diff --git a/crypto/evp/evp_extra_test.cc b/crypto/evp/evp_extra_test.cc
index 07cb782..fe7a002 100644
--- a/crypto/evp/evp_extra_test.cc
+++ b/crypto/evp/evp_extra_test.cc
@@ -16,6 +16,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include <utility>
 #include <vector>
 
 #include <openssl/bytestring.h>
@@ -233,6 +234,85 @@
     0x8c, 0x16,
 };
 
+// kBadPSSCert is an example RSA-PSS certificate with bad parameters.
+static const uint8_t kBadPSSCert[] = {
+    0x30, 0x82, 0x03, 0x76, 0x30, 0x82, 0x02, 0x3a, 0xa0, 0x03, 0x02, 0x01,
+    0x02, 0x02, 0x09, 0x00, 0xd7, 0x30, 0x64, 0xbc, 0x9f, 0x12, 0xfe, 0xc3,
+    0x30, 0x3e, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
+    0x0a, 0x30, 0x31, 0xa0, 0x0d, 0x30, 0x0b, 0x06, 0x09, 0x60, 0x86, 0x48,
+    0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0xa1, 0x1a, 0x30, 0x18, 0x06, 0x09,
+    0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x08, 0x30, 0x0b, 0x06,
+    0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0xa2, 0x04,
+    0x02, 0x02, 0x00, 0xde, 0x30, 0x27, 0x31, 0x25, 0x30, 0x23, 0x06, 0x03,
+    0x55, 0x04, 0x03, 0x0c, 0x1c, 0x54, 0x65, 0x73, 0x74, 0x20, 0x49, 0x6e,
+    0x76, 0x61, 0x6c, 0x69, 0x64, 0x20, 0x50, 0x53, 0x53, 0x20, 0x63, 0x65,
+    0x72, 0x74, 0x69, 0x66, 0x69, 0x63, 0x61, 0x74, 0x65, 0x30, 0x1e, 0x17,
+    0x0d, 0x31, 0x35, 0x31, 0x31, 0x30, 0x34, 0x31, 0x36, 0x30, 0x32, 0x33,
+    0x35, 0x5a, 0x17, 0x0d, 0x31, 0x35, 0x31, 0x32, 0x30, 0x34, 0x31, 0x36,
+    0x30, 0x32, 0x33, 0x35, 0x5a, 0x30, 0x27, 0x31, 0x25, 0x30, 0x23, 0x06,
+    0x03, 0x55, 0x04, 0x03, 0x0c, 0x1c, 0x54, 0x65, 0x73, 0x74, 0x20, 0x49,
+    0x6e, 0x76, 0x61, 0x6c, 0x69, 0x64, 0x20, 0x50, 0x53, 0x53, 0x20, 0x63,
+    0x65, 0x72, 0x74, 0x69, 0x66, 0x69, 0x63, 0x61, 0x74, 0x65, 0x30, 0x82,
+    0x01, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
+    0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00, 0x30, 0x82,
+    0x01, 0x0a, 0x02, 0x82, 0x01, 0x01, 0x00, 0xc4, 0xda, 0x33, 0xb5, 0x87,
+    0xa9, 0x50, 0x80, 0x18, 0x02, 0x00, 0xfb, 0x32, 0xf5, 0x29, 0x6b, 0xef,
+    0x01, 0x24, 0xeb, 0x86, 0x5a, 0xbe, 0xd5, 0xe3, 0xdd, 0x3b, 0xbc, 0x2c,
