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Diffstat (limited to 'extensions/about-render.lua')
| -rw-r--r-- | extensions/about-render.lua | 592 |
1 file changed, 0 insertions, 592 deletions
diff --git a/extensions/about-render.lua b/extensions/about-render.lua deleted file mode 100644 index 073b531..0000000 --- a/extensions/about-render.lua +++ /dev/null @@ -1,592 +0,0 @@ --- Server-side about-page rendering for cgit, used with the about-filter setting --- in cgitrc and the lua: prefix so it runs in cgit's embedded interpreter with --- no per-request process. --- --- about-filter=lua:/usr/lib/cgit/filters/about-render.lua --- --- One filter renders the three baseline about formats, chosen by the readme's --- file extension. --- --- markdown .md .markdown .mkd .mdown --- man page .1 through .9 and .man --- plain text everything else, and the fallback for anything that fails --- --- Add a format by giving it a render function and a row in the handler table --- near the foot of this file. Nothing else needs to change. --- --- SUPPORTED LUA --- --- Lua 5.1 through 5.4 and LuaJIT. --- --- REQUIREMENTS --- --- lpeg, the parsing module, for the Lua cgit is linked against. Markdown and --- man pages are parsed with lpeg grammars, so without lpeg both fall back to --- escaped plain text. It ships with cgit's syntax highlighter too, so a cgit --- that colours source already has it. --- --- # Debian and Ubuntu --- sudo apt install lua-lpeg --- # Fedora --- sudo dnf install lua-lpeg --- # Alpine --- sudo apk add lua5.1-lpeg --- # or with LuaRocks, matched to your Lua version --- sudo luarocks --lua-version 5.1 install lpeg --- --- Plain text needs only Lua itself. --- --- SECURITY --- --- The about page renders untrusted repository content, so the safety rule is --- that every run of text reaches the page through cgit's own html_txt, every --- attribute value through html_attr, and every link or image target through --- the safe_url scheme allowlist below before html_attr. Only http, https, --- mailto and relative targets survive, so a hostile readme cannot inject markup --- or a javascript: url. Because all output is routed through those sinks by --- construction, a bug in the parser can only mis-render, never inject. --- --- LIMITATIONS --- --- Markdown is a deliberate subset, not CommonMark. Headings, thematic breaks, --- fenced and inline code, blockquotes, pipe tables, single-level lists, links, --- images and emphasis. No reference links, no raw HTML passthrough, no nested --- lists, no setext headings. Emphasis does not span a hard line break inside a --- paragraph. Man rendering covers the common macros (section headings, filled --- and no-fill paragraphs, bold and italic, font escapes) and drops the rest. --- cgit sends filter output through a C string sink that stops at the first NUL --- byte, so content past a NUL is truncated. --- --- OUTPUT --- --- Markdown is wrapped in <div class='markdown'>, man pages in --- <div class='markdown manpage'>, plain text in <pre class='plaintext'>, all --- styled by assets/cgit.css. - -local ok_lpeg, lpeg = pcall(require, "lpeg") - - --- ===== configuration =================================================== - --- Readmes larger than this are served as escaped plain text rather than parsed. -local max_bytes = 512 * 1024 - --- Ceiling on blockquote and emphasis nesting, so a hostile readme of stacked --- markers cannot drive the recursive parser into a stack overflow. -local max_depth = 24 - -local filename, chunks = "", {} - - --- ===== helpers ========================================================= - -local function trim(s) - return (s:gsub("^%s+", ""):gsub("%s+$", "")) -end - --- Split on newlines after normalising CRLF and CR, returning the lines without --- their terminators. A trailing newline yields a final empty line, which every --- caller treats as blank. -local function split_lines(s) - s = s:gsub("\r\n?", "\n") - local lines, start = {}, 1 - while true do - local nl = s:find("\n", start, true) - if not nl then - lines[#lines + 1] = s:sub(start) - return lines - end - lines[#lines + 1] = s:sub(start, nl - 1) - start = nl + 1 - end -end - --- Split a table row into trimmed cells, dropping one optional leading and --- trailing pipe. -local function split_cells(row) - row = trim(row):gsub("^|", ""):gsub("|$", "") - local cells = {} - for c in (row .. "|"):gmatch("(.