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paseto_v2_public.c
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paseto_v2_public.c
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#include "paseto.h"
#include "helpers.h"
#include <sodium.h>
#include <string.h>
#include <errno.h>
paseto_static_assert(
paseto_v2_PUBLIC_PUBLICKEYBYTES == crypto_sign_PUBLICKEYBYTES,
"PUBLICKEYBYTES mismatch");
paseto_static_assert(
paseto_v2_PUBLIC_SECRETKEYBYTES == crypto_sign_SECRETKEYBYTES,
"SECRETKEYBYTES mismatch");
static const uint8_t header[] = "v2.public.";
static const size_t header_len = sizeof(header) - 1;
static const size_t signature_len = crypto_sign_BYTES;
bool paseto_v2_public_load_public_key_hex(
uint8_t key[paseto_v2_PUBLIC_PUBLICKEYBYTES],
const char *key_hex) {
return key_load_hex(key, paseto_v2_PUBLIC_PUBLICKEYBYTES, key_hex);
}
bool paseto_v2_public_load_public_key_base64(
uint8_t key[paseto_v2_PUBLIC_PUBLICKEYBYTES],
const char *key_base64) {
return key_load_base64(key, paseto_v2_PUBLIC_PUBLICKEYBYTES, key_base64);
}
bool paseto_v2_public_load_secret_key_hex(
uint8_t key[paseto_v2_PUBLIC_SECRETKEYBYTES],
const char *key_hex) {
return key_load_hex(key, paseto_v2_PUBLIC_SECRETKEYBYTES, key_hex);
}
bool paseto_v2_public_load_secret_key_base64(
uint8_t key[paseto_v2_PUBLIC_SECRETKEYBYTES],
const char *key_base64) {
return key_load_base64(key, paseto_v2_PUBLIC_SECRETKEYBYTES, key_base64);
}
char *paseto_v2_public_sign(
const uint8_t *message, size_t message_len,
const uint8_t key[paseto_v2_LOCAL_KEYBYTES],
const uint8_t *footer, size_t footer_len) {
if (!message || !key) {
errno = EINVAL;
return NULL;
}
if (!footer) footer_len = 0;
if (!footer_len) footer = NULL;
const size_t to_encode_len = message_len + signature_len;
uint8_t *to_encode = malloc(to_encode_len);
if (!to_encode) {
errno = ENOMEM;
return NULL;
}
memcpy(to_encode, message, message_len);
struct pre_auth pa;
if (!pre_auth_init(&pa, 3, header_len + message_len + footer_len)) {
free(to_encode);
errno = ENOMEM;
return NULL;
}
pre_auth_append(&pa, header, header_len);
pre_auth_append(&pa, message, message_len);
pre_auth_append(&pa, footer, footer_len);
size_t pre_auth_len = pa.current - pa.base;
uint8_t *ct = to_encode + message_len;
crypto_sign_detached(ct, NULL, pa.base, pre_auth_len, key);
free(pa.base);
size_t encoded_len = sodium_base64_ENCODED_LEN(to_encode_len,
sodium_base64_VARIANT_URLSAFE_NO_PADDING) - 1; // minus included trailing NULL byte
size_t output_len = header_len + encoded_len;
if (footer) output_len += sodium_base64_ENCODED_LEN(footer_len,
sodium_base64_VARIANT_URLSAFE_NO_PADDING) - 1 + 1; // minus included NULL byte, plus '.' separator
output_len += 1; // trailing NULL byte
char *output = malloc(output_len);
char *output_current = output;
size_t output_len_remaining = output_len;
if (!output) {
free(to_encode);
errno = ENOMEM;
return NULL;
}
memcpy(output_current, header, header_len);
output_current += header_len;
output_len_remaining -= header_len;
sodium_bin2base64(
output_current, output_len_remaining,
to_encode, to_encode_len,
sodium_base64_VARIANT_URLSAFE_NO_PADDING);
encoded_len = strlen(output_current);
output_current += encoded_len;
output_len_remaining -= encoded_len;
