Merge branch 'jk/hash-object-fsck'

"git hash-object" now checks that the resulting object is well
formed with the same code as "git fsck".

* jk/hash-object-fsck:
  fsck: do not assume NUL-termination of buffers
  hash-object: use fsck for object checks
  fsck: provide a function to fsck buffer without object struct
  t: use hash-object --literally when created malformed objects
  t7030: stop using invalid tag name
  t1006: stop using 0-padded timestamps
  t1007: modernize malformed object tests

21 files changed, 294 insertions, 96 deletions

diff --git a/fsck.c b/fsck.c
index 47eaeedd70..2b18717ee8 100644
--- a/fsck.c
+++ b/fsck.c
@@ -748,6 +748,23 @@ static int fsck_tree(const struct object_id *tree_oid,
 	return retval;
 }
 
+/*
+ * Confirm that the headers of a commit or tag object end in a reasonable way,
+ * either with the usual "\n\n" separator, or at least with a trailing newline
+ * on the final header line.
+ *
+ * This property is important for the memory safety of our callers. It allows
+ * them to scan the buffer linewise without constantly checking the remaining
+ * size as long as:
+ *
+ *   - they check that there are bytes left in the buffer at the start of any
+ *     line (i.e., that the last newline they saw was not the final one we
+ *     found here)
+ *
+ *   - any intra-line scanning they do will stop at a newline, which will worst
+ *     case hit the newline we found here as the end-of-header. This makes it
+ *     OK for them to use helpers like parse_oid_hex(), or even skip_prefix().
+ */
 static int verify_headers(const void *data, unsigned long size,
 			  const struct object_id *oid, enum object_type type,
 			  struct fsck_options *options)
@@ -808,6 +825,20 @@ static int fsck_ident(const char **ident,
 	if (*p != ' ')
 		return report(options, oid, type, FSCK_MSG_MISSING_SPACE_BEFORE_DATE, "invalid author/committer line - missing space before date");
 	p++;
+	/*
+	 * Our timestamp parser is based on the C strto*() functions, which
+	 * will happily eat whitespace, including the newline that is supposed
+	 * to prevent us walking past the end of the buffer. So do our own
+	 * scan, skipping linear whitespace but not newlines, and then
+	 * confirming we found a digit. We _could_ be even more strict here,
+	 * as we really expect only a single space, but since we have
+	 * traditionally allowed extra whitespace, we'll continue to do so.
+	 */
+	while (*p == ' ' || *p == '\t')
+		p++;
+	if (!isdigit(*p))
+		return report(options, oid, type, FSCK_MSG_BAD_DATE,
+			      "invalid author/committer line - bad date");
 	if (*p == '0' && p[1] != ' ')
 		return report(options, oid, type, FSCK_MSG_ZERO_PADDED_DATE, "invalid author/committer line - zero-padded date");
 	if (date_overflows(parse_timestamp(p, &end, 10)))
@@ -834,12 +865,18 @@ static int fsck_commit(const struct object_id *oid,
 	unsigned author_count;
 	int err;
 	const char *buffer_begin = buffer;
+	const char *buffer_end = buffer + size;
 	const char *p;
 
+	/*
+	 * We _must_ stop parsing immediately if this reports failure, as the
+	 * memory safety of the rest of the function depends on it. See the
+	 * comment above the definition of verify_headers() for more details.
+	 */
 	if (verify_headers(buffer, size, oid, OBJ_COMMIT, options))
 		return -1;
 
-	if (!skip_prefix(buffer, "tree ", &buffer))
+	if (buffer >= buffer_end || !skip_prefix(buffer, "tree ", &buffer))
 		return report(options, oid, OBJ_COMMIT, FSCK_MSG_MISSING_TREE, "invalid format - expected 'tree' line");
 	if (parse_oid_hex(buffer, &tree_oid, &p) || *p != '\n') {
 		err = report(options, oid, OBJ_COMMIT, FSCK_MSG_BAD_TREE_SHA1, "invalid 'tree' line format - bad sha1");
@@ -847,7 +884,7 @@ static int fsck_commit(const struct object_id *oid,
 			return err;
 	}
 	buffer = p + 1;
-	while (skip_prefix(buffer, "parent ", &buffer)) {
+	while (buffer < buffer_end && skip_prefix(buffer, "parent ", &buffer)) {
 		if (parse_oid_hex(buffer, &parent_oid, &p) || *p != '\n') {
 			err = report(options, oid, OBJ_COMMIT, FSCK_MSG_BAD_PARENT_SHA1, "invalid 'parent' line format - bad sha1");
 			if (err)
@@ -856,7 +893,7 @@ static int fsck_commit(const struct object_id *oid,
 		buffer = p + 1;
 	}
 	author_count = 0;
-	while (skip_prefix(buffer, "author ", &buffer)) {
+	while (buffer < buffer_end && skip_prefix(buffer, "author ", &buffer)) {
 		author_count++;
 		err = fsck_ident(&buffer, oid, OBJ_COMMIT, options);
 		if (err)
@@ -868,7 +905,7 @@ static int fsck_commit(const struct object_id *oid,
 		err = report(options, oid, OBJ_COMMIT, FSCK_MSG_MULTIPLE_AUTHORS, "invalid format - multiple 'author' lines");
 	if (err)
 		return err;
-	if (!skip_prefix(buffer, "committer ", &buffer))
+	if (buffer >= buffer_end || !skip_prefix(buffer, "committer ", &buffer))
 		return report(options, oid, OBJ_COMMIT, FSCK_MSG_MISSING_COMMITTER, "invalid format - expected 'committer' line");
 	err = fsck_ident(&buffer, oid, OBJ_COMMIT, options);
 	if (err)
@@ -899,13 +936,19 @@ int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
 	int ret = 0;
 	char *eol;
 	struct strbuf sb = STRBUF_INIT;
+	const char *buffer_end = buffer + size;
 	const char *p;
 
