Check AlgorithmIdentifier parameters for RSA and ECDSA signatures.

This aligns with the Chromium certificate verifier, which allows NULL or
empty for RSA and requires empty for ECDSA.

Bug: 342
Change-Id: I34acf68f63b4d133dd47b73144b2f27224c499ee
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/41804
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

crypto/x509/algorithm.c

@@ -142,6 +142,14 @@ int x509_digest_verify_init(EVP_MD_CTX *ctx, X509_ALGOR *sigalg,
     return 0;
   }
 
+  /* RSA signature algorithms include an explicit NULL parameter but we also
+   * accept omitted values for compatibility. Other algorithms must omit it. */
+  if (sigalg->parameter != NULL && (pkey_nid != EVP_PKEY_RSA ||
+                                    sigalg->parameter->type != V_ASN1_NULL)) {
+    OPENSSL_PUT_ERROR(X509, X509_R_INVALID_PARAMETER);
+    return 0;
+  }
+
   /* Otherwise, initialize with the digest from the OID. */
   const EVP_MD *digest = EVP_get_digestbynid(digest_nid);
   if (digest == NULL) {

crypto/x509/x509_test.cc

@@ -233,6 +233,13 @@ static const char kRSAKey[] =
     "moZWgjHvB2W9Ckn7sDqsPB+U2tyX0joDdQEyuiMECDY8oQ==\n"
     "-----END RSA PRIVATE KEY-----\n";
 
