/* * Copyright (c) 2011 and 2012, Dustin Lundquist * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * 1. Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /* * This is a minimal TLS implementation intended only to parse the server name * extension. This was created based primarily on Wireshark dissection of a * TLS handshake and RFC4366. */ #include #include /* malloc() */ #include "tls.h" #define TLS_HEADER_LEN 5 #define TLS_HANDSHAKE_CONTENT_TYPE 0x16 #define TLS_HANDSHAKE_TYPE_CLIENT_HELLO 0x01 #ifndef MIN #define MIN(X, Y) ((X) < (Y) ? (X) : (Y)) #endif struct TLSProtocol { int use_alpn; char** sni_hostname_list; char** alpn_protocol_list; }; static int parse_extensions(const struct TLSProtocol *, const char *, size_t); static int parse_server_name_extension(const struct TLSProtocol *, const char *, size_t); static int parse_alpn_extension(const struct TLSProtocol *, const char *, size_t); static int has_match(char**, const char*, size_t); /* Parse a TLS packet for the Server Name Indication and ALPN extension in the client * hello handshake, returning a status code * * Returns: * >=0 - length of the hostname and updates *hostname * caller is responsible for freeing *hostname * -1 - Incomplete request * -2 - No Host header included in this request * -3 - Invalid hostname pointer * < -4 - Invalid TLS client hello */ int parse_tls_header(const struct TLSProtocol *tls_data, const char *data, size_t data_len) { char tls_content_type; char tls_version_major; char tls_version_minor; size_t pos = TLS_HEADER_LEN; size_t len; /* Check that our TCP payload is at least large enough for a TLS header */ if (data_len < TLS_HEADER_LEN) return -1; tls_content_type = data[0]; if (tls_content_type != TLS_HANDSHAKE_CONTENT_TYPE) { if (verbose) fprintf(stderr, "Request did not begin with TLS handshake.\n"); return -5; } tls_version_major = data[1]; tls_version_minor = data[2]; if (tls_version_major < 3) { if (verbose) fprintf(stderr, "Received SSL %d.%d handshake which cannot be parsed.\n", tls_version_major, tls_version_minor); return -2; } /* TLS record length */ len = ((unsigned char)data[3] << 8) + (unsigned char)data[4] + TLS_HEADER_LEN; data_len = MIN(data_len, len); /* Check we received entire TLS record length */ if (data_len < len) return -1; /* * Handshake */ if (pos + 1 > data_len) { return -5; } if (data[pos] != TLS_HANDSHAKE_TYPE_CLIENT_HELLO) { if (verbose) fprintf(stderr, "Not a client hello\n"); return -5; } /* Skip past fixed length records: 1 Handshake Type 3 Length 2 Version (again) 32 Random to Session ID Length */ pos += 38; /* Session ID */ if (pos + 1 > data_len) return -5; len = (unsigned char)data[pos]; pos += 1 + len; /* Cipher Suites */ if (pos + 2 > data_len) return -5; len = ((unsigned char)data[pos] << 8) + (unsigned char)data[pos + 1]; pos += 2 + len; /* Compression Methods */ if (pos + 1 > data_len) return -5; len = (unsigned char)data[pos]; pos += 1 + len; if (pos == data_len && tls_version_major == 3 && tls_version_minor == 0) { if (verbose) fprintf(stderr, "Received SSL 3.0 handshake without extensions\n"); return -2; } /* Extensions */ if (pos + 2 > data_len) return -5; len = ((unsigned char)data[pos] << 8) + (unsigned char)data[pos + 1]; pos += 2; if (pos + len > data_len) return -5; return parse_extensions(tls_data, data + pos, len); } static int parse_extensions(const struct TLSProtocol *tls_data, const char *data, size_t data_len) { size_t pos = 0; size_t len; int last_matched = 0; if (tls_data == NULL) return -3; /* Parse each 4 bytes for the extension header */ while (pos + 4 <= data_len) { /* Extension