Update fuzzers with comments from OSS-Fuzz review

Add explicit length limitations, to prevent the fuzzer from just
giving us increasingly long inputs until timeout occurs due
to non-linear algorithms.

Use LLVM fuzzer interface in all cases, and just have AFL driver
call that API when a define is set to include a main function.
OSS-Fuzz will be using the LLVM API, regardless of the fuzzing engine.

[ci skip]

19 files changed, 56 insertions, 19 deletions

diff --git a/src/extra_tests/fuzzers/GNUmakefile b/src/extra_tests/fuzzers/GNUmakefile
index daa5c7a37..43866d0c3 100644
--- a/src/extra_tests/fuzzers/GNUmakefile
+++ b/src/extra_tests/fuzzers/GNUmakefile
@@ -3,11 +3,12 @@ FUZZERS=$(patsubst jigs/%.cpp,%,$(wildcard jigs/*.cpp))
 
 AFL_SAN_FLAGS=-fsanitize=address,undefined -fno-sanitize-recover=undefined
 CLANG_SAN_FLAGS=-fsanitize=address,undefined -fno-sanitize-recover=undefined -fsanitize-coverage=edge,indirect-calls,8bit-counters
+CLANG_SAN_FLAGS=-fsanitize-coverage=edge,indirect-calls,8bit-counters
 
-CFG_FLAGS=--enable-debug --unsafe-fuzzer-mode
+CFG_FLAGS=--with-debug-info --unsafe-fuzzer-mode
 SHARED_FLAGS=-O3 -g -std=c++11 -pthread
-LIBFUZZER_FLAGS=-DUSE_LLVM_FUZZER -Illvm-build/build/include $(SHARED_FLAGS) $(CLANG_SAN_FLAGS)
-AFL_FLAGS=-Iafl-build/build/include $(SHARED_FLAGS)
+LIBFUZZER_FLAGS=-Illvm-build/build/include $(SHARED_FLAGS) $(CLANG_SAN_FLAGS)
+AFL_FLAGS=-DINCLUDE_AFL_MAIN -Iafl-build/build/include $(SHARED_FLAGS)
 
 LIBFUZZER_LIBS=llvm-build/libbotan-1.11.a libFuzzer.a
 AFL_LIBS=afl-build/libbotan-1.11.a
@@ -28,7 +29,7 @@ afl: dirs afl-build $(AFL_PROGS)
 llvm: dirs llvm-build $(LIBFUZZER_PROGS)
 
 bin/llvm_fuzz_%: jigs/%.cpp $(LIBFUZZER_LIBS)
-	$(CLANG_CXX) $(LIBFUZZER_FLAGS) -DUSE_LLVM_FUZZER $< $(LIBFUZZER_LIBS) -o $@
+	$(CLANG_CXX) $(LIBFUZZER_FLAGS) $< $(LIBFUZZER_LIBS) -o $@
 
 bin/afl_fuzz_%: jigs/%.cpp $(AFL_LIBS)
 	$(AFL_CXX) $(AFL_FLAGS) $< $(AFL_LIBS) -o $@
diff --git a/src/extra_tests/fuzzers/jigs/ber_decode.cpp b/src/extra_tests/fuzzers/jigs/ber_decode.cpp
index 0f5cc9f20..6ec9cadba 100644
--- a/src/extra_tests/fuzzers/jigs/ber_decode.cpp
+++ b/src/extra_tests/fuzzers/jigs/ber_decode.cpp
@@ -9,6 +9,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 4096)
+      return;
+
    try
       {
       DataSource_Memory input(in, len);
diff --git a/src/extra_tests/fuzzers/jigs/bn_sqr.cpp b/src/extra_tests/fuzzers/jigs/bn_sqr.cpp
index 2bc5ebe33..aa76067f7 100644
--- a/src/extra_tests/fuzzers/jigs/bn_sqr.cpp
+++ b/src/extra_tests/fuzzers/jigs/bn_sqr.cpp
@@ -11,6 +11,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 8192/8)
+      return;
+
    Botan::BigInt x = Botan::BigInt::decode(in, len);
 
    Botan::BigInt x_sqr = square(x);
diff --git a/src/extra_tests/fuzzers/jigs/cert.cpp b/src/extra_tests/fuzzers/jigs/cert.cpp
index 2c13551e2..5620a4700 100644
--- a/src/extra_tests/fuzzers/jigs/cert.cpp
+++ b/src/extra_tests/fuzzers/jigs/cert.cpp
@@ -9,6 +9,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 8192)
+      return;
+
    try
       {
       DataSource_Memory input(in, len);
diff --git a/src/extra_tests/fuzzers/jigs/crl.cpp b/src/extra_tests/fuzzers/jigs/crl.cpp
index be61ae131..b3157e5fe 100644
--- a/src/extra_tests/fuzzers/jigs/crl.cpp
+++ b/src/extra_tests/fuzzers/jigs/crl.cpp
@@ -9,6 +9,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 4096)
+      return;
+
    try
       {
       DataSource_Memory input(in, len);
diff --git a/src/extra_tests/fuzzers/jigs/divide.cpp b/src/extra_tests/fuzzers/jigs/divide.cpp
index fba68b9a6..4ff50a680 100644
--- a/src/extra_tests/fuzzers/jigs/divide.cpp
+++ b/src/extra_tests/fuzzers/jigs/divide.cpp
@@ -8,6 +8,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len % 2 == 1 || len > 2*4096/8)
+      return;
+
    const BigInt x = BigInt::decode(in, len / 2);
    const BigInt y = BigInt::decode(in + len / 2, len / 2);
 
