1 /*
2 * UPnP XML helper routines
3 * Copyright (c) 2000-2003 Intel Corporation
4 * Copyright (c) 2006-2007 Sony Corporation
5 * Copyright (c) 2008-2009 Atheros Communications
6 * Copyright (c) 2009, Jouni Malinen <j@w1.fi>
7 *
8 * See wps_upnp.c for more details on licensing and code history.
9 */
10
11 #include "includes.h"
12
13 #include "common.h"
14 #include "base64.h"
15 #include "http.h"
16 #include "upnp_xml.h"
17
18
19 /*
20 * XML parsing and formatting
21 *
22 * XML is a markup language based on unicode; usually (and in our case,
23 * always!) based on utf-8. utf-8 uses a variable number of bytes per
24 * character. utf-8 has the advantage that all non-ASCII unicode characters are
25 * represented by sequences of non-ascii (high bit set) bytes, whereas ASCII
26 * characters are single ascii bytes, thus we can use typical text processing.
27 *
28 * (One other interesting thing about utf-8 is that it is possible to look at
29 * any random byte and determine if it is the first byte of a character as
30 * versus a continuation byte).
31 *
32 * The base syntax of XML uses a few ASCII punctionation characters; any
33 * characters that would appear in the payload data are rewritten using
34 * sequences, e.g., & for ampersand(&) and < for left angle bracket (<).
35 * Five such escapes total (more can be defined but that does not apply to our
36 * case). Thus we can safely parse for angle brackets etc.
37 *
38 * XML describes tree structures of tagged data, with each element beginning
39 * with an opening tag <label> and ending with a closing tag </label> with
40 * matching label. (There is also a self-closing tag <label/> which is supposed
41 * to be equivalent to <label></label>, i.e., no payload, but we are unlikely
42 * to see it for our purpose).
43 *
44 * Actually the opening tags are a little more complicated because they can
45 * contain "attributes" after the label (delimited by ascii space or tab chars)
46 * of the form attribute_label="value" or attribute_label='value'; as it turns
47 * out we do not have to read any of these attributes, just ignore them.
48 *
49 * Labels are any sequence of chars other than space, tab, right angle bracket
50 * (and ?), but may have an inner structure of <namespace><colon><plain_label>.
51 * As it turns out, we can ignore the namespaces, in fact we can ignore the
52 * entire tree hierarchy, because the plain labels we are looking for will be
53 * unique (not in general, but for this application). We do however have to be
54 * careful to skip over the namespaces.
55 *
56 * In generating XML we have to be more careful, but that is easy because
57 * everything we do is pretty canned. The only real care to take is to escape
58 * any special chars in our payload.
59 */
60
61 /**
62 * xml_next_tag - Advance to next tag
63 * @in: Input
64 * @out: OUT: start of tag just after '<'
65 * @out_tagname: OUT: start of name of tag, skipping namespace
66 * @end: OUT: one after tag
67 * Returns: 0 on success, 1 on failure
68 *
69 * A tag has form:
70 * <left angle bracket><...><right angle bracket>
71 * Within the angle brackets, there is an optional leading forward slash (which
72 * makes the tag an ending tag), then an optional leading label (followed by
73 * colon) and then the tag name itself.
74 *
75 * Note that angle brackets present in the original data must have been encoded
76 * as < and > so they will not trouble us.
77 */
xml_next_tag(const char * in,const char ** out,const char ** out_tagname,const char ** end)78 int xml_next_tag(const char *in, const char **out,
79 const char **out_tagname, const char **end)
80 {
81 while (*in && *in != '<')
82 in++;
83 if (*in != '<')
84 return 1;
85 *out = ++in;
86 if (*in == '/')
87 in++;
88 *out_tagname = in; /* maybe */
89 while (isalnum(*in) || *in == '-')
90 in++;
91 if (*in == ':')
92 *out_tagname = ++in;
93 while (*in && *in != '>')
94 in++;
95 if (*in != '>')
96 return 1;
97 *end = ++in;
98 return 0;
99 }
100
101
102 /* xml_data_encode -- format data for xml file, escaping special characters.
103 *
104 * Note that we assume we are using utf8 both as input and as output!
105 * In utf8, characters may be classed as follows:
106 * 0xxxxxxx(2) -- 1 byte ascii char
107 * 11xxxxxx(2) -- 1st byte of multi-byte char w/ unicode value >= 0x80
108 * 110xxxxx(2) -- 1st byte of 2 byte sequence (5 payload bits here)
109 * 1110xxxx(2) -- 1st byte of 3 byte sequence (4 payload bits here)
110 * 11110xxx(2) -- 1st byte of 4 byte sequence (3 payload bits here)
111 * 10xxxxxx(2) -- extension byte (6 payload bits per byte)
112 * Some values implied by the above are however illegal because they
113 * do not represent unicode chars or are not the shortest encoding.
