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![Jeff King](/assets/img/avatar_default.png)
When we generate tar headers, we sprintf() values directly into a struct with the fixed-size header values. For the most part this is fine, as we are formatting small values (e.g., the octal format of "mode & 0x7777" is of fixed length). But it's still a good idea to use xsnprintf here. It communicates to readers what our expectation is, and it provides a run-time check that we are not overflowing the buffers. The one exception here is the mtime, which comes from the epoch time of the commit we are archiving. For sane values, this fits into the 12-byte value allocated in the header. But since git can handle 64-bit times, if I claim to be a visitor from the year 10,000 AD, I can overflow the buffer. This turns out to be harmless, as we simply overflow into the chksum field, which is then overwritten. This case is also best as an xsnprintf. It should never come up, short of extremely malformed dates, and in that case we are probably better off dying than silently truncating the date value (and we cannot expand the size of the buffer, since it is dictated by the ustar format). Our friends in the year 5138 (when we legitimately flip to a 12-digit epoch) can deal with that problem then. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
454 lines
11 KiB
C
454 lines
11 KiB
C
/*
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* Copyright (c) 2005, 2006 Rene Scharfe
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*/
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#include "cache.h"
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#include "tar.h"
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#include "archive.h"
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#include "streaming.h"
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#include "run-command.h"
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#define RECORDSIZE (512)
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#define BLOCKSIZE (RECORDSIZE * 20)
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static char block[BLOCKSIZE];
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static unsigned long offset;
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static int tar_umask = 002;
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static int write_tar_filter_archive(const struct archiver *ar,
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struct archiver_args *args);
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/* writes out the whole block, but only if it is full */
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static void write_if_needed(void)
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{
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if (offset == BLOCKSIZE) {
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write_or_die(1, block, BLOCKSIZE);
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offset = 0;
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}
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}
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/*
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* queues up writes, so that all our write(2) calls write exactly one
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* full block; pads writes to RECORDSIZE
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*/
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static void do_write_blocked(const void *data, unsigned long size)
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{
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const char *buf = data;
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if (offset) {
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unsigned long chunk = BLOCKSIZE - offset;
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if (size < chunk)
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chunk = size;
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memcpy(block + offset, buf, chunk);
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size -= chunk;
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offset += chunk;
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buf += chunk;
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write_if_needed();
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}
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while (size >= BLOCKSIZE) {
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write_or_die(1, buf, BLOCKSIZE);
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size -= BLOCKSIZE;
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buf += BLOCKSIZE;
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}
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if (size) {
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memcpy(block + offset, buf, size);
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offset += size;
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}
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}
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static void finish_record(void)
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{
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unsigned long tail;
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tail = offset % RECORDSIZE;
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if (tail) {
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memset(block + offset, 0, RECORDSIZE - tail);
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offset += RECORDSIZE - tail;
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}
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write_if_needed();
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}
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static void write_blocked(const void *data, unsigned long size)
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{
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do_write_blocked(data, size);
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finish_record();
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}
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/*
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* The end of tar archives is marked by 2*512 nul bytes and after that
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* follows the rest of the block (if any).
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*/
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static void write_trailer(void)
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{
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int tail = BLOCKSIZE - offset;
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memset(block + offset, 0, tail);
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write_or_die(1, block, BLOCKSIZE);
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if (tail < 2 * RECORDSIZE) {
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memset(block, 0, offset);
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write_or_die(1, block, BLOCKSIZE);
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}
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}
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/*
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* queues up writes, so that all our write(2) calls write exactly one
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* full block; pads writes to RECORDSIZE
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*/
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static int stream_blocked(const unsigned char *sha1)
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{
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struct git_istream *st;
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enum object_type type;
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unsigned long sz;
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char buf[BLOCKSIZE];
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ssize_t readlen;
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st = open_istream(sha1, &type, &sz, NULL);
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if (!st)
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return error("cannot stream blob %s", sha1_to_hex(sha1));
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for (;;) {
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readlen = read_istream(st, buf, sizeof(buf));
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if (readlen <= 0)
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break;
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do_write_blocked(buf, readlen);
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}
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close_istream(st);
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if (!readlen)
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finish_record();
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return readlen;
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}
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/*
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* pax extended header records have the format "%u %s=%s\n". %u contains
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* the size of the whole string (including the %u), the first %s is the
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* keyword, the second one is the value. This function constructs such a
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* string and appends it to a struct strbuf.
