Remove support for constructed strings in crypto/asn1.
Constructed strings are a BER mechanism where a string type can be
represented as a tree of constructed nodes and primitive leaves, that
then have to be concatenated by the parser. This is prohibited in DER
and a significant source of complexity in our parser.
Note this change does not affect our PKCS#7 and PKCS#12 parsers (where
BER is sadly necessary for interop) because those use CBS.
Update-Note: Invalid certificates (and the few external structures using
asn1t.h) with BER constructed strings will now be rejected.
Bug: 354
Change-Id: I5a8ee028ec89ed4f2d5c099a0588f2029b864580
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/50286
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/x509/x509_test.cc b/crypto/x509/x509_test.cc
index 36d2a27..477e5a1 100644
--- a/crypto/x509/x509_test.cc
+++ b/crypto/x509/x509_test.cc
@@ -3463,3 +3463,38 @@
X509_VERIFY_PARAM_clear_flags(param, X509_V_FLAG_TRUSTED_FIRST);
}));
}
+
+// kConstructedBitString is an X.509 certificate where the signature is encoded
+// as a BER constructed BIT STRING. Note that, while OpenSSL's parser accepts
+// this input, it interprets the value incorrectly.
+static const char kConstructedBitString[] = R"(
+-----BEGIN CERTIFICATE-----
+MIIBJTCBxqADAgECAgIE0jAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDEwRUZXN0MCAX
+DTAwMDEwMTAwMDAwMFoYDzIxMDAwMTAxMDAwMDAwWjAPMQ0wCwYDVQQDEwRUZXN0
+MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE5itp4r9ln5e+Lx4NlIpM1Zdrt6ke
+DUb73ampHp3culoB59aXqAoY+cPEox5W4nyDSNsWGhz1HX7xlC1Lz3IiwaMQMA4w
+DAYDVR0TBAUwAwEB/zAKBggqhkjOPQQDAiNOAyQAMEYCIQCp0iIX5s30KXjihR4g
+KnJpd3seqGlVRqCVgrD0KGYDJgA1QAIhAKkx0vR82QU0NtHDD11KX/LuQF2T+2nX
+oeKp5LKAbMVi
+-----END CERTIFICATE-----
+)";
+
+// kConstructedOctetString is an X.509 certificate where an extension is encoded
+// as a BER constructed OCTET STRING.
+static const char kConstructedOctetString[] = R"(
+-----BEGIN CERTIFICATE-----
+MIIBJDCByqADAgECAgIE0jAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDEwRUZXN0MCAX
+DTAwMDEwMTAwMDAwMFoYDzIxMDAwMTAxMDAwMDAwWjAPMQ0wCwYDVQQDEwRUZXN0
+MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE5itp4r9ln5e+Lx4NlIpM1Zdrt6ke
+DUb73ampHp3culoB59aXqAoY+cPEox5W4nyDSNsWGhz1HX7xlC1Lz3IiwaMUMBIw
+EAYDVR0TJAkEAzADAQQCAf8wCgYIKoZIzj0EAwIDSQAwRgIhAKnSIhfmzfQpeOKF
+HiAqcml3ex6oaVVGoJWCsPQoZjVAAiEAqTHS9HzZBTQ20cMPXUpf8u5AXZP7adeh
+4qnksoBsxWI=
+-----END CERTIFICATE-----
+)";
+
+TEST(X509Test, BER) {
+ // Constructed strings are forbidden in DER.
+ EXPECT_FALSE(CertFromPEM(kConstructedBitString));
+ EXPECT_FALSE(CertFromPEM(kConstructedOctetString));
+}
