| Message ID | 20210319142001.2201-1-arne@rfc2549.org |
|---|---|
| State | Changes Requested |
| Delegated to: | Antonio Quartulli |
| Headers | show |
| Series | [Openvpn-devel,v2,1/5] Extend verify-hash to allow multiple hashes | expand |
Hi, On 19/03/2021 15:19, Arne Schwabe wrote: > This patch introduces support for verify-hash inlining. > When inlined, this options now allows to specify multiple fingerprints, > one per line. > > Since this is a new syntax, there is no backwards compatibility to take > care of, therefore we can drop support for SHA1. Inlined fingerprints > are assumed be to SHA-256 only. > > Also print a warning about SHA1 hash being deprecated to verify > certificates as it is not "industry standard" anymore. > > Patch v2: fix/clarify various comments, fix a few minor problems, allow > the option to be specified multiple times and have that > added to the list. > > Signed-off-by: Arne Schwabe <arne@rfc2549.org> > --- > doc/man-sections/inline-files.rst | 4 +- > doc/man-sections/tls-options.rst | 10 +++ > src/openvpn/options.c | 107 +++++++++++++++++++++++++++--- > src/openvpn/options.h | 10 ++- > src/openvpn/ssl_common.h | 2 +- > src/openvpn/ssl_verify.c | 17 ++++- > 6 files changed, 133 insertions(+), 17 deletions(-) > > diff --git a/doc/man-sections/inline-files.rst b/doc/man-sections/inline-files.rst > index 819bd3c8..303bb3c8 100644 > --- a/doc/man-sections/inline-files.rst > +++ b/doc/man-sections/inline-files.rst > @@ -4,8 +4,8 @@ INLINE FILE SUPPORT > OpenVPN allows including files in the main configuration for the ``--ca``, > ``--cert``, ``--dh``, ``--extra-certs``, ``--key``, ``--pkcs12``, > ``--secret``, ``--crl-verify``, ``--http-proxy-user-pass``, ``--tls-auth``, > -``--auth-gen-token-secret``, ``--tls-crypt`` and ``--tls-crypt-v2`` > -options. > +``--auth-gen-token-secret``, ``--tls-crypt``, ``--tls-crypt-v2`` and > +``--verify-hash`` options. > > Each inline file started by the line ``<option>`` and ended by the line > ``</option>`` > diff --git a/doc/man-sections/tls-options.rst b/doc/man-sections/tls-options.rst > index e13fb3c8..d8f9800e 100644 > --- a/doc/man-sections/tls-options.rst > +++ b/doc/man-sections/tls-options.rst > @@ -582,6 +582,16 @@ certificates and keys: https://github.com/OpenVPN/easy-rsa > The ``algo`` flag can be either :code:`SHA1` or :code:`SHA256`. If not > provided, it defaults to :code:`SHA1`. > > + This option can also be inlined > + :: > + > + <verify-hash> > + 00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff:00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff > + 11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff:00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff:00 > + </verify-hash> > + > +If the option is inlined, ``algo`` is always :code:`SHA256`. > + > --verify-x509-name args > Accept connections only if a host's X.509 name is equal to **name.** The > remote host must also pass all other tests of verification. > diff --git a/src/openvpn/options.c b/src/openvpn/options.c > index 86e78b05..e119e14c 100644 > --- a/src/openvpn/options.c > +++ b/src/openvpn/options.c > @@ -1078,12 +1078,24 @@ string_substitute(const char *src, int from, int to, struct gc_arena *gc) > return ret; > } > > -static uint8_t * > +/** > + * Parses a hexstring and checks if the string has the correct length. Return > + * a verify_hash_list containing the parsed hash string. > + * > + * @param str String to check/parse > + * @param nbytes Number of bytes expected in the hexstr (e.g. 20 for SHA1) > + * @param msglevel message level to use when printing warnings/errors > + * @param gc The returned object will be allocated in this gc > + */ > +static struct verify_hash_list * > parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_arena *gc) > { > int i; > const char *cp = str; > - uint8_t *ret = (uint8_t *) gc_malloc(nbytes, true, gc); > + > + struct verify_hash_list *ret; > + ALLOC_OBJ_CLEAR_GC(ret, struct verify_hash_list, gc); > + > char term = 1; > int byte; > char bs[3]; > @@ -1102,7 +1114,7 @@ parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_aren > { > msg(msglevel, "format error in hash fingerprint hex byte: %s", str); > } > - ret[i] = (uint8_t)byte; > + ret->hash[i] = (uint8_t)byte; > term = *cp++; > if (term != ':' && term != 0) > { > @@ -1116,10 +1128,55 @@ parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_aren > if (term != 0 || i != nbytes-1) > { > msg(msglevel, "hash fingerprint is different length than expected (%d bytes): %s", nbytes, str); > + return NULL; > } > return ret; > } > > +/** > + * Parses a string consisting of multiple lines of hexstrings and checks if each > + * string has the correct length. Empty lines are ignored. Returns > + * a linked list of (possibly) multiple verify_hash_list objects. > + * > + * @param str String to check/parse > + * @param nbytes Number of bytes expected in the hexstring (e.g. 20 for SHA1) > + * @param msglevel message level to use when printing warnings/errors > + * @param gc The returned list items will be allocated in this gc > + */ > +static struct verify_hash_list * > +parse_hash_fingerprint_multiline(const char *str, int nbytes, int msglevel, > + struct gc_arena *gc) > +{ > + struct gc_arena gc_temp = gc_new(); > + char *lines = string_alloc(str, &gc_temp); > + > + struct verify_hash_list *ret = NULL; > + > + const char *line; > + while ((line = strsep(&lines, "\n"))) > + { > + /* skip empty lines */ > + if (strlen(line) == 0) > + { > + continue; > + } > + > + struct verify_hash_list *hash = parse_hash_fingerprint(line, nbytes, > + msglevel, gc); > + > + if (!hash) > + { > + gc_free(&gc_temp); > + return NULL; > + } > + > + hash->next = ret; > + ret = hash; > + } > + gc_free(&gc_temp); > + > + return ret; > +} > #ifdef _WIN32 > > #ifndef ENABLE_SMALL > @@ -8063,22 +8120,50 @@ add_option(struct options *options, > } > else if (streq(p[0], "verify-hash") && p[1] && !p[3]) > { > - VERIFY_PERMISSION(OPT_P_GENERAL); > + VERIFY_PERMISSION(OPT_P_GENERAL|OPT_P_INLINE); > + options->verify_hash_algo = MD_SHA256; > + > + int digest_len = SHA256_DIGEST_LENGTH; > > - if (!p[2] || (p[2] && streq(p[2], "SHA1"))) > + if ((!p[2] && !is_inline) || (p[2] && streq(p[2], "SHA1"))) > { > - options->verify_hash = parse_hash_fingerprint(p[1], SHA_DIGEST_LENGTH, msglevel, &options->gc); > options->verify_hash_algo = MD_SHA1; > + msg(M_WARN, "DEPRECATED FEATURE: Usage of SHA1 fingerprints for " > + "verify-hash is deprecated. You should switch to SHA256."); > + options->verify_hash_algo = MD_SHA1; > + digest_len = SHA_DIGEST_LENGTH; > + } > + else if (p[2] && !streq(p[2], "SHA256")) > + { > + msg(msglevel, "invalid or unsupported hashing algorithm: %s (only SHA1 and SHA256 are valid)", p[2]); > + goto err; > + } > + > + struct verify_hash_list *newlist; > + if (is_inline) > + { > + newlist = parse_hash_fingerprint_multiline(p[1], digest_len, msglevel, > + &options->gc); indentation is now off here > } > - else if (p[2] && streq(p[2], "SHA256")) > + else > { > - options->verify_hash = parse_hash_fingerprint(p[1], SHA256_DIGEST_LENGTH, msglevel, &options->gc); > - options->verify_hash_algo = MD_SHA256; > + newlist = parse_hash_fingerprint(p[1], digest_len, msglevel, > + &options->gc); same here > + } Can we just kill the if above and always call parse_hash_fingerprint_multiline() ? This function should just work for both cases. > + > + /* Append the new list to the end of our current list */ > + if (!options->verify_hash) > + { > + options->verify_hash = newlist; > } > else > { > - msg(msglevel, "invalid or unsupported hashing algorithm: %s (only SHA1 and SHA256 are valid)", p[2]); > - goto err; > + struct verify_hash_list *listend = options->verify_hash; > + while (listend->next) > + { > + listend = listend->next; > + } > + listend->next = newlist; > } why not prepending instead of appending? prepending will require 1/10th of the code above. Actually you do prepending already when parsing the inlined peer-fingerprint. > } > #ifdef ENABLE_CRYPTOAPI > diff --git a/src/openvpn/options.h b/src/openvpn/options.h > index 56228668..a7b3174f 100644 > --- a/src/openvpn/options.h > +++ b/src/openvpn/options.h > @@ -191,6 +191,14 @@ enum genkey_type { > GENKEY_AUTH_TOKEN > }; > > +struct verify_hash_list > +{ > + /* We support SHA256 and SHA1 fingerpint. In the case of using the > + * deprecated SHA1, only the first 20 bytes of each list item are used */ > + uint8_t hash[SHA256_DIGEST_LENGTH]; > + struct verify_hash_list *next; > +}; > + > /* Command line options */ > struct options > { > @@ -550,7 +558,7 @@ struct options > int ns_cert_type; /* set to 0, NS_CERT_CHECK_SERVER, or NS_CERT_CHECK_CLIENT */ > unsigned remote_cert_ku[MAX_PARMS]; > const char *remote_cert_eku; > - uint8_t *verify_hash; > + struct verify_hash_list *verify_hash; > hash_algo_type verify_hash_algo; > unsigned int ssl_flags; /* set to SSLF_x flags from ssl.h */ > > diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h > index 2e3c98db..f6aaae98 100644 > --- a/src/openvpn/ssl_common.h > +++ b/src/openvpn/ssl_common.h > @@ -283,7 +283,7 @@ struct tls_options > int ns_cert_type; > unsigned remote_cert_ku[MAX_PARMS]; > const char *remote_cert_eku; > - uint8_t *verify_hash; > + struct verify_hash_list *verify_hash; > hash_algo_type verify_hash_algo; > #ifdef ENABLE_X509ALTUSERNAME > char *x509_username_field[MAX_PARMS]; > diff --git a/src/openvpn/ssl_verify.c b/src/openvpn/ssl_verify.c > index 4b120f7b..001ca82b 100644 > --- a/src/openvpn/ssl_verify.c > +++ b/src/openvpn/ssl_verify.c > @@ -748,9 +748,22 @@ verify_cert(struct tls_session *session, openvpn_x509_cert_t *cert, int cert_dep > goto cleanup; > } > > - if (memcmp(BPTR(&ca_hash), opt->verify_hash, BLEN(&ca_hash))) > + struct verify_hash_list *current_hash = opt->verify_hash; > + > + while (current_hash) > + { > + if (memcmp_constant_time(BPTR(&ca_hash), current_hash->hash, > + BLEN(&ca_hash)) == 0) > + { > + hash_matched = true; ehm, this variable is gone now :) the line above should go too. > + break; > + } > + current_hash = current_hash->next; > + } > + > + if (!current_hash) > { > - msg(D_TLS_ERRORS, "TLS Error: level-1 certificate hash verification failed"); > + msg(D_TLS_ERRORS, "TLS Error: --tls-verify certificate hash verification failed"); > goto cleanup; > } > } >
diff --git a/doc/man-sections/inline-files.rst b/doc/man-sections/inline-files.rst index 819bd3c8..303bb3c8 100644 --- a/doc/man-sections/inline-files.rst +++ b/doc/man-sections/inline-files.rst @@ -4,8 +4,8 @@ INLINE FILE SUPPORT OpenVPN allows including files in the main configuration for the ``--ca``, ``--cert``, ``--dh``, ``--extra-certs``, ``--key``, ``--pkcs12``, ``--secret``, ``--crl-verify``, ``--http-proxy-user-pass``, ``--tls-auth``, -``--auth-gen-token-secret``, ``--tls-crypt`` and ``--tls-crypt-v2`` -options. +``--auth-gen-token-secret``, ``--tls-crypt``, ``--tls-crypt-v2`` and +``--verify-hash`` options. Each inline file started by the line ``<option>`` and ended by the line ``</option>`` diff --git a/doc/man-sections/tls-options.rst b/doc/man-sections/tls-options.rst index e13fb3c8..d8f9800e 100644 --- a/doc/man-sections/tls-options.rst +++ b/doc/man-sections/tls-options.rst @@ -582,6 +582,16 @@ certificates and keys: https://github.com/OpenVPN/easy-rsa The ``algo`` flag can be either :code:`SHA1` or :code:`SHA256`. If not provided, it defaults to :code:`SHA1`. + This option can also be inlined + :: + + <verify-hash> + 00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff:00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff + 11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff:00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff:00 + </verify-hash> + +If the option is inlined, ``algo`` is always :code:`SHA256`. + --verify-x509-name args Accept connections only if a host's X.509 name is equal to **name.