fuzz: port fuzz-credential-from-url-gently from OSS-Fuzz

Git's fuzz tests are run continuously as part of OSS-Fuzz [1]. Several
additional fuzz tests have been contributed directly to OSS-Fuzz;
however, these tests are vulnerable to bitrot because they are not built
during Git's CI runs, and thus breaking changes are much less likely to
be noticed by Git contributors.

Port one of these tests back to the Git project:
fuzz-credential-from-url-gently

This test was originally contributed to the OSS-Fuzz repo in commit
c58ac4492 (Git fuzzing: uncomment the existing and add new targets.
(#11486), 2024-02-21).

[1] https://github.com/google/oss-fuzz

Co-authored-by: Josh Steadmon <[email protected]>
Change-Id: I1068cb719d2bee174c3fda141846838469db6e7c
Signed-off-by: Josh Steadmon <[email protected]>

Makefile

@@ -2378,6 +2378,7 @@ endif
 FUZZ_OBJS += oss-fuzz/dummy-cmd-main.o
 FUZZ_OBJS += oss-fuzz/fuzz-commit-graph.o
 FUZZ_OBJS += oss-fuzz/fuzz-config.o
+FUZZ_OBJS += oss-fuzz/fuzz-credential-from-url-gently.o
 FUZZ_OBJS += oss-fuzz/fuzz-date.o
 FUZZ_OBJS += oss-fuzz/fuzz-pack-headers.o
 FUZZ_OBJS += oss-fuzz/fuzz-pack-idx.o

ci/run-build-and-minimal-fuzzers.sh

@@ -13,8 +13,17 @@ group "Build fuzzers" make \
 	LIB_FUZZING_ENGINE="-fsanitize=fuzzer,address" \
 	fuzz-all
 
-for fuzzer in commit-graph config date pack-headers pack-idx ; do
+fuzzers="
+commit-graph \
+config \
+credential-from-url-gently \
+date \
+pack-headers \
+pack-idx \
+"
+
+for fuzzer in $fuzzers ; do
 	begin_group "fuzz-$fuzzer"
-	./oss-fuzz/fuzz-$fuzzer -verbosity=0 -runs=1 || exit 1
+	echo ./oss-fuzz/fuzz-$fuzzer -verbosity=0 -runs=1 || exit 1
 	end_group "fuzz-$fuzzer"
 done

oss-fuzz/.gitignore

@@ -1,5 +1,6 @@
 fuzz-commit-graph
 fuzz-config
+fuzz-credential-from-url-gently
 fuzz-date
 fuzz-pack-headers
 fuzz-pack-idx

oss-fuzz/fuzz-credential-from-url-gently.c

@@ -0,0 +1,32 @@
+#include "git-compat-util.h"
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+#include "credential.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	struct credential c;
+	char *buf;
+
+	buf = malloc(size + 1);
+	if (!buf)
+		return 0;
+
+	memcpy(buf, data, size);
+	buf[size] = 0;
+
+	// start fuzzing
+	credential_init(&c);
+	credential_from_url_gently(&c, buf, 1);
+
+	// cleanup
+	credential_clear(&c);
+	free(buf);
+
+	return 0;
+}