+    0xad, 0x65, 0xf6, 0x2a, 0x26, 0x28, 0x4d, 0x8a, 0xc9, 0x61, 0x39, 0xf1,
+    0x84, 0xb9, 0xe7, 0xd3, 0x0a, 0xc7, 0xa8, 0x0a, 0x6d, 0xef, 0xd9, 0xcb,
+    0x20, 0x11, 0xbb, 0x71, 0xf4, 0xa1, 0xc9, 0x9a, 0x85, 0x1c, 0xe6, 0x3f,
+    0x23, 0x39, 0x58, 0x3c, 0xc5, 0x6d, 0xfa, 0x03, 0xe8, 0xdb, 0xdd, 0xe0,
+    0xc3, 0xde, 0x85, 0x76, 0xce, 0x49, 0x06, 0xc8, 0xe1, 0x8e, 0x4c, 0x86,
+    0x9c, 0xec, 0xab, 0xf4, 0xe5, 0x27, 0xb4, 0x5a, 0xaf, 0xc4, 0x36, 0xd3,
+    0x20, 0x81, 0x54, 0xee, 0x8f, 0x48, 0x77, 0x10, 0xf8, 0x79, 0xd6, 0xaa,
+    0x8d, 0x1b, 0xfe, 0x7d, 0xe8, 0x15, 0x13, 0xe0, 0x7b, 0xf6, 0x90, 0xe4,
+    0xe2, 0xcd, 0x2e, 0x8e, 0xc9, 0x3a, 0x75, 0x42, 0xed, 0x0a, 0x0f, 0x51,
+    0xb2, 0xdd, 0x2e, 0x70, 0x61, 0x68, 0xd7, 0xd9, 0xab, 0xf9, 0xbe, 0xe4,
+    0x75, 0xb7, 0xe7, 0xf2, 0x96, 0x7b, 0xd9, 0x93, 0x43, 0x24, 0xfb, 0x9e,
+    0x55, 0xda, 0xd4, 0x01, 0x6c, 0x3d, 0xa2, 0x59, 0x7a, 0xd5, 0x47, 0x18,
+    0x7e, 0x4e, 0xf9, 0x5d, 0xda, 0xcb, 0x93, 0xa2, 0x65, 0x2f, 0x8d, 0x46,
+    0xad, 0x81, 0xdc, 0xf0, 0xa9, 0x5f, 0x5d, 0xfe, 0x37, 0x80, 0x64, 0x2a,
+    0x41, 0xfa, 0xe9, 0x1e, 0x48, 0x38, 0x22, 0x1d, 0x9c, 0x23, 0xa5, 0xad,
+    0xda, 0x78, 0x45, 0x18, 0x0c, 0xeb, 0x95, 0xca, 0x2b, 0xcc, 0xb9, 0x62,
+    0x40, 0x85, 0x09, 0x44, 0x88, 0x4c, 0xf2, 0x1e, 0x08, 0x80, 0x37, 0xe9,
+    0x06, 0x96, 0x8f, 0x75, 0x54, 0x0b, 0xa9, 0x2d, 0xa9, 0x15, 0xb5, 0xda,
+    0xe5, 0xe4, 0x23, 0xaa, 0x2c, 0x89, 0xc1, 0xa9, 0x36, 0xbc, 0x9f, 0x02,
+    0x03, 0x01, 0x00, 0x01, 0xa3, 0x50, 0x30, 0x4e, 0x30, 0x1d, 0x06, 0x03,
+    0x55, 0x1d, 0x0e, 0x04, 0x16, 0x04, 0x14, 0x2b, 0x75, 0xf3, 0x43, 0x78,
+    0xa0, 0x65, 0x2d, 0xe4, 0xb6, 0xf3, 0x07, 0x04, 0x38, 0x21, 0xaf, 0xb6,
+    0xe1, 0x5f, 0x7b, 0x30, 0x1f, 0x06, 0x03, 0x55, 0x1d, 0x23, 0x04, 0x18,
+    0x30, 0x16, 0x80, 0x14, 0x2b, 0x75, 0xf3, 0x43, 0x78, 0xa0, 0x65, 0x2d,
+    0xe4, 0xb6, 0xf3, 0x07, 0x04, 0x38, 0x21, 0xaf, 0xb6, 0xe1, 0x5f, 0x7b,
+    0x30, 0x0c, 0x06, 0x03, 0x55, 0x1d, 0x13, 0x04, 0x05, 0x30, 0x03, 0x01,
+    0x01, 0xff, 0x30, 0x31, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
