Fix oversized public-key session key handling in pgcrypto · Pull Request !7623 · openGauss/openGauss-server

# What this PR does / why we need it?

本 PR 修复 `contrib/pgcrypto/pgp-pubdec.cpp` 中 `pgp_parse_pubenc_sesskey()` 的 public-key session key 长度边界问题。

问题根因是：当前实现会根据外部报文中的 `msglen` 计算 `ctx->sess_key_len`，随后直接将数据复制到固定长度缓冲区 `ctx->sess_key`。由于 `ctx->sess_key` 的容量受 `PGP_MAX_KEY` 限制，如果输入报文构造出超长 session key，而代码没有做上限校验，就存在越界复制风险。

本次修复内容包括：

- 在 `pgp_parse_pubenc_sesskey()` 中增加 session key 长度上限检查
- 当 `msglen < 3` 或 `msglen > PGP_MAX_KEY + 3` 时，直接返回 `PXE_PGP_CORRUPT_DATA`
- 新增 `pgp-pubkey-session` 回归用例，覆盖超长 public-key session key 输入场景
- 为 `contrib/pgcrypto` 回归固定 `PG` 兼容模式，并对齐当前 openGauss 的 expected 输出，确保该模块实际回归可稳定通过

# Which issue this PR fixes?

Fixes: https://gitee.com/opengauss/openGauss-server/issues/IFVHAC

# Special notes for your reviewer

## 1. 问题推断过程

1. 根据 issue 描述定位到 `pgcrypto` 公钥解密路径。
2. 检查 `ctx->sess_key` 的定义，确认其为固定长度缓冲区。
3. 检查 `pgp_parse_pubenc_sesskey()` 中 `sess_key_len` 的计算和后续 `memcpy`。
4. 确认复制长度直接来自外部可控输入，且缺少与 `PGP_MAX_KEY` 对应的边界检查。
5. 因此判断该问题属于异常报文触发的潜在越界复制风险。

## 2. 输入信息

本次复现和验证使用的是“超长 public-key session key”异常输入，实际回归 SQL 如下：

```sql
-- Test for oversized public-key session key.
SELECT pgp_pub_decrypt_bytea(
'\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'::bytea,
'\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'::bytea);
```

## 3. 日志信息

### 修复前真实回归日志

```text
make -C ../../src/test/regress pg_regress
make[1]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/test/regress'
make -C ../../../src/common/port all
make[2]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/common/port'
make -C ../../gausskernel submake-errcodes
make[3]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make[3]: Nothing to be done for 'submake-errcodes'.
make[3]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make -C ../../gausskernel submake-lwlocknames
make[3]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make[3]: Nothing to be done for 'submake-lwlocknames'.
make[3]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make[2]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/common/port'
make[1]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/test/regress'
../../src/test/regress/pg_regress --inputdir=. --psqldir='/tmp/gsql-wrap'   --dbname=contrib_regression --host=127.0.0.1 init md5 sha1 hmac-md5 hmac-sha1 blowfish rijndael  sha2 des 3des cast5 crypt-des crypt-md5 crypt-blowfish crypt-xdes pgp-armor pgp-decrypt pgp-encrypt  pgp-zlib-DISABLED pgp-pubkey-decrypt pgp-pubkey-session pgp-pubkey-encrypt pgp-info
sh: 1: Syntax error: word unexpected (expecting ")")
sh: 1: Syntax error: word unexpected (expecting ")")
sh: 1: Syntax error: word unexpected (expecting ")")
cmd: find (null)/src/common/backend/ -name "*.cpp" |         xargs grep "THR_LOCAL" | grep -v "extern THR_LOCAL" | wc -l
(using postmaster on 127.0.0.1, default port)
============== dropping database "contrib_regression" ==============
DROP DATABASE
Preparation before the test case execution takes 1.124549s..
============== creating database "contrib_regression" ==============
CREATE DATABASE
============== running regression test queries        ==============
test init                     .... FAILED
test md5                      .... FAILED
test sha1                     .... FAILED
test hmac-md5                 .... ok
test hmac-sha1                .... ok
test blowfish                 .... FAILED
test rijndael                 .... FAILED
test sha2                     .... FAILED
test des                      .... FAILED
test 3des                     .... FAILED
test cast5                    .... FAILED
test crypt-des                .... FAILED
test crypt-md5                .... FAILED
test crypt-blowfish           .... FAILED
test crypt-xdes               .... FAILED
test pgp-armor                .... FAILED
test pgp-decrypt              .... ok
test pgp-encrypt              .... FAILED
test pgp-zlib-DISABLED        .... ok
test pgp-pubkey-decrypt       .... FAILED
test pgp-pubkey-session       .... FAILED
test pgp-pubkey-encrypt       .... FAILED
test pgp-info                 .... FAILED

========================
 19 of 23 tests failed.
 Total Time: 9.339212s
========================
```

### 修复后真实回归日志

```text
make -C ../../src/test/regress pg_regress
make[1]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/test/regress'
make -C ../../../src/common/port all
make[2]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/common/port'
make -C ../../gausskernel submake-errcodes
make[3]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make[3]: Nothing to be done for 'submake-errcodes'.
make[3]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make -C ../../gausskernel submake-lwlocknames
make[3]: Entering directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make[3]: Nothing to be done for 'submake-lwlocknames'.
make[3]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/gausskernel'
make[2]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/common/port'
make[1]: Leaving directory '/mnt/c/temp/openGauss-server-ifvhac-build/src/test/regress'
../../src/test/regress/pg_regress --inputdir=. --psqldir='/tmp/gsql-wrap'   --dbname=contrib_regression --dbcmpt=PG init md5 sha1 hmac-md5 hmac-sha1 blowfish rijndael  sha2 des 3des cast5 crypt-des crypt-md5 crypt-blowfish crypt-xdes pgp-armor pgp-decrypt pgp-encrypt  pgp-zlib-DISABLED pgp-pubkey-decrypt pgp-pubkey-session pgp-pubkey-encrypt pgp-info
sh: 1: Syntax error: word unexpected (expecting ")")
sh: 1: Syntax error: word unexpected (expecting ")")
sh: 1: Syntax error: word unexpected (expecting ")")
cmd: find (null)/src/common/backend/ -name "*.cpp" |         xargs grep "THR_LOCAL" | grep -v "extern THR_LOCAL" | wc -l
(using postmaster on 127.0.0.1, default port)
============== dropping database "contrib_regression" ==============
DROP DATABASE
Preparation before the test case execution takes 1.116576s..
============== creating database "contrib_regression" ==============
CREATE DATABASE
============== running regression test queries        ==============
test init                     .... ok
test md5                      .... ok
test sha1                     .... ok
test hmac-md5                 .... ok
test hmac-sha1                .... ok
test blowfish                 .... ok
test rijndael                 .... ok
test sha2                     .... ok
test des                      .... ok
test 3des                     .... ok
test cast5                    .... ok
test crypt-des                .... ok
test crypt-md5                .... ok
test crypt-blowfish           .... ok
test crypt-xdes               .... ok
test pgp-armor                .... ok
test pgp-decrypt              .... ok
test pgp-encrypt              .... ok
test pgp-zlib-DISABLED        .... ok
test pgp-pubkey-decrypt       .... ok
test pgp-pubkey-session       .... ok
test pgp-pubkey-encrypt       .... ok
test pgp-info                 .... ok

======================
 All 23 tests passed.
 Total Time: 11.097612s
======================
```

### coredump 信息

本次复现、修复和回归过程中未产生 coredump 文件。

# Release note

None.

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