-)|") do - cells[#cells + 1] = trim(c) - end - return cells -end - --- Return the url if its scheme is safe, else nil. Control and whitespace bytes --- are stripped anywhere first because a browser ignores them when resolving the --- scheme, so "java\nscript:" must still be caught as javascript. The class is --- %c%s rather than a literal 0x00 range so it is safe on Lua 5.1, where an --- embedded zero byte ends a pattern. -local function safe_url(url) - url = url:gsub("[%c%s]", "") - -- A leading "//" or "/\" is scheme-relative, which a browser resolves to - -- another origin, so it is not the local target the parser meant to allow. - if url:sub(1, 2) == "//" or url:sub(1, 2) == "/\\" then - return nil - end - local scheme = url:match("^(%a[%w%+%.%-]*):") - if scheme then - scheme = scheme:lower() - if scheme ~= "http" and scheme ~= "https" and scheme ~= "mailto" then - return nil - end - end - return url -end - - --- ===== emit ============================================================ --- html, html_txt and html_attr are injected by cgit's lua filter host. Tag --- scaffolding is a literal argument to html; every value that came from the --- repository goes through html_txt, html_attr or safe_url. - -local emit_inline - -emit_inline = function(list) - for _, nd in ipairs(list) do - local t = nd.t - if t == "text" then - html_txt(nd.v) - elseif t == "code" then - html("<code>"); html_txt(nd.v); html("</code>") - elseif t == "strong" then - html("<strong>"); emit_inline(nd.kids); html("</strong>") - elseif t == "em" then - html("<em>"); emit_inline(nd.kids); html("</em>") - elseif t == "link" then - local u = safe_url(nd.url) - if u then - html("<a href='"); html_attr(u); html("'>") - emit_inline(nd.kids) - html("</a>") - else - emit_inline(nd.kids) - end - elseif t == "image" then - local u = safe_url(nd.url) - if u then - html("<img src='"); html_attr(u) - html("' alt='"); html_attr(nd.alt); html("'/>") - else - html_txt("![" .. nd.alt .. "]") - end - end - end -end - -local emit_blocks - -emit_blocks = function(blocks) - for _, b in ipairs(blocks) do - local t = b.t - if t == "heading" then - html("<h" .. b.level .. ">") - emit_inline(b.kids) - html("</h" .. b.level .. ">") - elseif t == "hr" then - html("<hr/>") - elseif t == "code" then - html("<pre><code") - if b.lang and b.lang ~= "" then - html(" data-lang='"); html_attr(b.lang); html("'") - end - html(">"); html_txt(b.text); html("</code></pre>") - elseif t == "blockquote" then - html("<blockquote>"); emit_blocks(b.blocks); html("</blockquote>") - elseif t == "table" then - html("<table><thead><tr>") - for _, c in ipairs(b.head) do - html("<th>"); emit_inline(c); html("</th>") - end - html("</tr></thead><tbody>") - for _, row in ipairs(b.rows) do - html("<tr>") - for _, c in ipairs(row) do - html("<td>"); emit_inline(c); html("</td>") - end - html("</tr>") - end - html("</tbody></table>") - elseif t == "list" then - local tag = b.ordered and "ol" or "ul" - html("<" .. tag .. ">") - for _, item in ipairs(b.items) do - html("<li>"); emit_inline(item); html("</li>") - end - html("</" .. tag .. ">") - elseif t == "para" then - html("<p>") - for k, line in ipairs(b.lines) do - if k > 1 then html("<br/>") end - emit_inline(line) - end - html("</p>") - end - end -end - - --- ===== plain text ====================================================== - -local function render_plaintext(text) - html("<pre class='plaintext'>") - html_txt(text) - html("</pre>") -end - - --- ===== markdown and man ================================================ --- Both are parsed with lpeg into the block/inline node trees emit_blocks and --- emit_inline