+    0x01, 0x01, 0x0a, 0x30, 0x24, 0xa0, 0x0d, 0x30, 0x0b, 0x06, 0x09, 0x60,
+    0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0xa1, 0x0d, 0x30, 0x0b,
+    0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x08, 0xa2,
+    0x04, 0x02, 0x02, 0x00, 0xde, 0x03, 0x82, 0x01, 0x01, 0x00, 0x08, 0xc1,
+    0xb6, 0x6f, 0x74, 0x94, 0x6c, 0x60, 0x75, 0xd8, 0xdc, 0xe1, 0x7b, 0xbf,
+    0x9d, 0xb5, 0xd7, 0x14, 0x75, 0x6c, 0xdb, 0x35, 0x5c, 0x1e, 0xff, 0xe6,
+    0xa8, 0xe6, 0x68, 0x42, 0x41, 0x81, 0xf6, 0xbf, 0xc1, 0x56, 0x02, 0xdb,
+    0xc6, 0x11, 0xeb, 0x15, 0x9d, 0xa9, 0x1c, 0x61, 0x25, 0x6d, 0x46, 0x0f,
+    0x7e, 0x27, 0xdd, 0x4b, 0xdc, 0xed, 0x07, 0xbd, 0xde, 0xd5, 0xde, 0x09,
+    0xf8, 0xfd, 0xbd, 0xa3, 0x4c, 0x81, 0xa9, 0xf7, 0x78, 0xff, 0x01, 0x80,
+    0x73, 0xf2, 0x40, 0xf2, 0xa8, 0x27, 0xe8, 0x00, 0x04, 0x3b, 0xf5, 0xe7,
+    0xa6, 0x58, 0x45, 0x79, 0x34, 0x49, 0x42, 0xd2, 0xd9, 0x56, 0x5e, 0xf9,
+    0x0a, 0x41, 0xd7, 0x81, 0x41, 0x94, 0x77, 0x78, 0x7e, 0x00, 0x3b, 0xca,
+    0xb5, 0xc0, 0x6e, 0x5b, 0xd7, 0x52, 0x52, 0x77, 0x1a, 0x52, 0xb8, 0x0d,
+    0x29, 0x1f, 0x2e, 0xfe, 0x1f, 0xf6, 0xb0, 0xc1, 0xb7, 0xf1, 0x15, 0x98,
+    0x0f, 0x30, 0x5d, 0x74, 0x2f, 0xfa, 0xe9, 0x84, 0xda, 0xde, 0xbe, 0xca,
+    0x91, 0x55, 0x1f, 0x5b, 0xbc, 0xaa, 0x45, 0x07, 0xc4, 0x2e, 0x21, 0x8a,
+    0x75, 0xc9, 0xbe, 0x6e, 0x39, 0x53, 0x10, 0xcb, 0x2f, 0x4b, 0xe1, 0x21,
+    0x1e, 0xea, 0x7d, 0x0b, 0x36, 0xe9, 0xa0, 0x2c, 0x76, 0x17, 0x1f, 0x69,
+    0x34, 0xfb, 0x45, 0x63, 0x7c, 0x84, 0x39, 0xb4, 0x21, 0x98, 0xbd, 0x49,
+    0xca, 0x80, 0x91, 0x5a, 0xa0, 0x44, 0xef, 0x91, 0xb3, 0x14, 0xf6, 0xd1,
+    0x6a, 0x2b, 0xb1, 0xe5, 0x4a, 0x44, 0x92, 0x7b, 0x3e, 0x8b, 0x7b, 0x6b,
+    0x90, 0x6b, 0x2c, 0x67, 0x3b, 0x0e, 0xb9, 0x5a, 0x87, 0x35, 0x33, 0x59,
+    0x94, 0x2f, 0x7e, 0xf6, 0x13, 0xc7, 0x22, 0x87, 0x3d, 0x50, 0xc9, 0x80,
+    0x40, 0xda, 0x35, 0xbc, 0x62, 0x16, 0xdc, 0xd5, 0x95, 0xa1, 0xe1, 0x9b,
+    0x68, 0x9f,
+};
+
 // kExampleRSAKeyPKCS8 is kExampleRSAKeyDER encoded in a PKCS #8
 // PrivateKeyInfo.
 static const uint8_t kExampleRSAKeyPKCS8[] = {
@@ -493,16 +573,52 @@
   return true;
 }
 
