unzip: prevent attacks via malicious filenames

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

4 files changed, 63 insertions, 43 deletions

diff --git a/archival/libarchive/Kbuild.src b/archival/libarchive/Kbuild.src
index 7e89e9e..b7faaf7 100644
--- a/archival/libarchive/Kbuild.src
+++ b/archival/libarchive/Kbuild.src
@@ -30,6 +30,7 @@ COMMON_FILES:= \
 DPKG_FILES:= \
 	unpack_ar_archive.o \
 	filter_accept_list_reassign.o \
+	unsafe_prefix.o \
 	get_header_ar.o \
 	get_header_tar.o \
 	get_header_tar_gz.o \
@@ -44,7 +45,7 @@ lib-$(CONFIG_DPKG_DEB)                  += $(DPKG_FILES)
 
 lib-$(CONFIG_AR)                        += get_header_ar.o unpack_ar_archive.o
 lib-$(CONFIG_CPIO)                      += get_header_cpio.o
-lib-$(CONFIG_TAR)                       += get_header_tar.o
+lib-$(CONFIG_TAR)                       += get_header_tar.o unsafe_prefix.o
 lib-$(CONFIG_FEATURE_TAR_TO_COMMAND)    += data_extract_to_command.o
 lib-$(CONFIG_LZOP)                      += lzo1x_1.o lzo1x_1o.o lzo1x_d.o
 lib-$(CONFIG_LZOP_COMPR_HIGH)           += lzo1x_9x.o
@@ -53,7 +54,7 @@ lib-$(CONFIG_UNLZMA)                    += open_transformer.o decompress_unlzma.
 lib-$(CONFIG_UNXZ)                      += open_transformer.o decompress_unxz.o
 lib-$(CONFIG_GUNZIP)                    += open_transformer.o decompress_gunzip.o
 lib-$(CONFIG_UNCOMPRESS)                += open_transformer.o decompress_uncompress.o
-lib-$(CONFIG_UNZIP)                     += open_transformer.o decompress_gunzip.o
+lib-$(CONFIG_UNZIP)                     += open_transformer.o decompress_gunzip.o unsafe_prefix.o
 lib-$(CONFIG_RPM2CPIO)                  += open_transformer.o decompress_gunzip.o get_header_cpio.o
 lib-$(CONFIG_RPM)                       += open_transformer.o decompress_gunzip.o get_header_cpio.o
 
diff --git a/archival/libarchive/get_header_tar.c b/archival/libarchive/get_header_tar.c
index ba43bb0..0c663fb 100644
--- a/archival/libarchive/get_header_tar.c
+++ b/archival/libarchive/get_header_tar.c
@@ -17,36 +17,6 @@
 typedef uint32_t aliased_uint32_t FIX_ALIASING;
 typedef off_t    aliased_off_t    FIX_ALIASING;
 
-
-const char* FAST_FUNC strip_unsafe_prefix(const char *str)
-{
-	const char *cp = str;
-	while (1) {
-		char *cp2;
-		if (*cp == '/') {
-			cp++;
-			continue;
-		}
-		if (strncmp(cp, "/../"+1, 3) == 0) {
-			cp += 3;
-			continue;
-		}
-		cp2 = strstr(cp, "/../");
-		if (!cp2)
-			break;
-		cp = cp2 + 4;
-	}
-	if (cp != str) {
-		static smallint warned = 0;
-		if (!warned) {
-			warned = 1;
-			bb_error_msg("removing leading '%.*s' from member names",
-				(int)(cp - str), str);
-		}
-	}
-	return cp;
-}
-
 /* NB: _DESTROYS_ str[len] character! */
 static unsigned long long getOctal(char *str, int len)
 {
diff --git a/archival/libarchive/unsafe_prefix.c b/archival/libarchive/unsafe_prefix.c
new file mode 100644
index 0000000..826c673
--- /dev/null
+++ b/archival/libarchive/unsafe_prefix.c
@@ -0,0 +1,36 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+#include "libbb.h"
+#include "bb_archive.h"
+
+const char* FAST_FUNC strip_unsafe_prefix(const char *str)
+{
+	const char *cp = str;
+	while (1) {
+		char *cp2;
+		if (*cp == '/') {
+			cp++;
+			continue;
+		}
+		if (strncmp(cp, "/../"+1, 3) == 0) {
+			cp += 3;
+			continue;
+		}
+		cp2 = strstr(cp, "/../");
+		if (!cp2)
+			break;
+		cp = cp2 + 4;
+	}
+	if (cp != str) {
+		static smallint warned = 0;
+		if (!warned) {
+			warned = 1;
+			bb_error_msg("removing leading '%.*s' from member names",
+				(int)(cp - str), str);
+		}
+	}
+	return cp;
+}
diff --git a/archival/unzip.c b/archival/unzip.c
index 38a07e2..eed2256 100644
--- a/archival/unzip.c
+++ b/archival/unzip.c
@@ -596,14 +596,18 @@ int unzip_main(int argc, char **argv)
 		/* Skip extra header bytes */
 		unzip_skip(zip_header.formatted.extra_len);
 
