[sebastian-carpenter]

Description

Percent-decode the URI host before it is compared against 'Name Constraints'. Previously the comparison was done over the raw bytes.

Fix

• Decode (RFC 5280 §7.4): escaped unreserved characters in a reg-name host are decoded before comparison. Any other escape, or a malformed one, rejects the host.
• Host characters: the decoded host may contain only RFC 3986 unreserved characters: letters, digits, -, ., _ and ~.

The constraint base is never decoded, and IP literals in brackets aren't either.

Behavior

Constraint is host.example.com:

SAN host	Permitted	Excluded	Changed?
host.example.com	accept	reject	no
other.example.com	reject	accept	no
h%6Fst.example.com	accept	reject	yes
h_st.example.com, h~st.example.com, h%5Fst.example.com	reject	accept	no
h!st.example.com and other sub-delims	reject	reject	yes
Other invalid host characters (\, space, NUL, non-ASCII)	reject	reject	yes
Reserved or non-ASCII escapes (%2F, %40, %25, %00, %C3%A9)	reject	reject	yes
Malformed escapes (%ZZ, %6Z, %6, %)	reject	reject	yes
Decoded host over 254 octets	reject	reject	yes
IP host (12.31.2.3, [2001:db8::1])	reject	reject	no
Decodes to an IP (%31%32.31.2.3)	reject	reject	yes
No authority (urn:example:host.example.com)	reject	reject	no

Constraint base is malformed, SAN host is valid:

Base	Permitted	Excluded
h%6Fst.example.com, example..com, ., empty	reject	accept

These behave as they did before this branch. Such a base can't match a valid host, and RFC 5280 puts the FQDN requirement on the CA. So a malformed excluded base silently excludes nothing.

Host characters

Strict LDH (RFC 1123) would reject _, which real hosts use (SPIFFE trust domains, my_host.example.com). Rejecting it would make any URI name constraint, even an unrelated excluded-only one, fail the whole chain. The accepted set is therefore exactly RFC 3986 unreserved, the same set that percent-decoding accepts, so %5F and %7E decode to characters that are then allowed. Sub-delims (! $ & ' ( ) * + , ; =) are valid in an RFC 3986 reg-name but are not DNS host characters, so they are rejected.

For example, https://my_host.example.com/ still matches a permitted .example.com.

Tests

• test_wolfssl_local_MatchUriNameConstraint (tests/api/test_asn.c): matcher rows for decoding, malformed and reserved escapes, _ and ~ hosts raw and escaped, sub-delim hosts, decoded length limits, ACE hosts and malformed bases.
• test_wolfSSL_NAME_CONSTRAINTS_uri (tests/api/test_ossl_x509_ext.c): escaped, malformed and invalid hosts under the permitted .wolfssl.com from a real certificate.
• test_wolfSSL_NAME_CONSTRAINTS_check_name (tests/api/test_ossl_x509_ext.c):
  • h%6Fst under a permitted and an excluded host.example.com
  • URIs without a DNS host under an excluded constraint
  • h%5Fst.example.com passing an unrelated excluded constraint
  • h%6Fst.example.com as a malformed base in both directions
• tests/unit-mcdc/test_asn_fault_whitebox.c: updated for the new GetUriHost() signature.

Fixes zd#22727

Testing

Run ./configure --enable-opensslall to pull in the extra tests otherwise default covers the non-openssl stuff. The changed tests can be run with: ./tests/unit.test -test_wolfssl_local_MatchUriNameConstraint -test_wolfSSL_NAME_CONSTRAINTS_uri -test_wolfSSL_NAME_CONSTRAINTS_check_name.

For mc-dc build with ./configure --enable-all --enable-static --disable-shared CPPFLAGS=-DWOLFSSL_TEST_STATIC_BUILD. Run the tests with ./tests/unit-mcdc/run-whitebox-smoke.sh.

Checklist

• added tests
• updated/added doxygen
• updated appropriate READMEs
• Updated manual and documentation

[Copilot]

🟡 Changes recommended

The no-escape URI host path bypasses URI_HOST_MAX_SZ, allowing an oversized host that is rejected in its equivalent escaped form, and needs the same bound plus an unescaped boundary test.

