diff --git a/fuzz/tls_client_target.cc b/fuzz/tls_client_target.cc
index 5cb071250d..4b40257a90 100644
--- a/fuzz/tls_client_target.cc
+++ b/fuzz/tls_client_target.cc
@@ -81,7 +81,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t len) {
 
 #ifdef UNSAFE_FUZZER_MODE
   // Reset the RNG state.
-  assert(RNG_ResetForFuzzing() == SECSuccess);
+  assert(RNG_RandomUpdate(NULL, 0) == SECSuccess);
 #endif
 
   // Create and import dummy socket.
diff --git a/fuzz/tls_server_target.cc b/fuzz/tls_server_target.cc
index 84a5a75b29..9a533fb132 100644
--- a/fuzz/tls_server_target.cc
+++ b/fuzz/tls_server_target.cc
@@ -85,7 +85,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t len) {
 
 #ifdef UNSAFE_FUZZER_MODE
   // Reset the RNG state.
-  assert(RNG_ResetForFuzzing() == SECSuccess);
+  assert(RNG_RandomUpdate(NULL, 0) == SECSuccess);
 #endif
 
   // Create model socket.
diff --git a/gtests/common/gtest.gypi b/gtests/common/gtest.gypi
index e0ffc86e28..c4865bba51 100644
--- a/gtests/common/gtest.gypi
+++ b/gtests/common/gtest.gypi
@@ -27,7 +27,7 @@
           '-lstdc++',
         ],
       }],
-      [ 'fuzz_tls==1', {
+      [ 'fuzz==1', {
         'defines': [
           'UNSAFE_FUZZER_MODE',
         ],
diff --git a/gtests/pk11_gtest/pk11_prng_unittest.cc b/gtests/pk11_gtest/pk11_prng_unittest.cc
index fd28651696..ef05fe51cd 100644
--- a/gtests/pk11_gtest/pk11_prng_unittest.cc
+++ b/gtests/pk11_gtest/pk11_prng_unittest.cc
@@ -36,12 +36,12 @@ TEST_F(PK11PrngTest, Fuzz_DetPRNG_Reset) {
   std::vector<uint8_t> rnd1(2048, 0);
   std::vector<uint8_t> rnd2(2048, 0);
 
-  RNG_ResetForFuzzing();
+  EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
 
   SECStatus rv = PK11_GenerateRandom(rnd1.data(), rnd1.size());
   EXPECT_EQ(rv, SECSuccess);
 
-  RNG_ResetForFuzzing();
+  EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
 
   rv = PK11_GenerateRandom(rnd2.data(), rnd2.size());
   EXPECT_EQ(rv, SECSuccess);
@@ -54,7 +54,7 @@ TEST_F(PK11PrngTest, Fuzz_DetPRNG_StatefulReset) {
   std::vector<uint8_t> rnd1(2048, 0);
   std::vector<uint8_t> rnd2(2048, 0);
 
-  RNG_ResetForFuzzing();
+  EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
 
   SECStatus rv = PK11_GenerateRandom(rnd1.data(), rnd1.size() - 1024);
   EXPECT_EQ(rv, SECSuccess);
@@ -62,7 +62,50 @@ TEST_F(PK11PrngTest, Fuzz_DetPRNG_StatefulReset) {
   rv = PK11_GenerateRandom(rnd1.data() + 1024, rnd1.size() - 1024);
   EXPECT_EQ(rv, SECSuccess);
 