-static bool TestEVP_DigestVerifyInitFromAlgorithm(void) {
-  CBS cert, cert_body, tbs_cert, algorithm, signature;
-  CBS_init(&cert, kExamplePSSCert, sizeof(kExamplePSSCert));
-  if (!CBS_get_asn1(&cert, &cert_body, CBS_ASN1_SEQUENCE) ||
-      CBS_len(&cert) != 0 ||
+static bool ParseCertificate(CBS *out_tbs_cert,
+                             ScopedEVP_PKEY *out_pubkey,
+                             ScopedX509_ALGOR *out_algor,
+                             CBS *out_signature,
+                             const CBS *in_) {
+  CBS in = *in_;
+  CBS cert_body, tbs_cert, algorithm, signature;
+  if (!CBS_get_asn1(&in, &cert_body, CBS_ASN1_SEQUENCE) ||
+      CBS_len(&in) != 0 ||
       !CBS_get_any_asn1_element(&cert_body, &tbs_cert, NULL, NULL) ||
       !CBS_get_asn1_element(&cert_body, &algorithm, CBS_ASN1_SEQUENCE) ||
       !CBS_get_asn1(&cert_body, &signature, CBS_ASN1_BITSTRING) ||
       CBS_len(&cert_body) != 0) {
-    fprintf(stderr, "Failed to parse certificate\n");
+    return false;
+  }
+
+  CBS tbs_cert_copy = tbs_cert;
+  CBS tbs_cert_body, discard, spki;
+  if (!CBS_get_asn1(&tbs_cert_copy, &tbs_cert_body, CBS_ASN1_SEQUENCE) ||
+      CBS_len(&tbs_cert_copy) != 0 ||
+      !CBS_get_optional_asn1(
+          &tbs_cert_body, &discard, NULL,
+          CBS_ASN1_CONSTRUCTED | CBS_ASN1_CONTEXT_SPECIFIC | 0) ||
+      !CBS_get_asn1(&tbs_cert_body, &discard /* serialNumber */,
+                    CBS_ASN1_INTEGER) ||
+      !CBS_get_asn1(&tbs_cert_body, &discard /* signature */,
+                    CBS_ASN1_SEQUENCE) ||
+      !CBS_get_any_asn1_element(&tbs_cert_body, &discard /* issuer */,
+                                NULL, NULL) ||
+      !CBS_get_asn1(&tbs_cert_body, &discard /* validity */,
+                    CBS_ASN1_SEQUENCE) ||
+      !CBS_get_any_asn1_element(&tbs_cert_body, &discard /* subject */,
+                                NULL, NULL) ||
+      !CBS_get_asn1_element(&tbs_cert_body, &spki, CBS_ASN1_SEQUENCE)) {
+    return false;
+  }
+
+  const uint8_t *derp = CBS_data(&spki);
+  ScopedEVP_PKEY pubkey(d2i_PUBKEY(NULL, &derp, CBS_len(&spki)));
+  if (!pubkey || derp != CBS_data(&spki) + CBS_len(&spki)) {
+    return false;
+  }
+
+  derp = CBS_data(&algorithm);
+  ScopedX509_ALGOR algor(d2i_X509_ALGOR(NULL, &derp, CBS_len(&algorithm)));
+  if (!algor || derp != CBS_data(&algorithm) + CBS_len(&algorithm)) {
     return false;
   }
 
