Rewrite name constraints matching with CBS.
See also 8393de42498f8be75cf0353f5c9f906a43a748d2 from upstream and
CBS-2021-3712. But rather than do that, I've rewritten it with CBS, so
it's a bit clearer. The previous commit added tests.
Change-Id: Ie52e28f07b9bf805c8730eab7be5d40cb5d558b6
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49008
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/x509v3/v3_ncons.c b/crypto/x509v3/v3_ncons.c
index 593a520..35c826e 100644
--- a/crypto/x509v3/v3_ncons.c
+++ b/crypto/x509v3/v3_ncons.c
@@ -389,25 +389,73 @@
return X509_V_OK;
}
+static int starts_with(const CBS *cbs, uint8_t c)
+{
+ return CBS_len(cbs) > 0 && CBS_data(cbs)[0] == c;
+}
+
+static int equal_case(const CBS *a, const CBS *b)
+{
+ if (CBS_len(a) != CBS_len(b)) {
+ return 0;
+ }
+ /* Note we cannot use |OPENSSL_strncasecmp| because that would stop
+ * iterating at NUL. */
+ const uint8_t *a_data = CBS_data(a), *b_data = CBS_data(b);
+ for (size_t i = 0; i < CBS_len(a); i++) {
+ if (OPENSSL_tolower(a_data[i]) != OPENSSL_tolower(b_data[i])) {
+ return 0;
+ }
+ }
+ return 1;
+}
+
+static int has_suffix_case(const CBS *a, const CBS *b)
+{
+ if (CBS_len(a) < CBS_len(b)) {
+ return 0;
+ }
+ CBS copy = *a;
+ CBS_skip(©, CBS_len(a) - CBS_len(b));
+ return equal_case(©, b);
+}
+
static int nc_dns(ASN1_IA5STRING *dns, ASN1_IA5STRING *base)
{
- char *baseptr = (char *)base->data;
- char *dnsptr = (char *)dns->data;
+ CBS dns_cbs, base_cbs;
+ CBS_init(&dns_cbs, dns->data, dns->length);
+ CBS_init(&base_cbs, base->data, base->length);
+
/* Empty matches everything */
- if (!*baseptr)
+ if (CBS_len(&base_cbs) == 0) {
return X509_V_OK;
+ }
+
+ /* If |base_cbs| begins with a '.', do a simple suffix comparison. This is
+ * not part of RFC5280, but is part of OpenSSL's original behavior. */
+ if (starts_with(&base_cbs, '.')) {
+ if (has_suffix_case(&dns_cbs, &base_cbs)) {
+ return X509_V_OK;
+ }
+ return X509_V_ERR_PERMITTED_VIOLATION;
+ }
+
/*
* Otherwise can add zero or more components on the left so compare RHS
* and if dns is longer and expect '.' as preceding character.
*/
- if (dns->length > base->length) {
- dnsptr += dns->length - base->length;
- if (*baseptr != '.' && dnsptr[-1] != '.')
+ if (CBS_len(&dns_cbs) > CBS_len(&base_cbs)) {
+ uint8_t dot;
+ if (!CBS_skip(&dns_cbs, CBS_len(&dns_cbs) - CBS_len(&base_cbs) - 1) ||
+ !CBS_get_u8(&dns_cbs, &dot) ||
+ dot != '.') {
return X509_V_ERR_PERMITTED_VIOLATION;
+ }
}
- if (OPENSSL_strcasecmp(baseptr, dnsptr))
+ if (!equal_case(&dns_cbs, &base_cbs)) {
return X509_V_ERR_PERMITTED_VIOLATION;
+ }
return X509_V_OK;
@@ -415,86 +463,94 @@
static int nc_email(ASN1_IA5STRING *eml, ASN1_IA5STRING *base)
{
- const char *baseptr = (char *)base->data;
- const char *emlptr = (char *)eml->data;
+ CBS eml_cbs, base_cbs;
+ CBS_init(&eml_cbs, eml->data, eml->length);
+ CBS_init(&base_cbs, base->data, base->length);
- const char *baseat = strchr(baseptr, '@');
- const char *emlat = strchr(emlptr, '@');
- if (!emlat)
+ /* TODO(davidben): In OpenSSL 1.1.1, this switched from the first '@' to the
+ * last one. Match them here, or perhaps do an actual parse. Looks like
+ * multiple '@'s may be allowed in quoted strings. */
+ CBS eml_local, base_local;
+ if (!CBS_get_until_first(&eml_cbs, &eml_local, '@')) {
return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
+ }
+ int base_has_at = CBS_get_until_first(&base_cbs, &base_local, '@');
