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HMAC signing for http push #5

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HMAC signing for http push #5

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9d0572d
Added nodewatcher-agent development section to README.
redmoo Jun 26, 2017
0009463
Updated README styling.
redmoo Jun 27, 2017
a44c43e
Added commit hash warning and subsections to README.
redmoo Jun 27, 2017
8304689
Added LEDE repository link.
redmoo Jun 27, 2017
8f92420
Merge branch 'master' into development
redmoo Jul 21, 2017
da088ef
HMAC signing for http push using OpenSSL.
redmoo Jul 21, 2017
9489e58
Separate HMAC code block, HMAC key setting, variable renaming.
redmoo Jul 21, 2017
8453843
Hmac implementation, temporary sha256, updated http_push module.
redmoo Jul 23, 2017
7abca81
Style changes, variable renaming.
redmoo Jul 24, 2017
7e13185
Added missing licence to new files.
redmoo Jul 24, 2017
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54 changes: 43 additions & 11 deletions modules/http_push.c
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@

#include <syslog.h>
#include <curl.h>
#include <openssl/hmac.h>
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Is there some smaller HMAC implementation available? We don't want to depend on OpenSSL.

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Yeah, will look around if there's something appropriate and ask here if that's ok.


/* Timestamp when last successful push occurred. */
static time_t last_push_at = 0;
Expand Down Expand Up @@ -49,6 +50,7 @@ static int nw_http_push_start_acquire_data(struct nodewatcher_module *module,

/* Get the configured URL from UCI. */
char *url = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_url");

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Why this empty line?

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Readability habit I guess... You want me to stop doing that or just wanted an explanation? :)

if (url) {
/* Collect all the module data and perform the push. */
json_object *data = nw_module_get_output();
Expand All @@ -61,30 +63,60 @@ static int nw_http_push_start_acquire_data(struct nodewatcher_module *module,
/* Default. */
timeout = 5;
}

const char* data_string = json_object_to_json_string(data); // TODO: const?

curl_easy_setopt(curl, CURLOPT_TIMEOUT, timeout);
curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1);
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_POST, 1);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json_object_to_json_string(data));
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data_string);

#if LIBCURL_VERSION_NUM >= 0x072700
/* Pin server-side public key when configured. */
char *server_pubkey = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_server_pubkey");
char *auth_type = nw_uci_get_string(uci, "nodewatcher.@agent[0].authentication_method");
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I would rename this to push_authentication_method.

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Will do.


if (server_pubkey) {
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, server_pubkey);
if (strcmp(auth_type, "hmac") == 0) {
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Why is this inslide if (server_pubkey) block? It should be possible to configure no public key, only an HMAC (secret) key.

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Ohhh... My bad. Will add another option and separate block.

unsigned char *hmac_result = HMAC(EVP_sha256(), server_pubkey, strlen(server_pubkey), (unsigned char *)data_string, strlen(data_string), NULL, NULL);
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I see, so you are using server_pubkey as the secret key for HMAC. This is not good, you should instead introduce a new configuration option for this new key.

char signature[((strlen((char *)hmac_result)+2)/3)*4];

if (nw_base64_encode(hmac_result, strlen((char *)hmac_result), signature, sizeof(signature)) == 0) {
char sig_dest[26+sizeof(signature)];
strcat(strcpy(sig_dest, "X-Nodewatcher-Signature: "), signature);

struct curl_slist *chunk = NULL;
chunk = curl_slist_append(chunk, "X-Nodewatcher-Signature-Algorithm: hmac-sha256");
chunk = curl_slist_append(chunk, sig_dest);
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
}

free(hmac_result);

} else {
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, server_pubkey);
}

free(server_pubkey);
free(auth_type);
}
#endif

/* Setup client authentication when configured. */
char *client_certificate = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_certificate");
char *client_key = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_key");
if (client_certificate && client_key) {
curl_easy_setopt(curl, CURLOPT_SSLCERT, client_certificate);
curl_easy_setopt(curl, CURLOPT_SSLKEY, client_key);
}
if (strcmp(auth_type, "hmac") != 0) {
char *client_certificate = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_certificate");
char *client_key = nw_uci_get_string(uci, "nodewatcher.@agent[0].push_client_key");

free(client_certificate);
free(client_key);
if (client_certificate && client_key) {
curl_easy_setopt(curl, CURLOPT_SSLCERT, client_certificate);
curl_easy_setopt(curl, CURLOPT_SSLKEY, client_key);
}

free(client_certificate);
free(client_key);
}

/* Provide a buffer to store errors in. */
char errbuf[CURL_ERROR_SIZE];
Expand Down