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[libFuzzer] add a fuzzer test that finds CVE-2015-3193
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282892 91177308-0d34-0410-b5e6-96231b3b80d8
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‎lib/Fuzzer/fuzzer-test-suite/openssl-1.0.2d/build.sh

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#!/bin/bash
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[ -e $(basename $0) ] && echo "PLEASE USE THIS SCRIPT FROM ANOTHER DIR" && exit 1
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SCRIPT_DIR=$(dirname $0)
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EXECUTABLE_NAME_BASE=$(basename $SCRIPT_DIR)
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LIBFUZZER_SRC=$(dirname $(dirname $SCRIPT_DIR))
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JOBS=20
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# FUZZ_CXXFLAGS=" -g -fsanitize=address -fsanitize-coverage=edge"
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FUZZ_CXXFLAGS=" -g -fsanitize=address -fsanitize-coverage=trace-pc-guard,trace-cmp,trace-div,trace-gep"
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get() {
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[ ! -e SRC ] && git clone https://github.com/openssl/openssl.git SRC && (cd SRC && git checkout OpenSSL_1_0_2d)
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# [ ! -e SRC ] && wget https://www.openssl.org/source/openssl-1.0.1f.tar.gz && tar xf openssl-1.0.1f.tar.gz && mv openssl-1.0.1f SRC
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}
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build_lib() {
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rm -rf BUILD
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cp -rf SRC BUILD
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(cd BUILD && ./config && make clean && make CC="clang $FUZZ_CXXFLAGS" -j $JOBS)
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}
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get
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build_lib
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$LIBFUZZER_SRC/build.sh
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echo clang++ -g $SCRIPT_DIR/target.cc -DCERT_PATH=\"$SCRIPT_DIR/\" $FUZZ_CXXFLAGS BUILD/libssl.a BUILD/libcrypto.a libFuzzer.a -lgcrypt -o $EXECUTABLE_NAME_BASE

