Make verification match the new restricted directory symlink behavior

Only follow directory symlinks owned by target directory owner or root
during verification to match the behavior of fsmVerify() in the new
CVE-2017-7500 world order.

The code is klunkier than it should and the logic should use common code
with fsmVerify() instead of duplicating it here, but that needs more
changes than is comfortable to backport so starting with this.

Also worth noting that the previous "follow the link" logic from
commit 3ccd774255b8215733e0bdfdf5a683da9dd10923 was not quite right,
it'd fail with RPMVERIFY_LSTATFAIL on a broken symlink when it should've
ran verification on the symlink itself. This behavior is fixed here too.

Finally, once again fakechroot gets in the way and forces the related
verify testcase to be changed to be able to create a valid link. Reuse
the replacement testcase for the purpose and add another case for
verifying an invalid link.
static int verifyHeader(rpmts ts, Header h, rpmVerifyAttrs omitMask,
			rpmfileAttrs skipAttrs)
{
    rpmVerifyAttrs verifyResult = 0;
    rpmVerifyAttrs verifyAll = 0; /* assume no problems */
    rpmfi fi = rpmfiNew(ts, h, RPMTAG_BASENAMES, RPMFI_FLAGS_VERIFY);

    if (fi == NULL)
	return 1;

    rpmfiInit(fi, 0);
    while (rpmfiNext(fi) >= 0) {
	rpmfileAttrs fileAttrs = rpmfiFFlags(fi);
	char *buf = NULL, *attrFormat;
	const char *fstate = NULL;
	char ac;

	/* Skip on attributes (eg from --noghost) */
	if (skipAttrs & fileAttrs)
	    continue;

	verifyResult = rpmfiVerify(fi, omitMask);

	/* Filter out timestamp differences of shared files */
	if (verifyResult & RPMVERIFY_MTIME) {
	    rpmdbMatchIterator mi;
	    mi = rpmtsInitIterator(ts, RPMDBI_BASENAMES, rpmfiFN(fi), 0);
	    if (rpmdbGetIteratorCount(mi) > 1) 
		verifyResult &= ~RPMVERIFY_MTIME;
	    rpmdbFreeIterator(mi);
	}

	/* State is only meaningful for installed packages */
	if (headerGetInstance(h))
	    fstate = stateStr(rpmfiFState(fi));

	attrFormat = rpmFFlagsString(fileAttrs, "");
	ac = rstreq(attrFormat, "") ? ' ' : attrFormat[0];
	if (verifyResult & RPMVERIFY_LSTATFAIL) {
	    if (!(fileAttrs & (RPMFILE_MISSINGOK|RPMFILE_GHOST)) || rpmIsVerbose()) {
		rasprintf(&buf, _("missing   %c %s"), ac, rpmfiFN(fi));
		if ((verifyResult & RPMVERIFY_LSTATFAIL) != 0 &&
		    errno != ENOENT) {
		    char *app;
		    rasprintf(&app, " (%s)", strerror(errno));
		    rstrcat(&buf, app);
		    free(app);
		}
	    }
	} else if (verifyResult || fstate || rpmIsVerbose()) {
	    char *verifyFormat = rpmVerifyString(verifyResult, ".");
	    rasprintf(&buf, "%s  %c %s", verifyFormat, ac, rpmfiFN(fi));
	    free(verifyFormat);
	}
	free(attrFormat);

	if (buf) {
	    if (fstate)
		buf = rstrscat(&buf, " (", fstate, ")", NULL);
	    rpmlog(RPMLOG_NOTICE, "%s\n", buf);
	    buf = _free(buf);
	}
	verifyAll |= verifyResult;
    }
    rpmfiFree(fi);
	
    return (verifyAll != 0) ? 1 : 0;
}

static int verifyHeader(rpmts ts, Header h, rpmVerifyAttrs omitMask,
			rpmfileAttrs skipAttrs)
{
    rpmVerifyAttrs verifyResult = 0;
    rpmVerifyAttrs verifyAll = 0; /* assume no problems */
    rpmfi fi = rpmfiNew(ts, h, RPMTAG_BASENAMES, RPMFI_FLAGS_VERIFY);

    if (fi == NULL)
	return 1;

    rpmfiInit(fi, 0);
    while (rpmfiNext(fi) >= 0) {
	rpmfileAttrs fileAttrs = rpmfiFFlags(fi);
	char *buf = NULL, *attrFormat;
	const char *fstate = NULL;
	char ac;

	/* Skip on attributes (eg from --noghost) */
	if (skipAttrs & fileAttrs)
	    continue;

	verifyResult = rpmfiVerify(fi, omitMask);

	/* Filter out timestamp differences of shared files */
	if (verifyResult & RPMVERIFY_MTIME) {
	    rpmdbMatchIterator mi;
	    mi = rpmtsInitIterator(ts, RPMDBI_BASENAMES, rpmfiFN(fi), 0);
	    if (rpmdbGetIteratorCount(mi) > 1) 
		verifyResult &= ~RPMVERIFY_MTIME;
	    rpmdbFreeIterator(mi);
	}

	/* State is only meaningful for installed packages */
	if (headerGetInstance(h))
	    fstate = stateStr(rpmfiFState(fi));

	attrFormat = rpmFFlagsString(fileAttrs, "");
	ac = rstreq(attrFormat, "") ? ' ' : attrFormat[0];
	if (verifyResult & RPMVERIFY_LSTATFAIL) {
	    if (!(fileAttrs & (RPMFILE_MISSINGOK|RPMFILE_GHOST)) || rpmIsVerbose()) {
		rasprintf(&buf, _("missing   %c %s"), ac, rpmfiFN(fi));
		if ((verifyResult & RPMVERIFY_LSTATFAIL) != 0 &&
		    errno != ENOENT) {
		    char *app;
		    rasprintf(&app, " (%s)", strerror(errno));
		    rstrcat(&buf, app);
		    free(app);
		}
	    }
	} else if (verifyResult || fstate || rpmIsVerbose()) {
	    char *verifyFormat = rpmVerifyString(verifyResult, ".");
	    rasprintf(&buf, "%s  %c %s", verifyFormat, ac, rpmfiFN(fi));
	    free(verifyFormat);
	}
	free(attrFormat);

	if (buf) {
	    if (fstate)
		buf = rstrscat(&buf, " (", fstate, ")", NULL);
	    rpmlog(RPMLOG_NOTICE, "%s\n", buf);
	    buf = _free(buf);
	}
	verifyAll |= verifyResult;
    }
    rpmfiFree(fi);
	
    return (verifyAll != 0) ? 1 : 0;
}
