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tftp-hpa-google/tftpd/remap.c
H. Peter Anvin 2c86ff58dc remap: *actually* build, and fix masked logic errors 
Well, now it is actually being compiled, and should hopefully work
again...

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2024-06-10 21:09:46 -07:00

545 lines
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/* ----------------------------------------------------------------------- *
*
* Copyright 2001-2024 H. Peter Anvin - All Rights Reserved
*
* This program is free software available under the same license
* as the "OpenBSD" operating system, distributed at
* http://www.openbsd.org/.
*
* ----------------------------------------------------------------------- */
/*
* remap.c
*
* Perform regular-expression based filename remapping.
*/
#include "config.h" /* Must be included first! */
#include <ctype.h>
#include <syslog.h>
#include <regex.h>
#include "tftpd.h"
#include "remap.h"
#define DEADMAN_MAX_STEPS 4096 /* Timeout after this many steps */
#define MAXLINE 16384 /* Truncate a line at this many bytes */
#define RULE_REWRITE 0x01 /* This is a rewrite rule */
#define RULE_GLOBAL 0x02 /* Global rule (repeat until no match) */
#define RULE_EXIT 0x04 /* Exit after matching this rule */
#define RULE_RESTART 0x08 /* Restart at the top after matching this rule */
#define RULE_ABORT 0x10 /* Terminate processing with an error */
#define RULE_INVERSE 0x20 /* Execute if regex *doesn't* match */
#define RULE_IPV4 0x40 /* IPv4 only */
#define RULE_IPV6 0x80 /* IPv6 only */
#define RULE_HASFILE 0x100 /* Valid if rule results in a valid filename */
#define RULE_RRQ 0x200 /* Get (read) only */
#define RULE_WRQ 0x400 /* Put (write) only */
#define RULE_SEDG 0x800 /* sed-style global */
int deadman_max_steps = DEADMAN_MAX_STEPS;
struct rule {
struct rule *next;
int nrule;
unsigned int rule_flags;
regex_t rx;
const char *pattern;
};
static int xform_null(int c)
{
return c;
}
static int xform_toupper(int c)
{
return toupper(c);
}
static int xform_tolower(int c)
{
return tolower(c);
}
/*
* Do \-substitution. Call with string == NULL to get length only.
* "start" indicates an offset into the input buffer where the pattern
* match was started.
*/
static int do_genmatchstring(char *string, const char *pattern,
const char *ibuf,
const regmatch_t * pmatch,
match_pattern_callback macrosub,
int start, int *nextp)
{
int (*xform) (int) = xform_null;
int len = 0;
int n, mlen, sublen;
int endbytes;
const char *input = ibuf + start;
/* Get section before match; note pmatch[0] is the whole match */
endbytes = strlen(input) - pmatch[0].rm_eo;
len = start + pmatch[0].rm_so;
if (string) {
/* Copy the prefix before "start" as well! */
memcpy(string, ibuf, start + pmatch[0].rm_so);
string += start + pmatch[0].rm_so;
}
/* Transform matched section */
while (*pattern) {
mlen = 0;
if (*pattern == '\\' && pattern[1] != '\0') {
char macro = pattern[1];
switch (macro) {
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
n = pattern[1] - '0';
if (pmatch[n].rm_so != -1) {
mlen = pmatch[n].rm_eo - pmatch[n].rm_so;
len += mlen;
if (string) {
const char *p = input + start + pmatch[n].rm_so;
while (mlen--)
*string++ = xform(*p++);
}
}
break;
case 'L':
xform = xform_tolower;
break;
case 'U':
xform = xform_toupper;
break;
case 'E':
xform = xform_null;
break;
default:
if (macrosub && (sublen = macrosub(macro, string)) >= 0) {
while (sublen--) {
len++;
if (string) {
*string = xform(*string);
string++;
}
}
} else {
len++;
if (string)
*string++ = xform(pattern[1]);
}
}
pattern += 2;
} else {
len++;
if (string)
*string++ = xform(*pattern);
pattern++;
}
}
/* Pointer to post-substitution tail */
if (nextp)
*nextp = len;
/* Copy section after match */
len += endbytes;
if (string) {
memcpy(string, input + pmatch[0].rm_eo, endbytes);
string[endbytes] = '\0';
}
return len;
}
/*
* Ditto, but allocate the string in a new buffer
*/
static int genmatchstring(char **string, const char *pattern,
const char *ibuf,
const regmatch_t * pmatch,
match_pattern_callback macrosub,
int start, int *nextp)
{
int len;
char *buf;
len = do_genmatchstring(NULL, pattern, ibuf, pmatch,
macrosub, start, NULL);
*string = buf = tfmalloc(len + 1);
return do_genmatchstring(buf, pattern, ibuf, pmatch,
macrosub, start, nextp);
}
/*
* Extract a string terminated by non-escaped whitespace; ignoring
* leading whitespace. Consider an unescaped # to be a comment marker,
* functionally \n.
