From b18ce97c672615bb5ac44883676b37a9ec758d83 Mon Sep 17 00:00:00 2001 From: Stefan Fritsch Date: Sun, 1 May 2016 14:32:30 +0200 Subject: [PATCH] Implement checksum verification for gunzip This implements the crc32 check for the gzip format. Support for zlib's adler checksum is not included, yet. --- grub-core/io/gzio.c | 46 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 41 insertions(+), 5 deletions(-) diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c index a8e33033b..dcf3a8701 100644 --- a/grub-core/io/gzio.c +++ b/grub-core/io/gzio.c @@ -43,6 +43,7 @@ #include #include #include +#include GRUB_MOD_LICENSE ("GPLv3+"); @@ -94,6 +95,14 @@ struct grub_gzio struct huft *tl; /* The distance code table. */ struct huft *td; + /* The checksum algorithm */ + const gcry_md_spec_t *hdesc; + /* The wanted checksum */ + grub_uint32_t orig_checksum; + /* The uncompressed length */ + grub_size_t orig_len; + /* Context for checksum calculation */ + grub_uint8_t *hcontext; /* The lookup bits for the literal/length code table. */ int bl; /* The lookup bits for the distance code table. */ @@ -180,7 +189,7 @@ test_gzip_header (grub_file_t file) grub_uint8_t os_type; } hdr; grub_uint16_t extra_len; - grub_uint32_t orig_len; + grub_uint32_t crc32; grub_gzio_t gzio = file->data; if (grub_file_tell (gzio->file) != 0) @@ -215,12 +224,15 @@ test_gzip_header (grub_file_t file) /* FIXME: don't do this on not easily seekable files. */ { - grub_file_seek (gzio->file, grub_file_size (gzio->file) - 4); - if (grub_file_read (gzio->file, &orig_len, 4) != 4) + grub_file_seek (gzio->file, grub_file_size (gzio->file) - 8); + if (grub_file_read (gzio->file, &crc32, 4) != 4) + return 0; + gzio->orig_checksum = grub_le_to_cpu32 (crc32); + if (grub_file_read (gzio->file, &gzio->orig_len, 4) != 4) return 0; /* FIXME: this does not handle files whose original size is over 4GB. But how can we know the real original size? */ - file->size = grub_le_to_cpu32 (orig_len); + file->size = grub_le_to_cpu32 (gzio->orig_len); } initialize_tables (gzio); @@ -1095,7 +1107,23 @@ inflate_window (grub_gzio_t gzio) gzio->saved_offset += gzio->wp; - /* XXX do CRC calculation here! */ + if (gzio->hcontext) + { + gzio->hdesc->write (gzio->hcontext, gzio->slide, gzio->wp); + + if (gzio->saved_offset == gzio->orig_len) + { + grub_uint32_t csum; + + gzio->hdesc->final (gzio->hcontext); + csum = *(grub_uint32_t *)gzio->hdesc->read (gzio->hcontext); + csum = grub_be_to_cpu32 (csum); + if (csum != gzio->orig_checksum) + grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, + "checksum mismatch %08x/%08x", + gzio->orig_checksum, csum); + } + } } @@ -1118,6 +1146,9 @@ initialize_tables (grub_gzio_t gzio) huft_free (gzio->td); gzio->tl = NULL; gzio->td = NULL; + + if (gzio->hcontext) + gzio->hdesc->init(gzio->hcontext); } @@ -1143,6 +1174,9 @@ grub_gzio_open (grub_file_t io, const char *name __attribute__ ((unused))) gzio->file = io; + gzio->hdesc = GRUB_MD_CRC32; + gzio->hcontext = grub_malloc(gzio->hdesc->contextsize); + file->device = io->device; file->data = gzio; file->fs = &grub_gzio_fs; @@ -1151,6 +1185,7 @@ grub_gzio_open (grub_file_t io, const char *name __attribute__ ((unused))) if (! test_gzip_header (file)) { grub_errno = GRUB_ERR_NONE; + grub_free (gzio->hcontext); grub_free (gzio); grub_free (file); grub_file_seek (io, 0); @@ -1287,6 +1322,7 @@ grub_gzio_close (grub_file_t file) grub_file_close (gzio->file); huft_free (gzio->tl); huft_free (gzio->td); + grub_free (gzio->hcontext); grub_free (gzio); /* No need to close the same device twice. */ -- 2.17.1