Statically typed error handling PoC

[Tehforsch]

Notes for writedown:

• Always convert to highest error first, then attach general metadata (retryable, return value)
• keep return values for now even though need is unclear (easy to remove)
• with ergonomics debatable
• write down defaults explicitly
• demonstrate retryable being both a fine-grained local choice (at every construction site of an error) or a more coarse-grained choice (in the From impl for a specific error kind)
• write down steps needed to add a new error type for a new builtin mod

Todo:

• Get rid of clone impl?

[github-actions]

Dependency Review

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[nichtsfrei]

Nit: I am not sure if I like the term NaslError as it is just for builtin functions.

[Tehforsch]

That makes sense. I guess I'll rename it back to FunctionErrorKind for this draft (to make the changes I made more apparent and not flood it with 40 files of rename changes) and then we can discuss the name at some later point.

[nichtsfrei]

can we get rid of Dirty? Dirty in StorageError is used because it is short version of dirty data which includes but is not limited to corruption or undefined behaviour. I don't think it makes sense as an InternalError. I think we should be more considered and may define extra cases that are not Storage specific.

[Tehforsch]

Yes, I just wasnt finished and dirty is used a ton. Got rid of it in some of the newer commits.

[github-actions]

🔍 Vulnerabilities of harbor-os.greenbone.net/community/openvas-scanner:1752-merge-amd64

📦 Image Reference harbor-os.greenbone.net/community/openvas-scanner:1752-merge-amd64

digest	sha256:5df524dd4b949bf9549a4fd4f935b40450b3c1674cc4224c1155659736a493ad
vulnerabilities
size	141 MB
packages	262

📦 Base Image debian:stable-20241016-slim

also known as	stable-slim
digest	sha256:d337e8c1770de491cd165b65051f49455ff20fdd26b296d24650876aefaa445f
vulnerabilities

glibc 2.36-9+deb12u8 (deb) pkg:deb/debian/[email protected]%2Bdeb12u8?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 0.11% EPSS Percentile 45th percentile Description In the GNU C Library (aka glibc or libc6) through 2.29, check_dst_limits_calc_pos_1 in posix/regexec.c has Uncontrolled Recursion, as demonstrated by '(|)(\1\1)*' in grep, a different issue than CVE-2018-20796. NOTE: the software maintainer disputes that this is a vulnerability because the behavior occurs only with a crafted pattern Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 0.35% EPSS Percentile 73rd percentile Description GNU Libc current is affected by: Mitigation bypass. The impact is: Attacker may guess the heap addresses of pthread_created thread. The component is: glibc. NOTE: the vendor's position is "ASLR bypass itself is not a vulnerability. Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 3.02% EPSS Percentile 91st percentile Description GNU Libc current is affected by: Mitigation bypass. The impact is: Attacker may bypass ASLR using cache of thread stack and heap. The component is: glibc. NOTE: Upstream comments indicate "this is being treated as a non-security bug and no real threat. Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 1.20% EPSS Percentile 86th percentile Description GNU Libc current is affected by: Re-mapping current loaded library with malicious ELF file. The impact is: In worst case attacker may evaluate privileges. The component is: libld. The attack vector is: Attacker sends 2 ELF files to victim and asks to run ldd on it. ldd execute code. NOTE: Upstream comments indicate "this is being treated as a non-security bug and no real threat. Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 0.41% EPSS Percentile 75th percentile Description GNU Libc current is affected by: Mitigation bypass. The impact is: Attacker may bypass stack guard protection. The component is: nptl. The attack vector is: Exploit stack buffer overflow vulnerability and use this bypass vulnerability to bypass stack guard. NOTE: Upstream comments indicate "this is being treated as a non-security bug and no real threat. Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 0.44% EPSS Percentile 75th percentile Description In the GNU C Library (aka glibc or libc6) through 2.29, check_dst_limits_calc_pos_1 in posix/regexec.c has Uncontrolled Recursion, as demonstrated by '(\227|)(\1\1|t1|\\2537)+' in grep. Affected range >=2.36-9+deb12u8 Fixed version Not Fixed EPSS Score 0.82% EPSS Percentile 82nd percentile Description The glob implementation in the GNU C Library (aka glibc or libc6) allows remote authenticated users to cause a denial of service (CPU and memory consumption) via crafted glob expressions that do not match any pathnames, as demonstrated by glob expressions in STAT commands to an FTP daemon, a different vulnerability than CVE-2010-2632.

