/* This file is dedicated to the public domain. * * Gemini protocol adapter for Chawan. * Intended to be used through local CGI (by redirection in scheme-map). * * (FWIW, it should work with normal CGI or w3m's local CGI too. However, * it does not rewrite URLs, so you would have to figure out something for * that, e.g. by setting the base href or rewriting URLs in another layer.) * * Usage: gmifetch [URL] * * Environment variables: * - QUERY_STRING is used if no URL arguments are passed. * - GMIFETCH_KNOWN_HOSTS is used for setting the known_hosts file. If not set, * we use $XDG_CONFIG_HOME/gmifetch/known_hosts, where $XDG_CONFIG_HOME falls * back to $HOME/.config/gmifetch if not set. */ #include #include #include #include #include #include #include #include static SSL_CTX* ssl_ctx; static SSL *ssl; static BIO *conn; /* CGI responses */ #define INPUT_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "" \ "Input required" \ "" \ "

Input required

" \ "

" \ "%s" \ "

" \ "

" #define SUCCESS_RESPONSE "Content-Type: %s\r\n" \ "\r\n" #define REDIRECT_RESPONSE "Status: 30%c\r\n" \ "Location: %s\r\n" \ "\r\n" #define TEMPFAIL_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "" \ "Temporary failure" \ "

%s

" \ "

" \ "%s" #define PERMFAIL_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "" \ "Permanent failure" \ "

%s

" \ "

" \ "%s" #define CERTFAIL_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "" \ "Certificate failure" \ "

%s

" \ "

" \ "%s" #define INVALID_CERT_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "\n" \ "Invalid certificate\n" \ "

Invalid certificate

\n" \ "

\n" \ "The certificate received from the server does not match the\n" \ "stored certificate (expected %s, but got %s). Somebody may be\n" \ "tampering with your connection.\n" \ "

\n" \ "If you are sure that this is not a man-in-the-middle attack,\n" \ "please remove this host from %s.\n" #define UNKNOWN_CERT_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "" \ "Unknown certificate" \ "

Unknown certificate

" \ "

\n" \ "The hostname of the server you are visiting could not be found\n" \ "in your list of known hosts (%s).\n" \ "

\n" \ "The server has sent us a certificate with the following\n" \ "fingerprint:\n" \ "

%s

\n" \ "

Trust it?\n" \ "

" #define UPDATED_CERT_RESPONSE "Content-Type: text/html\r\n" \ "\r\n" \ "\n" \ "Certificate date changed\n" \ "

Certificate date changed

\n" \ "

\n" \ "The received certificate's date did not match the date in your\n" \ "list of known hosts (%s).\n" \ "

\n" \ "The new expiration date is: %s.\n" \ "

\n" \ "Update it?\n" \ "