-  RNG_ResetForFuzzing();
+  EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
+
+  rv = PK11_GenerateRandom(rnd2.data(), rnd2.size() - 1024);
+  EXPECT_EQ(rv, SECSuccess);
+
+  rv = PK11_GenerateRandom(rnd2.data() + 1024, rnd2.size() - 1024);
+  EXPECT_EQ(rv, SECSuccess);
+
+  EXPECT_EQ(rnd1, rnd2);
+}
+
+TEST_F(PK11PrngTest, Fuzz_DetPRNG_Seed) {
+  std::vector<uint8_t> rnd1(2048, 0);
+  std::vector<uint8_t> rnd2(2048, 0);
+  std::vector<uint8_t> seed = {0x01, 0x22, 0xAA, 0x45};
+
+  SECStatus rv = PK11_RandomUpdate(seed.data(), seed.size());
+  EXPECT_EQ(rv, SECSuccess);
+
+  rv = PK11_GenerateRandom(rnd1.data(), rnd1.size());
+  EXPECT_EQ(rv, SECSuccess);
+
+  rv = PK11_GenerateRandom(rnd2.data(), rnd2.size());
+  EXPECT_EQ(rv, SECSuccess);
+
+  EXPECT_NE(rnd1, rnd2);
+}
+
+TEST_F(PK11PrngTest, Fuzz_DetPRNG_StatefulReset_Seed) {
+  std::vector<uint8_t> rnd1(2048, 0);
+  std::vector<uint8_t> rnd2(2048, 0);
+  std::vector<uint8_t> seed = {0x01, 0x22, 0xAA, 0x45};
+
+  SECStatus rv = PK11_RandomUpdate(seed.data(), seed.size());
+  EXPECT_EQ(rv, SECSuccess);
+
+  rv = PK11_GenerateRandom(rnd1.data(), rnd1.size() - 1024);
+  EXPECT_EQ(rv, SECSuccess);
+
+  rv = PK11_GenerateRandom(rnd1.data() + 1024, rnd1.size() - 1024);
+  EXPECT_EQ(rv, SECSuccess);
+
+  rv = PK11_RandomUpdate(seed.data(), seed.size());
+  EXPECT_EQ(rv, SECSuccess);
 
   rv = PK11_GenerateRandom(rnd2.data(), rnd2.size() - 1024);
   EXPECT_EQ(rv, SECSuccess);
diff --git a/gtests/ssl_gtest/ssl_fuzz_unittest.cc b/gtests/ssl_gtest/ssl_fuzz_unittest.cc
index b2abfa9a8e..5dcdd964d4 100644
--- a/gtests/ssl_gtest/ssl_fuzz_unittest.cc
+++ b/gtests/ssl_gtest/ssl_fuzz_unittest.cc
@@ -17,9 +17,6 @@ namespace nss_test {
 #else
 #define FUZZ_F(c, f) TEST_F(c, DISABLED_Fuzz_##f)
 #define FUZZ_P(c, f) TEST_P(c, DISABLED_Fuzz_##f)
-// RNG_ResetForFuzzing() isn't exported from the shared libraries, rather than
-// fail to link to it, make it fail (we're not running it anyway).
-#define RNG_ResetForFuzzing() SECFailure
 #endif
 
 const uint8_t kShortEmptyFinished[8] = {0};
@@ -91,7 +88,7 @@ FUZZ_P(TlsConnectGeneric, DeterministicExporter) {
   DisableECDHEServerKeyReuse();
 
   // Reset the RNG state.
-  EXPECT_EQ(SECSuccess, RNG_ResetForFuzzing());
+  EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
   Connect();
 
   // Export a key derived from the MS and nonces.
@@ -105,7 +102,7 @@ FUZZ_P(TlsConnectGeneric, DeterministicExporter) {
   DisableECDHEServerKeyReuse();
 
   // Reset the RNG state.
-  EXPECT_EQ(SECSuccess, RNG_ResetForFuzzing());
+  EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
   Connect();
 
   // Export another key derived from the MS and nonces.
@@ -135,7 +132,7 @@ FUZZ_P(TlsConnectGeneric, DeterministicTranscript) {
     server_->SetPacketFilter(std::make_shared<TlsConversationRecorder>(buffer));
 
     // Reset the RNG state.
-    EXPECT_EQ(SECSuccess, RNG_ResetForFuzzing());
+    EXPECT_EQ(SECSuccess, RNG_RandomUpdate(NULL, 0));
     Connect();
 
     // Ensure the filters go away before |buffer| does.
diff --git a/lib/freebl/blapi.h b/lib/freebl/blapi.h
index e5a6cf30e0..592624bdf7 100644
--- a/lib/freebl/blapi.h
+++ b/lib/freebl/blapi.h
@@ -1429,8 +1429,6 @@ extern SECStatus RNG_RandomUpdate(const void *data, size_t bytes);
 */
 extern SECStatus RNG_GenerateGlobalRandomBytes(void *dest, size_t len);
 
