Revamped the read_passwd_file function to resolve issue #114

Add support for mulitple access id/secret access keys in passwd-s3fs file

This change applies to any passwd-s3fs files.

The format of the file is more robust, error checked and extended:

  - as before, any line beginning with # is ignored
  - any empty line is ignored
  - any non-ignored line which contains a space or tab is an error
  - any non-ignored line which does not contain a : separator is an error
  
The format of the file is:

[bucket:]AccessKeyId:SecretAccessKey

The bucket can now be specified to allow for multiple credentials.
A default entry is as before:

AccessKeyId:SecretAccessKey

Only one default entry is allowed, if more than one default entry
is found, that is an error.  A default entry is not required, if the
bucket that is being mounted has its own entry.

If the user's .passwd-s3fs file is present but credentials cannot
be determined from it, then the system-wide /etc/passwd-s3fs will
be consulted (if readable by the current user).

This change is completely backward compatable with the existing
scheme and has been well tested.



git-svn-id: http://s3fs.googlecode.com/svn/trunk@229 df820570-a93a-0410-bd06-b72b767a4274

s3fs/configure.ac

@@ -1,7 +1,7 @@
 dnl Process this file with autoconf to produce a configure script.
 
 AC_PREREQ(2.59)
-AC_INIT(s3fs, 1.10)
+AC_INIT(s3fs, 1.11)
 
 
 AC_CANONICAL_SYSTEM

s3fs/src/s3fs.cpp

@@ -1581,26 +1581,81 @@ static int s3fs_utimens(const char *path, const struct timespec ts[2]) {
   return put_headers(path, meta);
 }
 
-// This function needs to be a little bit more
-// robust - add support for per bucket credentials
+//////////////////////////////////////////////////////////////////
+// read_passwd_file
+//
+// Support for per bucket credentials
+// 
+// Format for the credentials file:
+// [bucket:]AccessKeyId:SecretAccessKey
+// 
+// Lines beginning with # are considered comments
+// and ignored, as are empty lines
+//
+// Uncommented lines without the ":" character are flagged as
+// an error, so are lines with spaces or tabs
+//
+// only one default key pair is allowed, but not required
+//////////////////////////////////////////////////////////////////
 static void read_passwd_file (void) {
   string line;
+  string field1, field2, field3;
+  size_t first_pos = string::npos;
+  size_t last_pos = string::npos;
+  bool default_found = 0;
+
   ifstream PF(passwd_file.c_str());
   if (PF.good()) {
     while (getline(PF, line)) {
-        if (line[0]=='#')
+      if (line[0]=='#') {
         continue;
+      }
+      if (line.size() == 0) {
+        continue;
+      }
 
-          size_t pos = line.find(':');
-          if (pos != string::npos) {
-            if (AWSAccessKeyId.size() == 0) {
-              AWSAccessKeyId = line.substr(0, pos);
+      first_pos = line.find_first_of(" \t");
+      if (first_pos != string::npos) {
+        printf ("%s: invalid line in passwd file, found whitespace character\n", 
+           program_name.c_str());
+        exit(1);
       }
-            if (AWSSecretAccessKey.size() == 0) {
-              if (line.substr(0, pos) == AWSAccessKeyId) {
-                AWSSecretAccessKey = line.substr(pos + 1, string::npos);
+
+      first_pos = line.find_first_of(":");
+      if (first_pos == string::npos) {
+        printf ("%s: invalid line in passwd file, no \":\" separator found\n", 
+           program_name.c_str());
+        exit(1);
       }
+      last_pos = line.find_last_of(":");
+
+      if (first_pos != last_pos) {
+        // bucket specified
+        field1 = line.substr(0,first_pos);
+        field2 = line.substr(first_pos + 1, last_pos - first_pos - 1);
+        field3 = line.substr(last_pos + 1, string::npos);
+      } else {
+        // no bucket specified - original style - found default key
+        if (default_found == 1) {
+          printf ("%s: more than one default key pair found in passwd file\n", 
+            program_name.c_str());
+          exit(1);
         }
+        default_found = 1;
+        field1.assign("");
+        field2 = line.substr(0,first_pos);
+        field3 = line.substr(first_pos + 1, string::npos);
+        AWSAccessKeyId = field2;
+        AWSSecretAccessKey = field3;
+      }
+
+      // does the bucket we are mounting match this passwd file entry?
+      // if so, use that key pair, otherwise use the default key, if found,
+      // will be used
+      if (field1.size() != 0 && field1 == bucket) {
+         AWSAccessKeyId = field2;
+         AWSSecretAccessKey = field3;
+         break;
       }
     }
   }
@@ -1677,9 +1732,14 @@ static void get_access_keys (void) {
      if (PF.good()) {
        PF.close();
        read_passwd_file();
+       // It is possible that the user's file was there but
+       // contained no key pairs i.e. commented out
+       // in that case, go look in the final location
+       if (AWSAccessKeyId.size() > 0 && AWSSecretAccessKey.size() > 0) {
           return;
        }
      }
+   }
 
   // 5 - from the system default location
   passwd_file.assign("/etc/passwd-s3fs"); 
@@ -2017,11 +2077,12 @@ int main(int argc, char *argv[]) {
          program_name.c_str());
         exit(1);
      }
+     // More error checking on the access key pair can be done
+     // like checking for appropriate lengths and characters  
   }
 
   // There's room for more command line error checking
 
-
   s3fs_oper.getattr = s3fs_getattr;
   s3fs_oper.readlink = s3fs_readlink;
   s3fs_oper.mknod = s3fs_mknod;