+static const char kP256Key[] =
+    "-----BEGIN PRIVATE KEY-----\n"
+    "MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgBw8IcnrUoEqc3VnJ\n"
+    "TYlodwi1b8ldMHcO6NHJzgqLtGqhRANCAATmK2niv2Wfl74vHg2UikzVl2u3qR4N\n"
+    "Rvvdqakendy6WgHn1peoChj5w8SjHlbifINI2xYaHPUdfvGULUvPciLB\n"
+    "-----END PRIVATE KEY-----\n";
+
 // kCRLTestRoot is a test root certificate. It has private key:
 //
 //     -----BEGIN RSA PRIVATE KEY-----
@@ -2442,3 +2449,112 @@ TEST(X509Test, InvalidVersion) {
   EXPECT_FALSE(CertFromPEM(kV1WithIssuerUniqueIDPEM));
   EXPECT_FALSE(CertFromPEM(kV1WithSubjectUniqueIDPEM));
 }
+
+// The following strings are test certificates signed by kP256Key and kRSAKey,
+// with missing, NULL, or invalid algorithm parameters.
+static const char kP256NoParam[] =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIBIDCBxqADAgECAgIE0jAKBggqhkjOPQQDAjAPMQ0wCwYDVQQDEwRUZXN0MCAX\n"
+    "DTAwMDEwMTAwMDAwMFoYDzIxMDAwMTAxMDAwMDAwWjAPMQ0wCwYDVQQDEwRUZXN0\n"
+    "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE5itp4r9ln5e+Lx4NlIpM1Zdrt6ke\n"
+    "DUb73ampHp3culoB59aXqAoY+cPEox5W4nyDSNsWGhz1HX7xlC1Lz3IiwaMQMA4w\n"
+    "DAYDVR0TBAUwAwEB/zAKBggqhkjOPQQDAgNJADBGAiEAqdIiF+bN9Cl44oUeICpy\n"
+    "aXd7HqhpVUaglYKw9ChmNUACIQCpMdL0fNkFNDbRww9dSl/y7kBdk/tp16HiqeSy\n"
+    "gGzFYg==\n"
+    "-----END CERTIFICATE-----\n";
+static const char kP256NullParam[] =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIBJDCByKADAgECAgIE0jAMBggqhkjOPQQDAgUAMA8xDTALBgNVBAMTBFRlc3Qw\n"
+    "IBcNMDAwMTAxMDAwMDAwWhgPMjEwMDAxMDEwMDAwMDBaMA8xDTALBgNVBAMTBFRl\n"
+    "c3QwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAATmK2niv2Wfl74vHg2UikzVl2u3\n"
+    "qR4NRvvdqakendy6WgHn1peoChj5w8SjHlbifINI2xYaHPUdfvGULUvPciLBoxAw\n"
+    "DjAMBgNVHRMEBTADAQH/MAwGCCqGSM49BAMCBQADSQAwRgIhAKILHmyo+F3Cn/VX\n"
+    "UUeSXOQQKX5aLzsQitwwmNF3ZgH3AiEAsYHcrVj/ftmoQIORARkQ/+PrqntXev8r\n"
+    "t6uPxHrmpUY=\n"
+    "-----END CERTIFICATE-----\n";
+static const char kP256InvalidParam[] =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIBMTCBz6ADAgECAgIE0jATBggqhkjOPQQDAgQHZ2FyYmFnZTAPMQ0wCwYDVQQD\n"
+    "EwRUZXN0MCAXDTAwMDEwMTAwMDAwMFoYDzIxMDAwMTAxMDAwMDAwWjAPMQ0wCwYD\n"
+    "VQQDEwRUZXN0MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE5itp4r9ln5e+Lx4N\n"
+    "lIpM1Zdrt6keDUb73ampHp3culoB59aXqAoY+cPEox5W4nyDSNsWGhz1HX7xlC1L\n"
+    "z3IiwaMQMA4wDAYDVR0TBAUwAwEB/zATBggqhkjOPQQDAgQHZ2FyYmFnZQNIADBF\n"
+    "AiAglpDf/YhN89LeJ2WAs/F0SJIrsuhS4uoInIz6WXUiuQIhAIu5Pwhp5E3Pbo8y\n"
+    "fLULTZnynuQUULQkRcF7S7T2WpIL\n"
+    "-----END CERTIFICATE-----\n";
+static const char kRSANoParam[] =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIBWzCBx6ADAgECAgIE0jALBgkqhkiG9w0BAQswDzENMAsGA1UEAxMEVGVzdDAg\n"
+    "Fw0wMDAxMDEwMDAwMDBaGA8yMTAwMDEwMTAwMDAwMFowDzENMAsGA1UEAxMEVGVz\n"
+    "dDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABOYraeK/ZZ+Xvi8eDZSKTNWXa7ep\n"
+    "Hg1G+92pqR6d3LpaAefWl6gKGPnDxKMeVuJ8g0jbFhoc9R1+8ZQtS89yIsGjEDAO\n"
+    "MAwGA1UdEwQFMAMBAf8wCwYJKoZIhvcNAQELA4GBAC1f8W3W0Ao7CPfIBQYDSbPh\n"
