SqMod/vendor/CivetWeb/handle_form.inl

/* Copyright (c) 2016-2021 the Civetweb developers
 *
 * 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.
 */

static int
url_encoded_field_found(const struct mg_connection *conn,
                        const char *key,
                        size_t key_len,
                        const char *filename,
                        size_t filename_len,
                        char *path,
                        size_t path_len,
                        struct mg_form_data_handler *fdh)
{
	char key_dec[1024];
	char filename_dec[1024];
	int key_dec_len;
	int filename_dec_len;
	int ret;

	key_dec_len =
	    mg_url_decode(key, (int)key_len, key_dec, (int)sizeof(key_dec), 1);

	if (((size_t)key_dec_len >= (size_t)sizeof(key_dec)) || (key_dec_len < 0)) {
		return MG_FORM_FIELD_STORAGE_SKIP;
	}

	if (filename) {
		filename_dec_len = mg_url_decode(filename,
		                                 (int)filename_len,
		                                 filename_dec,
		                                 (int)sizeof(filename_dec),
		                                 1);

		if (((size_t)filename_dec_len >= (size_t)sizeof(filename_dec))
		    || (filename_dec_len < 0)) {
			/* Log error message and skip this field. */
			mg_cry_internal(conn, "%s: Cannot decode filename", __func__);
			return MG_FORM_FIELD_STORAGE_SKIP;
		}
		remove_dot_segments(filename_dec);

	} else {
		filename_dec[0] = 0;
	}

	ret =
	    fdh->field_found(key_dec, filename_dec, path, path_len, fdh->user_data);

	if ((ret & 0xF) == MG_FORM_FIELD_STORAGE_GET) {
		if (fdh->field_get == NULL) {
			mg_cry_internal(conn,
			                "%s: Function \"Get\" not available",
			                __func__);
			return MG_FORM_FIELD_STORAGE_SKIP;
		}
	}
	if ((ret & 0xF) == MG_FORM_FIELD_STORAGE_STORE) {
		if (fdh->field_store == NULL) {
			mg_cry_internal(conn,
			                "%s: Function \"Store\" not available",
			                __func__);
			return MG_FORM_FIELD_STORAGE_SKIP;
		}
	}

	return ret;
}

static int
url_encoded_field_get(
    const struct mg_connection *conn,
    const char *key,
    size_t key_len,
    const char *value,
    size_t *value_len, /* IN: number of bytes available in "value", OUT: number
                          of bytes processed */
    struct mg_form_data_handler *fdh)
{
	char key_dec[1024];

	char *value_dec = (char *)mg_malloc_ctx(*value_len + 1, conn->phys_ctx);
	int value_dec_len, ret;

	if (!value_dec) {
		/* Log error message and stop parsing the form data. */
		mg_cry_internal(conn,
		                "%s: Not enough memory (required: %lu)",
		                __func__,
		                (unsigned long)(*value_len + 1));
		return MG_FORM_FIELD_STORAGE_ABORT;
	}

	mg_url_decode(key, (int)key_len, key_dec, (int)sizeof(key_dec), 1);

	if (*value_len >= 2 && value[*value_len - 2] == '%')
		*value_len -= 2;
	else if (*value_len >= 1 && value[*value_len - 1] == '%')
		(*value_len)--;
	value_dec_len = mg_url_decode(
	    value, (int)*value_len, value_dec, ((int)*value_len) + 1, 1);

	ret = fdh->field_get(key_dec,
	                     value_dec,
	                     (size_t)value_dec_len,
	                     fdh->user_data);

	mg_free(value_dec);

	return ret;
}

static int
unencoded_field_get(const struct mg_connection *conn,
                    const char *key,
                    size_t key_len,
                    const char *value,
                    size_t value_len,
                    struct mg_form_data_handler *fdh)
{
	char key_dec[1024];
	(void)conn;

	mg_url_decode(key, (int)key_len, key_dec, (int)sizeof(key_dec), 1);

	return fdh->field_get(key_dec, value, value_len, fdh->user_data);
}

static int
field_stored(const struct mg_connection *conn,
             const char *path,
             long long file_size,
             struct mg_form_data_handler *fdh)
{
	/* Equivalent to "upload" callback of "mg_upload". */

