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acme-client: encode unexpected SANs before printing

If a SAN isn't configured, it could be anything, so make printing it safe
using strvisx(). If it is configured but duplicate, printing it should be
fine, so don't bother. This removes two XXX added in the previous commit.

ok florian

/*	$Id: revokeproc.c,v 1.25 2022/12/18 12:04:55 tb Exp $ */
/*
 * Copyright (c) 2016 Kristaps Dzonsons <kristaps@bsd.lv>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <assert.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <vis.h>

#include <openssl/pem.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/err.h>

#include "extern.h"

#define	RENEW_ALLOW (30 * 24 * 60 * 60)

/*
 * Convert the X509's expiration time into a time_t value.
 */
static time_t
X509expires(X509 *x)
{
	ASN1_TIME	*atim;
	struct tm	 t;

	if ((atim = X509_getm_notAfter(x)) == NULL) {
		warnx("missing notAfter");
		return -1;
	}

	memset(&t, 0, sizeof(t));

	if (!ASN1_TIME_to_tm(atim, &t)) {
		warnx("invalid ASN1_TIME");
		return -1;
	}

	return timegm(&t);
}

int
revokeproc(int fd, const char *certfile, int force,
    int revocate, const char *const *alts, size_t altsz)
{
	GENERAL_NAMES			*sans = NULL;
	char				*der = NULL, *dercp, *der64 = NULL;
	int				 rc = 0, cc, i, len;
	size_t				*found = NULL;
	FILE				*f = NULL;
	X509				*x = NULL;
	long				 lval;
	enum revokeop			 op, rop;
	time_t				 t;
	size_t				 j;

	/*
	 * First try to open the certificate before we drop privileges
	 * and jail ourselves.
	 * We allow "f" to be NULL IFF the cert doesn't exist yet.
	 */

	if ((f = fopen(certfile, "r")) == NULL && errno != ENOENT) {
		warn("%s", certfile);
		goto out;
	}

	/* File-system and sandbox jailing. */

	ERR_load_crypto_strings();

	if (pledge("stdio", NULL) == -1) {
		warn("pledge");
		goto out;
	}

	/*
	 * If we couldn't open the certificate, it doesn't exist so we
	 * haven't submitted it yet, so obviously we can mark that it
	 * has expired and we should renew it.
	 * If we're revoking, however, then that's an error!
	 * Ignore if the reader isn't reading in either case.
	 */

	if (f == NULL && revocate) {
		warnx("%s: no certificate found", certfile);
		(void)writeop(fd, COMM_REVOKE_RESP, REVOKE_OK);
		goto out;
	} else if (f == NULL && !revocate) {
		if (writeop(fd, COMM_REVOKE_RESP, REVOKE_EXP) >= 0)
			rc = 1;
		goto out;
	}

	if ((x = PEM_read_X509(f, NULL, NULL, NULL)) == NULL) {
		warnx("PEM_read_X509");
		goto out;
	}

	/* Cache and sanity check X509v3 extensions. */

	if (X509_check_purpose(x, -1, -1) <= 0) {
		warnx("%s: invalid X509v3 extensions", certfile);
		goto out;
	}

	/* Read out the expiration date. */

	if ((t = X509expires(x)) == -1) {
		warnx("X509expires");
		goto out;
	}

	/* Extract list of SAN entries from the certificate. */

	sans = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL);
	if (sans == NULL) {
		warnx("%s: does not have a SAN entry", certfile);
		if (revocate)
			goto out;
		force = 2;
	}

	/* An array of buckets: the number of entries found. */

	if ((found = calloc(altsz, sizeof(size_t))) == NULL) {
		warn("calloc");
		goto out;
	}

	/*
	 * Ensure the certificate's SAN entries fully cover those from the
	 * configuration file and that all domains are represented only once.
	 */

	for (i = 0; i < sk_GENERAL_NAME_num(sans); i++) {
		GENERAL_NAME		*gen_name;
		const ASN1_IA5STRING	*name;
		const unsigned char	*name_buf;
		int			 name_len;
		int			 name_type;

		gen_name = sk_GENERAL_NAME_value(sans, i);
		assert(gen_name != NULL);

		name = GENERAL_NAME_get0_value(gen_name, &name_type);
		if (name_type != GEN_DNS)
			continue;

