From: Sergey Poznyakoff Date: Fri, 26 Nov 2004 19:09:26 +0000 (+0000) Subject: (tar_checksum): New function X-Git-Url: https://git.dogcows.com/gitweb?a=commitdiff_plain;h=b5db9788306d45cd9432fda71236f07b8a214212;p=chaz%2Ftar (tar_checksum): New function --- diff --git a/src/list.c b/src/list.c index b592c8b..0d96e8b 100644 --- a/src/list.c +++ b/src/list.c @@ -266,6 +266,61 @@ list_archive (void) assign_string (&save_name, 0); } +/* Check header checksum */ +/* The standard BSD tar sources create the checksum by adding up the + bytes in the header as type char. I think the type char was unsigned + on the PDP-11, but it's signed on the Next and Sun. It looks like the + sources to BSD tar were never changed to compute the checksum + correctly, so both the Sun and Next add the bytes of the header as + signed chars. This doesn't cause a problem until you get a file with + a name containing characters with the high bit set. So tar_checksum + computes two checksums -- signed and unsigned. */ + +enum read_header +tar_checksum (union block *header) +{ + size_t i; + int unsigned_sum = 0; /* the POSIX one :-) */ + int signed_sum = 0; /* the Sun one :-( */ + int recorded_sum; + uintmax_t parsed_sum; + char *p; + + p = header->buffer; + for (i = sizeof *header; i-- != 0;) + { + unsigned_sum += (unsigned char) *p; + signed_sum += (signed char) (*p++); + } + + if (unsigned_sum == 0) + return HEADER_ZERO_BLOCK; + + /* Adjust checksum to count the "chksum" field as blanks. */ + + for (i = sizeof header->header.chksum; i-- != 0;) + { + unsigned_sum -= (unsigned char) header->header.chksum[i]; + signed_sum -= (signed char) (header->header.chksum[i]); + } + unsigned_sum += ' ' * sizeof header->header.chksum; + signed_sum += ' ' * sizeof header->header.chksum; + + parsed_sum = from_header (header->header.chksum, + sizeof header->header.chksum, 0, + (uintmax_t) 0, + (uintmax_t) TYPE_MAXIMUM (int)); + if (parsed_sum == (uintmax_t) -1) + return HEADER_FAILURE; + + recorded_sum = parsed_sum; + + if (unsigned_sum != recorded_sum && signed_sum != recorded_sum) + return HEADER_FAILURE; + + return HEADER_SUCCESS; +} + /* Read a block that's supposed to be a header block. Return its address in "current_header", and if it is good, the file's size in current_stat_info.stat.st_size. @@ -279,23 +334,9 @@ list_archive (void) You must always set_next_block_after(current_header) to skip past the header which this routine reads. */ -/* The standard BSD tar sources create the checksum by adding up the - bytes in the header as type char. I think the type char was unsigned - on the PDP-11, but it's signed on the Next and Sun. It looks like the - sources to BSD tar were never changed to compute the checksum - correctly, so both the Sun and Next add the bytes of the header as - signed chars. This doesn't cause a problem until you get a file with - a name containing characters with the high bit set. So read_header - computes two checksums -- signed and unsigned. */ - enum read_header read_header (bool raw_extended_headers) { - size_t i; - int unsigned_sum; /* the POSIX one :-) */ - int signed_sum; /* the Sun one :-( */ - int recorded_sum; - uintmax_t parsed_sum; char *p; union block *header; union block *header_copy; @@ -309,44 +350,15 @@ read_header (bool raw_extended_headers) while (1) { + enum read_header status; + header = find_next_block (); current_header = header; if (!header) return HEADER_END_OF_FILE; - unsigned_sum = 0; - signed_sum = 0; - p = header->buffer; - for (i = sizeof *header; i-- != 0;) - { - unsigned_sum += (unsigned char) *p; - signed_sum += (signed char) (*p++); - } - - if (unsigned_sum == 0) - return HEADER_ZERO_BLOCK; - - /* Adjust checksum to count the "chksum" field as blanks. */ - - for (i = sizeof header->header.chksum; i-- != 0;) - { - unsigned_sum -= (unsigned char) header->header.chksum[i]; - signed_sum -= (signed char) (header->header.chksum[i]); - } - unsigned_sum += ' ' * sizeof header->header.chksum; - signed_sum += ' ' * sizeof header->header.chksum; - - parsed_sum = from_header (header->header.chksum, - sizeof header->header.chksum, 0, - (uintmax_t) 0, - (uintmax_t) TYPE_MAXIMUM (int)); - if (parsed_sum == (uintmax_t) -1) - return HEADER_FAILURE; - - recorded_sum = parsed_sum; - - if (unsigned_sum != recorded_sum && signed_sum != recorded_sum) - return HEADER_FAILURE; + if ((status = tar_checksum (header)) != HEADER_SUCCESS) + return status; /* Good block. Decode file size and return. */