pcre3 2:8.39-15 (deb) pkg:deb/debian/pcre3@2:8.39-15?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2:8.39-15 Fixed version Not Fixed EPSS Score 1.03% EPSS Percentile 84th percentile Description libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \X or \R has more than one fixed quantifier, a related issue to CVE-2019-20454. Affected range >=2:8.39-15 Fixed version Not Fixed EPSS Score 0.65% EPSS Percentile 80th percentile Description Stack-based buffer overflow in the pcre32_copy_substring function in pcre_get.c in libpcre1 in PCRE 8.40 allows remote attackers to cause a denial of service (WRITE of size 268) or possibly have unspecified other impact via a crafted file. Affected range >=2:8.39-15 Fixed version Not Fixed EPSS Score 0.65% EPSS Percentile 80th percentile Description Stack-based buffer overflow in the pcre32_copy_substring function in pcre_get.c in libpcre1 in PCRE 8.40 allows remote attackers to cause a denial of service (WRITE of size 4) or possibly have unspecified other impact via a crafted file. Affected range >=2:8.39-15 Fixed version Not Fixed EPSS Score 0.08% EPSS Percentile 37th percentile Description In PCRE 8.41, after compiling, a pcretest load test PoC produces a crash overflow in the function match() in pcre_exec.c because of a self-recursive call. NOTE: third parties dispute the relevance of this report, noting that there are options that can be used to limit the amount of stack that is used Affected range >=2:8.39-15 Fixed version Not Fixed EPSS Score 0.37% EPSS Percentile 73rd percentile Description In PCRE 8.41, the OP_KETRMAX feature in the match function in pcre_exec.c allows stack exhaustion (uncontrolled recursion) when processing a crafted regular expression.

systemd 252.30-1~deb12u2 (deb) pkg:deb/debian/[email protected]~deb12u2?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=252.30-1~deb12u2 Fixed version Not Fixed EPSS Score 0.10% EPSS Percentile 42nd percentile Description An issue was discovered in systemd 253. An attacker can modify the contents of past events in a sealed log file and then adjust the file such that checking the integrity shows no error, despite modifications. NOTE: the vendor reportedly sent "a reply denying that any of the finding was a security vulnerability." Affected range >=252.30-1~deb12u2 Fixed version Not Fixed EPSS Score 0.10% EPSS Percentile 42nd percentile Description An issue was discovered in systemd 253. An attacker can truncate a sealed log file and then resume log sealing such that checking the integrity shows no error, despite modifications. NOTE: the vendor reportedly sent "a reply denying that any of the finding was a security vulnerability." Affected range >=252.30-1~deb12u2 Fixed version Not Fixed EPSS Score 0.09% EPSS Percentile 39th percentile Description An issue was discovered in systemd 253. An attacker can modify a sealed log file such that, in some views, not all existing and sealed log messages are displayed. NOTE: the vendor reportedly sent "a reply denying that any of the finding was a security vulnerability." Affected range >=252.30-1~deb12u2 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 5th percentile Description systemd, when updating file permissions, allows local users to change the permissions and SELinux security contexts for arbitrary files via a symlink attack on unspecified files.