\n" #define PDIE(x) \ do { \ puts("Content-Type: text/plain\r\n"); \ puts(x); \ puts(strerror(errno)); \ exit(1); \ } while (0) #define SDIE(x) \ do { \ puts("Content-Type: text/plain\r\n"); \ puts(x); \ ERR_print_errors_fp(stdout); \ exit(1); \ } while (0) #define DIE(x) \ do { \ puts("Content-Type: text/plain\r\n\r\n" x); \ exit(1); \ } while (0) #define BUFSIZE 1024 static void setup_ssl(void) { #define FLAGS (SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_COMPRESSION | \ SSL_OP_NO_TLSv1_1) SSL_library_init(); SSL_load_error_strings(); ssl_ctx = SSL_CTX_new(TLS_client_method()); SSL_CTX_set_options(ssl_ctx, FLAGS); if (!(conn = BIO_new_ssl_connect(ssl_ctx))) SDIE("Error creating BIO"); #undef FLAGS } static void extract_hostname(const char *s, char **hostp, char **portp, char **pathp, char **endp, char *urlbuf) { const char *p; size_t i, schlen; if (!(p = strstr(s, "gemini://"))) DIE("Invalid URL: scheme delimiter not found"); p += strlen("gemini://"); schlen = p - s; if (schlen >= BUFSIZE) DIE("Scheme too long"); #define SCHEME "gemini://" schlen = strlen(SCHEME); strcpy(urlbuf, SCHEME); *hostp = &urlbuf[schlen]; for (i = schlen; *p && *p != ':' && *p != '/' && i < BUFSIZE; ++p, ++i) urlbuf[i] = *p; if (i + 2 >= BUFSIZE) /* +2 for CRLF */ DIE("Host too long"); *portp = &urlbuf[i]; if (*p != ':') { if (i + 5 >= BUFSIZE) DIE("Host too long"); strcpy(&urlbuf[i], ":1965"); i += 5; } else { for (; *p && *p != '/' && i < BUFSIZE; ++i, ++p) urlbuf[i] = *p; } *pathp = &urlbuf[i]; if (i < BUFSIZE) urlbuf[i++] = '/'; if (*p == '/') ++p; for (; *p && i < BUFSIZE; ++i, ++p) urlbuf[i] = *p; if (i + 2 >= BUFSIZE) /* +2 for CRLF */ DIE("Host too long"); *endp = &urlbuf[i]; urlbuf[i] = '\0'; } int check_cert(const char *theirs, char *hostp, char **stored_digestp, time_t their_time, FILE *known_hosts) { char *p, *q, *hashp, *timep; int found; time_t our_time; char linebuf[BUFSIZE + 1]; rewind(known_hosts); found = 0; while (!found && fgets(linebuf, BUFSIZE, known_hosts)) { p = strstr(linebuf, " "); if (!p) DIE("Incorrectly formatted known_hosts file"); *p = '\0'; found = !strcmp(linebuf, hostp); } if (!found) return -1; hashp = p + 1; if (!(q = strstr(hashp, " "))) DIE("Incorrectly formatted known_hosts file"); *q = '\0'; if (strcmp(hashp, "sha256") && strcmp(hashp, "SHA256")) DIE("Unsupported digest format"); *stored_digestp = q + 1; if (!(q = strstr(*stored_digestp, " "))) { timep = NULL; if ((q = strstr(*stored_digestp, "\n"))) *q = '\0'; } else { timep = q + 1; *q = '\0'; } if (strcmp(theirs, *stored_digestp)) return 0; if (!timep) return -2; our_time = (time_t)atol(timep); if (their_time != our_time) return -2; return 1; } static char HexTable[] = "0123456789ABCDEF"; void hex_encode(const unsigned char *inp, char *outbuf, int len) { const unsigned char *p; char *q; for (p = inp, q = outbuf; p < &inp[len]; ++p) { if (p != inp) *q++ = ':'; *q++ = HexTable[(*p >> 4) & 0xF]; *q++ = HexTable[*p & 0xF]; } *q++ = '\0'; } static void hash_buf(const unsigned char *ibuf, int len, char *obuf2) { unsigned int len2; EVP_MD_CTX* mdctx; unsigned char hashbuf[EVP_MAX_MD_SIZE]; if (!