diff --git a/src/extra_tests/fuzzers/jigs/driver.h b/src/extra_tests/fuzzers/jigs/driver.h
index 3eab8623d..bac0f572b 100644
--- a/src/extra_tests/fuzzers/jigs/driver.h
+++ b/src/extra_tests/fuzzers/jigs/driver.h
@@ -17,32 +17,26 @@
 
 using namespace Botan;
 
-void fuzz(const uint8_t in[], size_t len);
+extern void fuzz(const uint8_t in[], size_t len);
 
-void fuzzer_init()
+extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
    {
    /*
    * This disables the mlock pool, as overwrites within the pool are
    * opaque to ASan or other instrumentation.
    */
    ::setenv("BOTAN_MLOCK_POOL_SIZE", "0", 1);
+   return 0;
    }
 
-#if defined(USE_LLVM_FUZZER)
-
-// Called by main() in libFuzzer
+// Called by main() in libFuzzer or in main for AFL below
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t in[], size_t len)
    {
    fuzz(in, len);
    return 0;
    }
 
-int LLVMFuzzerInitialize(int *argc, char ***argv) {
-  fuzzer_init();
-  return 0;
-}
-
-#else
+#if defined(INCLUDE_AFL_MAIN)
 
 // Read stdin for AFL
 
@@ -50,7 +44,7 @@ int main(int argc, char* argv[])
    {
    const size_t max_read = 4096;
 
-   fuzzer_init();
+   LLVMFuzzerInitialize();
 
 #if defined(__AFL_LOOP)
    while(__AFL_LOOP(1000))
diff --git a/src/extra_tests/fuzzers/jigs/ecc_bp256.cpp b/src/extra_tests/fuzzers/jigs/ecc_bp256.cpp
index 5b979b03f..07833c639 100644
--- a/src/extra_tests/fuzzers/jigs/ecc_bp256.cpp
+++ b/src/extra_tests/fuzzers/jigs/ecc_bp256.cpp
@@ -8,6 +8,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*256/8)
+      return;
+
    static EC_Group bp256("brainpool256r1");
    return check_ecc_math(bp256, in, len);
    }
diff --git a/src/extra_tests/fuzzers/jigs/ecc_p256.cpp b/src/extra_tests/fuzzers/jigs/ecc_p256.cpp
index 429925ba1..f13104fda 100644
--- a/src/extra_tests/fuzzers/jigs/ecc_p256.cpp
+++ b/src/extra_tests/fuzzers/jigs/ecc_p256.cpp
@@ -8,6 +8,8 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*256/8)
+      return;
    static EC_Group p256("secp256r1");
    return check_ecc_math(p256, in, len);
    }
diff --git a/src/extra_tests/fuzzers/jigs/ecc_p384.cpp b/src/extra_tests/fuzzers/jigs/ecc_p384.cpp
index 0441b6dcf..47826e1d6 100644
--- a/src/extra_tests/fuzzers/jigs/ecc_p384.cpp
+++ b/src/extra_tests/fuzzers/jigs/ecc_p384.cpp
@@ -8,6 +8,8 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*384/8)
+      return;
    static EC_Group p384("secp384r1");
    return check_ecc_math(p384, in, len);
    }
diff --git a/src/extra_tests/fuzzers/jigs/ecc_p521.cpp b/src/extra_tests/fuzzers/jigs/ecc_p521.cpp
index cc998137c..c2d1e36bb 100644
--- a/src/extra_tests/fuzzers/jigs/ecc_p521.cpp
+++ b/src/extra_tests/fuzzers/jigs/ecc_p521.cpp
@@ -8,6 +8,8 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*(521+7)/8)
+      return;
    static EC_Group p521("secp521r1");
    return check_ecc_math(p521, in, len);
    }
diff --git a/src/extra_tests/fuzzers/jigs/invert.cpp b/src/extra_tests/fuzzers/jigs/invert.cpp
index fcda5770e..63c140139 100644
--- a/src/extra_tests/fuzzers/jigs/invert.cpp
+++ b/src/extra_tests/fuzzers/jigs/invert.cpp
@@ -51,6 +51,9 @@ BigInt inverse_mod_ref(const BigInt& n, const BigInt& mod)
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len % 2 == 1 || len > 2*4096/8)
+      return;
+
    const BigInt x = BigInt::decode(in, len / 2);
    BigInt mod = BigInt::decode(in + len / 2, len / 2);
 
