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#include "jwt.h"
#include <dynstr.h>
#include <sodium.h>
#include <errno.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define VARIANT sodium_base64_VARIANT_URLSAFE
static char *get_payload(const char *const name)
{
char *ret = NULL, *s = NULL;
struct dynstr d;
dynstr_init(&d);
if (dynstr_append(&d, "{\"name\": \"%s\"}", name))
{
fprintf(stderr, "%s: dynstr_append name failed\n", __func__);
goto end;
}
const size_t n = sodium_base64_encoded_len(d.len, VARIANT);
const unsigned char *const in = (const unsigned char *)d.str;
if (!(s = malloc(n)))
{
fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
goto end;
}
else if (!sodium_bin2base64(s, n, in, d.len, VARIANT))
{
fprintf(stderr, "%s: sodium_bin2base64 failed\n", __func__);
goto end;
}
ret = s;
end:
if (!ret)
free(s);
dynstr_free(&d);
return ret;
}
static char *get_hmac(const void *const buf, const size_t n,
const void *const key, const size_t keyn)
{
unsigned char hmac[crypto_auth_hmacsha256_KEYBYTES];
char *ret = NULL;
if (keyn != crypto_auth_hmacsha256_KEYBYTES)
{
fprintf(stderr, "%s: invalid key size (%zu), expected %u\n", __func__,
n, crypto_auth_hmacsha256_KEYBYTES);
goto failure;
}
else if (crypto_auth_hmacsha256(hmac, buf, n, key))
{
fprintf(stderr, "%s: HMAC failed\n", __func__);
goto failure;
}
const size_t b64n = sodium_base64_encoded_len(sizeof hmac, VARIANT);
if (!(ret = malloc(b64n)))
{
fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
goto failure;
}
else if (!sodium_bin2base64(ret, b64n, hmac, sizeof hmac, VARIANT))
{
fprintf(stderr, "%s: sodium_bin2base64 failed\n", __func__);
goto failure;
}
return ret;
failure:
free(ret);
return NULL;
}
char *jwt_encode(const char *const name, const void *const key, const size_t n)
{
static const char jwt_header[] = "{\"alg\": \"HS256\", \"typ\": \"JWT\"}";
struct dynstr jwt;
const size_t hlen = strlen(jwt_header),
sz = sodium_base64_encoded_len(hlen, VARIANT);
char *ret = NULL, *header = NULL, *hmac = NULL,
*const payload = get_payload(name);
dynstr_init(&jwt);
if (!payload)
{
fprintf(stderr, "%s: get_payload failed\n", __func__);
goto end;
}
else if (!(header = malloc(sz)))
{
fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
goto end;
}
else if (!sodium_bin2base64(header, sz, (const unsigned char *)jwt_header,
hlen, VARIANT))
{
fprintf(stderr, "%s: sodium_bin2base64 failed\n", __func__);
goto end;
}
else if (dynstr_append(&jwt, "%s.%s", header, payload))
{
fprintf(stderr, "%s: dynstr_append header+payload failed", __func__);
goto end;
}
else if (!(hmac = get_hmac(jwt.str, jwt.len, key, n)))
{
fprintf(stderr, "%s: get_hmac failed\n", __func__);
goto end;
}
else if (dynstr_append(&jwt, ".%s", hmac))
{
fprintf(stderr, "%s: dynstr_append hmac failed\n", __func__);
goto end;
}
ret = jwt.str;
end:
free(header);
free(payload);
free(hmac);
if (!ret)
dynstr_free(&jwt);
return ret;
}
int jwt_check(const char *const jwt, const void *const key,
const size_t n)
{
const char *const p = strrchr(jwt, '.');
const unsigned char *const in = (const unsigned char *)jwt;
unsigned char hmac[crypto_auth_hmacsha256_KEYBYTES];
if (n != crypto_auth_hmacsha256_KEYBYTES)
{
fprintf(stderr, "%s: invalid key size (%zu), expected %u\n", __func__,
n, crypto_auth_hmacsha256_KEYBYTES);
return -1;
}
else if (!p)
{
fprintf(stderr, "%s: expected '.'\n", __func__);
return 1;
}
else if (sodium_base642bin(hmac, sizeof hmac, p + 1, strlen(p + 1),
NULL, NULL, NULL, VARIANT))
{
fprintf(stderr, "%s: sodium_base642bin failed\n", __func__);
return 1;
}
else if (crypto_auth_hmacsha256_verify(hmac, in, p - jwt, key))
return 1;
return 0;
}
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