Add environment spoofing

Signed-off-by: Mattias Andrée <maandree@kth.se>

8 files changed, 187 insertions, 65 deletions

diff --git a/Makefile b/Makefile
index 6a96f96..7790c0e 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@ LIB_VERSION = $(LIB_MAJOR).$(LIB_MINOR)
 LIB_NAME = fonts
 
 
-OBJ =\
+PUBLIC_OBJ =\
 	libfonts_calculate_subpixel_order.o\
 	libfonts_decode_font_description.o\
 	libfonts_encode_font_description.o\
@@ -24,14 +24,20 @@ OBJ =\
 	libfonts_get_default_font_name.o\
 	libfonts_get_output_dpi.o\
 	libfonts_get_subpixel_order_class.o\
-	libfonts_unget_subpixel_order_class.o
+	libfonts_unget_subpixel_order_class.o\
+	libfonts_used_environs.o
+
+OBJ =\
+	$(PUBLIC_OBJ)\
+	libfonts_getenv__.o\
+	libfonts_gethome__.o\
 
 HDR =\
 	common.h\
 	libfonts.h
 
 LOBJ = $(OBJ:.o=.lo)
-TESTS = $(OBJ:.o=.test)
+TESTS = $(PUBLIC_OBJ:.o=.test)
 
 
 all: libfonts.a libfonts.$(LIBEXT) $(TESTS)
diff --git a/common.h b/common.h
index 4937a76..2451cb7 100644
--- a/common.h
+++ b/common.h
@@ -33,6 +33,10 @@ eq(double a, double b)
 }
 
 
+const char *libfonts_getenv__(const char *name, struct libfonts_context *ctx);
+char *libfonts_gethome__(struct libfonts_context *ctx);
+
+
 #ifdef TEST
 
 # define ASSERT(ASSERTION)\
diff --git a/config.mk b/config.mk
index ab163d4..8e10fd8 100644
--- a/config.mk
+++ b/config.mk
@@ -6,3 +6,6 @@ CC = c99
 CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
 CFLAGS   = -Wall -g
 LDFLAGS  =
+
+# Add -DVALIDATE to CPPFLAGS to run extra code checks,
+#   that are only useful for development, at run time
diff --git a/libfonts.h b/libfonts.h
index 25341ed..09cbb14 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -1571,11 +1571,53 @@ struct libfonts_font_description {
 	char _buf[256];
 };
 
+/**
+ * Structure that can be used to spoof the
+ * environment the library is executed in
+ */
+struct libfonts_context {
+	/**
+	 * Environment variables to add or override
+	 *
+	 * `libfonts_used_environs` can be used to
+	 * enumerate the environment variables that
+	 * affect the execution of the environment
+	 */
+	char **environ;
+
+	/**
+	 * The real user ID of the process
+	 *
+	 * Only used if `.use_context_uid` is non-zero
+	 */
+	uid_t uid;
+
+	/**
+	 * Non-zero to remove all environment
+	 * variables that are not included in
+	 * `.environ`
+	 */
+	int ignore_process_environ;
+
+	/**
+	 * Whether `.uid` is used
+	 */
+	int use_context_uid;
+};
+
+
+/**
+ * `NULL`-terminated list of environment variables
+ * that affect the execution of the library
+ */
+extern const char *const libfonts_used_environs[];
+
 
 /**
  * Get the font a default font name aliases to
  * 
  * @param   font  The default font
+ * @param   ctx   Optional `struct libfonts_context`
  * @return        The font the default font is an alias for
  *                (shall be deallocated using free(3) when no
  *                longer used), or `NULL` on failure; in the
@@ -1584,7 +1626,7 @@ struct libfonts_font_description {
  * 
  * @throws  EINVAL  Unrecognised value on `font`
  */
-char *libfonts_get_default_font(enum libfonts_default_font);
+char *libfonts_get_default_font(enum libfonts_default_font, struct libfonts_context *);
 
 /**
  * Get the alias for a default font
@@ -1674,11 +1716,12 @@ int libfonts_do_decoded_font_descriptions_match(const struct libfonts_font_descr
  * @param   settings  Output parameter for the rendering settings;
  *                    `settings->dpi_x` and `settings->dpi_y` will
  *                    have a fallback value assigned if configured to 0
+ * @param   ctx       Optional `struct libfonts_context`
  * @return            1 if rendering settings where found,
  *                    0 otherwise (`*settings` will be filled with fallback values),
  *                    -1 on failure
  */
-int libfonts_get_default_rendering_settings(struct libfonts_rendering_settings *);
+int libfonts_get_default_rendering_settings(struct libfonts_rendering_settings *, struct libfonts_context *);
 /* TODO implement libfonts_get_default_rendering_settings
  * 
  * /etc/libfonts/default-rendering.conf
@@ -1703,11 +1746,12 @@ int libfonts_get_default_rendering_settings(struct libfonts_rendering_settings *
  * 
  * @param   settings  Output parameter for the rendering settings
  * @param   name      The EDID (or other identifier) of the output
+ * @param   ctx       Optional `struct libfonts_context`
  * @return            1 if rendering settings where found,
  *                    0 otherwise (`*settings` will be unmodified),
  *                    -1 on failure
  */
-int libfonts_get_output_rendering_settings(struct libfonts_rendering_settings *, const char *);
+int libfonts_get_output_rendering_settings(struct libfonts_rendering_settings *, const char *, struct libfonts_context *);
 /* TODO implement libfonts_get_output_rendering_settings
  * 
  * /etc/libfonts/output-rendering.conf
diff --git a/libfonts_get_default_font.c b/libfonts_get_default_font.c
index d27e661..7c21b1f 100644
--- a/libfonts_get_default_font.c
+++ b/libfonts_get_default_font.c
@@ -10,43 +10,6 @@ find(const char *dir_part1, const char *dir_part2, const char *dir_part3)
 }
 
 static char *
-gethome(void)
-{
-	uid_t uid = getuid();
-	size_t size = 512;
-	char *buf = NULL, *new;
-	char *ret = NULL;
-	struct passwd pw, *pwp;
-	int err;
-
-	goto beginning;
-
-	do {
-		if (size > SIZE_MAX / 2)
-			goto enomem;
-		size *= 2;
-	beginning:
-		new = realloc(buf, size);
-		if (!new) {
-		enomem:
-			free(buf);
-			errno = ENOMEM;
-			return NULL;
-		}
-		buf = new;
-	} while ((err = getpwuid_r(uid, &pw, buf, size, &pwp)) == ERANGE);
-	if (err) {
-		free(buf);
-		return NULL;
-	}
-
-	if (pwp && pwp->pw_dir)
-		ret = strdup(pwp->pw_dir);
-	free(buf);
-	return ret;
-}
-
-static char *
 getn(const char *file_part1, size_t file_part1_len, const char *file_part2, const char *name)
 {
 	size_t file_part2_len = strlen(file_part2);
@@ -82,9 +45,9 @@ get(const char *file_part1, const char *file_part2, const char *name)
 }
 
 char *
-libfonts_get_default_font(enum libfonts_default_font font)
+libfonts_get_default_font(enum libfonts_default_font font, struct libfonts_context *ctx)
 {
-	const char *env, *var, *next;
+	const char *env, *var, *next, *confenv, *homeenv;
 	char *ret, *home = NULL;
 	int saved_errno = errno;
 	size_t len;
@@ -103,28 +66,28 @@ libfonts_get_default_font(enum libfonts_default_font font)
 		return NULL;
 	}
 
-	ret = getenv(env);
-	if (ret && *ret)
-		return strdup(ret);
+	env = libfonts_getenv__(env, ctx);
+	if (env && *env)
+		return strdup(env);
 
-	env = getenv("XDG_CONFIG_HOME");
-	if (env && *env) {
-		ret = get(env, "/libfonts/default-fonts.conf", var);
+	confenv = libfonts_getenv__("XDG_CONFIG_HOME", ctx);
+	if (confenv && *confenv) {
+		ret = get(confenv, "/libfonts/default-fonts.conf", var);
 		if (ret)
 			goto out;
 	}
 
-	env = getenv("HOME");
-	if (env && *env) {
-		ret = get(env, "/.config/libfonts/default-fonts.conf", var);
+	homeenv = libfonts_getenv__("HOME", ctx);
+	if (homeenv && *homeenv) {
+		ret = get(homeenv, "/.config/libfonts/default-fonts.conf", var);
 		if (ret)
 			goto out;
-		ret = get(env, "/.libfonts/default-fonts.conf", var);
+		ret = get(homeenv, "/.libfonts/default-fonts.conf", var);
 		if (ret)
 			goto out;
 	}
 
-	home = gethome();
+	home = libfonts_gethome__(ctx);
 	if (home && *home) {
 		ret = get(home, "/.config/libfonts/default-fonts.conf", var);
 		if (ret)
@@ -134,33 +97,31 @@ libfonts_get_default_font(enum libfonts_default_font font)
 			goto out;
 	}
 
-	env = getenv("XDG_CONFIG_HOME");
-	if (env && *env) {
+	if (confenv && *confenv) {
 		ret = find(env, "/libfonts/", var);
 		if (ret)
 			goto out;
 	}
 
-	env = getenv("HOME");
-	if (env && *env) {
-		ret = find(env, "/.config/libfonts/", var);
+	if (homeenv && *homeenv) {
+		ret = find(homeenv, "/.config/libfonts/", var);
 		if (ret)
 			goto out;
-		ret = find(env, "/.libfonts/", var);
+		ret = find(homeenv, "/.libfonts/", var);
 		if (ret)
 			goto out;
 	}
 
 	if (home && *home) {
-		ret = find(env, "/.config/libfonts/", var);
+		ret = find(home, "/.config/libfonts/", var);
 		if (ret)
 			goto out;
-		ret = find(env, "/.libfonts/", var);
+		ret = find(home, "/.libfonts/", var);
 		if (ret)
 			goto out;
 	}
 
-	env = getenv("XDG_CONFIG_DIRS");
+	env = libfonts_getenv__("XDG_CONFIG_DIRS", ctx);
 	if (env && *env) {
 		do {
 			next = strchr(&env[1], ':');
diff --git a/libfonts_getenv__.c b/libfonts_getenv__.c
new file mode 100644
index 0000000..d998337
--- /dev/null
+++ b/libfonts_getenv__.c
@@ -0,0 +1,30 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+const char *
+libfonts_getenv__(const char *name, struct libfonts_context *ctx)
+{
+	char **envp;
+	size_t len = strlen(name);
+
+#ifdef VALIDATE
+	size_t i;
+	if (!name) {
+		fprintf(stderr, "`name` parameter in libfonts_getenv__ is NULL\n");
+		abort();
+	}
+	for (i = 0; libfonts_used_environs[i]; i++)
+		if (!strcmp(name, libfonts_used_environs[i]))
+			goto ok;
+	fprintf(stderr, "Value of `name` parameter (\"%s\") in libfonts_getenv__ is not in libfonts_used_environs\n", name);
+	abort();
+ok:
+#endif
+
+	if (ctx && ctx->environ)
+		for (envp = ctx->environ; *envp; envp++)
+			if (strncmp(*envp, name, len) && (*envp)[len] == '=')
+				return *envp;
+	return ctx->ignore_process_environ ? NULL : getenv(name);
+}
diff --git a/libfonts_gethome__.c b/libfonts_gethome__.c
new file mode 100644
index 0000000..902029f
--- /dev/null
+++ b/libfonts_gethome__.c
@@ -0,0 +1,40 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+char *
+libfonts_gethome__(struct libfonts_context *ctx)
+{
+	uid_t uid = (ctx && ctx->use_context_uid) ? ctx->uid : getuid();
+	size_t size = 512;
+	char *buf = NULL, *new;
+	char *ret = NULL;
+	struct passwd pw, *pwp;
+	int err;
+
+	goto beginning;
+
+	do {
+		if (size > SIZE_MAX / 2)
+			goto enomem;
+		size *= 2;
+	beginning:
+		new = realloc(buf, size);
+		if (!new) {
+		enomem:
+			free(buf);
+			errno = ENOMEM;
+			return NULL;
+		}
+		buf = new;
+	} while ((err = getpwuid_r(uid, &pw, buf, size, &pwp)) == ERANGE);
+	if (err) {
+		free(buf);
+		return NULL;
+	}
+
+	if (pwp && pwp->pw_dir)
+		ret = strdup(pwp->pw_dir);
+	free(buf);
+	return ret;
+}
diff --git a/libfonts_used_environs.c b/libfonts_used_environs.c
new file mode 100644
index 0000000..54232b4
--- /dev/null
+++ b/libfonts_used_environs.c
@@ -0,0 +1,34 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+const char *const libfonts_used_environs[] = {
+	"LIBFONTS_DEFAULT_SANS_SERIF",
+	"LIBFONTS_DEFAULT_SERIF",
+	"LIBFONTS_DEFAULT_MONOSPACE",
+	"XDG_CONFIG_HOME",
+	"HOME",
+	NULL
+};
+
+
+#else
+
+
+int
+main(void)
+{
+	size_t i, j, n;
+	for (n = 0; n < 100; n++)
+		if (!libfonts_used_environs[n])
+			break;
+	ASSERT(n < 100);
+	for (i = 0; i < n; i++)
+		for (j = i + 1; j < n; j++)
+			ASSERT(strcmp(libfonts_used_environs[i], libfonts_used_environs[j]));
+	return 0;
+}
+
+
+#endif