	(void)conn; /* we do not need mg_cry here, so conn is currently unused */

	return fdh->field_store(path, file_size, fdh->user_data);
}

static const char *
search_boundary(const char *buf,
                size_t buf_len,
                const char *boundary,
                size_t boundary_len)
{
	/* We must do a binary search here, not a string search, since the buffer
	 * may contain '\x00' bytes, if binary data is transferred. */
	int clen = (int)buf_len - (int)boundary_len - 4;
	int i;

	for (i = 0; i <= clen; i++) {
		if (!memcmp(buf + i, "\r\n--", 4)) {
			if (!memcmp(buf + i + 4, boundary, boundary_len)) {
				return buf + i;
			}
		}
	}
	return NULL;
}

int
mg_handle_form_request(struct mg_connection *conn,
                       struct mg_form_data_handler *fdh)
{
	const char *content_type;
	char path[512];
	char buf[MG_BUF_LEN]; /* Must not be smaller than ~900 */
	int field_storage;
	int buf_fill = 0;
	int r;
	int field_count = 0;
	struct mg_file fstore = STRUCT_FILE_INITIALIZER;
	int64_t file_size = 0; /* init here, to a avoid a false positive
	                         "uninitialized variable used" warning */

	int has_body_data =
	    (conn->request_info.content_length > 0) || (conn->is_chunked);

	/* Unused without filesystems */
	(void)fstore;
	(void)file_size;

	/* There are three ways to encode data from a HTML form:
	 * 1) method: GET (default)
	 *    The form data is in the HTTP query string.
	 * 2) method: POST, enctype: "application/x-www-form-urlencoded"
	 *    The form data is in the request body.
	 *    The body is url encoded (the default encoding for POST).
	 * 3) method: POST, enctype: "multipart/form-data".
	 *    The form data is in the request body of a multipart message.
	 *    This is the typical way to handle file upload from a form.
	 */

	if (!has_body_data) {
		const char *data;

		if (0 != strcmp(conn->request_info.request_method, "GET")) {
			/* No body data, but not a GET request.
			 * This is not a valid form request. */
			return -1;
		}

		/* GET request: form data is in the query string. */
		/* The entire data has already been loaded, so there is no nead to
		 * call mg_read. We just need to split the query string into key-value
		 * pairs. */
		data = conn->request_info.query_string;
		if (!data) {
			/* No query string. */
			return -1;
		}

		/* Split data in a=1&b=xy&c=3&c=4 ... */
		while (*data) {
			const char *val = strchr(data, '=');
			const char *next;
			ptrdiff_t keylen, vallen;

			if (!val) {
				break;
			}
			keylen = val - data;

			/* In every "field_found" callback we ask what to do with the
			 * data ("field_storage"). This could be:
			 * MG_FORM_FIELD_STORAGE_SKIP (0):
			 *   ignore the value of this field
			 * MG_FORM_FIELD_STORAGE_GET (1):
			 *   read the data and call the get callback function
			 * MG_FORM_FIELD_STORAGE_STORE (2):
			 *   store the data in a file
			 * MG_FORM_FIELD_STORAGE_READ (3):
			 *   let the user read the data (for parsing long data on the fly)
			 * MG_FORM_FIELD_STORAGE_ABORT (flag):
			 *   stop parsing
			 */
			memset(path, 0, sizeof(path));
			field_count++;
			field_storage = url_encoded_field_found(conn,
			                                        data,
			                                        (size_t)keylen,
			                                        NULL,
			                                        0,
			                                        path,
			                                        sizeof(path) - 1,
			                                        fdh);

			val++;
			next = strchr(val, '&');
			if (next) {
				vallen = next - val;
			} else {
				vallen = (ptrdiff_t)strlen(val);
			}

			if (field_storage == MG_FORM_FIELD_STORAGE_GET) {
				/* Call callback */
				r = url_encoded_field_get(
				    conn, data, (size_t)keylen, val, (size_t *)&vallen, fdh);
				if (r == MG_FORM_FIELD_HANDLE_ABORT) {
					/* Stop request handling */
					break;
				}
				if (r == MG_FORM_FIELD_HANDLE_NEXT) {
					/* Skip to next field */
					field_storage = MG_FORM_FIELD_STORAGE_SKIP;
				}
			}

			if (next) {
				next++;
			} else {
				/* vallen may have been modified by url_encoded_field_get */
				next = val + vallen;
			}

