Honor the symbolic link option when copying files

Inspect source links without following them when COPYFILE_SYM is requested, before rejecting directories. This makes the documented option recreate link text instead of copying the referent, including dangling and directory links. Preserve requested link timestamps and report link-creation errors without overwriting the destination. Cover direct calls, destination directories, normal dereferencing and the existing rsync file caller.

test/copyfile-symlink.c

@@ -0,0 +1,114 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "check.h"
+
+static void check_link(const char *path, const char *target)
+{
+	char buf[256];
+	struct stat st;
+	ssize_t len;
+
+	fail_unless(lstat(path, &st) == 0 && S_ISLNK(st.st_mode));
+	len = readlink(path, buf, sizeof(buf));
+	fail_unless(len == (ssize_t)strlen(target));
+	fail_unless(memcmp(buf, target, len) == 0);
+}
+
+int main(void)
+{
+	char tmp[] = "/tmp/libite-copylink-XXXXXX";
+	const char payload[] = "target contents";
+	char buf[sizeof(payload)];
+	const char *targets[] = { "file", "dir", "missing", ".", "link" };
+	struct timespec times[2] = { { 1234567800, 0 }, { 1234567801, 0 } };
+	struct stat src_st, dst_st;
+	char cwd[4096];
+	size_t i;
+	FILE *fp;
+
+	fail_unless(getcwd(cwd, sizeof(cwd)) && mkdtemp(tmp));
+	fail_unless(chdir(tmp) == 0);
+	fail_unless(mkdir("dir", 0700) == 0);
+	fail_unless(mkdir("out", 0700) == 0);
+	fp = fopen("file", "w");
+	fail_unless(fp && fwrite(payload, 1, sizeof(payload), fp) == sizeof(payload));
+	fail_unless(fclose(fp) == 0);
+
+	for (i = 0; i < NELEMS(targets); i++) {
+		fail_unless(symlink(targets[i], "link") == 0);
+		fail_unless(copyfile("link", "copied", 0, LITE_FOPT_COPYFILE_SYM) == 1);
+		check_link("copied", targets[i]);
+		fail_unless(copyfile("link", "out", 0, LITE_FOPT_COPYFILE_SYM) == 1);
+		check_link("out/link", targets[i]);
+		/* Existing targets must survive a failed symlink creation. */
+		errno = 0;
+		fail_unless(copyfile("link", "file", 0, LITE_FOPT_COPYFILE_SYM) == 0);
+		fail_unless(errno == EEXIST);
+		check_link("copied", targets[i]);
+		fail_unless(unlink("copied") == 0 && unlink("out/link") == 0);
+		fail_unless(unlink("link") == 0);
+	}
+
+	fail_unless(symlink("file", "link") == 0);
+	/* Without SYM, continue to copy target data and preserve regular-file metadata. */
+	fail_unless(copyfile("link", "copied", 0, LITE_FOPT_KEEP_MTIME) == sizeof(payload));
+	fail_unless(lstat("copied", &dst_st) == 0 && S_ISREG(dst_st.st_mode));
+	fail_unless(stat("file", &src_st) == 0 && src_st.st_mtime == dst_st.st_mtime);
+	fp = fopen("copied", "r");
+	fail_unless(fp && fread(buf, 1, sizeof(buf), fp) == sizeof(payload));
+	fail_unless(memcmp(buf, payload, sizeof(payload)) == 0 && fclose(fp) == 0);
+	fail_unless(unlink("copied") == 0);
+
+	fail_unless(utimensat(AT_FDCWD, "link", times, AT_SYMLINK_NOFOLLOW) == 0);
+	fail_unless(copyfile("link", "copied", 0, LITE_FOPT_COPYFILE_SYM | LITE_FOPT_KEEP_MTIME) == 1);
+	check_link("copied", "file");
+	fail_unless(lstat("copied", &dst_st) == 0 && dst_st.st_mtime == times[1].tv_sec);
+	fail_unless(unlink("copied") == 0);
+	/* Exercise the existing rsync file caller, which requests SYM. */
+	fail_unless(rsync("link", "copied", 0, NULL) == 0);
+	check_link("copied", "file");
+	/* Reuse the destination after changing the source link. */
+	fail_unless(unlink("link") == 0 && symlink("file", "link") == 0);
+	fail_unless(rsync("link", "out", 0, NULL) == 0);
+	check_link("out/link", "file");
+	fail_unless(unlink("link") == 0 && symlink("copied", "link") == 0);
+	fail_unless(rsync("link", "out", 0, NULL) == 0);
+	check_link("out/link", "copied");
+	/* A same-path copy must not unlink its source. */
+	fail_unless(rsync("link", "link", 0, NULL) == 0);
+	check_link("link", "copied");
+	fail_unless(unlink("out/link") == 0);
+	/* Replacing a regular destination must also retain the source link. */
+	fail_unless(touch("out/link") == 0);
+	fail_unless(rsync("link", "out", 0, NULL) == 0);
+	check_link("out/link", "copied");
+	fail_unless(unlink("out/link") == 0);
+	/* A failed replacement must keep both the destination and source. */
+	fail_unless(mkdir("out/link", 0700) == 0);
+	fail_unless(touch("out/link/keep") == 0);
+	fail_unless(rsync("link", "out", 0, NULL) != 0);
+	fail_unless(fexist("out/link/keep"));
+	check_link("link", "copied");
+	fail_unless(unlink("out/link/keep") == 0 && rmdir("out/link") == 0);
+	if (getuid() != 0) {
+		fail_unless(mkdir("protected", 0700) == 0);
+		fail_unless(symlink("original", "protected/link") == 0);
+		fail_unless(chmod("protected", 0500) == 0);
+		fail_unless(rsync("link", "protected", 0, NULL) != 0);
+		check_link("protected/link", "original");
+		check_link("link", "copied");
+		fail_unless(chmod("protected", 0700) == 0);
+		fail_unless(unlink("protected/link") == 0 && rmdir("protected") == 0);
+	}
+	fail_unless(unlink("copied") == 0 && unlink("link") == 0);
+
+	errno = 0;
+	fail_unless(copyfile("dir", "copied", 0, LITE_FOPT_COPYFILE_SYM) == 0 && errno == EISDIR);
+	errno = 0;
+	fail_unless(copyfile("missing", "copied", 0, LITE_FOPT_COPYFILE_SYM) == -1 && errno == ENOENT);
+
+	fail_unless(unlink("file") == 0 && rmdir("dir") == 0 && rmdir("out") == 0);
+	fail_unless(chdir(cwd) == 0 && rmdir(tmp) == 0);
+	return 0;
+}