Initial step in integrating regex-based rewrite engine.

MCONFIG.in

@@ -32,6 +32,9 @@ LIBS    = @LIBS@
 # Additional library we need to build
 LIBOBJS	= @LIBOBJS@
 
+# Additional tftpd objects we need to build
+TFTPDOBJS = @TFTPDOBJS@
+
 # ar and ranlib (for making libraries)
 AR	= ar cq
 RANLIB	= @RANLIB@

config.h.in

@@ -22,3 +22,4 @@
 #undef HAVE_STRUCT_IN_PKTINFO
 #undef HAVE_SETREUID
 #undef HAVE_SETREGID
+#undef WITH_REGEX

configure.in

@@ -19,10 +19,20 @@ PA_WITH_BOOL(tcpwrappers, 1,
 [
 	AC_SEARCH_LIBS(yp_get_default_domain, [nsl resolv])
 	PA_HAVE_TCPWRAPPERS
-],
+],:)
+
+PA_WITH_BOOL(remap, 1,
+[ --without-remap       Disable regex-based filename remapping],
 [
-	:
-])
+	AC_CHECK_HEADER(regex.h,
+	[
+		AC_SEARCH_LIBS(regcomp, [regex rx],
+		[
+			AC_DEFINE(WITH_REGEX)
+			TFTPDOBJS="remap.o $TFTPDOBJS"
+		])
+	])
+],:)
 
 PA_ADD_CFLAGS(-Wall)
 PA_ADD_CFLAGS(-W)
@@ -39,17 +49,18 @@ PA_ADD_CFLAGS(-pipe)
 
 PA_SIGSETJMP([AC_DEFINE(HAVE_SIGSETJMP)])
 
-LIBXTRA=0
+LIBXTRA=false
 
-AC_SEARCH_LIBS(xmalloc, iberty, , LIBXTRA=1 LIBOBJS="$LIBOBJS xmalloc.o")
-AC_SEARCH_LIBS(xstrdup, iberty, , LIBXTRA=1 LIBOBJS="$LIBOBJS xstrdup.o")
-AC_SEARCH_LIBS(bsd_signal, bsd, , LIBXTRA=1 LIBOBJS="$LIBOBJS bsdsignal.o")
+AC_SEARCH_LIBS(xmalloc, iberty, , LIBXTRA=true LIBOBJS="$LIBOBJS xmalloc.o")
+AC_SEARCH_LIBS(xstrdup, iberty, , LIBXTRA=true LIBOBJS="$LIBOBJS xstrdup.o")
+AC_SEARCH_LIBS(bsd_signal, bsd, , LIBXTRA=true LIBOBJS="$LIBOBJS bsdsignal.o")
 
-if test "$LIBXTRA" -eq 1; then
+if $LIBXTRA; then
 	LIBS="../lib/libxtra.a $LIBS"
 fi
 
 AC_SUBST(LIBOBJS)
+AC_SUBST(TFTPDOBJS)
 
 AC_PROG_RANLIB
 AC_PROG_INSTALL

tftp/tftpsubs.h

@@ -42,6 +42,8 @@
  * Prototypes for read-ahead/write-behind subroutines for tftp user and
  * server.
  */
+#include <stdlib.h>
+
 struct tftphdr *r_init(void);
 void	read_ahead(FILE *, int);
 int	readit(FILE *, struct tftphdr **, int);
@@ -55,3 +57,8 @@ int	writeit(FILE *, struct tftphdr **, int, int);
 extern int segsize;
 #define MAX_SEGSIZE	65464
 
+/*
+ * Prototype for xmalloc/xstrdup
+ */
+extern void *xmalloc(size_t);
+extern char *xstrdup(const char *);

tftpd/Makefile

@@ -3,7 +3,7 @@ all: tftpd
 -include ../MCONFIG
 -include ../MRULES
 
-OBJS = tftpd.o tftpsubs.o recvfrom.o
+OBJS = tftpd.o tftpsubs.o recvfrom.o $(TFTPDOBJS)
 
