Refactor the sudoedit code to copy files so it can be shared.

The SELinux sudoedit code now extends the destination file the same way the non-SELinux version does.
2020-04-21 11:05:32 -06:00
parent 0bd39701b4
commit 009876bf36
6 changed files with 193 additions and 119 deletions
--- a/src/copy_file.c
+++ b/src/copy_file.c
@@ -0,0 +1,128 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <sys/types.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "sudo.h"
+
+/*
+ * Extend the given fd to the specified size in bytes.
+ * We do this to allocate disk space up-front before overwriting
+ * the original file with the temporary.  Otherwise, we could
+ * we run out of disk space after truncating the original file.
+ */
+static int
+sudo_extend_file(int fd, const char *name, off_t new_size)
+{
+    off_t old_size, size;
+    ssize_t nwritten;
+    char zeroes[BUFSIZ] = { '\0' };
+    debug_decl(sudo_extend_file, SUDO_DEBUG_UTIL);
+
+    if ((old_size = lseek(fd, 0, SEEK_END)) == -1) {
+	sudo_warn("lseek");
+	debug_return_int(-1);
+    }
+    sudo_debug_printf(SUDO_DEBUG_INFO, "%s: extending %s from %lld to %lld",
+	__func__, name, (long long)old_size, (long long)new_size);
+
+    for (size = old_size; size < new_size; size += nwritten) {
+	size_t len = new_size - size;
+	if (len > sizeof(zeroes))
+	    len = sizeof(zeroes);
+	nwritten = write(fd, zeroes, len);
+	if (nwritten == -1) {
+	    int serrno = errno;
+	    if (ftruncate(fd, old_size) == -1) {
+		sudo_debug_printf(
+		    SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+		    "unable to truncate %s to %lld", name, (long long)old_size);
+	    }
+	    errno = serrno;
+	    debug_return_int(-1);
+	}
+    }
+    if (lseek(fd, 0, SEEK_SET) == -1) {
+	sudo_warn("lseek");
+	debug_return_int(-1);
+    }
+
+    debug_return_int(0);
+}
+
+/*
+ * Copy the contents of src_fd into dst_fd.
+ * Returns 0 on success or -1 on error.
+ */
+int
+sudo_copy_file(const char *src, int src_fd, off_t src_len, const char *dst,
+    int dst_fd, off_t dst_len)
+{
+    char buf[BUFSIZ];
+    ssize_t nwritten, nread;
+    debug_decl(sudo_copy_file, SUDO_DEBUG_UTIL);
+
+    /* Extend the file to the new size if larger before copying. */
+    if (dst_len > 0 && src_len > dst_len) {
+	if (sudo_extend_file(dst_fd, dst, src_len) == -1)
+	    goto write_error;
+    }
+
+    /* Overwrite the old file with the new contents. */
+    while ((nread = read(src_fd, buf, sizeof(buf))) > 0) {
+	ssize_t off = 0;
+	do {
+	    nwritten = write(dst_fd, buf + off, nread - off);
+	    if (nwritten == -1)
+		goto write_error;
+	    off += nwritten;
+	} while (nread > off);
+    }
+    if (nread == 0) {
+	/* success, read to EOF */
+	if (src_len < dst_len) {
+	    /* We don't open with O_TRUNC so must truncate manually. */
+	    if (ftruncate(dst_fd, src_len) == -1) {
+		sudo_debug_printf(
+		    SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
+		    "unable to truncate %s to %lld", dst, (long long)src_len);
+		goto write_error;
+	    }
+	}
+	debug_return_int(0);
+    } else if (nread < 0) {
+	sudo_warn(U_("unable to read from %s"), src);
+	debug_return_int(-1);
+    } else {
+write_error:
+	sudo_warn(U_("unable to write to %s"), dst);
+	debug_return_int(-1);
+    }
+}