如何使用openssl提取和验证PDF签名(PKCS7)?

我想在PHP中检测签名的pdf并验证签名是否有效。从这个 document 我已经在下面编写了这个PHP代码。

1. 提取PKCS7代码(它工作,因为我可以从Openssl获得详细信息)
2. 计算文档的SHA256哈希。

现在,我想用PKCS7文件验证我的签名。我该怎么做?我最初希望 digest_enc_alg / sha256WithRSAEncryption / enc_digest ,但这似乎不是我要找的。

class VerifyPDF
{
    public static function getByteRange($filename)
    {
        $content = file_get_contents($filename);
        if (!preg_match_all('/ByteRange\[\s*(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s*\]/',
            $content, $matches))
        {
            throw new \Exception('Unable to get certificate');
        }

        return [
            intval($matches[1][0]), // Offset of the first part (usually 0)
            intval($matches[2][0]), // Size of the first part
            intval($matches[3][0]), // Offset to the second part
            intval($matches[4][0])  // Size of the second part
        ];
    }

    public static function get_pkcs7($filename)
    {
        [$o1, $l1, $o2, $l2] = self::getByteRange($filename);

        if (!$fp = fopen($filename, 'rb')) {
            throw new \Exception("Unable to open $filename");
        }

        $signature = stream_get_contents($fp, $o2 - $l1 - 2, $l1 + 1);
        fclose($fp);

        file_put_contents('out.pkcs7', hex2bin($signature));
    }

    public static function compute_hash($filename)
    {
        [$o1, $l1, $o2, $l2] = self::getByteRange($filename);

        if (!$fp = fopen($filename, 'rb')) {
            throw new \Exception("Unable to open $filename");
        }

        $i = stream_get_contents($fp, $l1, $o1);
        $j = stream_get_contents($fp, $l2, $o2);

        if (strlen($i) != $l1 || strlen($j) != $l2) {
            throw new \Exception('Invalid chunks');
        }

        fclose($fp);

        return hash('sha256', $i . $j);
    }
}

5036ae43aba11ce626f6f9b1d5246ba0700e217655b9ff927e31fbefadfa2182

灵感来源于 this

#!/bin/bash
PKCS7='out.pkcs7'

# Extract Digest (SHA256)
OFFSET=$(openssl asn1parse -inform der -in $PKCS7 | \
    perl -ne 'print $1 + $2 if /(\d+):d=\d\s+hl=(\d).*?256 prim.*HEX DUMP/m')
dd if=$PKCS7 of=signed-sha256.bin bs=1 skip=$OFFSET count=256

# Extract Public key 
openssl pkcs7 -print_certs -inform der -in $PKCS7 | \
    tac | sed '/-----BEGIN/q' | tac > client.pem
openssl x509 -in client.pem -pubkey -noout > client.pub.pem

# Verify the signature
openssl rsautl -verify -pubin -inkey client.pub.pem < signed-sha256.bin > verified.bin

# Get Hash and compare with the computed hash from the PDF
openssl asn1parse -inform der -in verified.bin | grep -Po '\[HEX DUMP\]:\K\w+$' | tr A-F a-f

给我这个:

C8581962753927BB57B66B1D0D0F4B33A29EF3E03DA12D2329DB72763AC7EDB6

所以不幸的是两个散列不匹配。。。

我遗漏了什么吗?