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When parsing, reject >1024-bit RSA private keys sooner.

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Private-key validation is fairly expensive for long keys in openssl,
so we need to avoid it sooner.
This commit is contained in:
Nick Mathewson 2020-02-05 11:11:35 -05:00
parent 41d52e9cd8
commit 9e1085c924
5 changed files with 49 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/feature/dirparse/parsecommon.c
View File

@ -389,7 +389,8 @@ get_next_token(memarea_t *area,
RET_ERR("Couldn't parse public key.");
} else if (!strcmp(tok->object_type, "RSA PRIVATE KEY")) { /* private key */
tok->key = crypto_pk_new();
if (crypto_pk_read_private_key_from_string(tok->key, obstart, eol-obstart))
if (crypto_pk_read_private_key1024_from_string(tok->key,
obstart, eol-obstart))
RET_ERR("Couldn't parse private key.");
} else { /* If it's something else, try to base64-decode it */
int r;

27
src/lib/crypt_ops/crypto_rsa.c
View File

@ -490,7 +490,7 @@ crypto_pk_write_private_key_to_string(crypto_pk_t *env,
static int
crypto_pk_read_from_string_generic(crypto_pk_t *env, const char *src,
size_t len, int severity,
bool private_key)
bool private_key, int max_bits)
{
if (len == (size_t)-1) // "-1" indicates "use the length of the string."
len = strlen(src);
@ -510,7 +510,7 @@ crypto_pk_read_from_string_generic(crypto_pk_t *env, const char *src,
}
crypto_pk_t *pk = private_key
? crypto_pk_asn1_decode_private((const char*)buf, n)
? crypto_pk_asn1_decode_private((const char*)buf, n, max_bits)
: crypto_pk_asn1_decode((const char*)buf, n);
if (! pk) {
log_fn(severity, LD_CRYPTO,
@ -539,7 +539,8 @@ int
crypto_pk_read_public_key_from_string(crypto_pk_t *env,
const char *src, size_t len)
{
return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, false);
return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, false,
-1);
}
/** Read a PEM-encoded private key from the <b>len</b>-byte string <b>src</b>
@ -550,7 +551,21 @@ int
crypto_pk_read_private_key_from_string(crypto_pk_t *env,
const char *src, ssize_t len)
{
return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, true);
return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, true,
-1);
}
/**
* As crypto_pk_read_private_key_from_string(), but reject any key
* with a modulus longer than 1024 bits before doing any expensive
* validation on it.
*/
int
crypto_pk_read_private_key1024_from_string(crypto_pk_t *env,
const char *src, ssize_t len)
{
return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, true,
1024);
}
/** If a file is longer than this, we won't try to decode its private key */
@ -578,7 +593,7 @@ crypto_pk_read_private_key_from_filename(crypto_pk_t *env,
}
int rv = crypto_pk_read_from_string_generic(env, buf, (ssize_t)st.st_size,
LOG_WARN, true);
LOG_WARN, true, -1);
if (rv < 0) {
log_warn(LD_CRYPTO, "Unable to decode private key from file %s",
escaped(keyfile));
@ -662,7 +677,7 @@ crypto_pk_base64_decode_private(const char *str, size_t len)
goto out;
}
pk = crypto_pk_asn1_decode_private(der, der_len);
pk = crypto_pk_asn1_decode_private(der, der_len, -1);
out:
memwipe(der, 0, len+1);

5
src/lib/crypt_ops/crypto_rsa.h
View File

@ -61,6 +61,8 @@ int crypto_pk_read_public_key_from_string(crypto_pk_t *env,
const char *src, size_t len);
int crypto_pk_read_private_key_from_string(crypto_pk_t *env,
const char *s, ssize_t len);
int crypto_pk_read_private_key1024_from_string(crypto_pk_t *env,
const char *src, ssize_t len);
int crypto_pk_write_private_key_to_filename(crypto_pk_t *env,
const char *fname);
@ -95,7 +97,8 @@ int crypto_pk_asn1_encode(const crypto_pk_t *pk, char *dest, size_t dest_len);
crypto_pk_t *crypto_pk_asn1_decode(const char *str, size_t len);
int crypto_pk_asn1_encode_private(const crypto_pk_t *pk,
char *dest, size_t dest_len);
crypto_pk_t *crypto_pk_asn1_decode_private(const char *str, size_t len);
crypto_pk_t *crypto_pk_asn1_decode_private(const char *str, size_t len,
int max_bits);
int crypto_pk_get_fingerprint(crypto_pk_t *pk, char *fp_out,int add_space);
int crypto_pk_get_hashed_fingerprint(crypto_pk_t *pk, char *fp_out);
void crypto_add_spaces_to_fp(char *out, size_t outlen, const char *in);

14
src/lib/crypt_ops/crypto_rsa_nss.c
View File

@ -679,9 +679,12 @@ crypto_pk_asn1_encode_private(const crypto_pk_t *pk,
/** Given a buffer containing the DER representation of the
* private key <b>str</b>, decode and return the result on success, or NULL
* on failure.
*
* If <b>max_bits</b> is nonnegative, reject any key longer than max_bits
* without performing any expensive validation on it.
*/
crypto_pk_t *
crypto_pk_asn1_decode_private(const char *str, size_t len)
crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits)
{
tor_assert(str);
tor_assert(len < INT_MAX);
@ -731,6 +734,15 @@ crypto_pk_asn1_decode_private(const char *str, size_t len)
output = NULL;
}
if (output) {
const int bits = SECKEY_PublicKeyStrengthInBits(output->pubkey);
if (max_bits > 0 && bits > max_bits) {
log_info(LD_CRYPTO, "Private key longer than expected.");
crypto_pk_free(output);
output = NULL;
}
}
if (slot)
PK11_FreeSlot(slot);

11
src/lib/crypt_ops/crypto_rsa_openssl.c
View File

@ -566,9 +566,12 @@ crypto_pk_asn1_encode_private(const crypto_pk_t *pk, char *dest,
/** Decode an ASN.1-encoded private key from <b>str</b>; return the result on
* success and NULL on failure.
*
* If <b>max_bits</b> is nonnegative, reject any key longer than max_bits
* without performing any expensive validation on it.
*/
crypto_pk_t *
crypto_pk_asn1_decode_private(const char *str, size_t len)
crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits)
{
RSA *rsa;
unsigned char *buf;
@ -578,7 +581,11 @@ crypto_pk_asn1_decode_private(const char *str, size_t len)
rsa = d2i_RSAPrivateKey(NULL, &cp, len);
tor_free(buf);
if (!rsa) {
crypto_openssl_log_errors(LOG_WARN,"decoding public key");
crypto_openssl_log_errors(LOG_WARN,"decoding private key");
return NULL;
}
if (max_bits >= 0 && RSA_bits(rsa) > max_bits) {
log_info(LD_CRYPTO, "Private key longer than expected.");
return NULL;
}
crypto_pk_t *result = crypto_new_pk_from_openssl_rsa_(rsa);