above consume. Parsing is pure and builds a tree; emit is the --- only step that writes output, so a parse failure falls back to plain text --- without leaving half a page behind. - -local render_markdown, render_man - -if ok_lpeg then - local P, R, S, C, Ct = lpeg.P, lpeg.R, lpeg.S, lpeg.C, lpeg.Ct - - local sp = S(" \t") - local ws = S(" \t\r\n\f\v") - local eol = P(-1) - - -- ----- markdown inline ----- - local marker = S("`![*_") - local urlchar = 1 - S(")") - ws - -- Bound the link and image inner scans. Without a cap a readme of unclosed - -- brackets ("[[[[...") makes each position scan to end of line for a "]" - -- that never comes, which is quadratic. Real link text and urls sit far - -- under this, and anything longer simply renders as plain text. - local CAP = 512 - - local parse_inline - local inline_depth = 0 - - local function node_text(s) return { t = "text", v = s } end - local function node_code(s) return { t = "code", v = s } end - local function node_strong(s) return { t = "strong", kids = parse_inline(s) } end - local function node_em(s) return { t = "em", kids = parse_inline(s) } end - local function node_link(text, url) return { t = "link", kids = parse_inline(text), url = url } end - local function node_image(alt, url) return { t = "image", alt = alt, url = url } end - - local inline_grammar = Ct(( - (P("`") * C((1 - P("`")) ^ 1) * P("`")) / node_code - + (P("![") * C((1 - P("]")) ^ (-CAP)) * P("]") * P("(") * sp ^ 0 - * C(urlchar * urlchar ^ (-CAP)) * (1 - P(")")) ^ (-CAP) * P(")")) / node_image - + (P("[") * C((1 - P("]")) ^ (-CAP)) * P("]") * P("(") * sp ^ 0 - * C(urlchar * urlchar ^ (-CAP)) * (1 - P(")")) ^ (-CAP) * P(")")) / node_link - + (P("**") * C((1 - P("**")) ^ 1) * P("**")) / node_strong - + (P("__") * C((1 - P("__")) ^ 1) * P("__")) / node_strong - + (P("*") * C((1 - ws) * (1 - P("*")) ^ 0) * P("*")) / node_em - + (P("_") * C((1 - ws) * (1 - P("_")) ^ 0) * P("_")) / node_em - + C((1 - marker) ^ 1) / node_text - + C(P(1)) / node_text - ) ^ 0) - - parse_inline = function(s) - if inline_depth >= max_depth then - return { node_text(s) } - end - inline_depth = inline_depth + 1 - local nodes = inline_grammar:match(s) or { node_text(s) } - inline_depth = inline_depth - 1 - return nodes - end - - -- ----- markdown blocks ----- - -- Line matchers. Each is anchored at the start of a single line and returns - -- its captures, or nil when the line is not of that kind. - local langchar = R("az", "AZ", "09") + S("_.+#-") - local m_heading = C(P("#") * P("#") ^ -5) * sp ^ 1 * C(P(1) ^ 0) - local function rule(c) return sp ^ 0 * P(c) * (sp ^ 0 * P(c)) ^ 2 * sp ^ 0 * eol end - local m_hr = rule("-") + rule("*") + rule("_") - local m_fence = sp ^ 0 * (C(P("`") ^ 3) + C(P("~") ^ 3)) * sp ^ 0 * C(langchar ^ 0) - local m_close_bt = sp ^ 0 * P("`") ^ 3 * sp ^ 0 * eol - local m_close_ti = sp ^ 0 * P("~") ^ 3 * sp ^ 0 * eol - local m_bq = sp ^ 0 * P(">") - local bullet = S("-*+") - local number = R("09") ^ 1 * S(".)") - local m_item = sp ^ 0 * C(bullet + number) * sp ^ 1 * C(P(1) ^ 0) - local dcell = sp ^ 0 * P(":") ^ -1 * P("-") ^ 1 * P(":") ^ -1 * sp ^ 0 - -- A delimiter row is dash-cells joined by pipes. Require at least one pipe, - -- a leading one or one between cells, so a bare rule of dashes stays a - -- thematic break and an ordinary paragraph line is never taken for a table. - local pipe = P("|") - local m_tdelim = sp ^ 0 * ( - pipe * dcell * (pipe * dcell) ^ 0 * pipe ^ -1 - + dcell * (pipe * dcell) ^ 1 * pipe ^ -1 - ) * sp ^ 0 * eol - local m_blockstart = sp ^ 0 * ((P("#") * P("#") ^ -5 * sp) + P(">") - + P("`") ^ 3 + P("~") ^ 3 + ((bullet + number) * sp)) - - local function ordered(mark) return mark:match("%d") ~= nil end - - local parse_blocks - - parse_blocks = function(lines, depth) - local blocks, i, n = {}, 1, #lines - while i <= n do - local line = lines[i] - local fence, lang = m_fence:match(line) - local hashes, htext = m_heading:match(line) - local mark = m_item:match(line) - if line:match("^%s*$") then - i = i + 1 - elseif fence then - local close = (fence:sub(1, 1) == "`") and m_close_bt or m_close_ti - local code = {} - i = i + 1 - while i <= n and not close:match(lines[i]) do - code[#code + 1] = lines[i]; i = i + 1 - end - i = i + 1 - local body = table.concat(code, "\n") - if #code > 0 then body = body .. "\n" end - blocks[#blocks + 1] = { t = "code", lang = lang, text = body } - elseif hashes then - blocks[#blocks + 1] = { - t = "heading", - level = #hashes, - kids = parse_inline((htext:gsub("%s*#*%s*$", ""))), - } - i = i + 1 - elseif m_hr:match(line) then - blocks[#blocks + 1] = { t = "hr" } - i = i + 1 - elseif m_bq:match(line) then - local inner = {} - while i <= n and m_bq:match(lines[i]) do - inner[#inner + 1] = (lines[i]:gsub("^%s*>%s?", "")) - i = i + 1 - end - if depth < max_depth then - blocks[#blocks + 1] = { t = "blockquote", blocks = parse_blocks(inner, depth + 1) } - else - local para = {} - for _, l in ipairs(inner) do para[#para + 1] = parse_inline(l) end - blocks[#blocks + 1] = { t = "para", lines = para } - end - elseif i + 1 <= n and line:find("|", 1, true) and m_tdelim:match(lines[i + 1]) then - local head = {} - for _, c in ipairs(split_cells(line)) do head[#head + 1] = parse_inline(c) end - local rows = {} - i = i + 2 - while i <= n and lines[i]:find("|", 1, true) and not lines[i]:match("^%s*$") do - local row = {} - for _, c in ipairs(split_cells(lines[i])) do row[#row + 1] = parse_inline(c) end - rows[#rows + 1] = row - i = i + 1 - end - blocks[#blocks + 1] = { t = "table", head = head, rows = rows } - elseif mark then - local is_ol = ordered(mark) - local items = {} - while i <= n do - local mk, ct = m_item:match(lines[i]) - if not mk or ordered(mk) ~= is_ol then break end - items[#items + 1] = parse_inline(ct) - i = i + 1 - end - blocks[#blocks + 1] = { t = "list", ordered = is_ol, items = items } - else - local para = { parse_inline(line) } - i = i + 1 - while i <= n and not lines[i]:match("^%s*$") and not m_blockstart:match(lines[i]) do - para[#para + 1] = parse_inline(lines[i]); i = i + 1 - end - blocks[#blocks + 1] = { t = "para", lines = para } - end - end - return blocks - end - - render_markdown = function(text) - if #text > max_bytes then - return render_plaintext(text) - end - local ok, blocks = pcall(parse_blocks, split_lines(text), 0) - if not ok then - return render_plaintext(text) - end - html("<div class='markdown'>") - -- Emit is wrapped so a parser bug can at worst truncate the page, never - -- error out and let the outer fallback duplicate what was already sent. - pcall(emit_blocks, blocks) - html("</div>") - end - - -- ----- man pages ----- - -- Macro lines are matched with lpeg, and the roff inline font and character - -- escapes are an lpeg grammar producing a flat token list that a fold turns - -- into the same inline nodes markdown emits. Bold and italic are the current - -- font, which carries across a run, so the inline pass tokenises and folds - -- rather than nesting the way markdown does. - local m_macro = S(".'") * sp ^ 0 * C((1 - sp) ^ 1) * sp ^ 0 * C(P(1) ^ 0) - - local one_font = { B = "B", I = "I" } - local two_font = { CB = "B", BI = "B", CI = "I" } - local man_chars = { - aq = "'", cq = "'", oq = "'", dq = '"', lq = '"', rq = '"', - hy = "-", en = "-", em = "-", - } - local esc = P("\\") - local function font_tok(f) return { k = "font", f = f } end - local function text_tok(v) return { k = "text", v = v } end - local skip_tok = { k = "skip" } - - local man_inline_grammar = Ct(( - (esc * P("f") * P("(") * C(P(1) * P(1))) / function(nm) return font_tok(two_font[nm] or "R") end - + (esc * P("f") * P("[") * C((1 - P("]")) ^ 0) * P("]")) / function(nm) return font_tok(one_font[nm] or "R") end - + (esc * P("f") * C(P(1))) / function(f) return font_tok(one_font[f] or "R") end - + (esc * P("-")) / function() return text_tok("-") end - + (esc * P("e")) / function() return text_tok("\\") end - + (esc * P(" ")) / function() return text_tok(" ") end - + (esc * S("&|^")) / function() return skip_tok end - + (esc * P("(") * C(P(1) * P(1))) / function(nm) return text_tok(man_chars[nm] or "") end - + (esc * P("*") * (P("(") * P(1) * P(1) + P(1))) / function() return skip_tok end - + (esc * C(P(1))) / text_tok - + esc / function() return skip_tok end - + C((1 - esc) ^ 1) / text_tok - ) ^ 0) - - local function man_inline(s) - local toks = man_inline_grammar:match(s) or {} - local nodes, buf, font = {}, {}, "R" - local function flush() - if #buf == 0 then return end - local txt = table.concat(buf); buf = {} - if txt == "" then return end - if font == "B" then - nodes[#nodes + 1] = { t = "strong", kids = { { t = "text", v = txt } } } - elseif font == "I" then - nodes[#nodes + 1] = { t = "em", kids = { { t = "text", v = txt } } } - else - nodes[#nodes + 1] = { t = "text", v = txt } - end - end - for _, tk in ipairs(toks) do - if tk.k == "text" then - buf[#buf + 1] = tk.v - elseif tk.k == "font" then - flush(); font = tk.f - end - end - flush() - return nodes - end - - local function parse_man(text) - local lines = split_lines(text) - local blocks = {} - local para, pre, nofill = nil, nil, false - local function flush_para() - if para and #para > 0 then - blocks[#blocks + 1] = { t = "para", lines = para } - end - para = nil - end - local function flush_pre() - if pre then - local body = table.concat(pre, "\n") - if #pre > 0 then body = body .. "\n" end - blocks[#blocks + 1] = { t = "code", text = body } - pre = nil - end - end - local function add_line(nodes) - para = para or {} - para[#para + 1] = nodes - end - for _, line in ipairs(lines) do - local macro, rest = m_macro:match(line) - if rest then rest = (rest:gsub('^"(.*)"$', "%1")) end - if nofill then - if macro == "fi" then - nofill = false; flush_pre() - else - pre[#pre + 1] = line - end - elseif line:match("^%s*$") then - flush_para() - elseif macro and macro:sub(1, 1) == "\\" then - -- roff comment, dropped - elseif macro == "SH" or macro == "SS" then - flush_para() - blocks[#blocks + 1] = { - t = "heading", - level = (macro == "SH") and 2 or 3, - kids = man_inline(rest), - } - elseif macro == "nf" then - flush_para(); nofill = true; pre = {} - elseif macro == "fi" then - flush_pre() - elseif macro == "B" or macro == "BR" or macro == "RB" - or macro == "BI" or macro == "IB" then - add_line({ { t = "strong", kids = man_inline(rest) } }) - elseif macro == "I" or macro == "IR" or macro == "RI" then - add_line({ { t = "em", kids = man_inline(rest) } }) - elseif macro == "TH" or macro == "PP" or macro == "LP" - or macro == "P" or macro == "TP" or macro == "IP" - or macro == "HP" or macro == "RS" or macro == "RE" - or macro == "sp" or macro == "br" then - flush_para() - elseif macro then - if rest ~= "" then add_line(man_inline(rest)) end - else - add_line(man_inline(line)) - end - end - flush_para(); flush_pre() - return blocks - end - - render_man = function(text) - if #text > max_bytes then - return render_plaintext(text) - end - local ok, blocks = pcall(parse_man, text) - if not ok then - return render_plaintext(text) - end - html("<div class='markdown manpage'>") - pcall(emit_blocks, blocks) - html("</div>") - end -else - -- No lpeg, so markdown and man readmes read as escaped source, not nothing. - render_markdown = render_plaintext - render_man = render_plaintext -end - - --- ===== dispatch ======================================================== - -local handlers = {} -for _, ext in ipairs({ "md", "markdown", "mkd", "mdown" }) do - handlers[ext] = render_markdown -end -for _, ext in ipairs({ "1", "2", "3", "4", "5", "6", "7", "8", "9", "man" }) do - handlers[ext] = render_man -end - -function filter_open(name) - filename = name or "" - chunks = {} -end - -function filter_write(str) - chunks[#chunks + 1] = str -end - -function filter_close() - local text = table.concat(chunks) - chunks = {} - local ext = (filename:match("%.([^.]+)$") or ""):lower() - local render = handlers[ext] or render_plaintext - local ok = pcall(render, text) - if not ok then - render_plaintext(text) - end - return 0 -end |