From 75216f239f663f66ea0358a6fc2354d39909c1e3 Mon Sep 17 00:00:00 2001 From: Henry Kleynhans Date: Wed, 22 Dec 2021 15:06:00 +0000 Subject: [PATCH] crypto: only verify CA certs in chain of trust MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The CA file provided to qemu may contain CA certificates which do not form part of the chain of trust for the specific certificate we are sanity checking. This patch changes the sanity checking from validating every CA certificate to only checking the CA certificates which are part of the chain of trust (issuer chain). Other certificates are ignored. Reviewed-by: Daniel P. Berrangé Reviewed-by: Eric Blake Signed-off-by: Henry Kleynhans [DB: changed 'int' to 'bool' in 'checking_issuer' variable] Signed-off-by: Daniel P. Berrangé --- crypto/tlscredsx509.c | 57 ++++++++++++++++++++++++--- tests/unit/test-crypto-tlscredsx509.c | 25 +++++++++++- 2 files changed, 75 insertions(+), 7 deletions(-) diff --git a/crypto/tlscredsx509.c b/crypto/tlscredsx509.c index cd1f5044715..3df2a33b0b9 100644 --- a/crypto/tlscredsx509.c +++ b/crypto/tlscredsx509.c @@ -315,6 +315,51 @@ qcrypto_tls_creds_check_cert(QCryptoTLSCredsX509 *creds, return 0; } +static int +qcrypto_tls_creds_check_authority_chain(QCryptoTLSCredsX509 *creds, + gnutls_x509_crt_t cert, + gnutls_x509_crt_t *cacerts, + unsigned int ncacerts, + const char *cacertFile, + bool isServer, + bool isCA, + Error **errp) +{ + gnutls_x509_crt_t *cert_to_check = &cert; + bool checking_issuer = true; + int retval = 0; + + while (checking_issuer) { + checking_issuer = false; + + if (gnutls_x509_crt_check_issuer(*cert_to_check, + *cert_to_check)) { + /* + * The cert is self-signed indicating we have + * reached the root of trust. + */ + return qcrypto_tls_creds_check_cert( + creds, *cert_to_check, cacertFile, + isServer, isCA, errp); + } + for (int i = 0; i < ncacerts; i++) { + if (gnutls_x509_crt_check_issuer(*cert_to_check, + cacerts[i])) { + retval = qcrypto_tls_creds_check_cert( + creds, cacerts[i], cacertFile, + isServer, isCA, errp); + if (retval < 0) { + return retval; + } + cert_to_check = &cacerts[i]; + checking_issuer = true; + break; + } + } + } + + return -1; +} static int qcrypto_tls_creds_check_cert_pair(gnutls_x509_crt_t cert, @@ -499,12 +544,12 @@ qcrypto_tls_creds_x509_sanity_check(QCryptoTLSCredsX509 *creds, goto cleanup; } - for (i = 0; i < ncacerts; i++) { - if (qcrypto_tls_creds_check_cert(creds, - cacerts[i], cacertFile, - isServer, true, errp) < 0) { - goto cleanup; - } + if (cert && + qcrypto_tls_creds_check_authority_chain(creds, cert, + cacerts, ncacerts, + cacertFile, isServer, + true, errp) < 0) { + goto cleanup; } if (cert && ncacerts && diff --git a/tests/unit/test-crypto-tlscredsx509.c b/tests/unit/test-crypto-tlscredsx509.c index 3c25d75ca1f..a7ea5f422d5 100644 --- a/tests/unit/test-crypto-tlscredsx509.c +++ b/tests/unit/test-crypto-tlscredsx509.c @@ -589,6 +589,12 @@ int main(int argc, char **argv) true, true, GNUTLS_KEY_KEY_CERT_SIGN, false, false, NULL, NULL, 0, 0); + TLS_CERT_REQ(cacertlevel1creq_invalid, cacertrootreq, + "UK", "qemu level 1c invalid", NULL, NULL, NULL, NULL, + true, true, true, + true, true, GNUTLS_KEY_KEY_CERT_SIGN, + false, false, NULL, NULL, + 360, 400); TLS_CERT_REQ(cacertlevel2areq, cacertlevel1areq, "UK", "qemu level 2a", NULL, NULL, NULL, NULL, true, true, true, @@ -617,16 +623,32 @@ int main(int argc, char **argv) cacertlevel2areq.crt, }; + test_tls_write_cert_chain(WORKDIR "cacertchain-ctx.pem", certchain, G_N_ELEMENTS(certchain)); + gnutls_x509_crt_t certchain_with_invalid[] = { + cacertrootreq.crt, + cacertlevel1areq.crt, + cacertlevel1breq.crt, + cacertlevel1creq_invalid.crt, + cacertlevel2areq.crt, + }; + + test_tls_write_cert_chain(WORKDIR "cacertchain-with-invalid-ctx.pem", + certchain_with_invalid, + G_N_ELEMENTS(certchain_with_invalid)); + TLS_TEST_REG(chain1, true, WORKDIR "cacertchain-ctx.pem", servercertlevel3areq.filename, false); TLS_TEST_REG(chain2, false, WORKDIR "cacertchain-ctx.pem", clientcertlevel2breq.filename, false); + TLS_TEST_REG(certchainwithexpiredcert, false, + WORKDIR "cacertchain-with-invalid-ctx.pem", + clientcertlevel2breq.filename, false); /* Some missing certs - first two are fatal, the last * is ok @@ -640,7 +662,6 @@ int main(int argc, char **argv) TLS_TEST_REG(missingclient, false, cacert1req.filename, "clientcertdoesnotexist.pem", false); - ret = g_test_run(); test_tls_discard_cert(&cacertreq); @@ -694,10 +715,12 @@ int main(int argc, char **argv) test_tls_discard_cert(&cacertrootreq); test_tls_discard_cert(&cacertlevel1areq); test_tls_discard_cert(&cacertlevel1breq); + test_tls_discard_cert(&cacertlevel1creq_invalid); test_tls_discard_cert(&cacertlevel2areq); test_tls_discard_cert(&servercertlevel3areq); test_tls_discard_cert(&clientcertlevel2breq); unlink(WORKDIR "cacertchain-ctx.pem"); + unlink(WORKDIR "cacertchain-with-invalid-ctx.pem"); test_tls_cleanup(KEYFILE); rmdir(WORKDIR); -- 2.47.3