-extern SECStatus RNG_ResetForFuzzing(void);
-
 /* Destroy the global RNG context.  After a call to RNG_RNGShutdown()
 ** a call to RNG_RNGInit() is required in order to use the generator again,
 ** along with seed data (see the comment above RNG_RNGInit()).
diff --git a/lib/freebl/det_rng.c b/lib/freebl/det_rng.c
index fcbf9b34a8..04fce30e80 100644
--- a/lib/freebl/det_rng.c
+++ b/lib/freebl/det_rng.c
@@ -9,10 +9,32 @@
 #include "seccomon.h"
 #include "secerr.h"
 
+#define GLOBAL_BYTES_SIZE 100
+static PRUint8 globalBytes[GLOBAL_BYTES_SIZE];
 static unsigned long globalNumCalls = 0;
+static PZLock *rng_lock = NULL;
 
 SECStatus
-prng_ResetForFuzzing(PZLock *rng_lock)
+RNG_RNGInit(void)
+{
+    rng_lock = PZ_NewLock(nssILockOther);
+    if (!rng_lock) {
+        PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
+        return SECFailure;
+    }
+    /* --- LOCKED --- */
+    PZ_Lock(rng_lock);
+    memset(globalBytes, 0, GLOBAL_BYTES_SIZE);
+    PZ_Unlock(rng_lock);
+    /* --- UNLOCKED --- */
+
+    return SECSuccess;
+}
+
+/* Take min(size, GLOBAL_BYTES_SIZE) bytes from data and use as seed and reset
+ * the rng state. */
+SECStatus
+RNG_RandomUpdate(const void *data, size_t bytes)
 {
     /* Check for a valid RNG lock. */
     PORT_Assert(rng_lock != NULL);
@@ -23,7 +45,11 @@ prng_ResetForFuzzing(PZLock *rng_lock)
 
     /* --- LOCKED --- */
     PZ_Lock(rng_lock);
+    memset(globalBytes, 0, GLOBAL_BYTES_SIZE);
     globalNumCalls = 0;
+    if (data) {
+        memcpy(globalBytes, (PRUint8 *)data, PR_MIN(bytes, GLOBAL_BYTES_SIZE));
+    }
     PZ_Unlock(rng_lock);
     /* --- UNLOCKED --- */
 
@@ -31,9 +57,9 @@ prng_ResetForFuzzing(PZLock *rng_lock)
 }
 
 SECStatus
-prng_GenerateDeterministicRandomBytes(PZLock *rng_lock, void *dest, size_t len)
+RNG_GenerateGlobalRandomBytes(void *dest, size_t len)
 {
-    static const uint8_t key[32];
+    static const uint8_t key[32] = { 0 };
     uint8_t nonce[12] = { 0 };
 
     /* Check for a valid RNG lock. */
@@ -58,10 +84,60 @@ prng_GenerateDeterministicRandomBytes(PZLock *rng_lock, void *dest, size_t len)
     }
 
     memset(dest, 0, len);
+    memcpy(dest, globalBytes, PR_MIN(len, GLOBAL_BYTES_SIZE));
     ChaCha20XOR(dest, dest, len, key, nonce, 0);
     ChaCha20Poly1305_DestroyContext(cx, PR_TRUE);
 
