Fix segfault in s3 credential parsing

src/H5FDs3comms.c

@@ -1751,6 +1751,7 @@ H5FD__s3comms_load_aws_creds_from_file(FILE *file, const char *profile_name, cha
  unsigned setting_i = 0;
  int found_setting = 0;
  char *line_buffer = &(buffer[0]);
+ size_t end = 0;
 
  FUNC_ENTER_PACKAGE
 
@@ -1761,8 +1762,7 @@ H5FD__s3comms_load_aws_creds_from_file(FILE *file, const char *profile_name, cha
  /* look for start of profile */
  do {
  /* clear buffer */
- for (buffer_i = 0; buffer_i < 128; buffer_i++)
- buffer[buffer_i] = 0;
+ memset(buffer, 0, 128);
 
  line_buffer = fgets(line_buffer, 128, file);
  if (line_buffer == NULL) /* reached end of file */
@@ -1772,8 +1772,7 @@ H5FD__s3comms_load_aws_creds_from_file(FILE *file, const char *profile_name, cha
  /* extract credentials from lines */
  do {
  /* clear buffer */
- for (buffer_i = 0; buffer_i < 128; buffer_i++)
- buffer[buffer_i] = 0;
+ memset(buffer, 0, 128);
 
  /* collect a line from file */
  line_buffer = fgets(line_buffer, 128, file);
@@ -1812,10 +1811,11 @@ H5FD__s3comms_load_aws_creds_from_file(FILE *file, const char *profile_name, cha
  strncpy(setting_pointers[setting_i], (const char *)line_buffer, strlen(line_buffer));
 
  /* "trim" tailing whitespace by replacing with null terminator*/
- buffer_i = 0;
- while (!isspace(setting_pointers[setting_i][buffer_i]))
- buffer_i++;
- setting_pointers[setting_i][buffer_i] = '\0';
+ end = strlen(line_buffer) - 1;
+ while (end >= 0 && isspace((unsigned char)setting_pointers[setting_i][end])) {
+ setting_pointers[setting_i][end] = '\0';
+ end--;
+ }
 
  break; /* have read setting; don't compare with others */
  } /* end if possible name match */