+	/*
+	 * We _must_ stop parsing immediately if this reports failure, as the
+	 * memory safety of the rest of the function depends on it. See the
+	 * comment above the definition of verify_headers() for more details.
+	 */
 	ret = verify_headers(buffer, size, oid, OBJ_TAG, options);
 	if (ret)
 		goto done;
 
-	if (!skip_prefix(buffer, "object ", &buffer)) {
+	if (buffer >= buffer_end || !skip_prefix(buffer, "object ", &buffer)) {
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_OBJECT, "invalid format - expected 'object' line");
 		goto done;
 	}
@@ -916,11 +959,11 @@ int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
 	}
 	buffer = p + 1;
 
-	if (!skip_prefix(buffer, "type ", &buffer)) {
+	if (buffer >= buffer_end || !skip_prefix(buffer, "type ", &buffer)) {
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TYPE_ENTRY, "invalid format - expected 'type' line");
 		goto done;
 	}
-	eol = strchr(buffer, '\n');
+	eol = memchr(buffer, '\n', buffer_end - buffer);
 	if (!eol) {
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TYPE, "invalid format - unexpected end after 'type' line");
 		goto done;
@@ -932,11 +975,11 @@ int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
 		goto done;
 	buffer = eol + 1;
 
-	if (!skip_prefix(buffer, "tag ", &buffer)) {
+	if (buffer >= buffer_end || !skip_prefix(buffer, "tag ", &buffer)) {
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TAG_ENTRY, "invalid format - expected 'tag' line");
 		goto done;
 	}
-	eol = strchr(buffer, '\n');
+	eol = memchr(buffer, '\n', buffer_end - buffer);
 	if (!eol) {
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TAG, "invalid format - unexpected end after 'type' line");
 		goto done;
@@ -952,7 +995,7 @@ int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
 	}
 	buffer = eol + 1;
 
-	if (!skip_prefix(buffer, "tagger ", &buffer)) {
+	if (buffer >= buffer_end || !skip_prefix(buffer, "tagger ", &buffer)) {
 		/* early tags do not contain 'tagger' lines; warn only */
 		ret = report(options, oid, OBJ_TAG, FSCK_MSG_MISSING_TAGGER_ENTRY, "invalid format - expected 'tagger' line");
 		if (ret)
@@ -960,10 +1003,8 @@ int fsck_tag_standalone(const struct object_id *oid, const char *buffer,
 	}
 	else
 		ret = fsck_ident(&buffer, oid, OBJ_TAG, options);
-	if (!*buffer)
-		goto done;
 
-	if (!starts_with(buffer, "\n")) {
+	if (buffer < buffer_end && !starts_with(buffer, "\n")) {
 		/*
 		 * The verify_headers() check will allow
 		 * e.g. "[...]tagger <tagger>\nsome
@@ -1237,19 +1278,26 @@ int fsck_object(struct object *obj, void *data, unsigned long size,
 	if (!obj)
 		return report(options, NULL, OBJ_NONE, FSCK_MSG_BAD_OBJECT_SHA1, "no valid object to fsck");
 