 tftpd: $(OBJS)
 	$(CC) $(LDFLAGS) $^ $(LIBS) -o $@

tftpd/remap.c

@@ -0,0 +1,282 @@
+/* $Id$ */
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2001 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 <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <regex.h>
+
+#include "tftpsubs.h"
+#include "remap.h"
+
+#define DEADMAN_MAX_STEPS	1024    /* Timeout after this many steps */
+#define LINE_MAX 		65536   /* 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_GETONLY	0x20	/* Applicable to GET only */
+#define RULE_PUTONLY	0x40	/* Applicable to PUT only */
+
+struct rule {
+  struct rule *next;
+  int nrule;
+  int rule_flags;
+  regex_t rx;
+  char *pattern;
+};
+
+/* Do \-substitution.  Call with string == NULL to get length only. */
+static int genmatchstring(char *string, const char *pattern, const char *input, const regmatch_t *pmatch)
+{
+  int len = 0;
+  int n, mlen;
+  int endbytes;
+
+  /* Get section before match; note pmatch[0] is the whole match */
+  endbytes = strlen(input) - pmatch[0].rm_eo;
+  len = pmatch[0].rm_so + endbytes;
+  if ( string ) {
+    memcpy(string, input, pmatch[0].rm_so);
+    string += pmatch[0].rm_so;
+  }
+
+  /* Transform matched section */
+  while ( *pattern ) {
+    if ( *pattern == '\\' && pattern[1] != '\0' ) {
+      if ( pattern[1] < '0' || pattern[1] > '9' ) {
+	len++;
+	if ( string )
+	  *string++ = pattern[1];
+      } else {
+	n = pattern[1] - '0';
+	
+	if ( pmatch[n].rm_so != -1 ) {
+	  mlen = pmatch[n].rm_eo - pmatch[n].rm_so;
+	  len += mlen;
+	  if ( string ) {
+	    memcpy(string, input+pmatch[n].rm_so, mlen);
+	    string += mlen;
+	  }
+	}
+      }
+      pattern += 2;
+    } else {
+      len++;
+      if ( string )
+	*string++ = *pattern;
+      pattern++;
+    }
+  }
+
+  /* Copy section after match */
+  if ( string ) {
+    memcpy(string, input+pmatch[0].rm_eo, endbytes);
+    string[endbytes] = '\0';
+  }
+
+  return len;
+}
+
+/* Extract a string terminated by non-escaped whitespace; ignore 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)
+{
+  char buffer[LINE_MAX];
+  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':
+      r->rule_flags |= RULE_GLOBAL;
+      break;
+    case 'e':
+      r->rule_flags |= RULE_EXIT;
+      break;
+    case 's':
+      r->rule_flags |= RULE_RESTART;
+      break;
+    case 'a':
+      r->rule_flags |= RULE_ABORT;
+      break;
+    case 'i':
+      rxflags |= REG_ICASE;
+      break;
+    case 'G':
+      r->rule_flags |= RULE_GETONLY;
+      break;
+    case 'P':
+      r->rule_flags |= RULE_PUTONLY;
+      break;
+    default:
+      /* boo hoo */
+      break;
+    }
+  }
+
+  /* RULE_GLOBAL only applies when RULE_REWRITE specified */
+  if ( !(r->rule_flags & RULE_REWRITE) )
+    r->rule_flags &= ~RULE_GLOBAL;
+
+  /* Read and compile the regex */
+  if ( !readescstring(buffer, &line) ) {
+    /* boo hoo */
+    return 0;			/* No rule found */
+  }
+
+  if ( (rv = regcomp(&r->rx, buffer, rxflags)) != 0 ) {
+    /* boo hoo */
+    return 0;			/* No rule found */
+  }
+
+  /* Read the rewrite pattern, if any */
+  if ( readescstring(buffer, &line) ) {
+    r->pattern = xstrdup(buffer);
+  } else {
+    r->pattern = "";
+  }
+
+  nrule++;
+  return 1;			/* Rule found */
+}
+
+/* Read a rule file */
+struct rule *parserulefile(FILE *f)
+{
+  char line[LINE_MAX];
+  struct rule *first_rule = NULL;
+  struct rule **last_rule = &first_rule;
+  struct rule *this_rule  = xmalloc(sizeof(struct rule));
+
+  while ( fgets(line, LINE_MAX, f) ) {
+    if ( parseline(line, this_rule) ) {
+      *last_rule = this_rule;
+      last_rule = &this_rule->next;
+      this_rule = xmalloc(sizeof(struct rule));
+    }
+  }
+
+  free(this_rule);		/* Last one is always unused */
+
+  return first_rule;
+}
+
+/* Execute a rule set on a string; returns a malloc'd new string. */
+char *rewrite_string(const char *input, const struct rule *rules, int is_put)
+{
+  char *current = xstrdup(input);
+  char *newstr;
+  const struct rule *ruleptr = rules;
+  regmatch_t pmatch[10];
+  int len;
+  int was_match = 0;
+  int deadman = DEADMAN_MAX_STEPS;
+
+  for ( ruleptr = rules ; ruleptr ; ruleptr = ruleptr->next ) {
+    if ( ((ruleptr->rule_flags & RULE_GETONLY) && is_put) ||
+	 ((ruleptr->rule_flags & RULE_PUTONLY) && !is_put) ) {
+      continue;			/* Rule not applicable, try next */
+    }
+
+    if ( ! deadman-- ) {
+      free(current);
+      return NULL;		/* Did not terminate! */
+    }
+
+    do {
+      if ( regexec(&ruleptr->rx, current, 10, pmatch, 0) == 0 ) {
+	/* Match on this rule */
+	was_match = 1;
+	
+	if ( ruleptr->rule_flags & RULE_ABORT ) {
+	  free(current);
+	  return(NULL);
+	}
+	
+	if ( ruleptr->rule_flags & RULE_REWRITE ) {
+	  len = genmatchstring(NULL, ruleptr->pattern, current, pmatch);
+	  newstr = xmalloc(len+1);
+	  genmatchstring(newstr, ruleptr->pattern, current, pmatch);
+	  free(current);
+	  current = newstr;
+	}
+      } else {
+	break;			/* No match, terminate unconditionally */
+      }
+      /* If the rule is global, keep going until no match */
+    } while ( ruleptr->rule_flags & RULE_GLOBAL );
+    
+    if ( was_match ) {
+      was_match = 0;
+
+      if ( ruleptr->rule_flags & RULE_EXIT ) {
+	break;			/* Exit here, we're done */
+      } else if ( ruleptr->rule_flags & RULE_RESTART ) {
+	ruleptr = rules;	/* Start from the top */
+      }
+    }
+  }
+
+  return current;
+}

tftpd/remap.h

@@ -0,0 +1,28 @@
+/* $Id$ */
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2001 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.h
+ *
+ * Prototypes for regular-expression based filename remapping.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+/* Opaque type */
+struct rule;
+
+/* Read a rule file */
+struct rule *parserulefile(FILE *);
+
+/* Execute a rule set on a string; returns a malloc'd new string. */
+char *rewrite_string(const char *input, const struct rule *rules, int is_put);

tftpd/tftpd.c

@@ -77,6 +77,9 @@ static const char *rcsid = "tftp-hpa $Id$";
 #include "../config.h"
 #include "tftpsubs.h"
 #include "recvfrom.h"
+#ifdef WITH_REGEX
+#include "remap.h"
+#endif
 
 #ifdef HAVE_TCPWRAPPERS
 #include <tcpd.h>