initial import

.gitignore

@@ -0,0 +1,4 @@
+src/*.o
+src/*.a
+src/*.so
+src/test

COPYING

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2017 Andrés J. Díaz
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

Makefile

@@ -0,0 +1,131 @@
+# Copyright (c) 2008 Andrés J. Díaz <ajdiaz@connectical.com>
+# This is a specific Makefile for C project. Distributed with
+# NO WARRANTY as a part of larger project.
+
+# There are the main configuration variables to make the project,
+# any other variables in .mk files must be imported automatically.
+# The USE and the ENABLED variables setup a lot of different values
+# in the application source.
+CC       = gcc
+INCLUDE  = include
+CFLAGS   = -O2 -fPIC -ggdb -Wall -I$(INCLUDE)
+SRCDIR   = src
+BINS     = example.so
+RM       = rm -f
+LD       = ld
+LDFLAGS  =
+ARFLAGS  = rcsu
+INSTALL  = install
+USE      =
+ENABLE   = # ASSERT
+
+-include config.mk
+
+# Dependencies for each binary is setting using a variable called
+# as output binary and contain a list of dependencies, for example
+# for binary out the dependencies are one and two::
+#
+#   out := one two
+
+# example.so := example.o
+
+# --- Do not touch below this line ---
+
+ifndef _ARCH
+	_ARCH := $(shell uname -m)
+	export _ARCH
+endif
+
+ifndef LIBDIR
+ifeq ($(_ARCH), x86_64)
+	LIBDIR := /lib64/
+endif
+ifeq ($(_ARCH), i386)
+	LIBDIR := /lib/
+endif
+endif
+
+SRCS=$(shell find $(SRCDIR) -name '*.c')
+OBJS=$(SRCS:.c=.o)
+ALLS=$(OBJS) $(addprefix $(SRCDIR)/,$(BINS))
+
+$(foreach name_,$(wildcard *.mk),$(eval include $(name_)))
+$(foreach name_,$(USE),$(eval CFLAGS=$(CFLAGS) -DUSE_$(name_)))
+$(foreach name_,$(ENABLE),$(eval CFLAGS=$(CFLAGS) -DENABLE_$(name_)))
+
+all: $(addprefix $(SRCDIR)/,$(BINS))
+
+define auto-dep
+ifneq ($(suffix $1),.a)
+	ifeq ($(suffix $1),.so)
+$$(SRCDIR)/$1: LDFLAGS += -shared
+	else
+$$(SRCDIR)/$1: CFLAGS += $(LDFLAGS)
+	endif
+else
+$$(SRCDIR)/$1: CFLAGS := $(CFLAGS) $$(CFLAGS_$1)
+endif
+$$(SRCDIR)/$1: $(addprefix $(SRCDIR)/,$($1))
+ifneq ($(suffix $1),.a)
+ifeq ($(suffix $1),.so)
+	@echo  "$$(CC)  $$@"
+	@$(CC) $(CFLAGS) -fPIC -shared -Wl,-soname,$1 $(LDFLAGS) $$(LDFLAGS_$1) -o $$@ $$(addprefix $$(SRCDIR)/,$$($1))
+else
+	@echo  "$$(CC)  $$@"
+	@$(CC) $(CFLAGS) $(LDFLAGS) $$(LDFLAGS_$1) -o $$@ $$(addprefix $$(SRCDIR)/,$$($1))
+endif
+else
+	@echo  "$$(AR)  $$@"
+	@$(AR) $(ARFLAGS) $$@ $$(addprefix $$(SRCDIR)/,$$($1))
+endif
+ifneq ($1, test)
+install_$1: $$(SRCDIR)/$1
+ifneq ($(suffix $1),.a)
+ifeq ($(suffix $1),.so)
+	@echo  "$$(INSTALL)  $$<"
+	@$(INSTALL) -s -D $$< $(DESTDIR)$$(LIBDIR)$$(notdir $$<)
+else
+	@echo  "$$(INSTALL)  $$<"
+	@$(INSTALL) -s -D $$< $(DESTDIR)$$(LIBDIR)$$(notdir $$<)
+endif
+else
+	@echo  "$$(INSTALL)  $$<"
+	@$(INSTALL) -s -D $$< $(DESTDIR)$$(BINDIR)$$(notdir $$<)
+endif
+uninstall_$1: $(DESTDIR)$$(LIBDIR)$$(notdir $1)
+ifneq ($(suffix $1),.a)
+ifeq ($(suffix $1),.so)
+	@echo  "$$(RM)  $$<"
+	@$(RM) $(DESTDIR)$$(LIBDIR)$$(notdir $$<)
+else
+	@echo  "$$(RM)  $$<"
+	@$(RM) $(DESTDIR)$$(LIBDIR)$$(notdir $$<)
+endif
+else
+	@echo  "$$(RM)  $$<"
+	@$(RM) $(DESTDIR)$$(BINDIR)$$(notdir $$<)
+endif
+endif
+endef
+
+$(foreach name_,$(BINS),$(eval $(call auto-dep,$(name_))))
+
+.c.o:
+	@echo  "$(CC)  $@"
+	@$(CC) $(CFLAGS) -c -o $@ $<
+
+clean:
+	@echo  "$(RM)  $(ALLS)"
+	@$(RM) $(ALLS)
+
+tags:
+	@which ctags 2>&1 >/dev/null && \
+		ctags --recurse=yes $(SRCS) || \
+		echo "Sorry :( Tags not available." >&2
+
+install: $(addprefix install_, $(BINS))
+
+uninstall: $(addprefix uninstall_, $(BINS))
+
+test: $(SRCDIR)/test
+	@$(SRCDIR)/test && echo 'Test OK'

