCA_cert.pem user1_cert.pem user1_cert.pem: OK [Where problems could occur] If a regression were to occur, it would occur around x509 certificate parsing and validation. It may cause certificates which had previously passed to fail, or certificates which failed to pass. It could potentially cause all certificates to fail or pass. Since this is the openssl package and the package is security- critical, this will need a lot of validation, testing, and likely a review by the security team. One of the commits which fixes the issue adds two testcases to the openssl testsuite, which tests the "CA:FALSE, pathlen:0" certificates with and without -x509_strict, and tests to see if it passes without, and fails with. [Other info] This was reported in the upstream issue #11456 [2]: [2] https://github.com/openssl/openssl/issues/11456 I believe these three commits fix the issue: commit 00a0da2f021e6a0bc9519a6a9e5be66d45e6fc91 Author: Tomas Mraz <tm...@fedoraproject.org> Date: Thu Apr 2 15:56:12 2020 +0200 Subject: Allow certificates with Basic Constraints CA:false, pathlen:0 Link: https://github.com/openssl/openssl/commit/00a0da2f021e6a0bc9519a6a9e5be66d45e6fc91 commit 29e94f285f7f05b1aec6fa275e320bc5fa37ab1e Author: Tomas Mraz <tm...@fedoraproject.org> Date: Thu Apr 2 17:31:21 2020 +0200 Subject: Set X509_V_ERR_INVALID_EXTENSION error for invalid basic constraints Link: https://github.com/openssl/openssl/commit/29e94f285f7f05b1aec6fa275e320bc5fa37ab1e commit e78f2a8f269a4dcf820ca994e2b89b77972d79e1 Author: Tomas Mraz <tm...@fedoraproject.org> Date: Fri Apr 3 10:24:40 2020 +0200 Subject: Add test cases for the non CA certificate with pathlen:0 Link: https://github.com/openssl/openssl/commit/e78f2a8f269a4dcf820ca994e2b89b77972d79e1 These landed in openssl 1.1.1g, and hirsute already has these fixes. 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