+		/* Guard against "/abspath", "/../" and similar attacks */
+		overlapping_strcpy(dst_fn, strip_unsafe_prefix(dst_fn));
+
 		/* Filter zip entries */
 		if (find_list_entry(zreject, dst_fn)
 		 || (zaccept && !find_list_entry(zaccept, dst_fn))
 		) { /* Skip entry */
 			i = 'n';
 
-		} else { /* Extract entry */
-			if (listing) { /* List entry */
+		} else {
+			if (listing) {
+				/* List entry */
 				unsigned dostime = zip_header.formatted.modtime | (zip_header.formatted.moddate << 16);
 				if (!verbose) {
 					//      "  Length     Date   Time    Name\n"
@@ -639,9 +643,11 @@ int unzip_main(int argc, char **argv)
 					total_size += zip_header.formatted.cmpsize;
 				}
 				i = 'n';
-			} else if (dst_fd == STDOUT_FILENO) { /* Extracting to STDOUT */
+			} else if (dst_fd == STDOUT_FILENO) {
+				/* Extracting to STDOUT */
 				i = -1;
-			} else if (last_char_is(dst_fn, '/')) { /* Extract directory */
+			} else if (last_char_is(dst_fn, '/')) {
+				/* Extract directory */
 				if (stat(dst_fn, &stat_buf) == -1) {
 					if (errno != ENOENT) {
 						bb_perror_msg_and_die("can't stat '%s'", dst_fn);
@@ -655,22 +661,27 @@ int unzip_main(int argc, char **argv)
 					}
 				} else {
 					if (!S_ISDIR(stat_buf.st_mode)) {
-						bb_error_msg_and_die("'%s' exists but is not directory", dst_fn);
+						bb_error_msg_and_die("'%s' exists but is not a %s",
+							dst_fn, "directory");
 					}
 				}
 				i = 'n';
 
-			} else {  /* Extract file */
+			} else {
+				/* Extract file */
  check_file:
-				if (stat(dst_fn, &stat_buf) == -1) { /* File does not exist */
+				if (stat(dst_fn, &stat_buf) == -1) {
+					/* File does not exist */
 					if (errno != ENOENT) {
 						bb_perror_msg_and_die("can't stat '%s'", dst_fn);
 					}
 					i = 'y';
-				} else { /* File already exists */
+				} else {
+					/* File already exists */
 					if (overwrite == O_NEVER) {
 						i = 'n';
-					} else if (S_ISREG(stat_buf.st_mode)) { /* File is regular file */
+					} else if (S_ISREG(stat_buf.st_mode)) {
+						/* File is regular file */
 						if (overwrite == O_ALWAYS) {
 							i = 'y';
 						} else {
@@ -678,8 +689,10 @@ int unzip_main(int argc, char **argv)
 							my_fgets80(key_buf);
 							i = key_buf[0];
 						}
-					} else { /* File is not regular file */
-						bb_error_msg_and_die("'%s' exists but is not regular file", dst_fn);
+					} else {
+						/* File is not regular file */
+						bb_error_msg_and_die("'%s' exists but is not a %s",
+							dst_fn, "regular file");
 					}
 				}
 			}