(mdctx = EVP_MD_CTX_new())) SDIE("Failed to initialize MD_CTX"); if (!EVP_DigestInit_ex(mdctx, EVP_sha256(), NULL)) SDIE("Failed to initialize sha256"); if (!EVP_DigestUpdate(mdctx, ibuf, len)) SDIE("Failed to update digest"); len2 = 0; if (!EVP_DigestFinal_ex(mdctx, hashbuf, &len2)) SDIE("Failed to finalize digest"); EVP_MD_CTX_free(mdctx); hex_encode(hashbuf, obuf2, len2); } /* 1: cert found & valid * 0: cert found & invalid * -1: cert not found * -2: cert found, but notAfter updated */ static int connect(char *hostp, char *portp, char *pathp, char *endp, char **stored_digestp, time_t *their_time, char *hashbuf2, FILE *known_hosts) { X509 *cert; const EVP_PKEY *pkey; #define PUBKEY_BUF_SIZE 8192 unsigned char pubkey_buf[PUBKEY_BUF_SIZE + 1], *r; int len, res; const ASN1_TIME *notAfter; struct tm their_tm; *pathp = '\0'; if (!BIO_set_conn_hostname(conn, hostp)) SDIE("Error setting BIO hostname"); *pathp = '/'; BIO_get_ssl(conn, &ssl); #define PREFERRED_CIPHERS "HIGH:!aNULL:!kRSA:!PSK:!SRP:!MD5:!RC4" if (!SSL_set_cipher_list(ssl, PREFERRED_CIPHERS)) SDIE("Error failed to set cipher list"); *portp = '\0'; if (!SSL_set_tlsext_host_name(ssl, hostp)) SDIE("Error failed to set tlsext host name"); if (BIO_do_connect(conn) <= 0) SDIE("Failed to connect"); if (!BIO_do_handshake(conn)) SDIE("Failed handshake"); if (!(cert = SSL_get_peer_certificate(ssl))) DIE("Failed to get certificate"); if (!(pkey = X509_get0_pubkey(cert))) SDIE("Failed to decode public key"); len = i2d_PUBKEY(pkey, NULL); if (len * 3 > PUBKEY_BUF_SIZE) DIE("Public key too long"); r = pubkey_buf; if (i2d_PUBKEY(pkey, &r) != len) DIE("wat"); hash_buf(pubkey_buf, len, hashbuf2); notAfter = X509_get0_notAfter(cert); if (!ASN1_TIME_to_tm(notAfter, &their_tm)) DIE("Failed to parse time"); if (X509_cmp_current_time(X509_get0_notBefore(cert)) >= 0) DIE("Wrong time"); if (X509_cmp_current_time(notAfter) <= 0) DIE("Wrong time"); *their_time = mktime(&their_tm); res = check_cert(hashbuf2, hostp, stored_digestp, *their_time, known_hosts); *portp = ':'; X509_free(cert); strcpy(endp, "\r\n"); return res; #undef PUBKEY_BUF_SIZE } static void read_response(const char *urlbuf) { int bytes, total; const char *tmp; char *q, status0, status1; char buffer[BUFSIZE + 1]; /* Read response */ total = 0; /* Status code */ while (((bytes = BIO_read(conn, buffer, 3 - total)) > 0 || BIO_should_retry(conn)) && total < 3) total += bytes; if (total < 3 || !isdigit(status0 = buffer[0]) || !isdigit(status1 = buffer[1]) || buffer[2] != ' ') DIE("Invalid status code"); /* Meta */ #define METALEN (total - 3) while (((bytes = BIO_read(conn, &buffer[METALEN], 1024 - METALEN)) > 0 || BIO_should_retry(conn)) && METALEN < BUFSIZE) total += bytes; q = strstr(buffer, "\r\n"); if (!q) DIE("Invalid status line"); *q = '\0'; /* buffer is now META. */ switch (status0) { case '1': /* input */ /* META is the prompt. */ printf(INPUT_RESPONSE, urlbuf, buffer, status1 == '1' ? "password" /* sensitive input */ : "search" /* input */); break; case '2': /* success */ /* META is the content type. */ printf(SUCCESS_RESPONSE, *buffer ? buffer : "text/gemini; charset=utf-8" /* fallback */); /* Body */ /* flush any data remaining in buffer */ total -= 5 + (q - buffer); /* code + space + meta + \r\n len */ if (total > 0) fwrite(&q[2], 1, total, stdout); while ((bytes = BIO_read(conn, buffer, BUFSIZE)) > 0 || BIO_should_retry(conn)) fwrite(buffer, 1, bytes, stdout); break; case '3': /* redirect */ /* META is the redirection URL. */ printf(REDIRECT_RESPONSE, status1 == '0' ? '7' /* temporary */ : '1' /* permanent */, buffer); break; case '4': /* temporary failure */ /* META is additional information. */ /* TODO maybe set status code too? */ switch (status1) { case '1': tmp = "Server unavailable"; break; case '2': tmp = "CGI error"; break; case '3': tmp = "Proxy error"; break; case '4': tmp = "Slow down!"; break; case '0': default: /* no additional information provided in the code */ tmp = "Temporary failure"; break; } printf(TEMPFAIL_RESPONSE, tmp, buffer); break; case '5': /* permanent failure */ /* TODO maybe set status code too? */ switch (status1) { case '1': tmp = "Not found"; break; case '2': tmp = "Gone"; break; case '3': tmp = "Proxy request refused"; break; case '9': tmp = "Bad request"; break; case '0': default: /* no additional information provided in the code */ tmp = "Permanent failure"; break; } printf(PERMFAIL_RESPONSE, tmp, buffer); break; case '6': /* permanent failure */ /* TODO maybe set status code too? */ switch (status1) { case '1': tmp = "Certificate not authorized"; break; case '2': tmp = "Certificate not valid"; break; case '0': default: /* no additional information provided in the code */ tmp = "Certificate failure"; break; } printf(CERTFAIL_RESPONSE, tmp, buffer); } } void decode_query(const char *input_url, char *output_buffer) { const char *p; char *q, *endp, c; endp = &output_buffer[BUFSIZE]; for (p = input_url, q = output_buffer; *p && q < endp; ++p, ++q) { if (*p != '%') { *q = *p; } else { if (!isxdigit(p[1] & 0xFF) || !isxdigit(p[2] & 0xFF)) DIE("Invalid percent encoding"); c = tolower(p[1] & 0xFF); *q = ('a' <= c && c <= 'z') ? c - 'a' + 10 : c - '0'; c = tolower(p[2] & 0xFF); *q = (*q << 4) | (('a' <= c || c <= 'z') ? c - 'a' + 10 : c - '0'); p += 2; } } if (q >= endp) DIE("Query too long"); *q = '\0'; } void read_post(const char *hostp, char *portp, char *pathp, const char *urlbuf, char *khsbuf, FILE *known_hosts) { /* TODO move query strings here */ size_t n; char *p, *q; FILE *known_hosts_tmp; long last_pos, len, total; size_t khslen; char inbuf[BUFSIZE + 1], buffer[BUFSIZE + 1]; n = fread(inbuf, 1, BUFSIZE, stdin); inbuf[n] = '\0'; if ((p = strstr(inbuf, "input="))) { decode_query(p + 6, buffer); if (!(q = strstr(pathp, "?"))) /* no query string */ q = &pathp[strlen(pathp)]; for (; *p && q < &urlbuf[BUFSIZE]; ++p, ++q) *q = *p; if (q >= &urlbuf[BUFSIZE]) DIE("Query too long"); } else if (!(p = strstr(inbuf, "trust_cert="))) { DIE("Invalid POST request: trust_cert missing"); } p += sizeof("trust_cert=") - 1; if (!strncmp(p, "always", 6)) { /* move to file end */ fseek(known_hosts, 0L, SEEK_END); last_pos = ftell(known_hosts); if (!(p = strstr(p, "entry="))) DIE("Invalid POST request: missing entry"); p += sizeof("entry=") - 1; decode_query(p, buffer); /* replace plus signs */ p = buffer; while ((p = strstr(p, "+"))) *p = ' '; fwrite(buffer, 1, strlen(buffer), known_hosts); fwrite("\n", 1, 1, known_hosts); khslen = strlen(khsbuf); khsbuf[khslen] = '~'; khsbuf[khslen + 1] = '\0'; if (!(known_hosts_tmp = fopen(khsbuf, "w+"))) PDIE("Error opening temporary hosts file"); rewind(known_hosts); *portp = '\0'; total = 0; while (fgets(buffer, BUFSIZE, known_hosts)) { len = strlen(buffer); if (!len) continue; if ((total += len) > last_pos) { /* finished */ fwrite(buffer, 1, len, known_hosts_tmp); break; } if (buffer[len - 1] != '\n') { /* clean up */ fclose(known_hosts_tmp); unlink(khsbuf); DIE("Line too long"); } if (!