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SubjectRe: [RFC-v3 07/12] iscsi-target: Add CHAP Authentication support using libcrypto
On Thu, 17 Mar 2011, Nicholas A. Bellinger wrote:

> From: Nicholas Bellinger <nab@linux-iscsi.org>
>

Minor nitpicks below.


> This patch adds support for libcrypto md5 based iSCSI CHAP authentication
> support for iscsi_target_mod. This includes support for mutual and one-way
> NodeACL authentication for SessionType=Normal and SessionType=Discovery
> via /sys/kernel/config/target/iscsi.
>
> Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
> ---
> drivers/target/iscsi/iscsi_target_auth.c | 500 ++++++++++++++++++++++++++++++
> drivers/target/iscsi/iscsi_target_auth.h | 33 ++
> 2 files changed, 533 insertions(+), 0 deletions(-)
> create mode 100644 drivers/target/iscsi/iscsi_target_auth.c
> create mode 100644 drivers/target/iscsi/iscsi_target_auth.h
>
> diff --git a/drivers/target/iscsi/iscsi_target_auth.c b/drivers/target/iscsi/iscsi_target_auth.c
> new file mode 100644
> index 0000000..d3711f4
> --- /dev/null
> +++ b/drivers/target/iscsi/iscsi_target_auth.c
> @@ -0,0 +1,500 @@
> +/*******************************************************************************
> + * This file houses the main functions for the iSCSI CHAP support
> + *
> + * ?? Copyright 2007-2011 RisingTide Systems LLC.

"??" ?


> +int chap_string_to_hex(unsigned char *dst, unsigned char *src, int len)
> +{
> + int i = 0, j = 0;
> +
> + for (i = 0; i < len; i += 2)

Initializing 'i' to zero twice is a little needless.


> +void chap_binaryhex_to_asciihex(char *dst, char *src, int src_len)
> +{
> + int i;
> +
> + for (i = 0; i < src_len; i++)

Do we still support compiler versions that don't understand 'for-scope'?

for (int i = 0; ...


> +void chap_set_random(char *data, int length)
> +{
> + long r;
> + unsigned n;
> +
> + while (length > 0) {
> +

Pointless newline IMHO.

> + get_random_bytes(&r, sizeof(long));
> + r = r ^ (r >> 8);
> + r = r ^ (r >> 4);
> + n = r & 0x7;
> +
> + get_random_bytes(&r, sizeof(long));
> + r = r ^ (r >> 8);
> + r = r ^ (r >> 5);
> + n = (n << 3) | (r & 0x7);
> +
> + get_random_bytes(&r, sizeof(long));
> + r = r ^ (r >> 8);
> + r = r ^ (r >> 5);
> + n = (n << 2) | (r & 0x3);
> +
> + *data++ = n;
> + length--;

Mixing space and tab in indentation here.


> +int chap_gen_challenge(
> + struct iscsi_conn *conn,
> + int caller,
> + char *C_str,
> + unsigned int *C_len)
> +{
> + unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
> + struct iscsi_chap *chap = (struct iscsi_chap *) conn->auth_protocol;
> +
> + memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
> +
> + chap_set_random(chap->challenge, CHAP_CHALLENGE_LENGTH);
> + chap_binaryhex_to_asciihex(challenge_asciihex, chap->challenge,
> + CHAP_CHALLENGE_LENGTH);
> + /*
> + * Set CHAP_C, and copy the generated challenge into C_str.
> + */
> + *C_len += sprintf(C_str + *C_len, "CHAP_C=0x%s", challenge_asciihex);
> + *C_len += 1;
> +
> + PRINT("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
> + challenge_asciihex);
> + return 0;

You only ever return '0', so why couldn't this function just return
'void'? - sorry, didn't bother to actually check how its used :-/


> +int chap_server_compute_md5(
> + struct iscsi_conn *conn,
> + struct iscsi_node_auth *auth,
> + char *NR_in_ptr,
> + char *NR_out_ptr,
> + unsigned int *NR_out_len)
> +{
> + char *endptr;
> + unsigned char id, digest[MD5_SIGNATURE_SIZE];
> + unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
> + unsigned char identifier[10], *challenge, *challenge_binhex;

If you changed the above line to

unsigned char identifier[10], *challenge;
unsigned char *challenge_binhex = 0;

> + unsigned char client_digest[MD5_SIGNATURE_SIZE];
> + unsigned char server_digest[MD5_SIGNATURE_SIZE];
> + unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
> + struct iscsi_chap *chap = (struct iscsi_chap *) conn->auth_protocol;
> + struct crypto_hash *tfm;
> + struct hash_desc desc;
> + struct scatterlist sg;
> + int auth_ret = -1, ret, challenge_len;
> +
> + memset(identifier, 0, 10);
> + memset(chap_n, 0, MAX_CHAP_N_SIZE);
> + memset(chap_r, 0, MAX_RESPONSE_LENGTH);
> + memset(digest, 0, MD5_SIGNATURE_SIZE);
> + memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
> + memset(client_digest, 0, MD5_SIGNATURE_SIZE);
> + memset(server_digest, 0, MD5_SIGNATURE_SIZE);
> +
> + challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
> + if (!(challenge)) {
> + printk(KERN_ERR "Unable to allocate challenge buffer\n");
> + return -1;

this could become "goto out;"

> + }
> +
> + challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
> + if (!(challenge_binhex)) {
> + printk(KERN_ERR "Unable to allocate challenge_binhex buffer\n");
> + kfree(challenge);
> + return -1;

and here the kfree() call could go away and the return be converted to
"goto out;".
kfree(0) is a no-op.

...
> + * One way authentication has succeeded, return now if mutual
> + * authentication is not enabled.
> + */
> + if (!auth->authenticate_target) {
> + kfree(challenge);
> + kfree(challenge_binhex);
> + return 0;

and here the two kfree() calls would also go away and "return 0" would be
replaced with

auth_ret = 0;
goto out;

...
> +out:
> + kfree(challenge);
> + kfree(challenge_binhex);
> + return auth_ret;
> +}

That would nicely consolidate *all* exits from the function in one
place.



> +
> +int chap_got_response(
> + struct iscsi_conn *conn,
> + struct iscsi_node_auth *auth,
> + char *NR_in_ptr,
> + char *NR_out_ptr,
> + unsigned int *NR_out_len)
> +{
> + struct iscsi_chap *chap = (struct iscsi_chap *) conn->auth_protocol;
> +
> + switch (chap->digest_type) {
> + case CHAP_DIGEST_MD5:
> + if (chap_server_compute_md5(conn, auth, NR_in_ptr,
> + NR_out_ptr, NR_out_len) < 0)
> + return -1;
> + break;
> + default:
> + printk(KERN_ERR "Unknown CHAP digest type %d!\n",
> + chap->digest_type);
> + return -1;
> + }
> +
> + return 0;

You could kill the 'return 0' and replace the 'break' above with 'return
0'. No difference in behaviour, but you'd save a few lines and it would be
just as readable IMHO.


--
Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please.



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