-	if (obj->type == OBJ_BLOB)
-		return fsck_blob(&obj->oid, data, size, options);
-	if (obj->type == OBJ_TREE)
-		return fsck_tree(&obj->oid, data, size, options);
-	if (obj->type == OBJ_COMMIT)
-		return fsck_commit(&obj->oid, data, size, options);
-	if (obj->type == OBJ_TAG)
-		return fsck_tag(&obj->oid, data, size, options);
+	return fsck_buffer(&obj->oid, obj->type, data, size, options);
+}
+
+int fsck_buffer(const struct object_id *oid, enum object_type type,
+		void *data, unsigned long size,
+		struct fsck_options *options)
+{
+	if (type == OBJ_BLOB)
+		return fsck_blob(oid, data, size, options);
+	if (type == OBJ_TREE)
+		return fsck_tree(oid, data, size, options);
+	if (type == OBJ_COMMIT)
+		return fsck_commit(oid, data, size, options);
+	if (type == OBJ_TAG)
+		return fsck_tag(oid, data, size, options);
 
-	return report(options, &obj->oid, obj->type,
+	return report(options, oid, type,
 		      FSCK_MSG_UNKNOWN_TYPE,
 		      "unknown type '%d' (internal fsck error)",
-		      obj->type);
+		      type);
 }
 
 int fsck_error_function(struct fsck_options *o,
diff --git a/fsck.h b/fsck.h
index fcecf4101c..668330880e 100644
--- a/fsck.h
+++ b/fsck.h
@@ -184,6 +184,14 @@ int fsck_object(struct object *obj, void *data, unsigned long size,
 	struct fsck_options *options);
 
 /*
+ * Same as fsck_object(), but for when the caller doesn't have an object
+ * struct.
+ */
+int fsck_buffer(const struct object_id *oid, enum object_type,
+		void *data, unsigned long size,
+		struct fsck_options *options);
+
+/*
  * fsck a tag, and pass info about it back to the caller. This is
  * exposed fsck_object() internals for git-mktag(1).
  */
diff --git a/object-file.c b/object-file.c
index ce9efae994..939865c1ae 100644
--- a/object-file.c
+++ b/object-file.c
@@ -33,6 +33,7 @@
 #include "object-store.h"
 #include "promisor-remote.h"
 #include "submodule.h"
+#include "fsck.h"
 
 /* The maximum size for an object header. */
 #define MAX_HEADER_LEN 32
@@ -2284,32 +2285,21 @@ int repo_has_object_file(struct repository *r,
 	return repo_has_object_file_with_flags(r, oid, 0);
 }
 
-static void check_tree(const void *buf, size_t size)
-{
-	struct tree_desc desc;
-	struct name_entry entry;
-
-	init_tree_desc(&desc, buf, size);
-	while (tree_entry(&desc, &entry))
-		/* do nothing
-		 * tree_entry() will die() on malformed entries */
-		;
-}
-
-static void check_commit(const void *buf, size_t size)
-{
-	struct commit c;
-	memset(&c, 0, sizeof(c));
-	if (parse_commit_buffer(the_repository, &c, buf, size, 0))
-		die(_("corrupt commit"));
-}
-
-static void check_tag(const void *buf, size_t size)
-{
-	struct tag t;
-	memset(&t, 0, sizeof(t));
-	if (parse_tag_buffer(the_repository, &t, buf, size))
-		die(_("corrupt tag"));
+/*
+ * We can't use the normal fsck_error_function() for index_mem(),
+ * because we don't yet have a valid oid for it to report. Instead,
+ * report the minimal fsck error here, and rely on the caller to
+ * give more context.
+ */
+static int hash_format_check_report(struct fsck_options *opts,
+				     const struct object_id *oid,
+				     enum object_type object_type,
+				     enum fsck_msg_type msg_type,
+				     enum fsck_msg_id msg_id,
+				     const char *message)
+{
+	error(_("object fails fsck: %s"), message);
+	return 1;
 }
 
 static int index_mem(struct index_state *istate,
@@ -2336,12 +2326,13 @@ static int index_mem(struct index_state *istate,
 		}
 	}
 	if (flags & HASH_FORMAT_CHECK) {
-		if (type == OBJ_TREE)
-			check_tree(buf, size);
-		if (type == OBJ_COMMIT)
-			check_commit(buf, size);
-		if (type == OBJ_TAG)
-			check_tag(buf, size);
+		struct fsck_options opts = FSCK_OPTIONS_DEFAULT;
+
+		opts.strict = 1;
+		opts.error_func = hash_format_check_report;
+		if (fsck_buffer(null_oid(), type, buf, size, &opts))
+			die(_("refusing to create malformed object"));
+		fsck_finish(&opts);
 	}
 
 	if (write_object)
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 23b8942edb..2d875b17d8 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -292,8 +292,8 @@ commit_message="Initial commit"
 commit_sha1=$(echo_without_newline "$commit_message" | git commit-tree $tree_sha1)
 commit_size=$(($(test_oid hexsz) + 137))
 commit_content="tree $tree_sha1
-author $GIT_AUTHOR_NAME <$GIT_AUTHOR_EMAIL> 0000000000 +0000
-committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 0000000000 +0000
+author $GIT_AUTHOR_NAME <$GIT_AUTHOR_EMAIL> 0 +0000
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 0 +0000
 
