From ac66a0fe120939817c34659f1c2f26e69e5ac046 Mon Sep 17 00:00:00 2001 From: Bram Matthys Date: Fri, 1 Sep 2017 17:02:36 +0200 Subject: [PATCH] Add hostname verification code from ssl conservatory & curl (will be used in next commit) --- include/h.h | 2 + include/openssl_hostname_validation.h | 81 ++++++ src/openssl_hostname_validation.c | 402 ++++++++++++++++++++++++++ 3 files changed, 485 insertions(+) create mode 100644 include/openssl_hostname_validation.h create mode 100644 src/openssl_hostname_validation.c diff --git a/include/h.h b/include/h.h index 60c2e4397..316a93cff 100644 --- a/include/h.h +++ b/include/h.h @@ -791,3 +791,5 @@ extern SSLOptions *FindSSLOptionsForUser(aClient *acptr); extern int IsWebsocket(aClient *acptr); extern PlaintextPolicy plaintextpolicy_strtoval(char *s); extern char *plaintextpolicy_valtostr(PlaintextPolicy policy); +extern int verify_certificate(aClient *acptr, char *hostname, char **errstr); +extern char *certificate_name(aClient *acptr); diff --git a/include/openssl_hostname_validation.h b/include/openssl_hostname_validation.h new file mode 100644 index 000000000..ead184647 --- /dev/null +++ b/include/openssl_hostname_validation.h @@ -0,0 +1,81 @@ +#ifndef HEADER_CURL_HOSTCHECK_H +#define HEADER_CURL_HOSTCHECK_H +/* Obtained from cURL + * Copyright (C) 1998 - 2012, Daniel Stenberg, , et al. + * + * This software is licensed as described in the file COPYING, which + * you should have received as part of this distribution. The terms + * are also available at http://curl.haxx.se/docs/copyright.html. + * + * You may opt to use, copy, modify, merge, publish, distribute and/or sell + * copies of the Software, and permit persons to whom the Software is + * furnished to do so, under the terms of the COPYING file. + * + * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY + * KIND, either express or implied. + * + ***************************************************************************/ + +#define CURL_HOST_NOMATCH 0 +#define CURL_HOST_MATCH 1 +int Curl_cert_hostcheck(const char *match_pattern, const char *hostname); + +#endif /* HEADER_CURL_HOSTCHECK_H */ + + +/* Obtained from: https://github.com/iSECPartners/ssl-conservatory */ + +/* +Copyright (C) 2012, iSEC Partners. + +Permission is hereby granted, free of charge, to any person obtaining a copy of +this software and associated documentation files (the "Software"), to deal in +the Software without restriction, including without limitation the rights to +use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies +of the Software, and to permit persons to whom the Software is furnished to do +so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all +copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. + */ + +/* + * Helper functions to perform basic hostname validation using OpenSSL. + * + * Please read "everything-you-wanted-to-know-about-openssl.pdf" before + * attempting to use this code. This whitepaper describes how the code works, + * how it should be used, and what its limitations are. + * + * Author: Alban Diquet + * License: See LICENSE + * + */ + +typedef enum { + MatchFound, + MatchNotFound, + NoSANPresent, + MalformedCertificate, + Error +} HostnameValidationResult; + +/** +* Validates the server's identity by looking for the expected hostname in the +* server's certificate. As described in RFC 6125, it first tries to find a match +* in the Subject Alternative Name extension. If the extension is not present in +* the certificate, it checks the Common Name instead. +* +* Returns MatchFound if a match was found. +* Returns MatchNotFound if no matches were found. +* Returns MalformedCertificate if any of the hostnames had a NUL character embedded in it. +* Returns Error if there was an error. +*/ +HostnameValidationResult validate_hostname(const char *hostname, const X509 *server_cert); diff --git a/src/openssl_hostname_validation.c b/src/openssl_hostname_validation.c new file mode 100644 index 000000000..5d9f0eb60 --- /dev/null +++ b/src/openssl_hostname_validation.c @@ -0,0 +1,402 @@ +/* This file contains both code from cURL and hostname + * validation code from the ssl conservatory (in that order). + * + * The goal is that all this code won't be needed anymore once + * everyone is running a recent OpenSSL/LibreSSL that has + * X509_check_host(). Until that time, unfortunately, we need + * these 400+ lines to do just that... -- Syzop, Sep/2017 + */ + +// Get rid of OSX 10.7 and greater deprecation warnings. +#if defined(__APPLE__) && defined(__clang__) +#pragma clang diagnostic ignored "-Wdeprecated-declarations" +#endif + +#include +#include +#include + +#include "openssl_hostname_validation.h" + +#define HOSTNAME_MAX_SIZE 255 + +#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER) +#define ASN1_STRING_get0_data ASN1_STRING_data +#endif + +/*************************************************************************** + * _ _ ____ _ + * Project ___| | | | _ \| | + * / __| | | | |_) | | + * | (__| |_| | _ <| |___ + * \___|\___/|_| \_\_____| + * + * Copyright (C) 1998 - 2012, Daniel Stenberg, , et al. + * + * This software is licensed as described in the file COPYING, which + * you should have received as part of this distribution. The terms + * are also available at http://curl.haxx.se/docs/copyright.html. + * + * You may opt to use, copy, modify, merge, publish, distribute and/or sell + * copies of the Software, and permit persons to whom the Software is + * furnished to do so, under the terms of the COPYING file. + * + * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY + * KIND, either express or implied. + * + ***************************************************************************/ + +/* This file is an amalgamation of hostcheck.c and most of rawstr.c + from cURL. The contents of the COPYING file mentioned above are: + +COPYRIGHT AND PERMISSION NOTICE + +Copyright (c) 1996 - 2013, Daniel Stenberg, . + +All rights reserved. + +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", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN +NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, +DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR +OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE +OR OTHER DEALINGS IN THE SOFTWARE. + +Except as contained in this notice, the name of a copyright holder shall not +be used in advertising or otherwise to promote the sale, use or other dealings +in this Software without prior written authorization of the copyright holder. +*/ + +/* Portable, consistent toupper (remember EBCDIC). Do not use toupper() because + its behavior is altered by the current locale. */ +static char Curl_raw_toupper(char in) +{ + switch (in) { + case 'a': + return 'A'; + case 'b': + return 'B'; + case 'c': + return 'C'; + case 'd': + return 'D'; + case 'e': + return 'E'; + case 'f': + return 'F'; + case 'g': + return 'G'; + case 'h': + return 'H'; + case 'i': + return 'I'; + case 'j': + return 'J'; + case 'k': + return 'K'; + case 'l': + return 'L'; + case 'm': + return 'M'; + case 'n': + return 'N'; + case 'o': + return 'O'; + case 'p': + return 'P'; + case 'q': + return 'Q'; + case 'r': + return 'R'; + case 's': + return 'S'; + case 't': + return 'T'; + case 'u': + return 'U'; + case 'v': + return 'V'; + case 'w': + return 'W'; + case 'x': + return 'X'; + case 'y': + return 'Y'; + case 'z': + return 'Z'; + } + return in; +} + +/* + * Curl_raw_equal() is for doing "raw" case insensitive strings. This is meant + * to be locale independent and only compare strings we know are safe for + * this. See http://daniel.haxx.se/blog/2008/10/15/strcasecmp-in-turkish/ for + * some further explanation to why this function is necessary. + * + * The function is capable of comparing a-z case insensitively even for + * non-ascii. + */ + +static int Curl_raw_equal(const char *first, const char *second) +{ + while(*first && *second) { + if(Curl_raw_toupper(*first) != Curl_raw_toupper(*second)) + /* get out of the loop as soon as