openldap 2.5.13+dfsg-5 (deb) pkg:deb/debian/[email protected]%2Bdfsg-5?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.5.13+dfsg-5 Fixed version Not Fixed EPSS Score 0.16% EPSS Percentile 54th percentile Description libldap in certain third-party OpenLDAP packages has a certificate-validation flaw when the third-party package is asserting RFC6125 support. It considers CN even when there is a non-matching subjectAltName (SAN). This is fixed in, for example, openldap-2.4.46-10.el8 in Red Hat Enterprise Linux. Affected range >=2.5.13+dfsg-5 Fixed version Not Fixed EPSS Score 0.41% EPSS Percentile 74th percentile Description contrib/slapd-modules/nops/nops.c in OpenLDAP through 2.4.45, when both the nops module and the memberof overlay are enabled, attempts to free a buffer that was allocated on the stack, which allows remote attackers to cause a denial of service (slapd crash) via a member MODDN operation. Affected range >=2.5.13+dfsg-5 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 11th percentile Description slapd in OpenLDAP 2.4.45 and earlier creates a PID file after dropping privileges to a non-root account, which might allow local users to kill arbitrary processes by leveraging access to this non-root account for PID file modification before a root script executes a "kill cat /pathname" command, as demonstrated by openldap-initscript. Affected range >=2.5.13+dfsg-5 Fixed version Not Fixed EPSS Score 0.42% EPSS Percentile 75th percentile Description The nss_parse_ciphers function in libraries/libldap/tls_m.c in OpenLDAP does not properly parse OpenSSL-style multi-keyword mode cipher strings, which might cause a weaker than intended cipher to be used and allow remote attackers to have unspecified impact via unknown vectors.

krb5 1.20.1-2+deb12u2 (deb) pkg:deb/debian/[email protected]%2Bdeb12u2?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=1.20.1-2+deb12u2 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 10th percentile Description Kerberos 5 (aka krb5) 1.21.2 contains a memory leak vulnerability in /krb5/src/lib/gssapi/krb5/k5sealv3.c. Affected range >=1.20.1-2+deb12u2 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 10th percentile Description Kerberos 5 (aka krb5) 1.21.2 contains a memory leak in /krb5/src/lib/rpc/pmap_rmt.c. Affected range >=1.20.1-2+deb12u2 Fixed version Not Fixed EPSS Score 0.10% EPSS Percentile 42nd percentile Description An issue was discovered in MIT Kerberos 5 (aka krb5) through 1.16. There is a variable "dbentry->n_key_data" in kadmin/dbutil/dump.c that can store 16-bit data but unknowingly the developer has assigned a "u4" variable to it, which is for 32-bit data. An attacker can use this vulnerability to affect other artifacts of the database as we know that a Kerberos database dump file contains trusted data.

gcc-12 12.2.0-14 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=12.2.0-14 Fixed version Not Fixed EPSS Score 0.06% EPSS Percentile 26th percentile Description DISPUTEDA failure in the -fstack-protector feature in GCC-based toolchains that target AArch64 allows an attacker to exploit an existing buffer overflow in dynamically-sized local variables in your application without this being detected. This stack-protector failure only applies to C99-style dynamically-sized local variables or those created using alloca(). The stack-protector operates as intended for statically-sized local variables. The default behavior when the stack-protector detects an overflow is to terminate your application, resulting in controlled loss of availability. An attacker who can exploit a buffer overflow without triggering the stack-protector might be able to change program flow control to cause an uncontrolled loss of availability or to go further and affect confidentiality or integrity. NOTE: The GCC project argues that this is a missed hardening bug and not a vulnerability by itself. Affected range >=12.2.0-14 Fixed version Not Fixed EPSS Score 0.09% EPSS Percentile 39th percentile Description libiberty/rust-demangle.c in GNU GCC 11.2 allows stack consumption in demangle_const, as demonstrated by nm-new.

libpcap 1.10.3-1 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=1.10.3-1 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 10th percentile Description Remote packet capture support is disabled by default in libpcap. When a user builds libpcap with remote packet capture support enabled, one of the functions that become available is pcap_findalldevs_ex(). One of the function arguments can be a filesystem path, which normally means a directory with input data files. When the specified path cannot be used as a directory, the function receives NULL from opendir(), but does not check the return value and passes the NULL value to readdir(), which causes a NULL pointer derefence. Affected range >=1.10.3-1 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 10th percentile Description In affected libpcap versions during the setup of a remote packet capture the internal function sock_initaddress() calls getaddrinfo() and possibly freeaddrinfo(), but does not clearly indicate to the caller function whether freeaddrinfo() still remains to be called after the function returns. This makes it possible in some scenarios that both the function and its caller call freeaddrinfo() for the same allocated memory block. A similar problem was reported in Apple libpcap, to which Apple assigned CVE-2023-40400.