#if !defined(NO_FILESYSTEMS)
			if (field_storage == MG_FORM_FIELD_STORAGE_STORE) {
				/* Store the content to a file */
				if (mg_fopen(conn, path, MG_FOPEN_MODE_WRITE, &fstore) == 0) {
					fstore.access.fp = NULL;
				}
				file_size = 0;
				if (fstore.access.fp != NULL) {
					size_t n = (size_t)
					    fwrite(val, 1, (size_t)vallen, fstore.access.fp);
					if ((n != (size_t)vallen) || (ferror(fstore.access.fp))) {
						mg_cry_internal(conn,
						                "%s: Cannot write file %s",
						                __func__,
						                path);
						(void)mg_fclose(&fstore.access);
						remove_bad_file(conn, path);
					}
					file_size += (int64_t)n;

					if (fstore.access.fp) {
						r = mg_fclose(&fstore.access);
						if (r == 0) {
							/* stored successfully */
							r = field_stored(conn, path, file_size, fdh);
							if (r == MG_FORM_FIELD_HANDLE_ABORT) {
								/* Stop request handling */
								break;
							}

						} else {
							mg_cry_internal(conn,
							                "%s: Error saving file %s",
							                __func__,
							                path);
							remove_bad_file(conn, path);
						}
						fstore.access.fp = NULL;
					}

				} else {
					mg_cry_internal(conn,
					                "%s: Cannot create file %s",
					                __func__,
					                path);
				}
			}
#endif /* NO_FILESYSTEMS */

			/* if (field_storage == MG_FORM_FIELD_STORAGE_READ) { */
			/* The idea of "field_storage=read" is to let the API user read
			 * data chunk by chunk and to some data processing on the fly.
			 * This should avoid the need to store data in the server:
			 * It should neither be stored in memory, like
			 * "field_storage=get" does, nor in a file like
			 * "field_storage=store".
			 * However, for a "GET" request this does not make any much
			 * sense, since the data is already stored in memory, as it is
			 * part of the query string.
			 */
			/* } */

			if ((field_storage & MG_FORM_FIELD_STORAGE_ABORT)
			    == MG_FORM_FIELD_STORAGE_ABORT) {
				/* Stop parsing the request */
				break;
			}

			/* Proceed to next entry */
			data = next;
		}

		return field_count;
	}

	content_type = mg_get_header(conn, "Content-Type");

	if (!content_type
	    || !mg_strncasecmp(content_type,
	                       "APPLICATION/X-WWW-FORM-URLENCODED",
	                       33)
	    || !mg_strncasecmp(content_type,
	                       "APPLICATION/WWW-FORM-URLENCODED",
	                       31)) {
		/* The form data is in the request body data, encoded in key/value
		 * pairs. */
		int all_data_read = 0;

		/* Read body data and split it in keys and values.
		 * The encoding is like in the "GET" case above: a=1&b&c=3&c=4.
		 * Here we use "POST", and read the data from the request body.
		 * The data read on the fly, so it is not required to buffer the
		 * entire request in memory before processing it. */
		for (;;) {
			const char *val;
			const char *next;
			ptrdiff_t keylen, vallen;
			ptrdiff_t used;
			int end_of_key_value_pair_found = 0;
			int get_block;

			if ((size_t)buf_fill < (sizeof(buf) - 1)) {

				size_t to_read = sizeof(buf) - 1 - (size_t)buf_fill;
				r = mg_read(conn, buf + (size_t)buf_fill, to_read);
				if ((r < 0) || ((r == 0) && all_data_read)) {
					/* read error */
					return -1;
				}
				if (r == 0) {
					/* TODO: Create a function to get "all_data_read" from
					 * the conn object. All data is read if the Content-Length
					 * has been reached, or if chunked encoding is used and
					 * the end marker has been read, or if the connection has
					 * been closed. */
					all_data_read = (buf_fill == 0);
				}
				buf_fill += r;
				buf[buf_fill] = 0;
				if (buf_fill < 1) {
					break;
				}
			}

			val = strchr(buf, '=');

			if (!val) {
				break;
			}
			keylen = val - buf;
			val++;

