git-check-ref-format: reject funny ref names.

Update check_ref_format() function to reject ref names that:

 * has a path component that begins with a ".", or
 * has a double dots "..", or
 * has ASCII control character, "~", "^", ":" or SP, anywhere, or
 * ends with a "/".

Use it in 'git-checkout -b', 'git-branch', and 'git-tag' to make sure
that newly created refs are well-formed.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -116,7 +116,7 @@ PROGRAMS = \
 	git-ssh-upload git-tar-tree git-unpack-file \
 	git-unpack-objects git-update-index git-update-server-info \
 	git-upload-pack git-verify-pack git-write-tree \
-	git-update-ref git-symbolic-ref \
+	git-update-ref git-symbolic-ref git-check-ref-format \
 	$(SIMPLE_PROGRAMS)
 
 # Backward compatibility -- to be removed after 1.0

check-ref-format.c

@@ -0,0 +1,17 @@
+/*
+ * GIT - The information manager from hell
+ */
+
+#include "cache.h"
+#include "refs.h"
+
+#include <stdio.h>
+
+int main(int ac, char **av)
+{
+	if (ac != 2)
+		usage("git-check-ref-format refname");
+	if (check_ref_format(av[1]))
+		exit(1);
+	return 0;
+}

git-branch.sh

@@ -13,38 +13,42 @@ If two arguments, create a new branch <branchname> based off of <start-point>.
 }
 
 delete_branch () {
-    option="$1" branch_name="$2"
+    option="$1"
+    shift
     headref=$(GIT_DIR="$GIT_DIR" git-symbolic-ref HEAD |
     	       sed -e 's|^refs/heads/||')
-    case ",$headref," in
-    ",$branch_name,")
-	die "Cannot delete the branch you are on." ;;
-    ,,)
-	die "What branch are you on anyway?" ;;
-    esac
-    branch=$(cat "$GIT_DIR/refs/heads/$branch_name") &&
-	branch=$(git-rev-parse --verify "$branch^0") ||
-	    die "Seriously, what branch are you talking about?"
-    case "$option" in
-    -D)
-	;;
-    *)
-	mbs=$(git-merge-base -a "$branch" HEAD | tr '\012' ' ')
-	case " $mbs " in
-	*' '$branch' '*)
-	    # the merge base of branch and HEAD contains branch --
-	    # which means that the HEAD contains everything in the HEAD.
+    for branch_name
+    do
+	case ",$headref," in
+	",$branch_name,")
+	    die "Cannot delete the branch you are on." ;;
+	,,)
+	    die "What branch are you on anyway?" ;;
+	esac
+	branch=$(cat "$GIT_DIR/refs/heads/$branch_name") &&
+	    branch=$(git-rev-parse --verify "$branch^0") ||
+		die "Seriously, what branch are you talking about?"
+	case "$option" in
+	-D)
 	    ;;
 	*)
-	    echo >&2 "The branch '$branch_name' is not a strict subset of your current HEAD.
-If you are sure you want to delete it, run 'git branch -D $branch_name'."
-	    exit 1
+	    mbs=$(git-merge-base -a "$branch" HEAD | tr '\012' ' ')
+	    case " $mbs " in
+	    *' '$branch' '*)
+		# the merge base of branch and HEAD contains branch --
+		# which means that the HEAD contains everything in the HEAD.
+		;;
+	    *)
+		echo >&2 "The branch '$branch_name' is not a strict subset of your current HEAD.
+    If you are sure you want to delete it, run 'git branch -D $branch_name'."
+		exit 1
+		;;
+	    esac
 	    ;;
 	esac
-	;;
-    esac
-    rm -f "$GIT_DIR/refs/heads/$branch_name"
-    echo "Deleted branch $branch_name."
+	rm -f "$GIT_DIR/refs/heads/$branch_name"
+	echo "Deleted branch $branch_name."
+    done
     exit 0
 }
 
@@ -52,7 +56,7 @@ while case "$#,$1" in 0,*) break ;; *,-*) ;; *) break ;; esac
 do
 	case "$1" in
 	-d | -D)
-		delete_branch "$1" "$2"
+		delete_branch "$@"
 		exit
 		;;
 	--)
@@ -93,6 +97,9 @@ branchname="$1"
 
 rev=$(git-rev-parse --verify "$head") || exit
 
-[ -e "$GIT_DIR/refs/heads/$branchname" ] && die "$branchname already exists"
+[ -e "$GIT_DIR/refs/heads/$branchname" ] &&
+	die "$branchname already exists."
+git-check-ref-format "heads/$branchname" ||
+	die "we do not like '$branchname' as a branch name."
 
 echo $rev > "$GIT_DIR/refs/heads/$branchname"

git-checkout.sh

@@ -17,6 +17,8 @@ while [ "$#" != "0" ]; do
 			die "git checkout: -b needs a branch name"
 		[ -e "$GIT_DIR/refs/heads/$newbranch" ] &&
 			die "git checkout: branch $newbranch already exists"
+		git-check-ref-format "heads/$newbranch" ||
+			die "we do not like '$newbranch' as a branch name."
 		;;
 	"-f")
 		force=1

git-tag.sh

@@ -46,6 +46,8 @@ if [ -e "$GIT_DIR/refs/tags/$name" -a -z "$force" ]; then
     die "tag '$name' already exists"
 fi
 shift
+git-check-ref-format "tags/$name" ||
+	die "we do not like '$name' as a tag name."
 
 object=$(git-rev-parse --verify --default HEAD "$@") || exit 1
 type=$(git-cat-file -t $object) || exit 1

refs.c

@@ -335,17 +335,54 @@ int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 	return retval;
 }
 
+/*
+ * Make sure "ref" is something reasonable to have under ".git/refs/";
+ * We do not like it if:
+ *
+ * - any path component of it begins with ".", or
+ * - it has double dots "..", or
+ * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
+ * - it ends with a "/".
+ */
+
+static inline int bad_ref_char(int ch)
+{
+	return (((unsigned) ch) <= ' ' ||
+		ch == '~' || ch == '^' || ch == ':');
+}
+
 int check_ref_format(const char *ref)
 {
-	char *middle;
-	if (ref[0] == '.' || ref[0] == '/')
-		return -1;
-	middle = strchr(ref, '/');
-	if (!middle || !middle[1])
-		return -1;
-	if (strchr(middle + 1, '/'))
-		return -1;
-	return 0;
+	int ch, level;
+	const char *cp = ref;
+
+	level = 0;
+	while (1) {
+		while ((ch = *cp++) == '/')
+			; /* tolerate duplicated slashes */
+		if (!ch)
+			return -1; /* should not end with slashes */
+
+		/* we are at the beginning of the path component */
+		if (ch == '.' || bad_ref_char(ch))
+			return -1;
+
+		/* scan the rest of the path component */
+		while ((ch = *cp++) != 0) {
+			if (bad_ref_char(ch))
+				return -1;
+			if (ch == '/')
+				break;
+			if (ch == '.' && *cp == '.')
+				return -1;
+		}
+		level++;
+		if (!ch) {
+			if (level < 2)
+				return -1; /* at least of form "heads/blah" */
+			return 0;
+		}
+	}
 }
 
 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)