perl 5.36.0-7+deb12u1 (deb) pkg:deb/debian/[email protected]%2Bdeb12u1?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=5.36.0-7+deb12u1 Fixed version Not Fixed EPSS Score 0.28% EPSS Percentile 69th percentile Description HTTP::Tiny before 0.083, a Perl core module since 5.13.9 and available standalone on CPAN, has an insecure default TLS configuration where users must opt in to verify certificates. Affected range >=5.36.0-7+deb12u1 Fixed version Not Fixed EPSS Score 0.24% EPSS Percentile 65th percentile Description _is_safe in the File::Temp module for Perl does not properly handle symlinks.

m4 1.4.19-3 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=1.4.19-3 Fixed version Not Fixed EPSS Score 2.99% EPSS Percentile 91st percentile Description Unspecified vulnerability in GNU m4 before 1.4.11 might allow context-dependent attackers to execute arbitrary code, related to improper handling of filenames specified with the -F option. NOTE: it is not clear when this issue crosses privilege boundaries. Affected range >=1.4.19-3 Fixed version Not Fixed EPSS Score 2.12% EPSS Percentile 90th percentile Description The (1) maketemp and (2) mkstemp builtin functions in GNU m4 before 1.4.11 do not quote their output when a file is created, which might allow context-dependent attackers to trigger a macro expansion, leading to unspecified use of an incorrect filename.

gnutls28 3.7.9-2+deb12u3 (deb) pkg:deb/debian/[email protected]%2Bdeb12u3?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=3.7.9-2+deb12u3 Fixed version Not Fixed EPSS Score 0.60% EPSS Percentile 79th percentile Description The SSL protocol, as used in certain configurations in Microsoft Windows and Microsoft Internet Explorer, Mozilla Firefox, Google Chrome, Opera, and other products, encrypts data by using CBC mode with chained initialization vectors, which allows man-in-the-middle attackers to obtain plaintext HTTP headers via a blockwise chosen-boundary attack (BCBA) on an HTTPS session, in conjunction with JavaScript code that uses (1) the HTML5 WebSocket API, (2) the Java URLConnection API, or (3) the Silverlight WebClient API, aka a "BEAST" attack.

gnupg2 2.2.40-1.1 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.2.40-1.1 Fixed version Not Fixed EPSS Score 0.05% EPSS Percentile 18th percentile Description GnuPG can be made to spin on a relatively small input by (for example) crafting a public key with thousands of signatures attached, compressed down to just a few KB.

net-tools 2.10-0.1 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.10-0.1 Fixed version Not Fixed EPSS Score 0.06% EPSS Percentile 26th percentile Description ifconfig, when used on the Linux kernel 2.2 and later, does not report when the network interface is in promiscuous mode if it was put in promiscuous mode using PACKET_MR_PROMISC, which could allow attackers to sniff the network without detection, as demonstrated using libpcap.

nmap 7.93+dfsg1-1 (deb) pkg:deb/debian/[email protected]%2Bdfsg1-1?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=7.93+dfsg1-1 Fixed version Not Fixed EPSS Score 2.28% EPSS Percentile 90th percentile Description Nmap through 7.70, when the -sV option is used, allows remote attackers to cause a denial of service (stack consumption and application crash) via a crafted TCP-based service.

shadow 1:4.13+dfsg1-1 (deb) pkg:deb/debian/shadow@1:4.13%2Bdfsg1-1?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=1:4.13+dfsg1-1 Fixed version Not Fixed EPSS Score 0.16% EPSS Percentile 53rd percentile Description initscripts in rPath Linux 1 sets insecure permissions for the /var/log/btmp file, which allows local users to obtain sensitive information regarding authentication attempts. NOTE: because sshd detects the insecure permissions and does not log certain events, this also prevents sshd from logging failed authentication attempts by remote attackers.