			/* Call callback */
			memset(path, 0, sizeof(path));
			field_count++;
			field_storage = url_encoded_field_found(conn,
			                                        buf,
			                                        (size_t)keylen,
			                                        NULL,
			                                        0,
			                                        path,
			                                        sizeof(path) - 1,
			                                        fdh);

			if ((field_storage & MG_FORM_FIELD_STORAGE_ABORT)
			    == MG_FORM_FIELD_STORAGE_ABORT) {
				/* Stop parsing the request */
				break;
			}

#if !defined(NO_FILESYSTEMS)
			if (field_storage == MG_FORM_FIELD_STORAGE_STORE) {
				if (mg_fopen(conn, path, MG_FOPEN_MODE_WRITE, &fstore) == 0) {
					fstore.access.fp = NULL;
				}
				file_size = 0;
				if (!fstore.access.fp) {
					mg_cry_internal(conn,
					                "%s: Cannot create file %s",
					                __func__,
					                path);
				}
			}
#endif /* NO_FILESYSTEMS */

			get_block = 0;
			/* Loop to read values larger than sizeof(buf)-keylen-2 */
			do {
				next = strchr(val, '&');
				if (next) {
					vallen = next - val;
					end_of_key_value_pair_found = 1;
				} else {
					vallen = (ptrdiff_t)strlen(val);
					end_of_key_value_pair_found = all_data_read;
				}

				if (field_storage == MG_FORM_FIELD_STORAGE_GET) {
#if 0
					if (!end_of_key_value_pair_found && !all_data_read) {
						/* This callback will deliver partial contents */
					}
#endif

					/* Call callback */
					r = url_encoded_field_get(conn,
					                          ((get_block > 0) ? NULL : buf),
					                          ((get_block > 0)
					                               ? 0
					                               : (size_t)keylen),
					                          val,
					                          (size_t *)&vallen,
					                          fdh);
					get_block++;
					if (r == MG_FORM_FIELD_HANDLE_ABORT) {
						/* Stop request handling */
						break;
					}
					if (r == MG_FORM_FIELD_HANDLE_NEXT) {
						/* Skip to next field */
						field_storage = MG_FORM_FIELD_STORAGE_SKIP;
					}
				}

				if (next) {
					next++;
				} else {
					/* vallen may have been modified by url_encoded_field_get */
					next = val + vallen;
				}

#if !defined(NO_FILESYSTEMS)
				if (fstore.access.fp) {
					size_t n = (size_t)
					    fwrite(val, 1, (size_t)vallen, fstore.access.fp);
					if ((n != (size_t)vallen) || (ferror(fstore.access.fp))) {
						mg_cry_internal(conn,
						                "%s: Cannot write file %s",
						                __func__,
						                path);
						mg_fclose(&fstore.access);
						remove_bad_file(conn, path);
					}
					file_size += (int64_t)n;
				}
#endif /* NO_FILESYSTEMS */

				if (!end_of_key_value_pair_found) {
					used = next - buf;
					memmove(buf,
					        buf + (size_t)used,
					        sizeof(buf) - (size_t)used);
					next = buf;
					buf_fill -= (int)used;
					if ((size_t)buf_fill < (sizeof(buf) - 1)) {

						size_t to_read = sizeof(buf) - 1 - (size_t)buf_fill;
						r = mg_read(conn, buf + (size_t)buf_fill, to_read);
						if ((r < 0) || ((r == 0) && all_data_read)) {
#if !defined(NO_FILESYSTEMS)
							/* read error */
							if (fstore.access.fp) {
								mg_fclose(&fstore.access);
								remove_bad_file(conn, path);
							}
							return -1;
#endif /* NO_FILESYSTEMS */
						}
						if (r == 0) {
							/* TODO: Create a function to get "all_data_read"
							 * from the conn object. All data is read if the
							 * Content-Length has been reached, or if chunked
							 * encoding is used and the end marker has been
							 * read, or if the connection has been closed. */
							all_data_read = (buf_fill == 0);
						}
						buf_fill += r;
						buf[buf_fill] = 0;
						if (buf_fill < 1) {
							break;
						}
						val = buf;
					}
				}