@@ -510,21 +626,28 @@
   // leading phase byte is just a zero.
   uint8_t padding;
   if (!CBS_get_u8(&signature, &padding) || padding != 0) {
-    fprintf(stderr, "Invalid signature padding\n");
     return false;
   }
 
-  const uint8_t *derp = CBS_data(&algorithm);
-  ScopedX509_ALGOR algor(d2i_X509_ALGOR(NULL, &derp, CBS_len(&algorithm)));
-  if (!algor || derp != CBS_data(&algorithm) + CBS_len(&algorithm)) {
-    fprintf(stderr, "Failed to parse algorithm\n");
+  *out_tbs_cert = tbs_cert;
+  *out_pubkey = std::move(pubkey);
+  *out_algor = std::move(algor);
+  *out_signature = signature;
+  return true;
+}
+
+static bool TestEVP_DigestVerifyInitFromAlgorithm(void) {
+  CBS in, tbs_cert, signature;
+  ScopedEVP_PKEY pkey;
+  ScopedX509_ALGOR algor;
+  CBS_init(&in, kExamplePSSCert, sizeof(kExamplePSSCert));
+  if (!ParseCertificate(&tbs_cert, &pkey, &algor, &signature, &in)) {
+    fprintf(stderr, "Failed to parse certificate\n");
     return false;
   }
 
-  ScopedEVP_PKEY pkey = LoadExampleRSAKey();
   ScopedEVP_MD_CTX md_ctx;
-  if (!pkey ||
-      !EVP_DigestVerifyInitFromAlgorithm(md_ctx.get(), algor.get(),
+  if (!EVP_DigestVerifyInitFromAlgorithm(md_ctx.get(), algor.get(),
                                          pkey.get()) ||
       !EVP_DigestVerifyUpdate(md_ctx.get(), CBS_data(&tbs_cert),
                               CBS_len(&tbs_cert)) ||
@@ -535,6 +658,26 @@
   return true;
 }
 
+static bool TestBadPSSParameters(void) {
+  CBS in, tbs_cert, signature;
+  ScopedEVP_PKEY pkey;
+  ScopedX509_ALGOR algor;
+  CBS_init(&in, kBadPSSCert, sizeof(kBadPSSCert));
+  if (!ParseCertificate(&tbs_cert, &pkey, &algor, &signature, &in)) {
+    fprintf(stderr, "Failed to parse certificate\n");
+    return false;
+  }
+
+  ScopedEVP_MD_CTX md_ctx;
+  if (EVP_DigestVerifyInitFromAlgorithm(md_ctx.get(), algor.get(),
+                                        pkey.get())) {
+    fprintf(stderr, "Unexpectedly processed bad signature parameters\n");
+    return false;
+  }
+  ERR_clear_error();
+  return true;
+}
+
 static bool TestValidPrivateKey(const uint8_t *input, size_t input_len,
                                 int expected_id) {
   const uint8_t *p = input;
@@ -693,6 +836,12 @@
     return 1;
   }
 
+  if (!TestBadPSSParameters()) {
+    fprintf(stderr, "TestBadPSSParameters failed\n");
+    ERR_print_errors_fp(stderr);
+    return 1;
+  }
+
   if (!Testd2i_AutoPrivateKey()) {
     fprintf(stderr, "Testd2i_AutoPrivateKey failed\n");
     ERR_print_errors_fp(stderr);
diff --git a/crypto/evp/p_rsa_asn1.c b/crypto/evp/p_rsa_asn1.c
index f60625b..db38d5c 100644
--- a/crypto/evp/p_rsa_asn1.c
+++ b/crypto/evp/p_rsa_asn1.c
@@ -303,7 +303,7 @@
   const uint8_t *p;
   int plen;
 
-  if (alg == NULL ||
+  if (alg == NULL || alg->parameter == NULL ||
       OBJ_obj2nid(alg->algorithm) != NID_mgf1 ||
       alg->parameter->type != V_ASN1_SEQUENCE) {
     return NULL;