free(to_encode);
if (footer) {
*output_current++ = '.';
output_len_remaining--;
sodium_bin2base64(
output_current, output_len_remaining,
footer, footer_len,
sodium_base64_VARIANT_URLSAFE_NO_PADDING);
}
return output;
}
uint8_t *paseto_v2_public_verify(
const char *encoded, size_t *message_len,
const uint8_t key[paseto_v2_LOCAL_KEYBYTES],
uint8_t **footer, size_t *footer_len) {
if (!encoded || !message_len || !key) {
errno = EINVAL;
return NULL;
}
if (strlen(encoded) < header_len + sodium_base64_ENCODED_LEN(
signature_len, sodium_base64_VARIANT_URLSAFE_NO_PADDING) - 1
|| memcmp(encoded, header, header_len) != 0) {
errno = EINVAL;
return NULL;
}
encoded += header_len;
size_t encoded_len = strlen(encoded);
const char *encoded_end = strchr(encoded, '.');
if (!encoded_end) encoded_end = encoded + encoded_len;
const size_t decoded_maxlen = encoded_end - encoded;
uint8_t *decoded = malloc(decoded_maxlen);
if (!decoded) {
errno = ENOMEM;
return NULL;
}
size_t decoded_len;
const char *encoded_footer;
if (sodium_base642bin(
decoded, decoded_maxlen,
encoded, encoded_len,
NULL, &decoded_len,
&encoded_footer,
sodium_base64_VARIANT_URLSAFE_NO_PADDING) != 0) {
free(decoded);
errno = EINVAL;
return NULL;
}
const size_t internal_message_len = decoded_len - signature_len;
const uint8_t *signature = decoded + internal_message_len;
size_t encoded_footer_len = strlen(encoded_footer);
uint8_t *decoded_footer = NULL;
size_t decoded_footer_len = 0;
if (encoded_footer_len > 1) {
// footer present and one or more bytes long
// skip '.'
encoded_footer_len--;
encoded_footer++;
decoded_footer = malloc(encoded_footer_len);
if (sodium_base642bin(
decoded_footer, encoded_len - decoded_len,
encoded_footer, encoded_footer_len,
NULL, &decoded_footer_len,
NULL,
sodium_base64_VARIANT_URLSAFE_NO_PADDING) != 0) {
free(decoded);
free(decoded_footer);
errno = EINVAL;
return NULL;
}
}
struct pre_auth pa;
if (!pre_auth_init(&pa, 3,
header_len + internal_message_len + decoded_footer_len)) {
free(decoded);
free(decoded_footer);
errno = ENOMEM;
return NULL;
}
pre_auth_append(&pa, header, header_len);
pre_auth_append(&pa, decoded, internal_message_len);
pre_auth_append(&pa, decoded_footer, decoded_footer_len);
size_t pre_auth_len = pa.current - pa.base;
uint8_t *message = malloc(internal_message_len + 1);
if (!message) {
free(decoded);
free(decoded_footer);
free(pa.base);
errno = ENOMEM;
return NULL;
}
if (crypto_sign_verify_detached(
signature, pa.base, pre_auth_len, key) != 0) {
free(decoded);
free(decoded_footer);
free(pa.base);
free(message);
errno = EINVAL;
return NULL;
}
memcpy(message, decoded, internal_message_len);
message[internal_message_len] = '\0';
free(pa.base);
free(decoded);
if (decoded_footer && footer && footer_len) {
uint8_t *internal_footer = malloc(decoded_footer_len + 1);
if (!internal_footer) {
free(decoded_footer);
free(message);
errno = ENOMEM;
return NULL;
}
memcpy(internal_footer, decoded_footer, decoded_footer_len);
internal_footer[decoded_footer_len] = '\0';
*footer = internal_footer;
*footer_len = decoded_footer_len;
} else {
if (footer) *footer = NULL;
if (footer_len) *footer_len = 0;
}
free(decoded_footer);
*message_len = internal_message_len;
return message;
}