evm: Check size of security.evm before using it
This patch checks the size for the EVM_IMA_XATTR_DIGSIG and
EVM_XATTR_PORTABLE_DIGSIG types to ensure that the algorithm is read from
the buffer returned by vfs_getxattr_alloc().
Cc: stable@vger.kernel.org # 4.19.x
Fixes: 5feeb61183
("evm: Allow non-SHA1 digital signatures")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
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@ -184,6 +184,12 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
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break;
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case EVM_IMA_XATTR_DIGSIG:
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case EVM_XATTR_PORTABLE_DIGSIG:
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/* accept xattr with non-empty signature field */
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if (xattr_len <= sizeof(struct signature_v2_hdr)) {
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evm_status = INTEGRITY_FAIL;
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goto out;
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}
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hdr = (struct signature_v2_hdr *)xattr_data;
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digest.hdr.algo = hdr->hash_algo;
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rc = evm_calc_hash(dentry, xattr_name, xattr_value,
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