tar 1.34+dfsg-1.2+deb12u1 (deb) pkg:deb/debian/[email protected]%2Bdfsg-1.2%2Bdeb12u1?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=1.34+dfsg-1.2+deb12u1 Fixed version Not Fixed EPSS Score 0.69% EPSS Percentile 81st percentile Description Tar 1.15.1 does not properly warn the user when extracting setuid or setgid files, which may allow local users or remote attackers to gain privileges.

libgcrypt20 1.10.1-3 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=1.10.1-3 Fixed version Not Fixed EPSS Score 0.19% EPSS Percentile 58th percentile Description cipher/elgamal.c in Libgcrypt through 1.8.2, when used to encrypt messages directly, improperly encodes plaintexts, which allows attackers to obtain sensitive information by reading ciphertext data (i.e., it does not have semantic security in face of a ciphertext-only attack). The Decisional Diffie-Hellman (DDH) assumption does not hold for Libgcrypt's ElGamal implementation.

util-linux 2.38.1-5+deb12u1 (deb) pkg:deb/debian/[email protected]%2Bdeb12u1?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.38.1-5+deb12u1 Fixed version Not Fixed EPSS Score 0.05% EPSS Percentile 18th percentile Description A flaw was found in the util-linux chfn and chsh utilities when compiled with Readline support. The Readline library uses an "INPUTRC" environment variable to get a path to the library config file. When the library cannot parse the specified file, it prints an error message containing data from the file. This flaw allows an unprivileged user to read root-owned files, potentially leading to privilege escalation. This flaw affects util-linux versions prior to 2.37.4.

coreutils 9.1-1 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=9.1-1 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 5th percentile Description In GNU Coreutils through 8.29, chown-core.c in chown and chgrp does not prevent replacement of a plain file with a symlink during use of the POSIX "-R -L" options, which allows local users to modify the ownership of arbitrary files by leveraging a race condition.

libxml2 2.9.14+dfsg-1.3~deb12u1 (deb) pkg:deb/debian/[email protected]%2Bdfsg-1.3~deb12u1?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.9.14+dfsg-1.3~deb12u1 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 11th percentile Description An issue was discovered in xmllint (from libxml2) before 2.11.8 and 2.12.x before 2.12.7. Formatting error messages with xmllint --htmlout can result in a buffer over-read in xmlHTMLPrintFileContext in xmllint.c.

curl 7.88.1-10+deb12u7 (deb) pkg:deb/debian/[email protected]%2Bdeb12u7?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=7.88.1-10+deb12u7 Fixed version Not Fixed EPSS Score 0.04% EPSS Percentile 14th percentile Description libcurl skips the certificate verification for a QUIC connection under certain conditions, when built to use wolfSSL. If told to use an unknown/bad cipher or curve, the error path accidentally skips the verification and returns OK, thus ignoring any certificate problems.

sqlite3 3.40.1-2 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=3.40.1-2 Fixed version Not Fixed EPSS Score 0.22% EPSS Percentile 61st percentile Description A Memory Leak vulnerability exists in SQLite Project SQLite3 3.35.1 and 3.37.0 via maliciously crafted SQL Queries (made via editing the Database File), it is possible to query a record, and leak subsequent bytes of memory that extend beyond the record, which could let a malicious user obtain sensitive information. NOTE: The developer disputes this as a vulnerability stating that If you give SQLite a corrupted database file and submit a query against the database, it might read parts of the database that you did not intend or expect.

glib2.0 2.74.6-2+deb12u3 (deb) pkg:deb/debian/[email protected]%2Bdeb12u3?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.74.6-2+deb12u3 Fixed version Not Fixed EPSS Score 0.16% EPSS Percentile 53rd percentile Description GLib 2.31.8 and earlier, when the g_str_hash function is used, computes hash values without restricting the ability to trigger hash collisions predictably, which allows context-dependent attackers to cause a denial of service (CPU consumption) via crafted input to an application that maintains a hash table. NOTE: this issue may be disputed by the vendor; the existence of the g_str_hash function is not a vulnerability in the library, because callers of g_hash_table_new and g_hash_table_new_full can specify an arbitrary hash function that is appropriate for the application.

