From ed17c7c146a79100bfba5609c3889bddb14f74a2 Mon Sep 17 00:00:00 2001 From: Richard Levitte Date: Sun, 19 Jun 2016 10:55:29 +0200 Subject: [PATCH] Fix proxy certificate pathlength verification While travelling up the certificate chain, the internal proxy_path_length must be updated with the pCPathLengthConstraint value, or verification will not work properly. This corresponds to RFC 3820, 4.1.4 (a). Reviewed-by: Rich Salz Reviewed-by: Stephen Henson --- crypto/x509/x509_vfy.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/crypto/x509/x509_vfy.c b/crypto/x509/x509_vfy.c index 360664a813..15920840f9 100644 --- a/crypto/x509/x509_vfy.c +++ b/crypto/x509/x509_vfy.c @@ -533,10 +533,24 @@ static int check_chain_extensions(X509_STORE_CTX *ctx) * the next certificate must be a CA certificate. */ if (x->ex_flags & EXFLAG_PROXY) { - if (x->ex_pcpathlen != -1 && i > x->ex_pcpathlen) { - if (!verify_cb_cert(ctx, x, i, - X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED)) - return 0; + /* + * RFC3820, 4.1.3 (b)(1) stipulates that if pCPathLengthConstraint + * is less than max_path_length, the former should be copied to + * the latter, and 4.1.4 (a) stipulates that max_path_length + * should be verified to be larger than zero and decrement it. + * + * Because we're checking the certs in the reverse order, we start + * with verifying that proxy_path_length isn't larger than pcPLC, + * and copy the latter to the former if it is, and finally, + * increment proxy_path_length. + */ + if (x->ex_pcpathlen != -1) { + if (proxy_path_length > x->ex_pcpathlen) { + if (!verify_cb_cert(ctx, x, i, + X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED)) + return 0; + } + proxy_path_length = x->ex_pcpathlen; } proxy_path_length++; must_be_ca = 0; -- 2.25.1