** The remote host must also pass all other tests of verification. diff --git a/src/openvpn/options.c b/src/openvpn/options.c index 86e78b05..e119e14c 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -1078,12 +1078,24 @@ string_substitute(const char *src, int from, int to, struct gc_arena *gc) return ret; } -static uint8_t * +/** + * Parses a hexstring and checks if the string has the correct length. Return + * a verify_hash_list containing the parsed hash string. + * + * @param str String to check/parse + * @param nbytes Number of bytes expected in the hexstr (e.g. 20 for SHA1) + * @param msglevel message level to use when printing warnings/errors + * @param gc The returned object will be allocated in this gc + */ +static struct verify_hash_list * parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_arena *gc) { int i; const char *cp = str; - uint8_t *ret = (uint8_t *) gc_malloc(nbytes, true, gc); + + struct verify_hash_list *ret; + ALLOC_OBJ_CLEAR_GC(ret, struct verify_hash_list, gc); + char term = 1; int byte; char bs[3]; @@ -1102,7 +1114,7 @@ parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_aren { msg(msglevel, "format error in hash fingerprint hex byte: %s", str); } - ret[i] = (uint8_t)byte; + ret->hash[i] = (uint8_t)byte; term = *cp++; if (term != ':' && term != 0) { @@ -1116,10 +1128,55 @@ parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_aren if (term != 0 || i != nbytes-1) { msg(msglevel, "hash fingerprint is different length than expected (%d bytes): %s", nbytes, str); + return NULL; } return ret; } +/** + * Parses a string consisting of multiple lines of hexstrings and checks if each + * string has the correct length. Empty lines are ignored. Returns + * a linked list of (possibly) multiple verify_hash_list objects. + * + * @param str String to check/parse + * @param nbytes Number of bytes expected in the hexstring (e.g. 20 for SHA1) + * @param msglevel message level to use when printing warnings/errors + * @param gc The returned list items will be allocated in this gc + */ +static struct verify_hash_list * +parse_hash_fingerprint_multiline(const char *str, int nbytes, int msglevel, + struct gc_arena *gc) +{ + struct gc_arena gc_temp = gc_new(); + char *lines = string_alloc(str, &gc_temp); + + struct verify_hash_list *ret = NULL; + + const char *line; + while ((line = strsep(&lines, "\n"))) + { + /* skip empty lines */ + if (strlen(line) == 0) + { + continue; + } + + struct verify_hash_list *hash = parse_hash_fingerprint(line, nbytes, + msglevel, gc); + + if (!hash) + { + gc_free(&gc_temp); + return NULL; + } + + hash->next = ret; + ret = hash; + } + gc_free(&gc_temp); + + return ret; +} #ifdef _WIN32 #ifndef ENABLE_SMALL @@ -8063,22 +8120,50 @@ add_option(struct options *options, } else if (streq(p[0], "verify-hash") && p[1] && !p[3]) { - VERIFY_PERMISSION(OPT_P_GENERAL); + VERIFY_PERMISSION(OPT_P_GENERAL|OPT_P_INLINE); + options->verify_hash_algo = MD_SHA256; + + int digest_len = SHA256_DIGEST_LENGTH; - if (!p[2] || (p[2] && streq(p[2], "SHA1"))) + if ((!p[2] && !is_inline) || (p[2] && streq(p[2], "SHA1"))) { - options->verify_hash = parse_hash_fingerprint(p[1], SHA_DIGEST_LENGTH, msglevel, &options->gc); options->verify_hash_algo = MD_SHA1; + msg(M_WARN, "DEPRECATED FEATURE: Usage of SHA1 fingerprints for " + "verify-hash is deprecated. You should switch to SHA256."); + options->verify_hash_algo = MD_SHA1; + digest_len = SHA_DIGEST_LENGTH; + } + else if (p[2] && !streq(p[2], "SHA256")) + { + msg(msglevel, "invalid or unsupported hashing algorithm: %s (only SHA1 and SHA256 are valid)", p[2]); + goto