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I'm working on a pure C99 practising project which can do a login simulation for our school's CAS login system.
Now I'm trying to use Gumbo HTML parser to parse our school's login page. Here is the form section and I need to get the login ticket from it before I run the POST request to submit the form, which is the "hidden" type input element with name "lt". (i.e. line with <input type="hidden" name="lt" value="LT-000000-b4LktCXyzXyzXyzXyzXyzXyz" />, and I need to parse the "value").
I've wrote some code, but it seems cannot find out this input element. Here is my C program's function:
const char * parse_login_ticket_old(char * raw_html)
{
// Parse HTML into Gumbo memory structure
GumboOutput * gumbo_output = gumbo_parse(raw_html);
// Prepare the node
GumboNode * gumbo_root = gumbo_output->root;
assert(gumbo_root->type == GUMBO_NODE_ELEMENT);
assert(gumbo_root->v.element.children.length >= 2);
const GumboVector* root_children = &gumbo_root->v.element.children;
GumboNode* page_body = NULL;
for (int i = 0; i < root_children->length; ++i)
{
GumboNode* child = root_children->data[i];
if (child->type == GUMBO_NODE_ELEMENT && child->v.element.tag == GUMBO_TAG_BODY)
{
page_body = child;
break;
}
}
assert(page_body != NULL);
GumboVector* page_body_children = &page_body->v.element.children;
for (int i = 0; i < page_body_children->length; ++i)
{
GumboNode* child = page_body_children->data[i];
GumboAttribute * input_name_attr = gumbo_get_attribute(&child->v.element.attributes, "name");
if (child->type == GUMBO_NODE_ELEMENT && child->v.element.tag == GUMBO_TAG_INPUT && strcmp(input_name_attr->value, "lt") == 0)
{
GumboAttribute * input_value_attr = gumbo_get_attribute(&child->v.element.attributes, "value");
return input_name_attr->value;
}
}
return NULL;
}
In case someone need for debugging, here is a example of our schools page. Possible sensitive data has been removed.
<body>
<div id="wrapper">
<div id="contentArea" role="main">
<div class="form login" role="form">
<h2 class="hidden">Login</h2>
<form id="fm1" class="fm-v clearfix" action="/schoolcas/login?jsessionid=1234567890" method="post"><div class="formRow">
<label for="username" class="label">Student ID</label>
<div class="textBox">
<input id="username" name="username" class="schoolcas text" aria-required="true" type="text" value="" size="25" maxlength="25"/></div>
</div>
<div class="formRow">
<label for="password" class="label">Password</label>
<div class="textBox">
<input id="password" name="password" class="schoolcas text" aria-required="true" type="password" value="" size="25" autocomplete="off"/></div>
</div>
<div class="formRow">
<input type="hidden" name="lt" value="LT-000000-b4LktCXyzXyzXyzXyzXyzXyz" />
<input type="hidden" name="execution" value="e2s1" />
<input type="hidden" name="_eventId" value="submit" />
<input class="button grey submit" name="submit" value="Login" type="submit" />
</div>
</form>
</div>
</div>
</div>
</body>
Anyway, my program seems just stop at the top of the body element and it returns NULL later on.
So I would like to know how to do a correct search, and find out the input element I need?
234
I've figured it out by myself from the Google sample code (https://github.com/google/gumbo-parser/blob/master/examples/find_links.cc).
Here's the code. It's crappy but it works anyway.
const char * find_attribute(GumboNode * current_node, GumboTag element_tag_type,
char * element_term_key, char * element_term_value, char * desired_result_key)
{
const char * lt_token = NULL;
// Return NULL if it is in WHITESPACE
if (current_node->type != GUMBO_NODE_ELEMENT)
{
return NULL;
}
// Set the element's term key,
// e.g. if we need to find something like <input name="foobar"> then element search term key is "name",
// and element search value is "foobar"
GumboAttribute* lt_attr = gumbo_get_attribute(¤t_node->v.element.attributes, element_term_key);
if (lt_attr != NULL && current_node->v.element.tag == element_tag_type && (strcmp(lt_attr->value, element_term_value) == 0))
{
lt_token = gumbo_get_attribute(¤t_node->v.element.attributes, desired_result_key)->value;
return lt_token;
}
GumboVector* children = ¤t_node->v.element.children;
for (unsigned int i = 0; i < children->length; ++i)
{
lt_token = find_attribute(children->data[i], element_tag_type,
element_term_key, element_term_value, desired_result_key);
// Force stop and return if it gets a non-null result.
if(lt_token != NULL)
{
return lt_token;
}
}
}
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