*/
static int readescstring(char *buf, char **str)
{
char *p = *str;
int wasbs = 0, len = 0;
while (*p && isspace(*p))
p++;
if (!*p) {
*buf = '\0';
*str = p;
return 0;
}
while (*p) {
if (!wasbs && (isspace(*p) || *p == '#')) {
*buf = '\0';
*str = p;
return len;
}
/* Important: two backslashes leave us in the !wasbs state! */
wasbs = !wasbs && (*p == '\\');
*buf++ = *p++;
len++;
}
*buf = '\0';
*str = p;
return len;
}
/* Parse a line into a set of instructions */
static int parseline(char *line, struct rule *r, int lineno)
{
char buffer[MAXLINE];
char *p;
int rv;
int rxflags = REG_EXTENDED;
static int nrule;
memset(r, 0, sizeof *r);
r->nrule = nrule;
if (!readescstring(buffer, &line))
return 0; /* No rule found */
for (p = buffer; *p; p++) {
switch (*p) {
case 'r':
r->rule_flags |= RULE_REWRITE;
break;
case 'g':
if (r->rule_flags & RULE_GLOBAL)
r->rule_flags |= RULE_SEDG;
else
r->rule_flags |= RULE_GLOBAL;
break;
case 'e':
r->rule_flags |= RULE_EXIT;
break;
case 'E':
r->rule_flags |= RULE_HASFILE;
break;
case 's':
r->rule_flags |= RULE_RESTART;
break;
case 'a':
r->rule_flags |= RULE_ABORT;
break;
case 'i':
rxflags |= REG_ICASE;
break;
case '~':
r->rule_flags |= RULE_INVERSE;
break;
case '4':
r->rule_flags |= RULE_IPV4;
break;
case '6':
r->rule_flags |= RULE_IPV6;
break;
case 'G':
r->rule_flags |= RULE_RRQ;
break;
case 'P':
r->rule_flags |= RULE_WRQ;
break;
default:
syslog(LOG_ERR,
"Remap command \"%s\" on line %d contains invalid char \"%c\"",
buffer, lineno, *p);
return -1; /* Error */
break;
}
}
if (r->rule_flags & RULE_REWRITE) {
if (r->rule_flags & RULE_INVERSE) {
syslog(LOG_ERR, "r rules cannot be inverted, line %d: %s\n",
lineno, line);
return -1; /* Error */
}
if ((r->rule_flags & (RULE_GLOBAL|RULE_SEDG|RULE_HASFILE))
== (RULE_GLOBAL|RULE_HASFILE)) {
syslog(LOG_ERR, "E rules cannot be combined with g (but gg is OK), line %d: %s\n",
lineno, line);
return -1; /* Error */
}
} else {
/* RULE_GLOBAL and RULE_SEDG are meaningless without RULE_REWRITE */
r->rule_flags &= ~(RULE_GLOBAL|RULE_SEDG);
}
/* Read and compile the regex */
if (!readescstring(buffer, &line)) {
syslog(LOG_ERR, "No regex on remap line %d: %s\n", lineno, line);
return -1; /* Error */
}
if ((rv = regcomp(&r->rx, buffer, rxflags)) != 0) {
char errbuf[BUFSIZ];
regerror(rv, &r->rx, errbuf, BUFSIZ);
syslog(LOG_ERR, "Bad regex in remap line %d: %s\n", lineno,
errbuf);
return -1; /* Error */
}
/* Read the rewrite pattern, if any */
if (readescstring(buffer, &line)) {
r->pattern = tfstrdup(buffer);
} else {
r->pattern = "";
}
nrule++;
return 1; /* Rule found */
}
/* Read a rule file */
struct rule *parserulefile(FILE * f)
{
char line[MAXLINE];
struct rule *first_rule = NULL;
struct rule **last_rule = &first_rule;
struct rule *this_rule = tfmalloc(sizeof(struct rule));
int rv;
int lineno = 0;
int err = 0;
while (lineno++, fgets(line, MAXLINE, f)) {
rv = parseline(line, this_rule, lineno);
if (rv < 0)
err = 1;
if (rv > 0) {
*last_rule = this_rule;
last_rule = &this_rule->next;
this_rule = tfmalloc(sizeof(struct rule));
}
}
free(this_rule); /* Last one is always unused */
if (err) {
/* Bail on error, we have already logged an error message */
exit(EX_CONFIG);
}
return first_rule;
}
/* Destroy a rule file data structure */
void freerules(struct rule *r)
{
struct rule *next;
while (r) {
next = r->next;
regfree(&r->rx);
/* "" patterns aren't allocated by malloc() */
if (r->pattern && *r->pattern)
free((void *)r->pattern);
free(r);
r = next;
}
}
/* Execute a rule set on a string; returns a malloc'd new string. */
char *rewrite_string(const struct formats *pf,