openssl 3.0.14-1~deb12u2 (deb) pkg:deb/debian/[email protected]~deb12u2?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=3.0.11-1~deb12u2 Fixed version Not Fixed EPSS Score 0.07% EPSS Percentile 30th percentile Description OpenSSL 0.9.8i on the Gaisler Research LEON3 SoC on the Xilinx Virtex-II Pro FPGA uses a Fixed Width Exponentiation (FWE) algorithm for certain signature calculations, and does not verify the signature before providing it to a caller, which makes it easier for physically proximate attackers to determine the private key via a modified supply voltage for the microprocessor, related to a "fault-based attack."

apt 2.6.1 (deb) pkg:deb/debian/[email protected]?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=2.6.1 Fixed version Not Fixed EPSS Score 0.16% EPSS Percentile 54th percentile Description It was found that apt-key in apt, all versions, do not correctly validate gpg keys with the master keyring, leading to a potential man-in-the-middle attack.

net-snmp 5.9.3+dfsg-2 (deb) pkg:deb/debian/[email protected]%2Bdfsg-2?os_distro=bookworm&os_name=debian&os_version=12 Affected range >=5.9.3+dfsg-2 Fixed version Not Fixed Description net-snmp 5.9.4 contains a memory leak vulnerability in /net-snmp/apps/snmpvacm.c.

[nichtsfrei]

Keep in mind that the io::ErrorKind is used to identify retry cases, see https://github.com/greenbone/openvas-scanner/blob/main/rust/src/nasl/interpreter/interpreter.rs#L196 for an incomplete example. The possibility to identify cases that can be retried transparently to the user should be considered.

[Tehforsch]

Keep in mind that the io::ErrorKind is used to identify retry cases, see https://github.com/greenbone/openvas-scanner/blob/main/rust/src/nasl/interpreter/interpreter.rs#L196 for an incomplete example. The possibility to identify cases that can be retried transparently to the user should be considered.

I think we need a more robust set up to identify these cases. Using IO errors to mean retryable might be a good heuristic, but is still not accurate, since there are both false positives (io::ErrorKind::NotADirectory is not something that will be solved by retrying) and false negatives (an ssh connection might fail due to a timeout but won't return an IO error).
I am not sure that we can find a high level structure that represents re-try-ability well and would prefer doing this on a "local" level, i.e. someting like

foo().map_err(|e| MyCustomError::MyCustomErrorVariant(e).retryable())`

(method naming very much up for debate)

[nichtsfrei]

Yes, it’s imperfect—I wasn’t suggesting we use it as-is. However, this concept is entirely missing from the current proposal, even though it’s available, albeit imperfectly, in the current handling.

I’m not in favor of implementing it at a local level because it relies too heavily on the function developer's knowledge and could lead to inconsistent handling, making it harder to reason about, inconvenient, and adding cognitive load—especially when you just want to quickly create a built-in function.

[Tehforsch]

Yes, it’s imperfect—I wasn’t suggesting we use it as-is. However, this concept is entirely missing from the current proposal, even though it’s available, albeit imperfectly, in the current handling.

Yes, youre right.

I’m not in favor of implementing it at a local level because it relies too heavily on the function developer's knowledge and could lead to inconsistent handling, making it harder to reason about, inconvenient, and adding cognitive load—especially when you just want to quickly create a built-in function.

I was also afraid of that, but if we don't trust the author of the builtin function to make the correct decision on whether an error is solvable by retrying or not, then I don't think we have a chance of solving this problem anyways. I would prefer doing this on a local level because it still gives us the room to discuss these things in code review etc.. I think making the overarching structure of the error type determine whether an error is "retryable" or not carries a larger risk because we will eventually have to fight our own system if we want more precise control over these errors.

This also doesn't always have to be solved on the most local level, because you could, for example, write an From impl for your error type such as

impl From<io::Error> for MyCustomError {
    fn from(val: io:Error) -> MyCustomError {
        MyCustomError::Foo(val).retryable()
    }
}

which effectively reproduces the original behavior of making any io::Error something that can be solved by retrying, but does it on a more fine-grained level (for an entire builtin module), where it might always make sense.