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*/
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static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
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const char *value, unsigned int valuelen)
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{
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int len, tmp;
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/* "%u %s=%s\n" */
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len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
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for (tmp = len; tmp > 9; tmp /= 10)
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len++;
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strbuf_grow(sb, len);
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strbuf_addf(sb, "%u %s=", len, keyword);
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strbuf_add(sb, value, valuelen);
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strbuf_addch(sb, '\n');
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}
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static unsigned int ustar_header_chksum(const struct ustar_header *header)
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{
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const unsigned char *p = (const unsigned char *)header;
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unsigned int chksum = 0;
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while (p < (const unsigned char *)header->chksum)
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chksum += *p++;
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chksum += sizeof(header->chksum) * ' ';
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p += sizeof(header->chksum);
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while (p < (const unsigned char *)header + sizeof(struct ustar_header))
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chksum += *p++;
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return chksum;
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}
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static size_t get_path_prefix(const char *path, size_t pathlen, size_t maxlen)
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{
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size_t i = pathlen;
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if (i > 1 && path[i - 1] == '/')
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i--;
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if (i > maxlen)
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i = maxlen;
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do {
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i--;
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} while (i > 0 && path[i] != '/');
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return i;
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}
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static void prepare_header(struct archiver_args *args,
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struct ustar_header *header,
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unsigned int mode, unsigned long size)
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{
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xsnprintf(header->mode, sizeof(header->mode), "%07o", mode & 07777);
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xsnprintf(header->size, sizeof(header->size), "%011lo", S_ISREG(mode) ? size : 0);
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xsnprintf(header->mtime, sizeof(header->mtime), "%011lo", (unsigned long) args->time);
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xsnprintf(header->uid, sizeof(header->uid), "%07o", 0);
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xsnprintf(header->gid, sizeof(header->gid), "%07o", 0);
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strlcpy(header->uname, "root", sizeof(header->uname));
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strlcpy(header->gname, "root", sizeof(header->gname));
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xsnprintf(header->devmajor, sizeof(header->devmajor), "%07o", 0);
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xsnprintf(header->devminor, sizeof(header->devminor), "%07o", 0);
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memcpy(header->magic, "ustar", 6);
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memcpy(header->version, "00", 2);
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snprintf(header->chksum, sizeof(header->chksum), "%07o", ustar_header_chksum(header));
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}
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static int write_extended_header(struct archiver_args *args,
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const unsigned char *sha1,
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const void *buffer, unsigned long size)
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{
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struct ustar_header header;
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unsigned int mode;
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memset(&header, 0, sizeof(header));
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*header.typeflag = TYPEFLAG_EXT_HEADER;
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mode = 0100666;
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xsnprintf(header.name, sizeof(header.name), "%s.paxheader", sha1_to_hex(sha1));
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prepare_header(args, &header, mode, size);
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write_blocked(&header, sizeof(header));
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write_blocked(buffer, size);
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return 0;
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}
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static int write_tar_entry(struct archiver_args *args,
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const unsigned char *sha1,
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const char *path, size_t pathlen,
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unsigned int mode)
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{
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struct ustar_header header;
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struct strbuf ext_header = STRBUF_INIT;
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unsigned int old_mode = mode;
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unsigned long size;
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void *buffer;
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int err = 0;
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memset(&header, 0, sizeof(header));
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if (S_ISDIR(mode) || S_ISGITLINK(mode)) {
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*header.typeflag = TYPEFLAG_DIR;
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mode = (mode | 0777) & ~tar_umask;
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} else if (S_ISLNK(mode)) {
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*header.typeflag = TYPEFLAG_LNK;
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mode |= 0777;
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} else if (S_ISREG(mode)) {
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*header.typeflag = TYPEFLAG_REG;
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mode = (mode | ((mode & 0100) ? 0777 : 0666)) & ~tar_umask;
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} else {
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return error("unsupported file mode: 0%o (SHA1: %s)",
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mode, sha1_to_hex(sha1));
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}
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if (pathlen > sizeof(header.name)) {
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size_t plen = get_path_prefix(path, pathlen,
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sizeof(header.prefix));
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size_t rest = pathlen - plen - 1;
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if (plen > 0 && rest <= sizeof(header.name)) {
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memcpy(header.prefix, path, plen);
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memcpy(header.name, path + plen + 1, rest);
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} else {
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xsnprintf(header.name, sizeof(header.name), "%s.data",
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sha1_to_hex(sha1));
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strbuf_append_ext_header(&ext_header, "path",
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path, pathlen);
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}
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} else
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memcpy(header.name, path, pathlen);
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if (S_ISREG(mode) && !args->convert &&
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sha1_object_info(sha1, &size) == OBJ_BLOB &&
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size > big_file_threshold)
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buffer = NULL;
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else if (S_ISLNK(mode) || S_ISREG(mode)) {
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enum object_type type;
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buffer = sha1_file_to_archive(args, path, sha1, old_mode, &type, &size);
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if (!buffer)
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return error("cannot read %s", sha1_to_hex(sha1));
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} else {
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buffer = NULL;
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size = 0;
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}
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if (S_ISLNK(mode)) {
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if (size > sizeof(header.linkname)) {
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xsnprintf(header.linkname, sizeof(header.linkname),
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"see %s.paxheader", sha1_to_hex(sha1));
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strbuf_append_ext_header(&ext_header, "linkpath",
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buffer, size);
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} else
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memcpy(header.linkname, buffer, size);
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}
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prepare_header(args, &header, mode, size);
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if (ext_header.len > 0) {
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err = write_extended_header(args, sha1, ext_header.buf,
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ext_header.len);
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if (err) {
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free(buffer);
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return err;
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}
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}
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strbuf_release(&ext_header);
