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Add a sanity check on the length of pkeyutl inputs

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When signing or verifying a file using pkeyutl the input is supposed to
be a hash. Some algorithms sanity check the length of the input, while
others don't and silently truncate. To avoid accidents we check that the
length of the input looks sane.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6284)
This commit is contained in:
Matt Caswell 2018-05-17 12:53:07 +01:00
parent 07824f304a
commit a0abb6a10f
3 changed files with 40 additions and 21 deletions
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4
CHANGES
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@ -8,6 +8,10 @@
release branch.
Changes between 1.1.0h and 1.1.1 [xx XXX xxxx]
*) Enforce checking in the pkeyutl command line app to ensure that the input
length does not exceed the maximum supported digest length when performing
a sign, verify or verifyrecover operation.
[Matt Caswell]
*) SSL_MODE_AUTO_RETRY is enabled by default. Applications that use blocking
I/O in combination with something like select() or poll() will hang. This

12
apps/pkeyutl.c
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@ -282,7 +282,7 @@ int pkeyutl_main(int argc, char **argv)
buf_inlen = bio_to_mem(&buf_in, keysize * 10, in);
if (buf_inlen < 0) {
BIO_printf(bio_err, "Error reading input Data\n");
exit(1);
goto end;
}
if (rev) {
size_t i;
@ -296,6 +296,16 @@ int pkeyutl_main(int argc, char **argv)
}
}
/* Sanity check the input */
if (buf_inlen > EVP_MAX_MD_SIZE
&& (pkey_op == EVP_PKEY_OP_SIGN
|| pkey_op == EVP_PKEY_OP_VERIFY
|| pkey_op == EVP_PKEY_OP_VERIFYRECOVER)) {
BIO_printf(bio_err,
"Error: The input data looks too long to be a hash\n");
goto end;
}
if (pkey_op == EVP_PKEY_OP_VERIFY) {
rv = EVP_PKEY_verify(ctx, sig, (size_t)siglen,
buf_in, (size_t)buf_inlen);

45
doc/man1/pkeyutl.pod
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@ -38,8 +38,8 @@ B<openssl> B<pkeyutl>
=head1 DESCRIPTION
The B<pkeyutl> command can be used to perform public key operations using
any supported algorithm.
The B<pkeyutl> command can be used to perform low level public key operations
using any supported algorithm.
=head1 OPTIONS
@ -99,17 +99,17 @@ Reverse the order of the input buffer. This is useful for some libraries
=item B<-sign>
Sign the input data and output the signed result. This requires
a private key.
Sign the input data (which must be a hash) and output the signed result. This
requires a private key.
=item B<-verify>
Verify the input data against the signature file and indicate if the
verification succeeded or failed.
Verify the input data (which must be a hash) against the signature file and
indicate if the verification succeeded or failed.
=item B<-verifyrecover>
Verify the input data and output the recovered data.
Verify the input data (which must be a hash) and output the recovered data.
=item B<-encrypt>
@ -184,20 +184,25 @@ and its implementation. The OpenSSL operations and options are indicated below.
Unless otherwise mentioned all algorithms support the B<digest:alg> option
which specifies the digest in use for sign, verify and verifyrecover operations.
The value B<alg> should represent a digest name as used in the
EVP_get_digestbyname() function for example B<sha1>.
This value is used only for sanity-checking the lengths of data passed in to
the B<pkeyutl> and for creating the structures that make up the signature
(e.g. B<DigestInfo> in RSASSA PKCS#1 v1.5 signatures).
In case of RSA, ECDSA and DSA signatures, this utility
will not perform hashing on input data but rather use the data directly as
input of signature algorithm. Depending on key type, signature type and mode
of padding, the maximum acceptable lengths of input data differ. In general,
with RSA the signed data can't be longer than the key modulus, in case of ECDSA
and DSA the data shouldn't be longer than field size, otherwise it will be
silently truncated to field size.
EVP_get_digestbyname() function for example B<sha1>. This value is not used to
hash the input data. It is used (by some algorithms) for sanity-checking the
lengths of data passed in to the B<pkeyutl> and for creating the structures that
make up the signature (e.g. B<DigestInfo> in RSASSA PKCS#1 v1.5 signatures).
In other words, if the value of digest is B<sha1> the input should be 20 bytes
long binary encoding of SHA-1 hash function output.
This utility does not hash the input data but rather it will use the data
directly as input to the signature algorithm. Depending on the key type,
signature type, and mode of padding, the maximum acceptable lengths of input
data differ. The signed data can't be longer than the key modulus with RSA. In
case of ECDSA and DSA the data shouldn't be longer than the field
size, otherwise it will be silently truncated to the field size. In any event
the input size must not be larger than the largest supported digest size.
In other words, if the value of digest is B<sha1> the input should be the 20
bytes long binary encoding of the SHA-1 hash function output.
The Ed25519 and Ed448 signature algorithms are not supported by this utility.
They accept non-hashed input, but this utility can only be used to sign hashed
input.
=head1 RSA ALGORITHM