they don't match */ + break; + first++; + second++; + } + /* we do the comparison here (possibly again), just to make sure that if the + loop above is skipped because one of the strings reached zero, we must not + return this as a successful match */ + return (Curl_raw_toupper(*first) == Curl_raw_toupper(*second)); +} + +static int Curl_raw_nequal(const char *first, const char *second, size_t max) +{ + while(*first && *second && max) { + if(Curl_raw_toupper(*first) != Curl_raw_toupper(*second)) { + break; + } + max--; + first++; + second++; + } + if(0 == max) + return 1; /* they are equal this far */ + + return Curl_raw_toupper(*first) == Curl_raw_toupper(*second); +} + +/* + * Match a hostname against a wildcard pattern. + * E.g. + * "foo.host.com" matches "*.host.com". + * + * We use the matching rule described in RFC6125, section 6.4.3. + * http://tools.ietf.org/html/rfc6125#section-6.4.3 + */ + +static int hostmatch(const char *hostname, const char *pattern) +{ + const char *pattern_label_end, *pattern_wildcard, *hostname_label_end; + int wildcard_enabled; + size_t prefixlen, suffixlen; + pattern_wildcard = strchr(pattern, '*'); + if(pattern_wildcard == NULL) + return Curl_raw_equal(pattern, hostname) ? + CURL_HOST_MATCH : CURL_HOST_NOMATCH; + + /* We require at least 2 dots in pattern to avoid too wide wildcard + match. */ + wildcard_enabled = 1; + pattern_label_end = strchr(pattern, '.'); + if(pattern_label_end == NULL || strchr(pattern_label_end+1, '.') == NULL || + pattern_wildcard > pattern_label_end || + Curl_raw_nequal(pattern, "xn--", 4)) { + wildcard_enabled = 0; + } + if(!wildcard_enabled) + return Curl_raw_equal(pattern, hostname) ? + CURL_HOST_MATCH : CURL_HOST_NOMATCH; + + hostname_label_end = strchr(hostname, '.'); + if(hostname_label_end == NULL || + !Curl_raw_equal(pattern_label_end, hostname_label_end)) + return CURL_HOST_NOMATCH; + + /* The wildcard must match at least one character, so the left-most + label of the hostname is at least as large as the left-most label + of the pattern. */ + if(hostname_label_end - hostname < pattern_label_end - pattern) + return CURL_HOST_NOMATCH; + + prefixlen = pattern_wildcard - pattern; + suffixlen = pattern_label_end - (pattern_wildcard+1); + return Curl_raw_nequal(pattern, hostname, prefixlen) && + Curl_raw_nequal(pattern_wildcard+1, hostname_label_end - suffixlen, + suffixlen) ? + CURL_HOST_MATCH : CURL_HOST_NOMATCH; +} + +int Curl_cert_hostcheck(const char *match_pattern, const char *hostname) +{ + if(!match_pattern || !*match_pattern || + !hostname || !*hostname) /* sanity check */ + return 0; + + if(Curl_raw_equal(hostname, match_pattern)) /* trivial case */ + return 1; + + if(hostmatch(hostname,match_pattern) == CURL_HOST_MATCH) + return 1; + return 0; +} +/* End of cURL related functions */ + +/* Start of host validation code */ +/* Obtained from: https://github.com/iSECPartners/ssl-conservatory */ + +/* +Copyright (C) 2012, iSEC Partners. + +Permission is hereby granted, free of charge, to any person obtaining a copy of +this software and associated documentation files (the "Software"), to deal in +the Software without restriction, including without limitation the rights to +use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies +of the Software, and to permit persons to whom the Software is furnished to do +so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all +copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. + */ + +/* + * Helper functions to perform basic hostname validation using OpenSSL. + * + * Please read "everything-you-wanted-to-know-about-openssl.pdf" before + * attempting to use this code. This whitepaper describes how the code works, + * how it should be used, and what its limitations are. + * + * Author: Alban Diquet + * License: See LICENSE + * + */ + +/** +* Tries to find a match for hostname in the certificate's Common Name field. +* +* Returns MatchFound if a match was found. +* Returns MatchNotFound if no matches were found. +* Returns