			} while (!end_of_key_value_pair_found);

#if !defined(NO_FILESYSTEMS)
			if (fstore.access.fp) {
				r = mg_fclose(&fstore.access);
				if (r == 0) {
					/* stored successfully */
					r = field_stored(conn, path, file_size, fdh);
					if (r == MG_FORM_FIELD_HANDLE_ABORT) {
						/* Stop request handling */
						break;
					}
				} else {
					mg_cry_internal(conn,
					                "%s: Error saving file %s",
					                __func__,
					                path);
					remove_bad_file(conn, path);
				}
				fstore.access.fp = NULL;
			}
#endif /* NO_FILESYSTEMS */

			if (all_data_read && (buf_fill == 0)) {
				/* nothing more to process */
				break;
			}

			/* Proceed to next entry */
			used = next - buf;
			memmove(buf, buf + (size_t)used, sizeof(buf) - (size_t)used);
			buf_fill -= (int)used;
		}

		return field_count;
	}

	if (!mg_strncasecmp(content_type, "MULTIPART/FORM-DATA;", 20)) {
		/* The form data is in the request body data, encoded as multipart
		 * content (see https://www.ietf.org/rfc/rfc1867.txt,
		 * https://www.ietf.org/rfc/rfc2388.txt). */
		char *boundary;
		size_t bl;
		ptrdiff_t used;
		struct mg_request_info part_header;
		char *hbuf;
		const char *content_disp, *hend, *fbeg, *fend, *nbeg, *nend;
		const char *next;
		unsigned part_no;
		int all_data_read = 0;

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

		/* Skip all spaces between MULTIPART/FORM-DATA; and BOUNDARY= */
		bl = 20;
		while (content_type[bl] == ' ') {
			bl++;
		}

		/* There has to be a BOUNDARY definition in the Content-Type header */
		if (mg_strncasecmp(content_type + bl, "BOUNDARY=", 9)) {
			/* Malformed request */
			return -1;
		}

		/* Copy boundary string to variable "boundary" */
		fbeg = content_type + bl + 9;
		bl = strlen(fbeg);
		boundary = (char *)mg_malloc(bl + 1);
		if (!boundary) {
			/* Out of memory */
			mg_cry_internal(conn,
			                "%s: Cannot allocate memory for boundary [%lu]",
			                __func__,
			                (unsigned long)bl);
			return -1;
		}
		memcpy(boundary, fbeg, bl);
		boundary[bl] = 0;

		/* RFC 2046 permits the boundary string to be quoted. */
		/* If the boundary is quoted, trim the quotes */
		if (boundary[0] == '"') {
			hbuf = strchr(boundary + 1, '"');
			if ((!hbuf) || (*hbuf != '"')) {
				/* Malformed request */
				mg_free(boundary);
				return -1;
			}
			*hbuf = 0;
			memmove(boundary, boundary + 1, bl);
			bl = strlen(boundary);
		}

		/* Do some sanity checks for boundary lengths */
		if (bl > 70) {
			/* From RFC 2046:
			 * Boundary delimiters must not appear within the
			 * encapsulated material, and must be no longer
			 * than 70 characters, not counting the two
			 * leading hyphens.
			 */

			/* The algorithm can not work if bl >= sizeof(buf), or if buf
			 * can not hold the multipart header plus the boundary.
			 * Requests with long boundaries are not RFC compliant, maybe they
			 * are intended attacks to interfere with this algorithm. */
			mg_free(boundary);
			return -1;
		}
		if (bl < 4) {
			/* Sanity check:  A boundary string of less than 4 bytes makes
			 * no sense either. */
			mg_free(boundary);
			return -1;
		}

		for (part_no = 0;; part_no++) {
			size_t towrite, fnlen, n;
			int get_block;
			size_t to_read = sizeof(buf) - 1 - (size_t)buf_fill;

