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/bytestring/bytestring_test.cc b/crypto/bytestring/bytestring_test.cc
index 484cd34..0877a2e 100644
--- a/crypto/bytestring/bytestring_test.cc
+++ b/crypto/bytestring/bytestring_test.cc
@@ -115,6 +115,28 @@
EXPECT_FALSE(CBS_get_u24_length_prefixed(&data, &prefixed));
}
+TEST(CBSTest, GetUntilFirst) {
+ static const uint8_t kData[] = {0, 1, 2, 3, 0, 1, 2, 3};
+ CBS data;
+ CBS_init(&data, kData, sizeof(kData));
+
+ CBS prefix;
+ EXPECT_FALSE(CBS_get_until_first(&data, &prefix, 4));
+ EXPECT_EQ(CBS_data(&data), kData);
+ EXPECT_EQ(CBS_len(&data), sizeof(kData));
+
+ ASSERT_TRUE(CBS_get_until_first(&data, &prefix, 0));
+ EXPECT_EQ(CBS_len(&prefix), 0u);
+ EXPECT_EQ(CBS_data(&data), kData);
+ EXPECT_EQ(CBS_len(&data), sizeof(kData));
+
+ ASSERT_TRUE(CBS_get_until_first(&data, &prefix, 2));
+ EXPECT_EQ(CBS_data(&prefix), kData);
+ EXPECT_EQ(CBS_len(&prefix), 2u);
+ EXPECT_EQ(CBS_data(&data), kData + 2);
+ EXPECT_EQ(CBS_len(&data), sizeof(kData) - 2);
+}
+
TEST(CBSTest, GetASN1) {
static const uint8_t kData1[] = {0x30, 2, 1, 2};
static const uint8_t kData2[] = {0x30, 3, 1, 2};
diff --git a/crypto/bytestring/cbs.c b/crypto/bytestring/cbs.c
index 5590ec88..803c97a 100644
--- a/crypto/bytestring/cbs.c
+++ b/crypto/bytestring/cbs.c
@@ -216,6 +216,14 @@
return cbs_get_length_prefixed(cbs, out, 3);
}
+int CBS_get_until_first(CBS *cbs, CBS *out, uint8_t c) {
+ const uint8_t *split = OPENSSL_memchr(CBS_data(cbs), c, CBS_len(cbs));
+ if (split == NULL) {
+ return 0;
+ }
+ return CBS_get_bytes(cbs, out, split - CBS_data(cbs));
+}
+
// parse_base128_integer reads a big-endian base-128 integer from |cbs| and sets
// |*out| to the result. This is the encoding used in DER for both high tag
// number form and OID components.
diff --git a/crypto/x509/x509_test.cc b/crypto/x509/x509_test.cc
index d897ff5..728bf7a 100644
--- a/crypto/x509/x509_test.cc
+++ b/crypto/x509/x509_test.cc
@@ -1557,6 +1557,9 @@
X509_V_ERR_PERMITTED_VIOLATION},
{GEN_DNS, "foo.example.com", ".unrelated.much.longer.name.example",
X509_V_ERR_PERMITTED_VIOLATION},
+ // NUL bytes, if not rejected, should not confuse the matching logic.
+ {GEN_DNS, std::string({'a', '\0', 'a'}), std::string({'a', '\0', 'b'}),
+ X509_V_ERR_PERMITTED_VIOLATION},
// Names must be emails.
{GEN_EMAIL, "not-an-email.example", "not-an-email.example",
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;
diff --git a/include/openssl/bytestring.h b/include/openssl/bytestring.h
index 180326d..5ef3742 100644
--- a/include/openssl/bytestring.h
+++ b/include/openssl/bytestring.h
@@ -154,6 +154,11 @@
// returns one on success and zero on error.
OPENSSL_EXPORT int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out);
+// CBS_get_until_first finds the first instance of |c| in |cbs|. If found, it
+// sets |*out| to the text before the match, advances |cbs| over it, and returns
+// one. Otherwise, it returns zero and leaves |cbs| unmodified.
+OPENSSL_EXPORT int CBS_get_until_first(CBS *cbs, CBS *out, uint8_t c);
+
// Parsing ASN.1
//