const char *input, const struct rule *rules,
int mode, int af, match_pattern_callback macrosub,
const char **errmsg)
{
char *current = tfstrdup(input);
char *newstr, *newerstr;
const char *accerr;
const struct rule *ruleptr = rules;
regmatch_t pmatch[10];
int i;
int len;
int was_match = 0;
int deadman = deadman_max_steps;
int matchsense;
int pmatches;
unsigned int bad_flags;
int ggoffset;
/* Default error */
*errmsg = "Remap table failure";
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: input: %s", current);
}
bad_flags = 0;
if (mode != RRQ) bad_flags |= RULE_RRQ;
if (mode != WRQ) bad_flags |= RULE_WRQ;
if (af != AF_INET) bad_flags |= RULE_IPV4;
if (af != AF_INET6) bad_flags |= RULE_IPV6;
for (ruleptr = rules; ruleptr; ruleptr = ruleptr->next) {
if (ruleptr->rule_flags & bad_flags)
continue; /* This rule is excluded by flags */
matchsense = ruleptr->rule_flags & RULE_INVERSE ? REG_NOMATCH : 0;
pmatches = ruleptr->rule_flags & RULE_INVERSE ? 0 : 10;
/* Clear the pmatch[] array */
for (i = 0; i < 10; i++)
pmatch[i].rm_so = pmatch[i].rm_eo = -1;
was_match = 0;
do {
if (!deadman--)
goto dead;
if (regexec(&ruleptr->rx, current, pmatches, pmatch, 0)
!= matchsense)
break; /* No match, break out of do loop */
/* Match on this rule */
was_match = 1;
if (ruleptr->rule_flags & RULE_ABORT) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: abort: %s",
ruleptr->nrule, current);
}
if (ruleptr->pattern[0]) {
/* Custom error message */
genmatchstring(&newstr, ruleptr->pattern, current,
pmatch, macrosub, 0, NULL);
*errmsg = newstr;
} else {
*errmsg = NULL;
}
free(current);
return (NULL);
}
if (ruleptr->rule_flags & RULE_REWRITE) {
len = genmatchstring(&newstr, ruleptr->pattern, current,
pmatch, macrosub, 0, &ggoffset);
if (ruleptr->rule_flags & RULE_SEDG) {
/* sed-style partial-matching global */
while (ggoffset < len &&
regexec(&ruleptr->rx, newstr + ggoffset,
pmatches, pmatch,
ggoffset ? REG_NOTBOL : 0)
== matchsense) {
if (!deadman--) {
free(current);
current = newstr;
goto dead;
}
len = genmatchstring(&newerstr, ruleptr->pattern,
newstr, pmatch, macrosub,
ggoffset, &ggoffset);
free(newstr);
newstr = newerstr;
}
}
if ((ruleptr->rule_flags & RULE_HASFILE) &&
pf->f_validate(newstr, mode, pf, &accerr)) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: ignored rewrite (%s): %s",
ruleptr->nrule, accerr, newstr);
}
free(newstr);
was_match = 0;
break;
}
free(current);
current = newstr;
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: rewrite: %s",
ruleptr->nrule, current);
}
} else if (ruleptr->rule_flags & RULE_HASFILE) {
if (pf->f_validate(current, mode, pf, &accerr)) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: not exiting (%s)\n",
ruleptr->nrule, accerr);
}
was_match = 0;
break;
}
}
/* If the rule is (old-style) global, keep going until no match */
} while ((ruleptr->rule_flags & (RULE_GLOBAL|RULE_SEDG)) == RULE_GLOBAL);
if (!was_match)
continue; /* Next rule */
if (ruleptr->rule_flags & (RULE_EXIT|RULE_HASFILE)) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: exit",
ruleptr->nrule);
}
return current; /* Exit here, we're done */
} else if (ruleptr->rule_flags & RULE_RESTART) {
ruleptr = rules; /* Start from the top */
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: restart",
ruleptr->nrule);
}
}
}
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: done");
}
return current;
dead: /* Deadman expired */
syslog(LOG_ERR,
"remap: Breaking loop after %d steps, input = %s, last = %s",
deadman_max_steps, input, current);
free(current);
return NULL; /* Did not terminate! */
}
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