Length */ len = ((unsigned char) data[pos + 2] << 8) + (unsigned char) data[pos + 3]; if (pos + 4 + len > data_len) return -5; size_t extension_type = ((unsigned char) data[pos] << 8) + (unsigned char) data[pos + 1]; /* Check if it's a server name extension */ /* There can be only one extension of each type, so we break our state and move pos to beginning of the extension here */ if (tls_data->use_alpn == 2) { /* we want BOTH alpn and sni to match */ if (extension_type == 0x00) { /* Server Name */ if (parse_server_name_extension(tls_data, data + pos + 4, len)) { /* SNI matched */ if(last_matched) { /* this is only true if ALPN matched, so return true */ return last_matched; } else { /* otherwise store that SNI matched */ last_matched = 1; } } else { // both can't match return -2; } } else if (extension_type == 0x10) { /* ALPN */ if (parse_alpn_extension(tls_data, data + pos + 4, len)) { /* ALPN matched */ if(last_matched) { /* this is only true if SNI matched, so return true */ return last_matched; } else { /* otherwise store that ALPN matched */ last_matched = 1; } } else { // both can't match return -2; } } } else if (extension_type == 0x00 && tls_data->use_alpn == 0) { /* Server Name */ return parse_server_name_extension(tls_data, data + pos + 4, len); } else if (extension_type == 0x10 && tls_data->use_alpn == 1) { /* ALPN */ return parse_alpn_extension(tls_data, data + pos + 4, len); } pos += 4 + len; /* Advance to the next extension header */ } /* Check we ended where we expected to */ if (pos != data_len) return -5; return -2; } static int parse_server_name_extension(const struct TLSProtocol *tls_data, const char *data, size_t data_len) { size_t pos = 2; /* skip server name list length */ size_t len; while (pos + 3 < data_len) { len = ((unsigned char)data[pos + 1] << 8) + (unsigned char)data[pos + 2]; if (pos + 3 + len > data_len) return -5; switch (data[pos]) { /* name type */ case 0x00: /* host_name */ if(has_match(tls_data->sni_hostname_list, data + pos + 3, len)) { return len; } else { return -2; } default: if (verbose) fprintf(stderr, "Unknown server name extension name type: %d\n", data[pos]); } pos += 3 + len; } /* Check we ended where we expected to */ if (pos != data_len) return -5; return -2; } static int parse_alpn_extension(const struct TLSProtocol *tls_data, const char *data, size_t data_len) { size_t pos = 2; size_t len; while (pos + 1 < data_len) { len = (unsigned char)data[pos]; if (pos + 1 + len > data_len) return -5; if (len > 0 && has_match(tls_data->alpn_protocol_list, data + pos + 1, len)) { return len; } else if (len > 0) { if (verbose) fprintf(stderr, "Unknown ALPN name: %.*s\n", (int)len, data + pos + 1); } pos += 1 + len; } /* Check we ended where we expected to */ if (pos != data_len) return -5; return -2; } static int has_match(char** list, const char* name, size_t name_len) { char **item; for (item = list; *item; item++) { if (verbose) fprintf(stderr, "matching [%.*s] with [%s]\n", (int)name_len, name, *item); if(!strncmp(*item, name, name_len)) { return 1; } } return 0; } struct TLSProtocol * new_tls_data() { struct TLSProtocol *tls_data = malloc(sizeof(struct TLSProtocol)); if (tls_data != NULL) { tls_data->use_alpn = -1; } return tls_data; } struct TLSProtocol * tls_data_set_list(struct TLSProtocol *tls_data, int alpn, char** list) { if (alpn) { tls_data->alpn_protocol_list = list; if(tls_data->use_alpn == 0) tls_data->use_alpn = 2; else tls_data->use_alpn = 1; } else { tls_data->sni_hostname_list = list; if(tls_data->use_alpn == 1) tls_data->use_alpn = 2; else tls_data->use_alpn = 0; } return tls_data; }