err; + } + + struct verify_hash_list *newlist; + if (is_inline) + { + newlist = parse_hash_fingerprint_multiline(p[1], digest_len, msglevel, + &options->gc); } - else if (p[2] && streq(p[2], "SHA256")) + else { - options->verify_hash = parse_hash_fingerprint(p[1], SHA256_DIGEST_LENGTH, msglevel, &options->gc); - options->verify_hash_algo = MD_SHA256; + newlist = parse_hash_fingerprint(p[1], digest_len, msglevel, + &options->gc); + } + + /* Append the new list to the end of our current list */ + if (!options->verify_hash) + { + options->verify_hash = newlist; } else { - msg(msglevel, "invalid or unsupported hashing algorithm: %s (only SHA1 and SHA256 are valid)", p[2]); - goto err; + struct verify_hash_list *listend = options->verify_hash; + while (listend->next) + { + listend = listend->next; + } + listend->next = newlist; } } #ifdef ENABLE_CRYPTOAPI diff --git a/src/openvpn/options.h b/src/openvpn/options.h index 56228668..a7b3174f 100644 --- a/src/openvpn/options.h +++ b/src/openvpn/options.h @@ -191,6 +191,14 @@ enum genkey_type { GENKEY_AUTH_TOKEN }; +struct verify_hash_list +{ + /* We support SHA256 and SHA1 fingerpint. In the case of using the + * deprecated SHA1, only the first 20 bytes of each list item are used */ + uint8_t hash[SHA256_DIGEST_LENGTH]; + struct verify_hash_list *next; +}; + /* Command line options */ struct options { @@ -550,7 +558,7 @@ struct options int ns_cert_type; /* set to 0, NS_CERT_CHECK_SERVER, or NS_CERT_CHECK_CLIENT */ unsigned remote_cert_ku[MAX_PARMS]; const char *remote_cert_eku; - uint8_t *verify_hash; + struct verify_hash_list *verify_hash; hash_algo_type verify_hash_algo; unsigned int ssl_flags; /* set to SSLF_x flags from ssl.h */ diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h index 2e3c98db..f6aaae98 100644 --- a/src/openvpn/ssl_common.h +++ b/src/openvpn/ssl_common.h @@ -283,7 +283,7 @@ struct tls_options int ns_cert_type; unsigned remote_cert_ku[MAX_PARMS]; const char *remote_cert_eku; - uint8_t *verify_hash; + struct verify_hash_list *verify_hash; hash_algo_type verify_hash_algo; #ifdef ENABLE_X509ALTUSERNAME char *x509_username_field[MAX_PARMS]; diff --git a/src/openvpn/ssl_verify.c b/src/openvpn/ssl_verify.c index 4b120f7b..001ca82b 100644 --- a/src/openvpn/ssl_verify.c +++ b/src/openvpn/ssl_verify.c @@ -748,9 +748,22 @@ verify_cert(struct tls_session *session, openvpn_x509_cert_t *cert, int cert_dep goto cleanup; } - if (memcmp(BPTR(&ca_hash), opt->verify_hash, BLEN(&ca_hash))) + struct verify_hash_list *current_hash = opt->verify_hash; + + while (current_hash) + { + if (memcmp_constant_time(BPTR(&ca_hash), current_hash->hash, + BLEN(&ca_hash)) == 0) + { + hash_matched = true; + break; + } + current_hash = current_hash->next; + } + + if (!current_hash) { - msg(D_TLS_ERRORS, "TLS Error: level-1 certificate hash verification failed"); + msg(D_TLS_ERRORS, "TLS Error: --tls-verify certificate hash verification failed"); goto cleanup; } }
This patch introduces support for verify-hash inlining. When inlined, this options now allows to specify multiple fingerprints, one per line. Since this is a new syntax, there is no backwards compatibility to take care of, therefore we can drop support for SHA1. Inlined fingerprints are assumed be to SHA-256 only. Also print a warning about SHA1 hash being deprecated to verify certificates as it is not "industry standard" anymore. Patch v2: fix/clarify various comments, fix a few minor problems, allow the option to be specified multiple times and have that added to the list. Signed-off-by: Arne Schwabe <arne@rfc2549.org> --- doc/man-sections/inline-files.rst | 4 +- doc/man-sections/tls-options.rst | 10 +++ src/openvpn/options.c | 107 +++++++++++++++++++++++++++--- src/openvpn/options.h | 10 ++- src/openvpn/ssl_common.h | 2 +- src/openvpn/ssl_verify.c | 17 ++++- 6 files changed, 133 insertions(+), 17 deletions(-)