1 open issue

• Enforce host-length limit on the no-escape fast path · New

What changed in this PR

This PR normalizes URI hosts before certificate name-constraint matching and restricts host characters to letters, digits, hyphens, and dots.

Changes:

• Decode escaped unreserved host characters and reject malformed or disallowed escapes.
• Add matcher and OpenSSL-compatible API tests for normalization and invalid hosts.
• Update white-box tests for the host parser’s new buffer parameter.

File	Description
wolfcrypt/​src/​asn.c	Adds host percent-decoding and character validation before constraint matching.
tests/​unit-mcdc/​test_asn_fault_whitebox.c	Supplies the new host buffer to parser tests.
tests/​api/​test_ossl_x509_ext.c	Tests encoded and invalid hosts under permitted and excluded constraints.
tests/​api/​test_asn.c	Adds decoding, host-length, invalid-character, and malformed-base cases.

_{Review effort: Balanced}

[github-actions]

MemBrowse Memory Report · Explore what changed →

gcc-arm-cortex-m0plus

• FLASH: .text +252 B (+0.4%, 71,447 B / 262,144 B, total: 27% used)

gcc-arm-cortex-m3

• FLASH: .text +252 B (+0.2%, 132,481 B / 262,144 B, total: 51% used)

gcc-arm-cortex-m4

• FLASH: .text +256 B (+0.1%, 209,804 B / 262,144 B, total: 80% used)

gcc-arm-cortex-m4-baremetal

• FLASH: .text +256 B (+0.3%, 74,231 B / 262,144 B, total: 28% used)

gcc-arm-cortex-m4-crypto-only

• FLASH: .text +256 B (+0.1%, 182,547 B / 262,144 B, total: 70% used)

gcc-arm-cortex-m4-dtls13

• FLASH: .text +256 B (+0.1%, 196,760 B / 1,048,576 B, total: 19% used)

gcc-arm-cortex-m4-min-ecc

• FLASH: .text +256 B (+0.4%, 68,697 B / 262,144 B, total: 26% used)

gcc-arm-cortex-m4-openssl-compat

• FLASH: .text +192 B (+0.0%, 802,372 B / 1,048,576 B, total: 77% used)

gcc-arm-cortex-m4-pkcs7

• FLASH: .text +256 B (+0.1%, 223,636 B / 262,144 B, total: 85% used)

gcc-arm-cortex-m4-pq

• FLASH: .text +256 B (+0.1%, 313,680 B / 1,048,576 B, total: 30% used)

gcc-arm-cortex-m4-rsa-only

• FLASH: .text +256 B (+0.1%, 344,208 B / 1,048,576 B, total: 33% used)

gcc-arm-cortex-m4-sp-math

• FLASH: .text +256 B (+0.4%, 68,697 B / 262,144 B, total: 26% used)

gcc-arm-cortex-m4-tls12

• FLASH: .text +256 B (+0.2%, 133,265 B / 262,144 B, total: 51% used)

gcc-arm-cortex-m4-tls13

• FLASH: .text +256 B (+0.1%, 250,402 B / 262,144 B, total: 96% used)

gcc-arm-cortex-m7

• FLASH: .text +256 B (+0.1%, 209,804 B / 262,144 B, total: 80% used)

gcc-arm-cortex-m7-pq

• FLASH: .text +256 B (+0.1%, 314,512 B / 1,048,576 B, total: 30% used)

gcc-arm-cortex-m7-tls13

• FLASH: .text +256 B (+0.1%, 250,402 B / 262,144 B, total: 96% used)

stm32-sim-stm32h753

• FLASH: .text +448 B (+0.2%, 205,356 B / 2,097,152 B, total: 10% used)

zephyr-frdm_rw612

• FLASH: datas +16 B, log_const_area -8 B, rodata +36 B, text +11,960 B (+4.2%, 294,468 B / 67,108,864 B, total: 0% used)
• RAM: bss +49 B, datas +16 B (+0.1%, 58,423 B / 983,040 B, total: 6% used)

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[sebastian-carpenter]

Jenkins retest this please.

[sebastian-carpenter]

Jenkins retest this please.

[SparkiDev]

@claude review

[sebastian-carpenter]

relaxed restriction on both '_' and '~'