‎lib/Fuzzer/fuzzer-test-suite/openssl-1.0.2d/target.cc

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// Find CVE-2015-3193. Derived from
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// https://github.com/hannob/bignum-fuzz/blob/master/CVE-2015-3193-openssl-vs-gcrypt-modexp.c
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/* Fuzz-compare the OpenSSL function BN_mod_exp() and the libgcrypt function gcry_mpi_powm().
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*
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* To use this you should compile both libgcrypt and openssl with american fuzzy lop and then statically link everything together, e.g.:
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* afl-clang-fast -o [output] [input] libgcrypt.a libcrypto.a -lgpg-error
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*
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* Input is a binary file, the first bytes will decide how the rest of the file will be split into three bignums.
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*
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* by Hanno Böck, license CC0 (public domain)
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <assert.h>
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#include <openssl/bn.h>
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#include <gcrypt.h>
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#define MAXBUF 1000000
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struct big_results {
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char *name;
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char *a;
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char *b;
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char *c;
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char *exptmod;
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};
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void printres(struct big_results *res) {
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printf("\n%s:\n", res->name);
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printf("a: %s\n", res->a);
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printf("b: %s\n", res->b);
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printf("c: %s\n", res->c);
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printf("b^c mod a: %s\n", res->exptmod);
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}
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void freeres(struct big_results *res) {
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free(res->a);
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free(res->b);
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free(res->c);
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free(res->exptmod);
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}
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char *gcrytostring(gcry_mpi_t in) {
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char *a, *b;
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size_t i;
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size_t j=0;
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gcry_mpi_aprint(GCRYMPI_FMT_HEX, (unsigned char**) &a, &i, in);
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while(a[j]=='0' && j<(i-2)) j++;
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if ((j%2)==1) j--;
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if (strncmp(&a[j],"00",2)==0) j++;
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b=(char*)malloc(i-j);
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strcpy(b, &a[j]);
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free(a);
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return b;
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}
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/* test gcry functions from libgcrypt */
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void gcrytest(unsigned char* a_raw, int a_len, unsigned char* b_raw, int b_len, unsigned char* c_raw, int c_len, struct big_results *res) {
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gcry_mpi_t a, b, c, res1, res2;
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/* unknown leak here */
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gcry_mpi_scan(&a, GCRYMPI_FMT_USG, a_raw, a_len, NULL);
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res->a = gcrytostring(a);
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gcry_mpi_scan(&b, GCRYMPI_FMT_USG, b_raw, b_len, NULL);
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res->b = gcrytostring(b);
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gcry_mpi_scan(&c, GCRYMPI_FMT_USG, c_raw, c_len, NULL);
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res->c = gcrytostring(c);
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res1=gcry_mpi_new(0);
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gcry_mpi_powm(res1, b, c, a);
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res->exptmod=gcrytostring(res1);
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gcry_mpi_release(a);
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gcry_mpi_release(b);
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gcry_mpi_release(c);
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gcry_mpi_release(res1);
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}
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/* test bn functions from openssl/libcrypto */
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void bntest(unsigned char* a_raw, int a_len, unsigned char* b_raw, int b_len, unsigned char* c_raw, int c_len, struct big_results *res) {
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BN_CTX *bctx = BN_CTX_new();
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BIGNUM *a = BN_new();
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BIGNUM *b = BN_new();
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BIGNUM *c = BN_new();
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BIGNUM *res1 = BN_new();
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BN_bin2bn(a_raw, a_len, a);
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BN_bin2bn(b_raw, b_len, b);
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BN_bin2bn(c_raw, c_len, c);
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res->a = BN_bn2hex(a);
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res->b = BN_bn2hex(b);
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res->c = BN_bn2hex(c);
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BN_mod_exp(res1, b, c, a, bctx);
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res->exptmod = BN_bn2hex(res1);
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BN_free(a);
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BN_free(b);
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BN_free(c);
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BN_free(res1);
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BN_CTX_free(bctx);
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}
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extern "C" int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size) {
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size_t len, l1, l2,l3;
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unsigned int divi1, divi2;
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unsigned char *a, *b, *c;
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struct big_results openssl_results= {"openssl",0,0,0,0};
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struct big_results gcrypt_results= {"libgcrypt",0,0,0,0};
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len = Size;
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if (len<5) return 0;
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divi1=Data[0];
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divi2=Data[1];
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divi1++;divi2++;
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l1 = (len-2)*divi1/256;
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l2 = (len-2-l1)*divi2/256;
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l3 = (len-2-l1-l2);
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assert(l1+l2+l3==len-2);
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//printf("div1 div2 %i %i\n", divi1, divi2);
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//printf("len l1 l2 l3 %i %i %i %i\n", (int)len,(int)l1,(int)l2,(int)l3);
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a=const_cast<unsigned char*>(Data)+2;
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b=const_cast<unsigned char*>(Data)+2+l1;
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c=const_cast<unsigned char*>(Data)+2+l1+l2;
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bntest(a, l1, b, l2, c, l3, &openssl_results);
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//printres(&openssl_results);
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if ((strcmp(openssl_results.a,"0")==0) || (strcmp(openssl_results.c,"0")==0)) goto END;
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gcrytest(a, l1, b, l2, c, l3, &gcrypt_results);
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//printres(&gcrypt_results);
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assert(strcmp(openssl_results.exptmod, gcrypt_results.exptmod)==0);
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END:
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freeres(&openssl_results);
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freeres(&gcrypt_results);
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return 0;
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}

‎lib/Fuzzer/fuzzer-test-suite/openssl-1.0.2d/test.sh

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#!/bin/bash
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set -x
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SCRIPT_DIR=$(dirname $0)
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EXECUTABLE_NAME_BASE=$(basename $SCRIPT_DIR)
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CORPUS=CORPUS-$EXECUTABLE_NAME_BASE
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JOBS=8
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rm -rf $CORPUS
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mkdir $CORPUS
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[ -e $EXECUTABLE_NAME_BASE ] && ./$EXECUTABLE_NAME_BASE -artifact_prefix=$CORPUS/ -max_len=512 -jobs=$JOBS -workers=$JOBS $CORPUS
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grep 'Assertion `strcmp(openssl_results.exptmod, gcrypt_results.exptmod)==0. failed.' fuzz-0.log

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