			/* Unused without filesystems */
			(void)n;

			r = mg_read(conn, buf + (size_t)buf_fill, to_read);
			if ((r < 0) || ((r == 0) && all_data_read)) {
				/* read error */
				mg_free(boundary);
				return -1;
			}
			if (r == 0) {
				all_data_read = (buf_fill == 0);
			}

			buf_fill += r;
			buf[buf_fill] = 0;
			if (buf_fill < 1) {
				/* No data */
				mg_free(boundary);
				return -1;
			}

			if (part_no == 0) {
				int d = 0;
				while ((d < buf_fill) && (buf[d] != '-')) {
					d++;
				}
				if ((d > 0) && (buf[d] == '-')) {
					memmove(buf, buf + d, (unsigned)buf_fill - (unsigned)d);
					buf_fill -= d;
					buf[buf_fill] = 0;
				}
			}

			if (buf[0] != '-' || buf[1] != '-') {
				/* Malformed request */
				mg_free(boundary);
				return -1;
			}
			if (0 != strncmp(buf + 2, boundary, bl)) {
				/* Malformed request */
				mg_free(boundary);
				return -1;
			}
			if (buf[bl + 2] != '\r' || buf[bl + 3] != '\n') {
				/* Every part must end with \r\n, if there is another part.
				 * The end of the request has an extra -- */
				if (((size_t)buf_fill != (size_t)(bl + 6))
				    || (strncmp(buf + bl + 2, "--\r\n", 4))) {
					/* Malformed request */
					mg_free(boundary);
					return -1;
				}
				/* End of the request */
				break;
			}

			/* Next, we need to get the part header: Read until \r\n\r\n */
			hbuf = buf + bl + 4;
			hend = strstr(hbuf, "\r\n\r\n");
			if (!hend) {
				/* Malformed request */
				mg_free(boundary);
				return -1;
			}

			part_header.num_headers =
			    parse_http_headers(&hbuf, part_header.http_headers);
			if ((hend + 2) != hbuf) {
				/* Malformed request */
				mg_free(boundary);
				return -1;
			}

			/* Skip \r\n\r\n */
			hend += 4;

			/* According to the RFC, every part has to have a header field like:
			 * Content-Disposition: form-data; name="..." */
			content_disp = get_header(part_header.http_headers,
			                          part_header.num_headers,
			                          "Content-Disposition");
			if (!content_disp) {
				/* Malformed request */
				mg_free(boundary);
				return -1;
			}

			/* Get the mandatory name="..." part of the Content-Disposition
			 * header. */
			nbeg = strstr(content_disp, "name=\"");
			while ((nbeg != NULL) && (strcspn(nbeg - 1, ":,; \t") != 0)) {
				/* It could be somethingname= instead of name= */
				nbeg = strstr(nbeg + 1, "name=\"");
			}

			/* This line is not required, but otherwise some compilers
			 * generate spurious warnings. */
			nend = nbeg;
			/* And others complain, the result is unused. */
			(void)nend;

			/* If name=" is found, search for the closing " */
			if (nbeg) {
				nbeg += 6;
				nend = strchr(nbeg, '\"');
				if (!nend) {
					/* Malformed request */
					mg_free(boundary);
					return -1;
				}
			} else {
				/* name= without quotes is also allowed */
				nbeg = strstr(content_disp, "name=");
				while ((nbeg != NULL) && (strcspn(nbeg - 1, ":,; \t") != 0)) {
					/* It could be somethingname= instead of name= */
					nbeg = strstr(nbeg + 1, "name=");
				}
				if (!nbeg) {
					/* Malformed request */
					mg_free(boundary);
					return -1;
				}
				nbeg += 5;

				/* RFC 2616 Sec. 2.2 defines a list of allowed
				 * separators, but many of them make no sense
				 * here, e.g. various brackets or slashes.
				 * If they are used, probably someone is
				 * trying to attack with curious hand made
				 * requests. Only ; , space and tab seem to be
				 * reasonable here. Ignore everything else. */
				nend = nbeg + strcspn(nbeg, ",; \t");
			}