+
/* Special case: inital '.' is RHS match */
- if (!baseat && (*baseptr == '.')) {
- if (eml->length > base->length) {
- emlptr += eml->length - base->length;
- if (!OPENSSL_strcasecmp(baseptr, emlptr))
- return X509_V_OK;
+ if (!base_has_at && starts_with(&base_cbs, '.')) {
+ if (has_suffix_case(&eml_cbs, &base_cbs)) {
+ return X509_V_OK;
}
return X509_V_ERR_PERMITTED_VIOLATION;
}
/* If we have anything before '@' match local part */
-
- if (baseat) {
- if (baseat != baseptr) {
- if ((baseat - baseptr) != (emlat - emlptr))
- return X509_V_ERR_PERMITTED_VIOLATION;
+ if (base_has_at) {
+ /* TODO(davidben): This interprets a constraint of "@example.com" as
+ * "example.com", which is not part of RFC5280. */
+ if (CBS_len(&base_local) > 0) {
/* Case sensitive match of local part */
- if (strncmp(baseptr, emlptr, emlat - emlptr))
+ if (!CBS_mem_equal(&base_local, CBS_data(&eml_local),
+ CBS_len(&eml_local))) {
return X509_V_ERR_PERMITTED_VIOLATION;
+ }
}
/* Position base after '@' */
- baseptr = baseat + 1;
+ assert(starts_with(&base_cbs, '@'));
+ CBS_skip(&base_cbs, 1);
}
- emlptr = emlat + 1;
+
/* Just have hostname left to match: case insensitive */
- if (OPENSSL_strcasecmp(baseptr, emlptr))
+ assert(starts_with(&eml_cbs, '@'));
+ CBS_skip(&eml_cbs, 1);
+ if (!equal_case(&base_cbs, &eml_cbs)) {
return X509_V_ERR_PERMITTED_VIOLATION;
+ }
return X509_V_OK;
-
}
static int nc_uri(ASN1_IA5STRING *uri, ASN1_IA5STRING *base)
{
- const char *baseptr = (char *)base->data;
- const char *hostptr = (char *)uri->data;
- const char *p = strchr(hostptr, ':');
- int hostlen;
+ CBS uri_cbs, base_cbs;
+ CBS_init(&uri_cbs, uri->data, uri->length);
+ CBS_init(&base_cbs, base->data, base->length);
+
/* Check for foo:// and skip past it */
- if (!p || (p[1] != '/') || (p[2] != '/'))
+ CBS scheme;
+ uint8_t byte;
+ if (!CBS_get_until_first(&uri_cbs, &scheme, ':') ||
+ !CBS_skip(&uri_cbs, 1) || // Skip the colon
+ !CBS_get_u8(&uri_cbs, &byte) || byte != '/' ||
+ !CBS_get_u8(&uri_cbs, &byte) || byte != '/') {
return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
- hostptr = p + 3;
+ }
- /* Determine length of hostname part of URI */
+ /* Look for a port indicator as end of hostname first. Otherwise look for
+ * trailing slash, or the end of the string.
+ * TODO(davidben): This is not a correct URI parser and mishandles IPv6
+ * literals. */
+ CBS host;
+ if (!CBS_get_until_first(&uri_cbs, &host, ':') &&
+ !CBS_get_until_first(&uri_cbs, &host, '/')) {
+ host = uri_cbs;
+ }
- /* Look for a port indicator as end of hostname first */
-
- p = strchr(hostptr, ':');
- /* Otherwise look for trailing slash */
- if (!p)
- p = strchr(hostptr, '/');
-
- if (!p)
- hostlen = strlen(hostptr);
- else
- hostlen = p - hostptr;
-
- if (hostlen == 0)
+ if (CBS_len(&host) == 0) {
return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
+ }
/* Special case: inital '.' is RHS match */
- if (*baseptr == '.') {
- if (hostlen > base->length) {
- p = hostptr + hostlen - base->length;
- if (!OPENSSL_strncasecmp(p, baseptr, base->length))
- return X509_V_OK;
+ if (starts_with(&base_cbs, '.')) {
+ if (has_suffix_case(&host, &base_cbs)) {
+ return X509_V_OK;
}
return X509_V_ERR_PERMITTED_VIOLATION;
}
- if ((base->length != (int)hostlen)
- || OPENSSL_strncasecmp(hostptr, baseptr, hostlen))
+ if (!equal_case(&base_cbs, &host)) {
return X509_V_ERR_PERMITTED_VIOLATION;
+ }
return X509_V_OK;
