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tar: Add routine to test if the tar archive is "legit"

This commit is contained in:
sin 2015-04-23 16:31:02 +01:00
parent 74f680948e
commit ac694e6c4a
1 changed files with 30 additions and 0 deletions
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30
tar.c
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@ -352,6 +352,35 @@ sanitize(struct header *h)
fields[i].f[j] = '\0';
}
static void
chktar(struct header *h)
{
char tmp[8], *err;
char *p = (char *)h;
long s1, s2, i;
if (h->prefix[0] == '\0' && h->name[0] == '\0')
goto bad;
if (strncmp("ustar", h->magic, 5))
goto bad;
memcpy(tmp, h->chksum, sizeof(tmp));
for (i = 0; i < sizeof(tmp); i++)
if (tmp[i] == ' ')
tmp[i] = '\0';
s1 = strtol(tmp, &err, 8);
if (s1 < 0 || *err != '\0')
goto bad;
memset(h->chksum, ' ', sizeof(h->chksum));
for (i = 0, s2 = 0; i < sizeof(*h); i++)
s2 += p[i];
if (s1 != s2)
goto bad;
memcpy(h->chksum, tmp, sizeof(h->chksum));
return;
bad:
eprintf("malformed tar archive\n");
}
static void
xt(int argc, char *argv[], int (*fn)(char *, ssize_t, char[BLKSIZ]))
{
@ -363,6 +392,7 @@ xt(int argc, char *argv[], int (*fn)(char *, ssize_t, char[BLKSIZ]))
int i, n;
while (eread(tarfd, b, BLKSIZ) > 0 && h->name[0]) {
chktar(h);
sanitize(h), n = 0;
/* small dance around non-null terminated fields */