fsck: detect null sha1 in tree entries

Short of somebody happening to beat the 1 in 2^160 odds of
actually generating content that hashes to the null sha1, we
should never see this value in a tree entry. So let's have
fsck warn if it it seen.

As in the previous commit, we test both blob and submodule
entries to future-proof the test suite against the
implementation depending on connectivity to notice the
error.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/fsck.c b/fsck.c
index 6c855f84f01c19678399d85181da1094bd61b371..da53cf41f9c58f9779d00c28b9735b2b965dfaa9 100644 (file)
--- a/fsck.c
+++ b/fsck.c
@@ -139,6 +139,7 @@ static int verify_ordered(unsigned mode1, const char *name1, unsigned mode2, con
 static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
 {
        int retval;
+       int has_null_sha1 = 0;
        int has_full_path = 0;
        int has_empty_name = 0;
        int has_zero_pad = 0;
@@ -157,9 +158,12 @@ static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
        while (desc.size) {
                unsigned mode;
                const char *name;
+               const unsigned char *sha1;
 
-               tree_entry_extract(&desc, &name, &mode);
+               sha1 = tree_entry_extract(&desc, &name, &mode);
 
+               if (is_null_sha1(sha1))
+                       has_null_sha1 = 1;
                if (strchr(name, '/'))
                        has_full_path = 1;
                if (!*name)
@@ -207,6 +211,8 @@ static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
        }
 
        retval = 0;
+       if (has_null_sha1)
+               retval += error_func(&item->object, FSCK_WARN, "contains entries pointing to null sha1");
        if (has_full_path)
                retval += error_func(&item->object, FSCK_WARN, "contains full pathnames");
        if (has_empty_name)

diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 5b8ebd805378dc79e449ec1eecd1e97e333a7902..5e36cc71b4cc5f60b3c3a1782f95ae36448020c5 100755 (executable)
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -217,4 +217,30 @@ test_expect_success 'rev-list --verify-objects with bad sha1' '
        grep -q "error: sha1 mismatch 63ffffffffffffffffffffffffffffffffffffff" out
 '
 
+_bz='\0'
+_bz5="$_bz$_bz$_bz$_bz$_bz"
+_bz20="$_bz5$_bz5$_bz5$_bz5"
+
+test_expect_success 'fsck notices blob entry pointing to null sha1' '
+       (git init null-blob &&
+        cd null-blob &&
+        sha=$(printf "100644 file$_bz$_bz20" |
+              git hash-object -w --stdin -t tree) &&
+         git fsck 2>out &&
+         cat out &&
+         grep "warning.*null sha1" out
+       )
+'
+
+test_expect_success 'fsck notices submodule entry pointing to null sha1' '
+       (git init null-commit &&
+        cd null-commit &&
+        sha=$(printf "160000 submodule$_bz$_bz20" |
+              git hash-object -w --stdin -t tree) &&
+         git fsck 2>out &&
+         cat out &&
+         grep "warning.*null sha1" out
+       )
+'
+
 test_done