     PZ_Unlock(rng_lock);
     /* --- UNLOCKED --- */
+
     return SECSuccess;
 }
+
+void
+RNG_RNGShutdown(void)
+{
+    PZ_DestroyLock(rng_lock);
+    rng_lock = NULL;
+}
+
+/* Test functions are not implemented! */
+SECStatus
+PRNGTEST_Instantiate(const PRUint8 *entropy, unsigned int entropy_len,
+                     const PRUint8 *nonce, unsigned int nonce_len,
+                     const PRUint8 *personal_string, unsigned int ps_len)
+{
+    return SECFailure;
+}
+
+SECStatus
+PRNGTEST_Reseed(const PRUint8 *entropy, unsigned int entropy_len,
+                const PRUint8 *additional, unsigned int additional_len)
+{
+    return SECFailure;
+}
+
+SECStatus
+PRNGTEST_Generate(PRUint8 *bytes, unsigned int bytes_len,
+                  const PRUint8 *additional, unsigned int additional_len)
+{
+    return SECFailure;
+}
+
+SECStatus
+PRNGTEST_Uninstantiate()
+{
+    return SECFailure;
+}
+
+SECStatus
+PRNGTEST_RunHealthTests()
+{
+    return SECFailure;
+}
+
+SECStatus
+PRNGTEST_Instantiate_Kat()
+{
+    return SECFailure;
+}
diff --git a/lib/freebl/drbg.c b/lib/freebl/drbg.c
index 0f8819938d..224bbe87d8 100644
--- a/lib/freebl/drbg.c
+++ b/lib/freebl/drbg.c
@@ -20,10 +20,6 @@
 #include "secrng.h" /* for RNG_SystemRNG() */
 #include "secmpi.h"
 
-#ifdef UNSAFE_FUZZER_MODE
-#include "det_rng.h"
-#endif
-
 /* PRNG_SEEDLEN defined in NIST SP 800-90 section 10.1
  * for SHA-1, SHA-224, and SHA-256 it's 440 bits.
  * for SHA-384 and SHA-512 it's 888 bits */
@@ -401,10 +397,8 @@ static PRStatus
 rng_init(void)
 {
     PRUint8 bytes[PRNG_SEEDLEN * 2]; /* entropy + nonce */
-#ifndef UNSAFE_RNG_NO_URANDOM_SEED
     unsigned int numBytes;
     SECStatus rv = SECSuccess;
-#endif
 
     if (globalrng == NULL) {
         /* bytes needs to have enough space to hold
@@ -421,7 +415,6 @@ rng_init(void)
             return PR_FAILURE;
         }
 
-#ifndef UNSAFE_RNG_NO_URANDOM_SEED
         /* Try to get some seed data for the RNG */
         numBytes = (unsigned int)RNG_SystemRNG(bytes, sizeof bytes);
         PORT_Assert(numBytes == 0 || numBytes == sizeof bytes);
@@ -444,7 +437,6 @@ rng_init(void)
         if (rv != SECSuccess) {
             return PR_FAILURE;
         }
-#endif
 
         /* the RNG is in a valid state */
         globalrng->isValid = PR_TRUE;
@@ -662,21 +654,7 @@ prng_GenerateGlobalRandomBytes(RNGContext *rng,
 SECStatus
 RNG_GenerateGlobalRandomBytes(void *dest, size_t len)
 {
-#ifdef UNSAFE_FUZZER_MODE
-    return prng_GenerateDeterministicRandomBytes(globalrng->lock, dest, len);
-#else
     return prng_GenerateGlobalRandomBytes(globalrng, dest, len);
-#endif
-}
-
-SECStatus
-RNG_ResetForFuzzing(void)
-{
-#ifdef UNSAFE_FUZZER_MODE
-    return prng_ResetForFuzzing(globalrng->lock);
-#else
-    return SECFailure;
-#endif
 }
 
 void
diff --git a/lib/freebl/freebl_base.gypi b/lib/freebl/freebl_base.gypi
index 9e4d8031bc..91f186a457 100644
--- a/lib/freebl/freebl_base.gypi
+++ b/lib/freebl/freebl_base.gypi
@@ -158,15 +158,11 @@
         }],
       ],
     }],
-    [ 'fuzz_oss==1', {
-      'defines': [
-        'UNSAFE_RNG_NO_URANDOM_SEED',
-      ],
+    [ 'fuzz==1', {
+      'sources!': [ 'drbg.c' ],
+      'sources': [ 'det_rng.c' ],
     }],
     [ 'fuzz_tls==1', {
-      'sources': [
-        'det_rng.c',
-      ],
       'defines': [
         'UNSAFE_FUZZER_MODE',
       ],