			/* Get the optional filename="..." part of the Content-Disposition
			 * header. */
			fbeg = strstr(content_disp, "filename=\"");
			while ((fbeg != NULL) && (strcspn(fbeg - 1, ":,; \t") != 0)) {
				/* It could be somethingfilename= instead of filename= */
				fbeg = strstr(fbeg + 1, "filename=\"");
			}

			/* This line is not required, but otherwise some compilers
			 * generate spurious warnings. */
			fend = fbeg;

			/* If filename=" is found, search for the closing " */
			if (fbeg) {
				fbeg += 10;
				fend = strchr(fbeg, '\"');

				if (!fend) {
					/* Malformed request (the filename field is optional, but if
					 * it exists, it needs to be terminated correctly). */
					mg_free(boundary);
					return -1;
				}

				/* TODO: check Content-Type */
				/* Content-Type: application/octet-stream */
			}
			if (!fbeg) {
				/* Try the same without quotes */
				fbeg = strstr(content_disp, "filename=");
				while ((fbeg != NULL) && (strcspn(fbeg - 1, ":,; \t") != 0)) {
					/* It could be somethingfilename= instead of filename= */
					fbeg = strstr(fbeg + 1, "filename=");
				}
				if (fbeg) {
					fbeg += 9;
					fend = fbeg + strcspn(fbeg, ",; \t");
				}
			}

			if (!fbeg || !fend) {
				fbeg = NULL;
				fend = NULL;
				fnlen = 0;
			} else {
				fnlen = (size_t)(fend - fbeg);
			}

			/* In theory, it could be possible that someone crafts
			 * a request like name=filename=xyz. Check if name and
			 * filename do not overlap. */
			if (!(((ptrdiff_t)fbeg > (ptrdiff_t)nend)
			      || ((ptrdiff_t)nbeg > (ptrdiff_t)fend))) {
				mg_free(boundary);
				return -1;
			}

			/* Call callback for new field */
			memset(path, 0, sizeof(path));
			field_count++;
			field_storage = url_encoded_field_found(conn,
			                                        nbeg,
			                                        (size_t)(nend - nbeg),
			                                        ((fnlen > 0) ? fbeg : NULL),
			                                        fnlen,
			                                        path,
			                                        sizeof(path) - 1,
			                                        fdh);

			/* If the boundary is already in the buffer, get the address,
			 * otherwise next will be NULL. */
			next = search_boundary(hbuf,
			                       (size_t)((buf - hbuf) + buf_fill),
			                       boundary,
			                       bl);

#if !defined(NO_FILESYSTEMS)
			if (field_storage == MG_FORM_FIELD_STORAGE_STORE) {
				/* Store the content to a file */
				if (mg_fopen(conn, path, MG_FOPEN_MODE_WRITE, &fstore) == 0) {
					fstore.access.fp = NULL;
				}
				file_size = 0;

				if (!fstore.access.fp) {
					mg_cry_internal(conn,
					                "%s: Cannot create file %s",
					                __func__,
					                path);
				}
			}
#endif /* NO_FILESYSTEMS */

			get_block = 0;
			while (!next) {
				/* Set "towrite" to the number of bytes available
				 * in the buffer */
				towrite = (size_t)(buf - hend + buf_fill);

				if (towrite < bl + 4) {
					/* Not enough data stored. */
					/* Incomplete request. */
					mg_free(boundary);
					return -1;
				}

				/* Subtract the boundary length, to deal with
				 * cases the boundary is only partially stored
				 * in the buffer. */
				towrite -= bl + 4;

				if (field_storage == MG_FORM_FIELD_STORAGE_GET) {
					r = unencoded_field_get(conn,
					                        ((get_block > 0) ? NULL : nbeg),
					                        ((get_block > 0)
					                             ? 0
					                             : (size_t)(nend - nbeg)),
					                        hend,
					                        towrite,
					                        fdh);
					get_block++;
					if (r == MG_FORM_FIELD_HANDLE_ABORT) {
						/* Stop request handling */
						break;
					}
					if (r == MG_FORM_FIELD_HANDLE_NEXT) {
						/* Skip to next field */
						field_storage = MG_FORM_FIELD_STORAGE_SKIP;
					}
				}

