[lxc-devel] [PATCH] Validate container name during creation

[Robert Vogelgesang]

Hello,

On Thu, Feb 05, 2015 at 05:50:39PM +0200, Joel Nider wrote:
> The name used to identify the container on the host is also used as the 
> host
> name of the container itself. Therefore, the name should be restricted to 
> a
> legal Linux hostname, which is specified in RFC 1123

no, this should not be the job of the lxc create API, IMHO.
It's the template script that re-uses the container name as the
container's hostname, so it should be the template's job to ensure
the name conforms to the rules.

I don't mind checking the value of the configuration item lxc.utsname,
which actually defines the container's hostname, according to the
RFC 1123 rules, but please don't do this for the container's name.

	Robert

> (http://tools.ietf.org/html/rfc1123#page-13). Basically it says the host 
> name
> is composed of up to 63 alphanumeric ASCII characters (case insensitive) 
> as
> well as '-'.
> 
> See this thread for more details:
> https://lists.linuxcontainers.org/pipermail/lxc-devel/2014-December/011007.html
> 
> Signed-off-by: Joel Nider <joeln at il.ibm.com>
> ---
>  src/lxc/lxccontainer.c | 42 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> index e02ee93..7cba771 100644
> --- a/src/lxc/lxccontainer.c
> +++ b/src/lxc/lxccontainer.c
> @@ -36,6 +36,7 @@
>  #include <stdint.h>
>  #include <grp.h>
>  #include <sys/syscall.h>
> +#include <ctype.h>
> 
>  #include <lxc/lxccontainer.h>
>  #include <lxc/version.h>
> @@ -66,7 +67,7 @@
>  #endif
> 
>  #define MAX_BUFFER 4096
> -
> +#define MAX_LENGTH_HOSTNAME 63
>  #define NOT_SUPPORTED_ERROR "the requested function %s is not currently 
> supported with unprivileged containers"
> 
>  /* Define faccessat() if missing from the C library */
> @@ -190,6 +191,37 @@ static void remove_partial(struct lxc_container *c, 
> int fd)
>                 SYSERROR("Error unlink partial file %s", path);
>  }
> 
> +/* Ensure requested hostname follows RFC 1123
> + * In our case, that means simple host name (not FQDN)
> + * characters in the set {[A-Z], [0-9], '-'} (no '.')
> + * maximum length of 63 characters
> + */
> +static int validate_hostname(struct lxc_container *c)
> +{
> +   char *a;
> +   int count = 0;
> +
> +   if (!c)
> +      return MAX_LENGTH_HOSTNAME;
> +
> +   a = c->name;
> +   while (*a) {
> +      count++;
> +      if (count > MAX_LENGTH_HOSTNAME)
> +         return MAX_LENGTH_HOSTNAME;
> +
> +      if (!(isalnum(*a) | (*a == '-')))
> +         return count;
> +
> +     a++;
> +   }
> +
> +   if (count == 0)
> +      return MAX_LENGTH_HOSTNAME;
> +
> +   return 0;
> +}
> +
>  /* LOCKING
>   * 1. container_mem_lock(c) protects the struct lxc_container from 
> multiple threads.
>   * 2. container_disk_lock(c) protects the on-disk container data - in 
> particular the
> @@ -1235,6 +1267,7 @@ static bool lxcapi_create(struct lxc_container *c, 
> const char *t,
>         pid_t pid;
>         char *tpath = NULL;
>         int partial_fd;
> +   int err;
> 
>         if (!c)
>                 return false;
> @@ -1247,6 +1280,13 @@ static bool lxcapi_create(struct lxc_container *c, 
> const char *t,
>                 }
>         }
> 
> +   /* validate the container name */
> +   err = validate_hostname(c);
> +   if (err) {
> +      ERROR("Invalid hostname: %s (character %i)", c->name, err);
> +      goto out;
> +   }
> +
>         /*
>          * If a template is passed in, and the rootfs already is defined 
> in
>          * the container config and exists, then * caller is trying to 
> create
> --
> 1.9.1
> 
> 
> 
> Joel Nider
> Virtualization Research
> IBM Research and Development
> Haifa Research Lab
> 
> Phone: 972-4-829-6326 | Mobile: 972-54-3155635
> E-mail: JOELN at il.ibm.com
> 
> 
> 
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