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 Copyright (c) 2016, 2017 Ingo Schwarze <schwarze (at] openbsd.org>

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 purpose with or without fee is hereby granted, provided that the above
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 WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.Dd March 15, 2017
.Dt MAN.CGI 3
.Os
.Sh NAME
.Nm man.cgi
.Nd internals of the CGI program to search and display manual pages
.Sh DESCRIPTION
The source code of
.Xr man.cgi 8
is organized in four levels:

p
l -enum -compact t .Sx Top level
t .Sx Page generators
t .Sx Result generators
t .Sx Utility routines
.El
.Ss Top level
The top level of
.Xr man.cgi 8
consists of the
.Fn main
program and a few parser routines.
l -tag -width 1n t Ft int Fn main void The main program
l -dash -compact t limits execution time;
t changes to
.Dv MAN_DIR ,
the data directory containing all the manual trees;
t calls
.Fn parse_manpath_conf ;
t if
.Ev PATH_INFO
is empty, calls
.Fn parse_query_string ;
otherwise,
calls
.Fn parse_path_info ;
t validates the manpath and the architecture;
t calls the appropriate one among the
.Sx Page generators .
.El
t Ft void Fn parse_manpath_conf "struct req *req" Parses and validates

a manpath.conf
and fills
.Va req->p
and
.Va req->psz .
t Ft void Fn parse_path_info "struct req *req" "const char *path" Parses and validates
.Ev PATH_INFO ,
clears
.Va req->isquery ,
and fills
.Va req->q .
t Ft void Fn parse_query_string "struct req *req" "const char *qs" Parses and validates
.Ev QUERY_STRING ,
sets
.Va req->isquery ,
and fills
.Va req->q .
This function is the only user of the utility functions
.Fn http_decode
and
.Fn set_query_attr .
.El
.Ss Page generators
The purpose of each page generator is to print a complete HTML page,
starting with the HTTP headers and continuing to the page footer.
Before starting HTML output with
.Fn resp_begin_html ,
some page generators do some preparatory work, for example to decide
which page to show.
Each page generator ends with a call to
.Fn resp_end_html .
l -tag -width 1n t Ft void Fn pg_show "struct req *req" "const char *fullpath" This page generator is used when
.Ev PATH_INFO
contains the complete path to a manual page including manpath,
section directory, optional architecture subdirectory, manual name
and section number suffix.
It validates the manpath, changes into it, validate the filename,
and then calls
.Fn resp_begin_html ,
.Fn resp_searchform ,
.Fn resp_show ,
and
.Fn resp_end_html
in that order.
t Ft void Fn pg_search "const struct req *req" This page generator is used when
.Ev PATH_INFO
contains a search query in short format or when
.Ev PATH_INFO
is empty and a
.Ev QUERY_STRING
is provided.
If possible, requests using
.Ev QUERY_STRING
are redirected to URIs using
.Ev PATH_INFO
by calling
.Fn pg_redirect .
Otherwise, it changes into the manpath and calls
.Xr mansearch 3 .
Depending on the result, it calls either
.Fn pg_noresult
or
.Fn pg_searchres .
t Ft void Fn pg_redirect "const struct req *req" "const char *name" This function is special in so far as it does not print an HTML page,
but only an HTTP 303 response with a Location: of the form:
.Sm off
.No http://
.Ar host Ns /
.Op Ar scriptname Ns /
.Op Ar manpath Ns /
.Op Ar arch Ns /
.Fa name
.Op Pf . Ar sec
.Sm on
t Ft void Fn pg_noresult "const struct req *req" "const char *msg" This function calls
.Fn resp_begin_html ,
.Fn resp_searchform ,
prints the
.Fa msg
passed to it, and calls
.Fn resp_end_html .
t Ft void Fn pg_searchres "const struct req *req" "struct manpage *r"\  "size_t sz"
This function first validates the filenames found.
If
.Ev QUERY_STRING
was used and there is exactly one result,
it writes an HTTP redirect to that result.
Otherwise, it writes an HTML result page beginning with
.Fn resp_begin_html
and
.Fn resp_searchform .
If there is more than one result, it writes a list of links
to all the results.
If it was a
.Xr man 1
rather than an
.Xr apropos 1
query or if there is only one single result, it calls
.Fn resp_show .
Finally, it calls
.Fn resp_end_html .
t Ft void Fn pg_index "const struct req *req" This page generator is used when
.Ev PATH_INFO
and
.Ev QUERY_STRING
are both empty.
It calls
.Fn resp_begin_html
and
.Fn resp_searchform ,
writes links to help pages, and calls
.Fn resp_end_html .
t Ft void Fn pg_error_badrequest "const char *msg" This page generator is used when
.Fn main
or
.Fn pg_show
detect an invalid URI.
It calls
.Fn resp_begin_html ,
prints the
.Fa msg
provided, and calls
.Fn resp_end_html .
t Ft void Fn pg_error_internal void This page generator is used by various functions when errors are
detected in the