#if !defined(NO_FILESYSTEMS)
				if (field_storage == MG_FORM_FIELD_STORAGE_STORE) {
					if (fstore.access.fp) {

						/* Store the content of the buffer. */
						n = (size_t)fwrite(hend, 1, towrite, fstore.access.fp);
						if ((n != towrite) || (ferror(fstore.access.fp))) {
							mg_cry_internal(conn,
							                "%s: Cannot write file %s",
							                __func__,
							                path);
							mg_fclose(&fstore.access);
							remove_bad_file(conn, path);
						}
						file_size += (int64_t)n;
					}
				}
#endif /* NO_FILESYSTEMS */

				memmove(buf, hend + towrite, bl + 4);
				buf_fill = (int)(bl + 4);
				hend = buf;

				/* Read new data */
				to_read = sizeof(buf) - 1 - (size_t)buf_fill;
				r = mg_read(conn, buf + (size_t)buf_fill, to_read);
				if ((r < 0) || ((r == 0) && all_data_read)) {
#if !defined(NO_FILESYSTEMS)
					/* read error */
					if (fstore.access.fp) {
						mg_fclose(&fstore.access);
						remove_bad_file(conn, path);
					}
#endif /* NO_FILESYSTEMS */
					mg_free(boundary);
					return -1;
				}
				/* r==0 already handled, all_data_read is false here */

				buf_fill += r;
				buf[buf_fill] = 0;
				/* buf_fill is at least 8 here */

				/* Find boundary */
				next = search_boundary(buf, (size_t)buf_fill, boundary, bl);

				if (!next && (r == 0)) {
					/* incomplete request */
					all_data_read = 1;
				}
			}

			towrite = (next ? (size_t)(next - hend) : 0);

			if (field_storage == MG_FORM_FIELD_STORAGE_GET) {
				/* Call callback */
				r = unencoded_field_get(conn,
				                        ((get_block > 0) ? NULL : nbeg),
				                        ((get_block > 0)
				                             ? 0
				                             : (size_t)(nend - nbeg)),
				                        hend,
				                        towrite,
				                        fdh);
				if (r == MG_FORM_FIELD_HANDLE_ABORT) {
					/* Stop request handling */
					break;
				}
				if (r == MG_FORM_FIELD_HANDLE_NEXT) {
					/* Skip to next field */
					field_storage = MG_FORM_FIELD_STORAGE_SKIP;
				}
			}

#if !defined(NO_FILESYSTEMS)
			if (field_storage == MG_FORM_FIELD_STORAGE_STORE) {

				if (fstore.access.fp) {
					n = (size_t)fwrite(hend, 1, towrite, fstore.access.fp);
					if ((n != towrite) || (ferror(fstore.access.fp))) {
						mg_cry_internal(conn,
						                "%s: Cannot write file %s",
						                __func__,
						                path);
						mg_fclose(&fstore.access);
						remove_bad_file(conn, path);
					} else {
						file_size += (int64_t)n;
						r = mg_fclose(&fstore.access);
						if (r == 0) {
							/* stored successfully */
							r = field_stored(conn, path, file_size, fdh);
							if (r == MG_FORM_FIELD_HANDLE_ABORT) {
								/* Stop request handling */
								break;
							}
						} else {
							mg_cry_internal(conn,
							                "%s: Error saving file %s",
							                __func__,
							                path);
							remove_bad_file(conn, path);
						}
					}
					fstore.access.fp = NULL;
				}
			}
#endif /* NO_FILESYSTEMS */

			if ((field_storage & MG_FORM_FIELD_STORAGE_ABORT)
			    == MG_FORM_FIELD_STORAGE_ABORT) {
				/* Stop parsing the request */
				break;
			}

			/* Remove from the buffer */
			if (next) {
				used = next - buf + 2;
				memmove(buf, buf + (size_t)used, sizeof(buf) - (size_t)used);
				buf_fill -= (int)used;
			} else {
				buf_fill = 0;
			}
		}

		/* All parts handled */
		mg_free(boundary);
		return field_count;
	}

	/* Unknown Content-Type */
	return -1;
}

/* End of handle_form.inl */