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write_blocked(&header, sizeof(header));
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if (S_ISREG(mode) && size > 0) {
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if (buffer)
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write_blocked(buffer, size);
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else
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err = stream_blocked(sha1);
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}
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free(buffer);
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return err;
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}
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static int write_global_extended_header(struct archiver_args *args)
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{
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const unsigned char *sha1 = args->commit_sha1;
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struct strbuf ext_header = STRBUF_INIT;
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struct ustar_header header;
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unsigned int mode;
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int err = 0;
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strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
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memset(&header, 0, sizeof(header));
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*header.typeflag = TYPEFLAG_GLOBAL_HEADER;
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mode = 0100666;
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xsnprintf(header.name, sizeof(header.name), "pax_global_header");
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prepare_header(args, &header, mode, ext_header.len);
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write_blocked(&header, sizeof(header));
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write_blocked(ext_header.buf, ext_header.len);
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strbuf_release(&ext_header);
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return err;
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}
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static struct archiver **tar_filters;
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static int nr_tar_filters;
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static int alloc_tar_filters;
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static struct archiver *find_tar_filter(const char *name, int len)
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{
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int i;
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for (i = 0; i < nr_tar_filters; i++) {
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struct archiver *ar = tar_filters[i];
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if (!strncmp(ar->name, name, len) && !ar->name[len])
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return ar;
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}
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return NULL;
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}
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static int tar_filter_config(const char *var, const char *value, void *data)
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{
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struct archiver *ar;
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const char *name;
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const char *type;
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int namelen;
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if (parse_config_key(var, "tar", &name, &namelen, &type) < 0 || !name)
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return 0;
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ar = find_tar_filter(name, namelen);
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if (!ar) {
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ar = xcalloc(1, sizeof(*ar));
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ar->name = xmemdupz(name, namelen);
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ar->write_archive = write_tar_filter_archive;
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ar->flags = ARCHIVER_WANT_COMPRESSION_LEVELS;
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ALLOC_GROW(tar_filters, nr_tar_filters + 1, alloc_tar_filters);
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tar_filters[nr_tar_filters++] = ar;
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}
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if (!strcmp(type, "command")) {
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if (!value)
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return config_error_nonbool(var);
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free(ar->data);
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ar->data = xstrdup(value);
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return 0;
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}
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if (!strcmp(type, "remote")) {
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if (git_config_bool(var, value))
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ar->flags |= ARCHIVER_REMOTE;
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else
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ar->flags &= ~ARCHIVER_REMOTE;
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return 0;
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}
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return 0;
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}
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static int git_tar_config(const char *var, const char *value, void *cb)
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{
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if (!strcmp(var, "tar.umask")) {
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if (value && !strcmp(value, "user")) {
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tar_umask = umask(0);
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umask(tar_umask);
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} else {
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tar_umask = git_config_int(var, value);
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}
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return 0;
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}
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return tar_filter_config(var, value, cb);
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}
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static int write_tar_archive(const struct archiver *ar,
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struct archiver_args *args)
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{
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int err = 0;
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if (args->commit_sha1)
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err = write_global_extended_header(args);
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if (!err)
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err = write_archive_entries(args, write_tar_entry);
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if (!err)
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write_trailer();
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return err;
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}
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static int write_tar_filter_archive(const struct archiver *ar,
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struct archiver_args *args)
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{
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struct strbuf cmd = STRBUF_INIT;
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struct child_process filter = CHILD_PROCESS_INIT;
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const char *argv[2];
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int r;
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if (!ar->data)
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die("BUG: tar-filter archiver called with no filter defined");
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strbuf_addstr(&cmd, ar->data);
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if (args->compression_level >= 0)
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strbuf_addf(&cmd, " -%d", args->compression_level);
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argv[0] = cmd.buf;
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argv[1] = NULL;
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filter.argv = argv;
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filter.use_shell = 1;
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filter.in = -1;
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if (start_command(&filter) < 0)
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die_errno("unable to start '%s' filter", argv[0]);
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close(1);
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if (dup2(filter.in, 1) < 0)
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die_errno("unable to redirect descriptor");
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close(filter.in);
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r = write_tar_archive(ar, args);
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close(1);
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if (finish_command(&filter) != 0)
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die("'%s' filter reported error", argv[0]);
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strbuf_release(&cmd);
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return r;
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}
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static struct archiver tar_archiver = {
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"tar",
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write_tar_archive,
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ARCHIVER_REMOTE
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};
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void init_tar_archiver(void)
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{
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int i;
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register_archiver(&tar_archiver);
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tar_filter_config("tar.tgz.command", "gzip -cn", NULL);
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tar_filter_config("tar.tgz.remote", "true", NULL);
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tar_filter_config("tar.tar.gz.command", "gzip -cn", NULL);
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tar_filter_config("tar.tar.gz.remote", "true", NULL);
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git_config(git_tar_config, NULL);
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for (i = 0; i < nr_tar_filters; i++) {
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/* omit any filters that never had a command configured */
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if (tar_filters[i]->data)
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register_archiver(tar_filters[i]);
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}
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}
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