 $commit_message"
 
@@ -304,7 +304,7 @@ type blob
 tag hellotag
 tagger $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
 tag_description="This is a tag"
-tag_content="$tag_header_without_timestamp 0000000000 +0000
+tag_content="$tag_header_without_timestamp 0 +0000
 
 $tag_description"
 
diff --git a/t/t1007-hash-object.sh b/t/t1007-hash-object.sh
index ac5ad8c740..ac3d173767 100755
--- a/t/t1007-hash-object.sh
+++ b/t/t1007-hash-object.sh
@@ -203,23 +203,34 @@ done
 test_expect_success 'too-short tree' '
 	echo abc >malformed-tree &&
 	test_must_fail git hash-object -t tree malformed-tree 2>err &&
-	test_i18ngrep "too-short tree object" err
+	grep "too-short tree object" err
 '
 
 test_expect_success 'malformed mode in tree' '
-	hex_sha1=$(echo foo | git hash-object --stdin -w) &&
-	bin_sha1=$(echo $hex_sha1 | hex2oct) &&
-	printf "9100644 \0$bin_sha1" >tree-with-malformed-mode &&
+	hex_oid=$(echo foo | git hash-object --stdin -w) &&
+	bin_oid=$(echo $hex_oid | hex2oct) &&
+	printf "9100644 \0$bin_oid" >tree-with-malformed-mode &&
 	test_must_fail git hash-object -t tree tree-with-malformed-mode 2>err &&
-	test_i18ngrep "malformed mode in tree entry" err
+	grep "malformed mode in tree entry" err
 '
 
 test_expect_success 'empty filename in tree' '
-	hex_sha1=$(echo foo | git hash-object --stdin -w) &&
-	bin_sha1=$(echo $hex_sha1 | hex2oct) &&
-	printf "100644 \0$bin_sha1" >tree-with-empty-filename &&
+	hex_oid=$(echo foo | git hash-object --stdin -w) &&
+	bin_oid=$(echo $hex_oid | hex2oct) &&
+	printf "100644 \0$bin_oid" >tree-with-empty-filename &&
 	test_must_fail git hash-object -t tree tree-with-empty-filename 2>err &&
-	test_i18ngrep "empty filename in tree entry" err
+	grep "empty filename in tree entry" err
+'
+
+test_expect_success 'duplicate filename in tree' '
+	hex_oid=$(echo foo | git hash-object --stdin -w) &&
+	bin_oid=$(echo $hex_oid | hex2oct) &&
+	{
+		printf "100644 file\0$bin_oid" &&
+		printf "100644 file\0$bin_oid"
+	} >tree-with-duplicate-filename &&
+	test_must_fail git hash-object -t tree tree-with-duplicate-filename 2>err &&
+	grep "duplicateEntries" err
 '
 
 test_expect_success 'corrupt commit' '
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index de0f6d5e7f..fdb886dfe4 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -212,7 +212,7 @@ test_expect_success 'email without @ is okay' '
 test_expect_success 'email with embedded > is not okay' '
 	git cat-file commit HEAD >basis &&
 	sed "s/@[a-z]/&>/" basis >bad-email &&
-	new=$(git hash-object -t commit -w --stdin <bad-email) &&
+	new=$(git hash-object --literally -t commit -w --stdin <bad-email) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -223,7 +223,7 @@ test_expect_success 'email with embedded > is not okay' '
 test_expect_success 'missing < email delimiter is reported nicely' '
 	git cat-file commit HEAD >basis &&
 	sed "s/<//" basis >bad-email-2 &&
-	new=$(git hash-object -t commit -w --stdin <bad-email-2) &&
+	new=$(git hash-object --literally -t commit -w --stdin <bad-email-2) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -234,7 +234,7 @@ test_expect_success 'missing < email delimiter is reported nicely' '
 test_expect_success 'missing email is reported nicely' '
 	git cat-file commit HEAD >basis &&
 	sed "s/[a-z]* <[^>]*>//" basis >bad-email-3 &&
-	new=$(git hash-object -t commit -w --stdin <bad-email-3) &&
+	new=$(git hash-object --literally -t commit -w --stdin <bad-email-3) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -245,7 +245,7 @@ test_expect_success 'missing email is reported nicely' '
 test_expect_success '> in name is reported' '
 	git cat-file commit HEAD >basis &&
 	sed "s/ </> </" basis >bad-email-4 &&
-	new=$(git hash-object -t commit -w --stdin <bad-email-4) &&
+	new=$(git hash-object --literally -t commit -w --stdin <bad-email-4) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -258,7 +258,7 @@ test_expect_success 'integer overflow in timestamps is reported' '
 	git cat-file commit HEAD >basis &&
 	sed "s/^\\(author .*>\\) [0-9]*/\\1 18446744073709551617/" \
 		<basis >bad-timestamp &&
-	new=$(git hash-object -t commit -w --stdin <bad-timestamp) &&
+	new=$(git hash-object --literally -t commit -w --stdin <bad-timestamp) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -269,7 +269,7 @@ test_expect_success 'integer overflow in timestamps is reported' '
 test_expect_success 'commit with NUL in header' '
 	git cat-file commit HEAD >basis &&
 	sed "s/author ./author Q/" <basis | q_to_nul >commit-NUL-header &&
-	new=$(git hash-object -t commit -w --stdin <commit-NUL-header) &&
+	new=$(git hash-object --literally -t commit -w --stdin <commit-NUL-header) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -292,7 +292,7 @@ test_expect_success 'tree object with duplicate entries' '
 			git cat-file tree $T &&
 			git cat-file tree $T
 		) |
-		git hash-object -w -t tree --stdin
+		git hash-object --literally -w -t tree --stdin
 	) &&
 	test_must_fail git fsck 2>out &&
 	test_i18ngrep "error in tree .*contains duplicate file entries" out
@@ -426,7 +426,7 @@ test_expect_success 'tag with incorrect tag name & missing tagger' '
 	This is an invalid tag.
 	EOF
 