a manpath.conf
configuration file, in
.Xr mandoc.db 5
databases, in the
.Xr mandoc 3
parser, in file system permissions, or when setting up timeouts.
It calls
.Fn resp_begin_html ,
prints
.Qq "Internal Server Error" ,
and calls
.Fn resp_end_html .
Before calling
.Fn pg_error_internal ,
call
.Xr warn 3
or
.Xr warnx 3
to log the reason of the error to the
.Xr httpd 8
server log file.
.El
.Ss Result generators
The purpose of result generators is to print a chunk of HTML code.
When they print untrusted strings or characters,
.Fn html_print
and
.Fn html_putchar
are used.
The highest level result generators are:
l -tag -width 1n t Ft void Fn resp_begin_html "int code" "const char *msg" "const char *file" This generator calls
.Fn resp_begin_http
to print the HTTP headers, then prints the HTML header up to the
opening tag of the <body> element, then copies the file

a header.html
to the output, if it exists and is readable.
If
.Fa file
is not
.Dv NULL ,
it is used for the <title> element.
t Ft void Fn resp_searchform "const struct req *req" "enum focus focus" This generator prints a search form, filling it with data
from the provided request object.
If the
.Fa focus
argument is
.Dv FOCUS_QUERY ,
it sets the document's autofocus to the query input box.
t Ft void Fn resp_show "const struct req *req" "const char *file" This wrapper dispatches to either
.Fn resp_catman
or
.Fn resp_format ,
depending on whether
.Ar file
starts with

a cat
or

a man ,
respectively.
t Ft void Fn resp_catman "const struct req *req" "const char *file" This generator translates a preformatted, backspace-encoded manual
page to HTML and prints it to the output.
t Ft void Fn resp_format "const struct req *req" "const char *file" This generator formats a manual page on the standard output,
using the functions documented in
.Xr mchars_alloc 3
and
.Xr mandoc 3 .
t Ft void Fn resp_end_html void This generator copies the file

a footer.html
to the output, if it exists and is readable,
and closes the <body> and <html> elements.
.El
.Ss Utility routines
These functions take a string and return 1 if it is valid, or 0 otherwise.
l -tag -width 1n t Ft int Fn validate_urifrag "const char *frag" Checks that the string only contains alphanumeric ASCII characters,
dashes, dots, slashes, and underscores.
t Ft int Fn validate_manpath "const struct req *req" "const char* manpath" Checks that the string is either
.Qq mandoc
or one of the manpaths configured in

a manpath.conf .
t Ft int Fn validate_filename "const char *file" Checks that the string starts with
.Qq man
or
.Qq cat
and does not ascend to parent directories.
.El
.Sh SEE ALSO
.Xr mandoc 3 ,
.Xr mansearch 3 ,
.Xr mchars_alloc 3 ,
.Xr mandoc.db 5 ,
.Xr man.cgi 8