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MEDIUM: log-format: make the LF parser aware of sample expressions' end

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For a very long time it used to be impossible to pass a closing square
bracket as a valid character in argument to a sample fetch function or
to a converter because the LF parser used to stop on the first such
character found and to pass what was between the first '[' and the first
']' to sample_parse_expr().

This patch addresses this by passing the whole string to sample_parse_expr()
which is the only one authoritative to indicate the first character that
does not belong to the expression. The LF parser then verifies it matches
a ']' or fails. As a result it is finally possible to write rules such as
the following, which is totally valid an unambigous :

    http-request redirect location %[url,regsub([.:/?-],!,g)]
                                                |-----| | |
                                                  arg1  | `---> arg3
                                                        `-----> arg2
                                         |-----------------|
                                              converter
                                     |---------------------|
                                        sample expression
                                   |------------------------|
                                         log-format tag
This commit is contained in:
Willy Tarreau 2020-02-14 17:33:06 +01:00
parent e3b57bf92f
commit cd0d2ed6ee
2 changed files with 30 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
doc/configuration.txt
View File

@ -14151,13 +14151,16 @@ regsub(<regex>,<subst>[,<flags>])
second level is usable for argument. It is recommended to use single quotes
outside since these ones do not try to resolve backslashes nor dollar signs.
Example :
Examples:
# de-duplicate "/" in header "x-path".
# input: x-path: /////a///b/c/xzxyz/
# output: x-path: /a/b/c/xzxyz/
http-request set-header x-path "%[hdr(x-path),regsub('/+','/','g')]"
# copy query string to x-query and drop all leading '?', ';' and '&'
http-request set-header x-query "%[query,regsub([?;&]*,'')]"
capture-req(<id>)
Capture the string entry in the request slot <id> and returns the entry as
is. If the slot doesn't exist, the capture fails silently.

34
src/log.c
View File

@ -473,11 +473,13 @@ int add_to_logformat_list(char *start, char *end, int type, struct list *list_fo
/*
* Parse the sample fetch expression <text> and add a node to <list_format> upon
* success. At the moment, sample converters are not yet supported but fetch arguments
* should work. The curpx->conf.args.ctx must be set by the caller.
* should work. The curpx->conf.args.ctx must be set by the caller. If an end pointer
* is passed in <endptr>, it will be updated with the pointer to the first character
* not part of the sample expression.
*
* In error case, the function returns 0, otherwise it returns 1.
*/
int add_sample_to_logformat_list(char *text, char *arg, int arg_len, struct proxy *curpx, struct list *list_format, int options, int cap, char **err)
int add_sample_to_logformat_list(char *text, char *arg, int arg_len, struct proxy *curpx, struct list *list_format, int options, int cap, char **err, char **endptr)
{
char *cmd[2];
struct sample_expr *expr = NULL;
@ -488,7 +490,7 @@ int add_sample_to_logformat_list(char *text, char *arg, int arg_len, struct prox
cmd[1] = "";
cmd_arg = 0;
expr = sample_parse_expr(cmd, &cmd_arg, curpx->conf.args.file, curpx->conf.args.line, err, &curpx->conf.args, NULL);
expr = sample_parse_expr(cmd, &cmd_arg, curpx->conf.args.file, curpx->conf.args.line, err, &curpx->conf.args, endptr);
if (!expr) {
memprintf(err, "failed to parse sample expression <%s> : %s", text, *err);
goto error_free;
@ -648,10 +650,26 @@ int parse_logformat_string(const char *fmt, struct proxy *curproxy, struct list
goto fail;
case LF_STEXPR: // text immediately following '%['
if (*str == ']') { // end of arg
cformat = LF_EDEXPR;
var_len = str - var;
*str = 0; // needed for parsing the expression
/* the whole sample expression is parsed at once,
* returning the pointer to the first character not
* part of the expression, which MUST be the trailing
* angle bracket.
*/
if (!add_sample_to_logformat_list(var, arg, arg_len, curproxy, list_format, options, cap, err, &str))
goto fail;
if (*str == ']') {
// end of arg, go on with next state
cformat = pformat = LF_EDEXPR;
sp = str;
}
else {
char c = *str;
*str = 0;
if (isprint(c))
memprintf(err, "expected ']' after '%s', but found '%c'", var, c);
else
memprintf(err, "missing ']' after '%s'", var);
}
break;
@ -681,7 +699,7 @@ int parse_logformat_string(const char *fmt, struct proxy *curproxy, struct list
goto fail;
break;
case LF_STEXPR:
if (!add_sample_to_logformat_list(var, arg, arg_len, curproxy, list_format, options, cap, err))
if (!add_sample_to_logformat_list(var, arg, arg_len, curproxy, list_format, options, cap, err, &sp))
goto fail;
break;
case LF_TEXT: