[PATCH] notmuch-config: replace config reading function

[Ioan-Adrian Ratiu]

Config files are currently read using glib's g_key_file_load_from_file
function which is very inconvenient because it's limited by design to read
only from "regular data files" in a filesystem. Because of this limitation
notmuch can't read configs from pipes, fifos, sockets, stdin, etc. Not even
"notmuch --config=/dev/stdin" works:

Error reading configuration file /dev/stdin: Not a regular file

So replace g_key_file_load_from_file with g_key_file_load_from_data which
gives us much more freedom to read configs from multiple sources.

This also helps the more security sensitive users: If someone has private
information in the config file, it can be encrypted on disk, then decrypted
in RAM and passed through a pipe directly to notmuch without the use of
intermediate plain text files.

Signed-off-by: Ioan-Adrian Ratiu <adi at adirat.com>
---
 notmuch-config.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 59 insertions(+), 4 deletions(-)

diff --git a/notmuch-config.c b/notmuch-config.c
index e5d42a0..8435815 100644
--- a/notmuch-config.c
+++ b/notmuch-config.c
@@ -202,6 +202,64 @@ get_username_from_passwd_file (void *ctx)
     return name;
 }
 
+static gboolean
+get_config_from_file (notmuch_config_t *config, GError **error)
+{
+    #define BUF_SIZE 4096
+    char buffer[BUF_SIZE];
+    size_t content_size = 1; // includes NULL
+
+    FILE *fp = fopen(config->filename, "r");
+    if (fp == NULL) {
+	*error = g_error_new(G_FILE_ERROR,
+			     G_FILE_ERROR_NOENT,
+			     "Couldn't open config file '%s': %s.\n",
+			     config->filename,
+			     strerror(errno));
+	return FALSE;
+    }
+
+    char *config_str = talloc_zero_array (config, char, BUF_SIZE);
+    if (config_str == NULL)
+    {
+	*error = g_error_new(G_FILE_ERROR,
+			     G_FILE_ERROR_NOMEM,
+			     "Out of memory while reading config.\n");
+	return FALSE;
+    }
+
+    while (fgets (buffer, BUF_SIZE, fp))
+    {
+	content_size += strlen(buffer);
+	config_str = talloc_realloc(config, config_str, char, content_size);
+	if (config_str == NULL)
+	{
+	    *error = g_error_new(G_FILE_ERROR,
+				 G_FILE_ERROR_NOMEM,
+				 "Failed to reallocate config memory.\n");
+	    return FALSE;
+	}
+	strcat (config_str, buffer);
+    }
+
+    if (ferror (fp))
+    {
+	*error = g_error_new(G_FILE_ERROR,
+			     G_FILE_ERROR_IO,
+			     "I/O error reading configuration from '%s'.\n",
+			     config->filename);
+	return FALSE;
+    }
+
+    fclose(fp);
+
+    return g_key_file_load_from_data (config->key_file,
+				      config_str,
+				      strlen(config_str),
+				      G_KEY_FILE_KEEP_COMMENTS,
+				      error);
+}
+
 /* Open the named notmuch configuration file. If the filename is NULL,
  * the value of the environment variable $NOTMUCH_CONFIG will be used.
  * If $NOTMUCH_CONFIG is unset, the default configuration file
@@ -289,10 +347,7 @@ notmuch_config_open (void *ctx,
     config->search_exclude_tags_length = 0;
     config->crypto_gpg_path = NULL;
 
-    if (! g_key_file_load_from_file (config->key_file,
-				     config->filename,
-				     G_KEY_FILE_KEEP_COMMENTS,
-				     &error))
+    if (! get_config_from_file (config, &error))
     {
 	if (error->domain == G_FILE_ERROR && error->code == G_FILE_ERROR_NOENT) {
 	    /* If create_new is true, then the caller is prepared for a
-- 
2.10.2