diff --git a/src/extra_tests/fuzzers/jigs/os2ecp.cpp b/src/extra_tests/fuzzers/jigs/os2ecp.cpp
index 2b939eb5b..61ce1bd7b 100644
--- a/src/extra_tests/fuzzers/jigs/os2ecp.cpp
+++ b/src/extra_tests/fuzzers/jigs/os2ecp.cpp
@@ -18,6 +18,9 @@ void check_os2ecp(const EC_Group& group, const uint8_t in[], size_t len)
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len >= 256)
+      return;
+
    static EC_Group p192("secp192r1");
    static EC_Group p224("secp224r1");
    static EC_Group p256("secp256r1");
diff --git a/src/extra_tests/fuzzers/jigs/redc_p192.cpp b/src/extra_tests/fuzzers/jigs/redc_p192.cpp
index a27e6a37b..9bece4595 100644
--- a/src/extra_tests/fuzzers/jigs/redc_p192.cpp
+++ b/src/extra_tests/fuzzers/jigs/redc_p192.cpp
@@ -10,6 +10,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*192/8)
+      return;
+
    static const BigInt& prime = Botan::prime_p192();
    static const BigInt prime_2 = prime * prime;
    static Botan::Modular_Reducer prime_redc(prime);
diff --git a/src/extra_tests/fuzzers/jigs/redc_p256.cpp b/src/extra_tests/fuzzers/jigs/redc_p256.cpp
index 86f0910a0..cbb7f4fef 100644
--- a/src/extra_tests/fuzzers/jigs/redc_p256.cpp
+++ b/src/extra_tests/fuzzers/jigs/redc_p256.cpp
@@ -10,6 +10,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*256/8)
+      return;
+
    static const BigInt& prime = Botan::prime_p256();
    static const BigInt prime_2 = prime * prime;
    static Botan::Modular_Reducer prime_redc(prime);
diff --git a/src/extra_tests/fuzzers/jigs/redc_p384.cpp b/src/extra_tests/fuzzers/jigs/redc_p384.cpp
index 9a9ac896a..3b990fb63 100644
--- a/src/extra_tests/fuzzers/jigs/redc_p384.cpp
+++ b/src/extra_tests/fuzzers/jigs/redc_p384.cpp
@@ -10,6 +10,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*384/8)
+      return;
+
    static const BigInt& prime = Botan::prime_p384();
    static const BigInt prime_2 = prime * prime;
    static Botan::Modular_Reducer prime_redc(prime);
diff --git a/src/extra_tests/fuzzers/jigs/redc_p521.cpp b/src/extra_tests/fuzzers/jigs/redc_p521.cpp
index fe164217d..5142a44c2 100644
--- a/src/extra_tests/fuzzers/jigs/redc_p521.cpp
+++ b/src/extra_tests/fuzzers/jigs/redc_p521.cpp
@@ -10,6 +10,9 @@
 
 void fuzz(const uint8_t in[], size_t len)
    {
+   if(len > 2*(521+7)/8)
+      return;
+
    static const BigInt& prime = Botan::prime_p521();
    static const BigInt prime_2 = prime * prime;
    static Botan::Modular_Reducer prime_redc(prime);
diff --git a/src/extra_tests/fuzzers/jigs/ressol.cpp b/src/extra_tests/fuzzers/jigs/ressol.cpp
index 3f7f82502..97130255c 100644
--- a/src/extra_tests/fuzzers/jigs/ressol.cpp
+++ b/src/extra_tests/fuzzers/jigs/ressol.cpp
@@ -39,9 +39,9 @@ void fuzz(const uint8_t in[], size_t len)
             if(is_prime(n, fuzzer_rng(), 64))
                {
                std::cout << "A = " << a << "\n";
-               std::cout << "Ressol = " << a_sqrt << "\n";
                std::cout << "N = " << n << "\n";
-               std::cout << "Z = " << z << "\n";
+               std::cout << "Ressol = " << a_sqrt << "\n";
+               std::cout << "recomputed = " << z << "\n";
                abort();
                }
             }
diff --git a/src/extra_tests/fuzzers/readme.txt b/src/extra_tests/fuzzers/readme.txt
index e195b4e70..1bee1a785 100644
--- a/src/extra_tests/fuzzers/readme.txt
+++ b/src/extra_tests/fuzzers/readme.txt
@@ -16,7 +16,7 @@ and implement the function with the signature
 
 void fuzz(const uint8_t buf[], size_t len);
 
-This function should abort or crash if something is incorrect.
+This function should abort/crash if something is incorrect.
 
 Run it with