imap-send: move common code into function host_matches()

Move the ASN1_STRING access, the associated cast and the check for
embedded NUL bytes into host_matches() to simplify both callers.

Reformulate the NUL check using memchr() and add a comment to make it
more obvious what it is about.

Signed-off-by: Beat Bolli <dev+git@drbeat.li>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/imap-send.c b/imap-send.c
index 2a904314dd4bfb91e1b0c6126a03a83ea2bc1d85..af02c6a689495e8c64faa78c3772ceb6e7fae5cc 100644 (file)
--- a/imap-send.c
+++ b/imap-send.c
@@ -219,8 +219,14 @@ static int ssl_socket_connect(struct imap_socket *sock UNUSED,
 
 #else
 
-static int host_matches(const char *host, const char *pattern)
+static int host_matches(const char *host, const ASN1_STRING *asn1_str)
 {
+       const char *pattern = (const char *)ASN1_STRING_get0_data(asn1_str);
+
+       /* embedded NUL characters may open a security hole */
+       if (memchr(pattern, '\0', ASN1_STRING_length(asn1_str)))
+           return 0;
+
        if (pattern[0] == '*' && pattern[1] == '.') {
                pattern += 2;
                if (!(host = strchr(host, '.')))
@@ -252,10 +258,7 @@ static int verify_hostname(X509 *cert, const char *hostname)
                        GENERAL_NAME *subj_alt_name = sk_GENERAL_NAME_value(subj_alt_names, i);
                        ASN1_STRING *subj_alt_str = GENERAL_NAME_get0_value(subj_alt_name, &ntype);
 
-                       if (ntype == GEN_DNS &&
-                           strlen((const char *)ASN1_STRING_get0_data(subj_alt_str)) ==
-                                   ASN1_STRING_length(subj_alt_str) &&
-                           host_matches(hostname, (const char *)ASN1_STRING_get0_data(subj_alt_str)))
+                       if (ntype == GEN_DNS && host_matches(hostname, subj_alt_str))
                                found = 1;
                }
                sk_GENERAL_NAME_pop_free(subj_alt_names, GENERAL_NAME_free);
@@ -270,8 +273,7 @@ static int verify_hostname(X509 *cert, const char *hostname)
            (cname_entry = X509_NAME_get_entry(subj, i)) == NULL ||
            (cname = X509_NAME_ENTRY_get_data(cname_entry)) == NULL)
                return error("cannot get certificate common name");
-       if (strlen((const char *)ASN1_STRING_get0_data(cname)) == ASN1_STRING_length(cname) &&
-           host_matches(hostname, (const char *)ASN1_STRING_get0_data(cname)))
+       if (host_matches(hostname, cname))
                return 0;
        return error("certificate owner '%s' does not match hostname '%s'",
                     ASN1_STRING_get0_data(cname), hostname);