-	tag=$(git hash-object -t tag -w --stdin <wrong-tag) &&
+	tag=$(git hash-object --literally -t tag -w --stdin <wrong-tag) &&
 	test_when_finished "remove_object $tag" &&
 	echo $tag >.git/refs/tags/wrong &&
 	test_when_finished "git update-ref -d refs/tags/wrong" &&
@@ -558,7 +558,7 @@ test_expect_success 'rev-list --verify-objects with commit graph (parent)' '
 test_expect_success 'force fsck to ignore double author' '
 	git cat-file commit HEAD >basis &&
 	sed "s/^author .*/&,&/" <basis | tr , \\n >multiple-authors &&
-	new=$(git hash-object -t commit -w --stdin <multiple-authors) &&
+	new=$(git hash-object --literally -t commit -w --stdin <multiple-authors) &&
 	test_when_finished "remove_object $new" &&
 	git update-ref refs/heads/bogus "$new" &&
 	test_when_finished "git update-ref -d refs/heads/bogus" &&
@@ -573,7 +573,7 @@ test_expect_success 'fsck notices blob entry pointing to null sha1' '
 	(git init null-blob &&
 	 cd null-blob &&
 	 sha=$(printf "100644 file$_bz$_bzoid" |
-	       git hash-object -w --stdin -t tree) &&
+	       git hash-object --literally -w --stdin -t tree) &&
 	  git fsck 2>out &&
 	  test_i18ngrep "warning.*null sha1" out
 	)
@@ -583,7 +583,7 @@ test_expect_success 'fsck notices submodule entry pointing to null sha1' '
 	(git init null-commit &&
 	 cd null-commit &&
 	 sha=$(printf "160000 submodule$_bz$_bzoid" |
-	       git hash-object -w --stdin -t tree) &&
+	       git hash-object --literally -w --stdin -t tree) &&
 	  git fsck 2>out &&
 	  test_i18ngrep "warning.*null sha1" out
 	)
@@ -648,7 +648,7 @@ test_expect_success 'NUL in commit' '
 		git commit --allow-empty -m "initial commitQNUL after message" &&
 		git cat-file commit HEAD >original &&
 		q_to_nul <original >munged &&
-		git hash-object -w -t commit --stdin <munged >name &&
+		git hash-object --literally -w -t commit --stdin <munged >name &&
 		git branch bad $(cat name) &&
 