(p = strstr(buffer, " "))) DIE("Invalid entry in known_hosts file"); *p = '\0'; if (strcmp(buffer, hostp)) { *p = ' '; fwrite(buffer, 1, len, known_hosts_tmp); } } *portp = ':'; memcpy(buffer, khsbuf, BUFSIZE + 1); buffer[khslen] = '\0'; fclose(known_hosts); fclose(known_hosts_tmp); if (rename(khsbuf, buffer)) PDIE("Failed to rename temporary file"); khsbuf[khslen] = '\0'; if (!(known_hosts = fopen(khsbuf, "a+"))) PDIE("Failed to re-open known hosts file"); } else if (strncmp(p, "once", 4)) { DIE("Invalid POST request"); } } FILE *open_known_hosts(char *khsbuf) { const char *known_hosts_path, *xdg_dir, *home_dir; char *p; size_t len; struct stat s; FILE *known_hosts; known_hosts_path = getenv("GMIFETCH_KNOWN_HOSTS"); if (!known_hosts_path) { xdg_dir = getenv("XDG_CONFIG_HOME"); if ((xdg_dir = getenv("XDG_CONFIG_HOME"))) { len = strlen(xdg_dir); #define CONFIG_REL "/gmifetch/known_hosts" if (len + sizeof(CONFIG_REL) > BUFSIZE) DIE("Error: config directory path too long"); memcpy(khsbuf, xdg_dir, len); memcpy(&khsbuf[len], CONFIG_REL, sizeof(CONFIG_REL)); } else { if (!(home_dir = getenv("HOME"))) home_dir = getpwuid(getuid())->pw_dir; if (!home_dir) DIE("Error: failed to get HOME directory"); #undef CONFIG_REL #define CONFIG_REL "/.config/gmifetch/known_hosts" len = strlen(home_dir); if (len + sizeof(CONFIG_REL) > BUFSIZE) DIE("Error: home directory path too long"); memcpy(khsbuf, home_dir, len); memcpy(&khsbuf[len], CONFIG_REL, sizeof(CONFIG_REL)); } } else { len = strlen(known_hosts_path); if (len > BUFSIZE) DIE("Error: known hosts path too long"); memcpy(khsbuf, known_hosts_path, len); } p = khsbuf; if (*p == '/') ++p; for (; *p; ++p) { if (*p == '/') { *p = '\0'; if (stat(khsbuf, &s) == -1) { if (errno != ENOENT) PDIE("Error calling stat"); if (mkdir(khsbuf, 0755) == -1) PDIE("Error calling mkdir"); } else if (!S_ISDIR(s.st_mode)) { if (mkdir(khsbuf, 0755) == -1) PDIE("Error calling mkdir"); } *p = '/'; } } if (!(known_hosts = fopen(khsbuf, "a+"))) PDIE("Error opening known hosts file"); return known_hosts; } int main(int argc, const char *argv[]) { const char *input_url, *method; char *hostp, *portp, *pathp, *endp, *stored_digestp; int connect_res; time_t their_time; char hashbuf2[EVP_MAX_MD_SIZE * 3 + 1]; char urlbuf[BUFSIZE + 1], buffer[BUFSIZE + 1], khsbuf[BUFSIZE + 2]; FILE *known_hosts; if (argc != 2) { input_url = getenv("QUERY_STRING"); if (!input_url) DIE("Usage: gmifetch [url] (or set QUERY_STRING)"); decode_query(input_url, buffer); input_url = buffer; } else { input_url = argv[1]; } known_hosts = open_known_hosts(khsbuf); setup_ssl(); extract_hostname(input_url, &hostp, &portp, &pathp, &endp, urlbuf); method = getenv("REQUEST_METHOD"); if (method && !strcmp(method, "POST")) read_post(hostp, portp, pathp, urlbuf, khsbuf, known_hosts); connect_res = connect(hostp, portp, pathp, endp, &stored_digestp, &their_time, hashbuf2, known_hosts); if (connect_res == 1) { /* valid certificate */ BIO_puts(conn, urlbuf); read_response(urlbuf); } else if (connect_res == 0) { /* invalid certificate */ printf(INVALID_CERT_RESPONSE, stored_digestp, buffer, khsbuf); } else if (connect_res == -1) { /* no certificate */ *portp = '\0'; printf(UNKNOWN_CERT_RESPONSE, khsbuf, hashbuf2, hostp, hashbuf2, (unsigned long)their_time); } else { /* -2: updated expiration date */ *portp = '\0'; printf(UPDATED_CERT_RESPONSE, khsbuf, ctime(&their_time), hostp, hashbuf2, (unsigned long)their_time); } BIO_free_all(conn); exit(0); }