README

@@ -0,0 +1,54 @@
+libdothosts.so
+==============
+
+The dothosts library is a LD_PRELOAD based library which allows you to
+have a user based hosts file.
+
+The library will catch all calls to gethostbyname(3), gethostbyname2(3),
+getaddrinfo(3),gethostbyname_r(3) and gethostbyname2_r(3) and perform
+a search of the requested host in a local (i.e. a file into home user
+directory) to resolve the hostname. If not found in this file, then proceed
+with the regular resolv mechanism.
+
+---- Install ---------------------------------------------------------------
+
+make && make test && make install
+
+If you want to use the 'dothosts' helper, just copy the script to your path.
+The make install proccess will not copy helper script.
+
+---- Usage -----------------------------------------------------------------
+
+To use dothosts just type:
+
+  export LD_PRELOAD=path/to/libdothosts.so
+
+And then new applications will use ~/.hosts file as /etc/hosts (the original
+/etc/hosts will be also used if host does not match in ~/.hosts).
+
+Aditionally, environment variable DOTHOSTS will use to change the path of
+local .hosts file, for exaple:
+
+  export DOTHOSTS=~/.config/hosts
+
+You can use the dothost utility to run an application with library loaded,
+in the form:
+
+  dothosts wget http://test
+
+---- Limitations ----------------------------------------------------------
+
+- Only works for programs that use glibc calls to resolve hostnames.
+- No working for SUID programs for security reasons.
+
+---- Development ----------------------------------------------------------
+
+For bug report please fill a issue in the github project [1], or send an
+email to ajdiaz+dothosts at ajdiaz.me
+
+[1] https://github.com/ajdiaz/dothosts/issues
+
+Any pull-request is also welcome.
+
+
+Happy Hacking!