 		test_must_fail git -c fsck.nulInCommit=error fsck 2>warn.1 &&
@@ -794,8 +794,8 @@ test_expect_success 'fsck errors in packed objects' '
 	git cat-file commit HEAD >basis &&
 	sed "s/</one/" basis >one &&
 	sed "s/</foo/" basis >two &&
-	one=$(git hash-object -t commit -w one) &&
-	two=$(git hash-object -t commit -w two) &&
+	one=$(git hash-object --literally -t commit -w one) &&
+	two=$(git hash-object --literally -t commit -w two) &&
 	pack=$(
 		{
 			echo $one &&
diff --git a/t/t1451-fsck-buffer.sh b/t/t1451-fsck-buffer.sh
new file mode 100755
index 0000000000..9ac270abab
--- /dev/null
+++ b/t/t1451-fsck-buffer.sh
@@ -0,0 +1,140 @@
+#!/bin/sh
+
+test_description='fsck on buffers without NUL termination
+
+The goal here is to make sure that the various fsck parsers never look
+past the end of the buffer they are given, even when encountering broken
+or truncated objects.
+
+We have to use "hash-object" for this because most code paths that read objects
+append an extra NUL for safety after the buffer. But hash-object, since it is
+reading straight from a file (and possibly even mmap-ing it) cannot always do
+so.
+
+These tests _might_ catch such overruns in normal use, but should be run with
+ASan or valgrind for more confidence.
+'
+. ./test-lib.sh
+
+# the general idea for tags and commits is to build up the "base" file
+# progressively, and then test new truncations on top of it.
+reset () {
+	test_expect_success 'reset input to empty' '
+		>base
+	'
+}
+
+add () {
+	content="$1"
+	type=${content%% *}
+	test_expect_success "add $type line" '
+		echo "$content" >>base
+	'
+}
+
+check () {
+	type=$1
+	fsck=$2
+	content=$3
+	test_expect_success "truncated $type ($fsck, \"$content\")" '
+		# do not pipe into hash-object here; we want to increase
+		# the chance that it uses a fixed-size buffer or mmap,
+		# and a pipe would be read into a strbuf.
+		{
+			cat base &&
+			echo "$content"
+		} >input &&
+		test_must_fail git hash-object -t "$type" input 2>err &&
+		grep "$fsck" err
+	'
+}
+
+test_expect_success 'create valid objects' '
+	git commit --allow-empty -m foo &&
+	commit=$(git rev-parse --verify HEAD) &&
+	tree=$(git rev-parse --verify HEAD^{tree})
+'
+
+reset
+check commit missingTree ""
+check commit missingTree "tr"
+check commit missingTree "tree"
+check commit badTreeSha1 "tree "
+check commit badTreeSha1 "tree 1234"
+add "tree $tree"
+
+# these expect missingAuthor because "parent" is optional
+check commit missingAuthor ""
+check commit missingAuthor "par"
+check commit missingAuthor "parent"
+check commit badParentSha1 "parent "
+check commit badParentSha1 "parent 1234"
+add "parent $commit"
+
+check commit missingAuthor ""
+check commit missingAuthor "au"
+check commit missingAuthor "author"
+ident_checks () {
+	check $1 missingEmail "$2 "
+	check $1 missingEmail "$2 name"
+	check $1 badEmail "$2 name <"
+	check $1 badEmail "$2 name <email"
+	check $1 missingSpaceBeforeDate "$2 name <email>"
+	check $1 badDate "$2 name <email> "
+	check $1 badDate "$2 name <email> 1234"
+	check $1 badTimezone "$2 name <email> 1234 "
+	check $1 badTimezone "$2 name <email> 1234 +"
+}
+ident_checks commit author
+add "author name <email> 1234 +0000"
+
+check commit missingCommitter ""
+check commit missingCommitter "co"
+check commit missingCommitter "committer"
+ident_checks commit committer
+add "committer name <email> 1234 +0000"
+
+reset
+check tag missingObject ""
+check tag missingObject "obj"
+check tag missingObject "object"
+check tag badObjectSha1 "object "
+check tag badObjectSha1 "object 1234"
+add "object $commit"
+
+check tag missingType ""
+check tag missingType "ty"
+check tag missingType "type"
+check tag badType "type "
+check tag badType "type com"
+add "type commit"
+
+check tag missingTagEntry ""
+check tag missingTagEntry "ta"
+check tag missingTagEntry "tag"
+check tag badTagName "tag "
+add "tag foo"
+
+check tag missingTagger ""
+check tag missingTagger "ta"
+check tag missingTagger "tagger"
+ident_checks tag tagger
+
+# trees are a binary format and can't use our earlier helpers
+test_expect_success 'truncated tree (short hash)' '
+	printf "100644 foo\0\1\1\1\1" >input &&
+	test_must_fail git hash-object -t tree input 2>err &&
+	grep badTree err
+'
+
+test_expect_success 'truncated tree (missing nul)' '
+	# these two things are indistinguishable to the parser. The important
+	# thing about this is example is that there are enough bytes to
+	# make up a hash, and that there is no NUL (and we confirm that the
+	# parser does not walk past the end of the buffer).
+	printf "100644 a long filename, or a hash with missing nul?" >input &&
+	test_must_fail git hash-object -t tree input 2>err &&
+	grep badTree err
+'
+
+test_done
diff --git a/t/t4054-diff-bogus-tree.sh b/t/t4054-diff-bogus-tree.sh
index 294fb55313..05c88f8cdf 100755
--- a/t/t4054-diff-bogus-tree.sh
+++ b/t/t4054-diff-bogus-tree.sh
@@ -10,7 +10,7 @@ test_expect_success 'create bogus tree' '
 	bogus_tree=$(
 		printf "100644 fooQ$name" |
 		q_to_nul |
-		git hash-object -w --stdin -t tree
+		git hash-object --literally -w --stdin -t tree
 	)
 '
 
diff --git a/t/t4058-diff-duplicates.sh b/t/t4058-diff-duplicates.sh
index 54614b814d..2501c89c1c 100755
--- a/t/t4058-diff-duplicates.sh
+++ b/t/t4058-diff-duplicates.sh
@@ -29,7 +29,7 @@ make_tree () {
 		make_tree_entry "$1" "$2" "$3"
 		shift; shift; shift
 	done |
-	git hash-object -w -t tree --stdin
+	git hash-object --literally -w -t tree --stdin
 }
 
 # this is kind of a convoluted setup, but matches
diff --git a/t/t4212-log-corrupt.sh b/t/t4212-log-corrupt.sh
index 30a219894b..e89e1f54b6 100755
--- a/t/t4212-log-corrupt.sh
+++ b/t/t4212-log-corrupt.sh
@@ -10,7 +10,7 @@ test_expect_success 'setup' '
 
 	git cat-file commit HEAD |
 	sed "/^author /s/>/>-<>/" >broken_email.commit &&
-	git hash-object -w -t commit broken_email.commit >broken_email.hash &&
+	git hash-object --literally -w -t commit broken_email.commit >broken_email.hash &&
 	git update-ref refs/heads/broken_email $(cat broken_email.hash)
 '
 
@@ -46,7 +46,7 @@ test_expect_success 'git log --format with broken author email' '
 munge_author_date () {
 	git cat-file commit "$1" >commit.orig &&
 	sed "s/^\(author .*>\) [0-9]*/\1 $2/" <commit.orig >commit.munge &&
-	git hash-object -w -t commit commit.munge
+	git hash-object --literally -w -t commit commit.munge
 }
 
 test_expect_success 'unparsable dates produce sentinel value' '
diff --git a/t/t5302-pack-index.sh b/t/t5302-pack-index.sh
index b0095ab41d..59e9e77223 100755
--- a/t/t5302-pack-index.sh
+++ b/t/t5302-pack-index.sh
@@ -263,7 +263,7 @@ tag guten tag
 This is an invalid tag.
 EOF
 
-	tag=$(git hash-object -t tag -w --stdin <wrong-tag) &&
+	tag=$(git hash-object -t tag -w --stdin --literally <wrong-tag) &&
 	pack1=$(echo $tag $sha | git pack-objects tag-test) &&
 	echo remove tag object &&
 	thirtyeight=${tag#??} &&
diff --git a/t/t5504-fetch-receive-strict.sh b/t/t5504-fetch-receive-strict.sh
index ac4099ca89..88d3c56750 100755
--- a/t/t5504-fetch-receive-strict.sh
+++ b/t/t5504-fetch-receive-strict.sh
@@ -138,7 +138,7 @@ This commit object intentionally broken
 EOF
 
 test_expect_success 'setup bogus commit' '
-	commit="$(git hash-object -t commit -w --stdin <bogus-commit)"
+	commit="$(git hash-object --literally -t commit -w --stdin <bogus-commit)"
 '
 
 test_expect_success 'fsck with no skipList input' '
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index b33cd4afca..e4db7513f4 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -1114,7 +1114,7 @@ test_expect_success 'packfile-uri with transfer.fsckobjects fails on bad object'
 
 	This commit object intentionally broken
 	EOF
-	BOGUS=$(git -C "$P" hash-object -t commit -w --stdin <bogus-commit) &&
+	BOGUS=$(git -C "$P" hash-object -t commit -w --stdin --literally <bogus-commit) &&
 	git -C "$P" branch bogus-branch "$BOGUS" &&
 
 	echo my-blob >"$P/my-blob" &&
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index 2ae1fc721b..c466fd989f 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -606,7 +606,7 @@ test_expect_success 'create tag without tagger' '
 	git tag -a -m "Broken tag" taggerless &&
 	git tag -f taggerless $(git cat-file tag taggerless |
 		sed -e "/^tagger /d" |
-		git hash-object --stdin -w -t tag)
+		git hash-object --literally --stdin -w -t tag)
 '
 
 test_atom refs/tags/taggerless type 'commit'
diff --git a/t/t7030-verify-tag.sh b/t/t7030-verify-tag.sh
index 10faa64515..6f526c37c2 100755
--- a/t/t7030-verify-tag.sh
+++ b/t/t7030-verify-tag.sh
@@ -115,7 +115,7 @@ test_expect_success GPGSM 'verify and show signatures x509 with high minTrustLev
 
