是什么导致证书的 basicConstraints 出现警告？

Question

我使用 OpenSSL 的req -x509命令和 CONF 文件创建了一个自签名服务器证书。CONF 文件如下所示。

当我使用 Microsoft 证书查看器检查证书时，它显示警告basicConstraints（注意小感叹号）：

CONF 文件使用以下内容来构建 basicConstraints：

basicConstraints = critical,CA:FALSE

根据RFC 5280，pathLen只有当CA:TRUE和keyCertSign存在时才应该存在。服务器的证书不满足任一条件（另外，测试pathLen导致相同的警告）。

为什么 Microsoft 证书工具警告打开basicConstraints？它有什么问题或我应该怎么做才能解决它？

---

# Self Signed (note the addition of -x509):
#     openssl req -config example.conf -new -x509 -sha256 -newkey rsa:2048 -nodes -keyout example.key.pem -days 365 -out example.cert.pem

# Self Signed with existing key (note the addition of -x509):
#     openssl req -config example.conf -new -x509 -sha256 -key example.key.pem -days 365 -out example.cert.pem

# Signing Request (note the lack of -x509):
#     openssl req -config example.conf -new -newkey rsa:2048 -nodes -keyout example.key.pem -days 365 -out example.req.pem

# Signing Request with existing key (note the lack of -x509):
#     openssl req -config example.conf -new -key example.key.pem -days 365 -out example.req.pem

# Print it:
#     openssl x509 -in example.cert.pem -text -noout
#     openssl req -in example.req.pem -text -noout

[ req ]
default_bits        = 2048
default_keyfile     = server-key.pem
distinguished_name  = subject
req_extensions      = req_ext
x509_extensions     = x509_ext
string_mask         = utf8only

# The Subject DN can be formed using X501 or RFC 4514 (see RFC 4519 for a description).
#   Its sort of a mashup. For example, RFC 4514 does not provide emailAddress.
[ subject ]
countryName         = Country Name (2 letter code)
countryName_default     = US

stateOrProvinceName     = State or Province Name (full name)
stateOrProvinceName_default = MD

localityName            = Locality Name (eg, city)
localityName_default        = Baltimore

organizationName         = Organization Name (eg, company)
organizationName_default    =

# Use a friendly name here because its presented to the user. The server's DNS
#   names are placed in Subject Alternate Names. Plus, DNS names here is deprecated
#   by both IETF and CA/Browser Forums.
commonName          = Common Name (e.g. server FQDN or YOUR name)
commonName_default      = Example, LLC

emailAddress            = Email Address
emailAddress_default        = webmaster@example.com

# Section x509_ext is used when generating a self-signed certificate. I.e., openssl req -x509 ...
[ x509_ext ]

subjectKeyIdentifier        = hash
authorityKeyIdentifier  = keyid,issuer

basicConstraints        = critical,CA:FALSE
keyUsage            = digitalSignature, keyEncipherment
subjectAltName          = @alternate_names
nsComment           = "OpenSSL Generated Certificate"

# RFC 5280, Section 4.2.1.12 makes EKU optional
# CA/Browser Baseline Requirements, Appendix (B)(3)(G) makes me confused
extendedKeyUsage    = serverAuth

# Section req_ext is used when generating a certificate signing request. I.e., openssl req ...
[ req_ext ]

subjectKeyIdentifier        = hash

basicConstraints        = critical,CA:FALSE
keyUsage            = digitalSignature, keyEncipherment
subjectAltName          = @alternate_names
nsComment           = "OpenSSL Generated Certificate"

# RFC 5280, Section 4.2.1.12 makes EKU optional
# CA/Browser Baseline Requirements, Appendix (B)(3)(G) makes me confused
extendedKeyUsage    = serverAuth

[ alternate_names ]

DNS.1       = example.com
DNS.2       = www.example.com
DNS.3       = mail.example.com
DNS.4       = ftp.example.com

# Add these if you need them. But usually you don't want them or
#   need them in production. You may need them for development.
# DNS.5       = localhost
# DNS.6       = localhost.localdomain
# DNS.7       = 127.0.0.1

# IPv6 localhost
# DNS.8     = ::1

Answer 1

带有感叹号的黄色小三角形告诉您扩展名被标记为关键。要去掉该图标，请从 OpenSSL 配置中删除“关键”动词。

此外，没有要求使用cA布尔值设置为 false的基本约束来标记最终实体证书，因为这在所有未设置为 true 的证书中暗示。把它放在那里并不违反；但它不需要。