		/* name_buf isn't a C string and could contain embedded NULs. */
		name_buf = ASN1_STRING_get0_data(name);
		name_len = ASN1_STRING_length(name);

		for (j = 0; j < altsz; j++) {
			if ((size_t)name_len != strlen(alts[j]))
				continue;
			if (memcmp(name_buf, alts[j], name_len) == 0)
				break;
		}
		if (j == altsz) {
			if (revocate) {
				char *visbuf;

				visbuf = calloc(4, name_len + 1);
				if (visbuf == NULL) {
					warn("%s: unexpected SAN", certfile);
					goto out;
				}
				strvisx(visbuf, name_buf, name_len, VIS_SAFE);
				warnx("%s: unexpected SAN entry: %s",
				    certfile, visbuf);
				free(visbuf);
				goto out;
			}
			force = 2;
			continue;
		}
		if (found[j]++) {
			if (revocate) {
				warnx("%s: duplicate SAN entry: %.*s",
				    certfile, name_len, name_buf);
				goto out;
			}
			force = 2;
		}
	}

	for (j = 0; j < altsz; j++) {
		if (found[j])
			continue;
		if (revocate) {
			warnx("%s: domain not listed: %s", certfile, alts[j]);
			goto out;
		}
		force = 2;
	}

	/*
	 * If we're going to revoke, write the certificate to the
	 * netproc in DER and base64-encoded format.
	 * Then exit: we have nothing left to do.
	 */

	if (revocate) {
		dodbg("%s: revocation", certfile);

		/*
		 * First, tell netproc we're online.
		 * If they're down, then just exit without warning.
		 */

		cc = writeop(fd, COMM_REVOKE_RESP, REVOKE_EXP);
		if (cc == 0)
			rc = 1;
		if (cc <= 0)
			goto out;

		if ((len = i2d_X509(x, NULL)) < 0) {
			warnx("i2d_X509");
			goto out;
		} else if ((der = dercp = malloc(len)) == NULL) {
			warn("malloc");
			goto out;
		} else if (len != i2d_X509(x, (u_char **)&dercp)) {
			warnx("i2d_X509");
			goto out;
		} else if ((der64 = base64buf_url(der, len)) == NULL) {
			warnx("base64buf_url");
			goto out;
		} else if (writestr(fd, COMM_CSR, der64) >= 0)
			rc = 1;

		goto out;
	}

	rop = time(NULL) >= (t - RENEW_ALLOW) ? REVOKE_EXP : REVOKE_OK;

	if (rop == REVOKE_EXP)
		dodbg("%s: certificate renewable: %lld days left",
		    certfile, (long long)(t - time(NULL)) / 24 / 60 / 60);
	else
		dodbg("%s: certificate valid: %lld days left",
		    certfile, (long long)(t - time(NULL)) / 24 / 60 / 60);

	if (rop == REVOKE_OK && force) {
		warnx("%s: %sforcing renewal", certfile,
		    force == 2 ? "domain list changed, " : "");
		rop = REVOKE_EXP;
	}

	/*
	 * We can re-submit it given RENEW_ALLOW time before.
	 * If netproc is down, just exit.
	 */

	if ((cc = writeop(fd, COMM_REVOKE_RESP, rop)) == 0)
		rc = 1;
	if (cc <= 0)
		goto out;

	op = REVOKE__MAX;
	if ((lval = readop(fd, COMM_REVOKE_OP)) == 0)
		op = REVOKE_STOP;
	else if (lval == REVOKE_CHECK)
		op = lval;

	if (op == REVOKE__MAX) {
		warnx("unknown operation from netproc");
		goto out;
	} else if (op == REVOKE_STOP) {
		rc = 1;
		goto out;
	}

	rc = 1;
out:
	close(fd);
	if (f != NULL)
		fclose(f);
	X509_free(x);
	GENERAL_NAMES_free(sans);
	free(der);
	free(found);
	free(der64);
	ERR_print_errors_fp(stderr);
	ERR_free_strings();
	return rc;
}