 test_expect_success GPG 'detect fudged signature' '
 	git cat-file tag seventh-signed >raw &&
-	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
+	sed -e "/^tag / s/seventh/7th-forged/" raw >forged1 &&
 	git hash-object -w -t tag forged1 >forged1.tag &&
 	test_must_fail git verify-tag $(cat forged1.tag) 2>actual1 &&
 	grep "BAD signature from" actual1 &&
diff --git a/t/t7031-verify-tag-signed-ssh.sh b/t/t7031-verify-tag-signed-ssh.sh
index 1cb36b9ab8..36eb86a4b1 100755
--- a/t/t7031-verify-tag-signed-ssh.sh
+++ b/t/t7031-verify-tag-signed-ssh.sh
@@ -125,7 +125,7 @@ test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'verify-tag failes with tag date ou
 test_expect_success GPGSSH 'detect fudged ssh signature' '
 	test_config gpg.ssh.allowedSignersFile "${GPGSSH_ALLOWED_SIGNERS}" &&
 	git cat-file tag seventh-signed >raw &&
-	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
+	sed -e "/^tag / s/seventh/7th-forged/" raw >forged1 &&
 	git hash-object -w -t tag forged1 >forged1.tag &&
 	test_must_fail git verify-tag $(cat forged1.tag) 2>actual1 &&
 	grep "${GPGSSH_BAD_SIGNATURE}" actual1 &&
diff --git a/t/t7509-commit-authorship.sh b/t/t7509-commit-authorship.sh
index 21c668f75e..5d890949f7 100755
--- a/t/t7509-commit-authorship.sh
+++ b/t/t7509-commit-authorship.sh
@@ -105,7 +105,7 @@ test_expect_success '--amend option with empty author' '
 test_expect_success '--amend option with missing author' '
 	git cat-file commit Initial >tmp &&
 	sed "s/author [^<]* </author </" tmp >malformed &&
-	sha=$(git hash-object -t commit -w malformed) &&
+	sha=$(git hash-object --literally -t commit -w malformed) &&
 	test_when_finished "remove_object $sha" &&
 	git checkout $sha &&
 	test_when_finished "git checkout Initial" &&
diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 8593b7e3cb..bc7a31ba3e 100755
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -202,7 +202,7 @@ test_expect_success GPG 'detect fudged signature with NUL' '
 	git cat-file commit seventh-signed >raw &&
 	cat raw >forged2 &&
 	echo Qwik | tr "Q" "\000" >>forged2 &&
-	git hash-object -w -t commit forged2 >forged2.commit &&
+	git hash-object --literally -w -t commit forged2 >forged2.commit &&
 	test_must_fail git verify-commit $(cat forged2.commit) &&
 	git show --pretty=short --show-signature $(cat forged2.commit) >actual2 &&
 	grep "BAD signature from" actual2 &&
diff --git a/t/t7528-signed-commit-ssh.sh b/t/t7528-signed-commit-ssh.sh
index f47e995179..065f780636 100755
--- a/t/t7528-signed-commit-ssh.sh
+++ b/t/t7528-signed-commit-ssh.sh
@@ -270,7 +270,7 @@ test_expect_success GPGSSH 'detect fudged signature with NUL' '
 	git cat-file commit seventh-signed >raw &&
 	cat raw >forged2 &&
 	echo Qwik | tr "Q" "\000" >>forged2 &&
-	git hash-object -w -t commit forged2 >forged2.commit &&
+	git hash-object --literally -w -t commit forged2 >forged2.commit &&
 	test_must_fail git verify-commit $(cat forged2.commit) &&
 	git show --pretty=short --show-signature $(cat forged2.commit) >actual2 &&
 	grep "${GPGSSH_BAD_SIGNATURE}" actual2 &&
diff --git a/t/t8003-blame-corner-cases.sh b/t/t8003-blame-corner-cases.sh
index d751d48b7d..8bcd39e81b 100755
--- a/t/t8003-blame-corner-cases.sh
+++ b/t/t8003-blame-corner-cases.sh
@@ -201,7 +201,7 @@ committer David Reiss <dreiss@facebook.com> 1234567890 +0000
 
 some message
 EOF
-  COMMIT=$(git hash-object -t commit -w badcommit) &&
+  COMMIT=$(git hash-object --literally -t commit -w badcommit) &&
   git --no-pager blame $COMMIT -- uno >/dev/null
 '
 
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index ff21a12ee6..26c25c0eb2 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -373,7 +373,7 @@ EOF
 
 test_expect_success 'cope with tagger-less tags' '
 
-	TAG=$(git hash-object -t tag -w tag-content) &&
+	TAG=$(git hash-object --literally -t tag -w tag-content) &&
 	git update-ref refs/tags/sonnenschein $TAG &&
 	git fast-export -C -C --signed-tags=strip --all > output &&
 	test $(grep -c "^tag " output) = 4 &&