114 * Actually, we can almost entirely ignore the above and just do
115 * text processing same as for ascii text.
116 *
117 * XML is written with arbitrary unicode characters, except that five
118 * characters have special meaning and so must be escaped where they
119 * appear in payload data... which we do here.
120 */
xml_data_encode(struct wpabuf * buf,const char * data,int len)121 void xml_data_encode(struct wpabuf *buf, const char *data, int len)
122 {
123 int i;
124 for (i = 0; i < len; i++) {
125 u8 c = ((u8 *) data)[i];
126 if (c == '<') {
127 wpabuf_put_str(buf, "<");
128 continue;
129 }
130 if (c == '>') {
131 wpabuf_put_str(buf, ">");
132 continue;
133 }
134 if (c == '&') {
135 wpabuf_put_str(buf, "&");
136 continue;
137 }
138 if (c == '\'') {
139 wpabuf_put_str(buf, "'");
140 continue;
141 }
142 if (c == '"') {
143 wpabuf_put_str(buf, """);
144 continue;
145 }
146 /*
147 * We could try to represent control characters using the
148 * sequence: &#x; where x is replaced by a hex numeral, but not
149 * clear why we would do this.
150 */
151 wpabuf_put_u8(buf, c);
152 }
153 }
154
155
156 /* xml_add_tagged_data -- format tagged data as a new xml line.
157 *
158 * tag must not have any special chars.
159 * data may have special chars, which are escaped.
160 */
xml_add_tagged_data(struct wpabuf * buf,const char * tag,const char * data)161 void xml_add_tagged_data(struct wpabuf *buf, const char *tag, const char *data)
162 {
163 wpabuf_printf(buf, "<%s>", tag);
164 xml_data_encode(buf, data, os_strlen(data));
165 wpabuf_printf(buf, "</%s>\n", tag);
166 }
167
168
169 /* A POST body looks something like (per upnp spec):
170 * <?xml version="1.0"?>
171 * <s:Envelope
172 * xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"
173 * s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
174 * <s:Body>
175 * <u:actionName xmlns:u="urn:schemas-upnp-org:service:serviceType:v">
176 * <argumentName>in arg value</argumentName>
177 * other in args and their values go here, if any
178 * </u:actionName>
179 * </s:Body>
180 * </s:Envelope>
181 *
182 * where :
183 * s: might be some other namespace name followed by colon
184 * u: might be some other namespace name followed by colon
185 * actionName will be replaced according to action requested
186 * schema following actionName will be WFA scheme instead
187 * argumentName will be actual argument name
188 * (in arg value) will be actual argument value
189 */
xml_get_first_item(const char * doc,const char * item)190 char * xml_get_first_item(const char *doc, const char *item)
191 {
192 const char *match = item;
193 int match_len = os_strlen(item);
194 const char *tag, *tagname, *end;
195 char *value;
196
197 /*
198 * This is crude: ignore any possible tag name conflicts and go right
199 * to the first tag of this name. This should be ok for the limited
200 * domain of UPnP messages.
201 */
202 for (;;) {
203 if (xml_next_tag(doc, &tag, &tagname, &end))
204 return NULL;
205 doc = end;
206 if (!os_strncasecmp(tagname, match, match_len) &&
207 *tag != '/' &&
208 (tagname[match_len] == '>' ||
209 !isgraph(tagname[match_len]))) {
210 break;
211 }
212 }
213 end = doc;
214 while (*end && *end != '<')
215 end++;
216 value = os_zalloc(1 + (end - doc));
217 if (value == NULL)
218 return NULL;
219 os_memcpy(value, doc, end - doc);
220 return value;
221 }
222
223
xml_get_base64_item(const char * data,const char * name,enum http_reply_code * ret)224 struct wpabuf * xml_get_base64_item(const char *data, const char *name,
225 enum http_reply_code *ret)
226 {
227 char *msg;
228 struct wpabuf *buf;
229 unsigned char *decoded;
230 size_t len;
231
232 msg = xml_get_first_item(data, name);
233 if (msg == NULL) {
234 *ret = UPNP_ARG_VALUE_INVALID;
235 return NULL;
236 }
237
238 decoded = base64_decode((unsigned char *) msg, os_strlen(msg), &len);
239 os_free(msg);
240 if (decoded == NULL) {
241 *ret = UPNP_OUT_OF_MEMORY;
242 return NULL;
243 }
244
245 buf = wpabuf_alloc_ext_data(decoded, len);
246 if (buf == NULL) {
247 os_free(decoded);
248 *ret = UPNP_OUT_OF_MEMORY;
249 return NULL;
250 }
251 return buf;
252 }
253