+    "brZpbxdBU5x27JOS7iSa+Lc9pEH5VCX9vIypHVHXLPEfZ38yIt11eiyrmZB6w62N\n"
+    "l9kIeZ6FVPmC30d3sXx70Jjs+ZX9yt7kD1gLyNAQQfeYfa4rORAZT1n2YitD74NY\n"
+    "TWUH2ieFP3l+ecj1SeQR\n"
+    "-----END CERTIFICATE-----\n";
+static const char kRSANullParam[] =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIBXzCByaADAgECAgIE0jANBgkqhkiG9w0BAQsFADAPMQ0wCwYDVQQDEwRUZXN0\n"
+    "MCAXDTAwMDEwMTAwMDAwMFoYDzIxMDAwMTAxMDAwMDAwWjAPMQ0wCwYDVQQDEwRU\n"
+    "ZXN0MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE5itp4r9ln5e+Lx4NlIpM1Zdr\n"
+    "t6keDUb73ampHp3culoB59aXqAoY+cPEox5W4nyDSNsWGhz1HX7xlC1Lz3IiwaMQ\n"
+    "MA4wDAYDVR0TBAUwAwEB/zANBgkqhkiG9w0BAQsFAAOBgQAzVcfIv+Rq1KrMXqIL\n"
+    "fPq/cWZjgqFZA1RGaGElNaqp+rkJfamq5tDGzckWpebrK+jjRN7yIlcWDtPpy3Gy\n"
+    "seZfvtBDR0TwJm0S/pQl8prKB4wgALcwe3bmi56Rq85nzY5ZLNcP16LQxL+jAAua\n"
+    "SwmQUz4bRpckRBj+sIyp1We+pg==\n"
+    "-----END CERTIFICATE-----\n";
+static const char kRSAInvalidParam[] =
+    "-----BEGIN CERTIFICATE-----\n"
+    "MIIBbTCB0KADAgECAgIE0jAUBgkqhkiG9w0BAQsEB2dhcmJhZ2UwDzENMAsGA1UE\n"
+    "AxMEVGVzdDAgFw0wMDAxMDEwMDAwMDBaGA8yMTAwMDEwMTAwMDAwMFowDzENMAsG\n"
+    "A1UEAxMEVGVzdDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABOYraeK/ZZ+Xvi8e\n"
+    "DZSKTNWXa7epHg1G+92pqR6d3LpaAefWl6gKGPnDxKMeVuJ8g0jbFhoc9R1+8ZQt\n"
+    "S89yIsGjEDAOMAwGA1UdEwQFMAMBAf8wFAYJKoZIhvcNAQELBAdnYXJiYWdlA4GB\n"
+    "AHTJ6cWWjCNrZhqiWWVI3jdK+h5xpRG8jGMXxR4JnjtoYRRusJLOXhmapwCB6fA0\n"
+    "4vc+66O27v36yDmQX+tIc/hDrTpKNJptU8q3n2VagREvoHhkOTYkcCeS8vmnMtn8\n"
+    "5OMNZ/ajVwOssw61GcAlScRqEHkZFBoGp7e+QpgB2tf9\n"
+    "-----END CERTIFICATE-----\n";
+
+TEST(X509Test, AlgorithmParameters) {
+  // P-256 requires the parameter be omitted.
+  bssl::UniquePtr<EVP_PKEY> key = PrivateKeyFromPEM(kP256Key);
+  ASSERT_TRUE(key);
+
+  bssl::UniquePtr<X509> cert = CertFromPEM(kP256NoParam);
+  ASSERT_TRUE(cert);
+  EXPECT_TRUE(X509_verify(cert.get(), key.get()));
+
+  cert = CertFromPEM(kP256NullParam);
+  ASSERT_TRUE(cert);
+  EXPECT_FALSE(X509_verify(cert.get(), key.get()));
+  uint32_t err = ERR_get_error();
+  EXPECT_EQ(ERR_LIB_X509, ERR_GET_LIB(err));
+  EXPECT_EQ(X509_R_INVALID_PARAMETER, ERR_GET_REASON(err));
+
+  cert = CertFromPEM(kP256InvalidParam);
+  ASSERT_TRUE(cert);
+  EXPECT_FALSE(X509_verify(cert.get(), key.get()));
+  err = ERR_get_error();
+  EXPECT_EQ(ERR_LIB_X509, ERR_GET_LIB(err));
+  EXPECT_EQ(X509_R_INVALID_PARAMETER, ERR_GET_REASON(err));
+
+  // RSA parameters should be NULL, but we accept omitted ones.
+  key = PrivateKeyFromPEM(kRSAKey);
+  ASSERT_TRUE(key);
+
+  cert = CertFromPEM(kRSANoParam);
+  ASSERT_TRUE(cert);
+  EXPECT_TRUE(X509_verify(cert.get(), key.get()));
+
+  cert = CertFromPEM(kRSANullParam);
+  ASSERT_TRUE(cert);
+  EXPECT_TRUE(X509_verify(cert.get(), key.get()));
+
+  cert = CertFromPEM(kRSAInvalidParam);
+  ASSERT_TRUE(cert);
+  EXPECT_FALSE(X509_verify(cert.get(), key.get()));
+  err = ERR_get_error();
+  EXPECT_EQ(ERR_LIB_X509, ERR_GET_LIB(err));
+  EXPECT_EQ(X509_R_INVALID_PARAMETER, ERR_GET_REASON(err));
+}