MalformedCertificate if the Common Name had a NUL character embedded in it. +* Returns Error if the Common Name could not be extracted. +*/ +static HostnameValidationResult matches_common_name(const char *hostname, const X509 *server_cert) { + int common_name_loc = -1; + X509_NAME_ENTRY *common_name_entry = NULL; + ASN1_STRING *common_name_asn1 = NULL; + const char *common_name_str = NULL; + + // Find the position of the CN field in the Subject field of the certificate + common_name_loc = X509_NAME_get_index_by_NID(X509_get_subject_name((X509 *) server_cert), NID_commonName, -1); + if (common_name_loc < 0) { + return Error; + } + + // Extract the CN field + common_name_entry = X509_NAME_get_entry(X509_get_subject_name((X509 *) server_cert), common_name_loc); + if (common_name_entry == NULL) { + return Error; + } + + // Convert the CN field to a C string + common_name_asn1 = X509_NAME_ENTRY_get_data(common_name_entry); + if (common_name_asn1 == NULL) { + return Error; + } + common_name_str = (char *) ASN1_STRING_get0_data(common_name_asn1); + + // Make sure there isn't an embedded NUL character in the CN + if ((size_t)ASN1_STRING_length(common_name_asn1) != strlen(common_name_str)) { + return MalformedCertificate; + } + + // Compare expected hostname with the CN + if (Curl_cert_hostcheck(common_name_str, hostname) == CURL_HOST_MATCH) { + return MatchFound; + } + else { + return MatchNotFound; + } +} + + +/** +* Tries to find a match for hostname in the certificate's Subject Alternative Name extension. +* +* Returns MatchFound if a match was found. +* Returns MatchNotFound if no matches were found. +* Returns MalformedCertificate if any of the hostnames had a NUL character embedded in it. +* Returns NoSANPresent if the SAN extension was not present in the certificate. +*/ +static HostnameValidationResult matches_subject_alternative_name(const char *hostname, const X509 *server_cert) { + HostnameValidationResult result = MatchNotFound; + int i; + int san_names_nb = -1; + STACK_OF(GENERAL_NAME) *san_names = NULL; + + // Try to extract the names within the SAN extension from the certificate + san_names = X509_get_ext_d2i((X509 *) server_cert, NID_subject_alt_name, NULL, NULL); + if (san_names == NULL) { + return NoSANPresent; + } + san_names_nb = sk_GENERAL_NAME_num(san_names); + + // Check each name within the extension + for (i=0; itype == GEN_DNS) { + // Current name is a DNS name, let's check it + const char *dns_name = (char *) ASN1_STRING_get0_data(current_name->d.dNSName); + + // Make sure there isn't an embedded NUL character in the DNS name + if ((size_t)ASN1_STRING_length(current_name->d.dNSName) != strlen(dns_name)) { + result = MalformedCertificate; + break; + } + else { // Compare expected hostname with the DNS name + if (Curl_cert_hostcheck(dns_name, hostname) + == CURL_HOST_MATCH) { + result = MatchFound; + break; + } + } + } + } + sk_GENERAL_NAME_pop_free(san_names, GENERAL_NAME_free); + + return result; +} + + +/** +* Validates the server's identity by looking for the expected hostname in the +* server's certificate. As described in RFC 6125, it first tries to find a match +* in the Subject Alternative Name extension. If the extension is not present in +* the certificate, it checks the Common Name instead. +* +* Returns MatchFound if a match was found. +* Returns MatchNotFound if no matches were found. +* Returns MalformedCertificate if any of the hostnames had a NUL character embedded in it. +* Returns Error if there was an error. +*/ +HostnameValidationResult validate_hostname(const char *hostname, const X509 *server_cert) { + HostnameValidationResult result; + + if((hostname == NULL) || (server_cert == NULL)) + return Error; + + // First try the Subject Alternative Names extension + result = matches_subject_alternative_name(hostname, server_cert); + if (result == NoSANPresent) { + // Extension was not found: try the Common Name + result = matches_common_name(hostname, server_cert); + } + + return result; +}