config.mk

@@ -0,0 +1,8 @@
+BINS = libdothosts.so test
+LDFLAGS = -ldl
+
+libdothosts.so := dothosts.o
+
+CFLAGS_test = -DUSE_TEST
+test := test.o
+

dothosts

@@ -0,0 +1,4 @@
+#! /bin/sh
+# libdothosts.so helper
+export LD_PRELOAD=/usr/local/lib/libdothosts.so
+exec "$@"

src/dothosts.c

@@ -0,0 +1,146 @@
+/*
+ * dothosts.c
+ * Copyright (C) 2017 Andres J. Diaz <ajdiaz@ajdiaz.me>
+ *
+ * Distributed under terms of the MIT license.
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <dlfcn.h>
+
+#define _errexit(_s) {perror((_s)); exit(1);}
+
+
+static char *
+parse_host_line(char *hosts_line, const char *hname)
+{
+  const char *delim = " \t\n\r";
+	char *r = NULL;
+	char *ret = NULL;
+	char *token = NULL;
+
+  /* Replace comment by 0x00 */
+	if ((r = index(hosts_line, '#')))
+		*r = '\0';
+
+	ret = strtok_r(hosts_line, delim, &r); /* ip addr */
+	while ((token = strtok_r(NULL, delim, &r))) {
+		if (!strcmp(hname, token))
+			return ret;
+  }
+	return NULL;
+}
+
+
+static char *
+lookup(const char *hname)
+{
+  FILE *fp = NULL;
+  char *env_file = NULL;
+  char *line = NULL;
+  char *ret = NULL;
+  size_t size;
+
+  if (hname == NULL)
+    return NULL;
+
+  if ((env_file = getenv("DOTHOSTS")) == NULL)
+  {
+    /* No DOTHOSTS variable, composing from HOME */
+    if ((env_file = getenv("HOME")) == NULL)
+      env_file = strdup("/.hosts");
+    else
+    {
+      if ((env_file = strdup(env_file)) == NULL)
+        _errexit("Not enough memory");
+
+      if ((env_file = (char *) realloc(env_file, strlen(env_file) + 8)) == NULL)
+        _errexit("Not enough memory");
+
+      (void) strcat(env_file, "/.hosts");
+    }
+  }
+  else
+    env_file = strdup(env_file);
+
+
+  if ((fp = fopen(env_file, "r")) == NULL)
+  {
+    free(env_file);
+    _errexit("File not found");
+  }
+
+	while (getline(&line, &size, fp) >= 0)
+	{
+	  if (line == NULL || *line == '\0')
+	    continue;
+
+		if ((ret = parse_host_line(line, hname)) != NULL)
+			goto finish;
+	}
+
+finish:
+	fclose(fp);
+	free(env_file);
+
+  if (ret != NULL)
+    ret = strdup(ret);
+
+  free(line); /* free after strdup */
+	return ret;
+}
+
+/* Override library calls (note that some struct points are casting to
+ * void pointers to avoid includes */
+
+#ifndef USE_TEST
+#define _lcall_override(_r, _f, _n, ...) {        \
+  _r ret = (_r)0; char *n = NULL;                 \
+  char *p = (char *)(_n);                         \
+  _r (*orig)() = dlsym(RTLD_NEXT, #_f);           \
+  if ((n = lookup(_n)) != NULL) p = n;            \
+  ret = (_r) orig(p,  ## __VA_ARGS__);            \
+  if (n != NULL) free(n);                         \
+  return ret; }
+
+
+int
+getaddrinfo(const char *node, const char *service,
+            const void *hints, void *res)
+{
+  _lcall_override(int, getaddrinfo, node, service, hints, res);
+}
+
+void *
+gethostbyname(const char *name)
+{
+  _lcall_override(void *, gethostbyname, name);
+}
+
+void *
+gethostbyname2(const char *name, int af)
+{
+  _lcall_override(void *, gethostbyname2, name, af);
+}
+
+int
+gethostbyname_r(const char *name, void *ret, char *buf,
+                size_t buflen, void *result, int *h_errnop)
+{
+  _lcall_override(int, gethostbyname_r, name, ret, buf,
+                  buflen, result, h_errnop);
+}
+
+int
+gethostbyname2_r(const char *name, int af,
+                 void *ret, char *buf, size_t buflen,
+                 void *result, int *h_errnop)
+{
+  _lcall_override(int, gethostbyname2_r, name, af, ret, buf, buflen,
+                  result, h_errnop);
+}
+#endif