Re: [PATCH v5 1/6] lib/base64: Add support for multiple variants

David Laight
2025-11-14T09:13:52Z

On Fri, 14 Nov 2025 14:00:45 +0800
Guan-Chun Wu <409411716@gms.tku.edu.tw> wrote:

> From: Kuan-Wei Chiu <visitorckw@gmail.com>
>
> Extend the base64 API to support multiple variants (standard, URL-safe,
> and IMAP) as defined in RFC 4648 and RFC 3501. The API now takes a
> variant parameter and an option to control padding. Update NVMe auth
> code to use the new interface with BASE64_STD.
>
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> Co-developed-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
> Signed-off-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>

Reviewed-by: David Laight <david.laight.linux@gmail.com>

> ---
> drivers/nvme/common/auth.c | 4 +--
> include/linux/base64.h | 10 ++++--
> lib/base64.c | 62 ++++++++++++++++++++++----------------
> 3 files changed, 46 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
> index 1f51fbebd9fa..e07e7d4bf8b6 100644
> --- a/drivers/nvme/common/auth.c
> +++ b/drivers/nvme/common/auth.c
> @@ -178,7 +178,7 @@ struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
> if (!key)
> return ERR_PTR(-ENOMEM);
>
> - key_len = base64_decode(secret, allocated_len, key->key);
> + key_len = base64_decode(secret, allocated_len, key->key, true, BASE64_STD);
> if (key_len < 0) {
> pr_debug("base64 key decoding error %d\n",
> key_len);
> @@ -663,7 +663,7 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
> if (ret)
> goto out_free_digest;
>
> - ret = base64_encode(digest, digest_len, enc);
> + ret = base64_encode(digest, digest_len, enc, true, BASE64_STD);
> if (ret < hmac_len) {
> ret = -ENOKEY;
> goto out_free_digest;
> diff --git a/include/linux/base64.h b/include/linux/base64.h
> index 660d4cb1ef31..a2c6c9222da3 100644
> --- a/include/linux/base64.h
> +++ b/include/linux/base64.h
> @@ -8,9 +8,15 @@
>
> #include <linux/types.h>
>
> +enum base64_variant {
> + BASE64_STD, /* RFC 4648 (standard) */
> + BASE64_URLSAFE, /* RFC 4648 (base64url) */
> + BASE64_IMAP, /* RFC 3501 */
> +};
> +
> #define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3)
>
> -int base64_encode(const u8 *src, int len, char *dst);
> -int base64_decode(const char *src, int len, u8 *dst);
> +int base64_encode(const u8 *src, int len, char *dst, bool padding, enum base64_variant variant);
> +int base64_decode(const char *src, int len, u8 *dst, bool padding, enum base64_variant variant);
>
> #endif /* _LINUX_BASE64_H */
> diff --git a/lib/base64.c b/lib/base64.c
> index b736a7a431c5..a7c20a8e8e98 100644
> --- a/lib/base64.c
> +++ b/lib/base64.c
> @@ -1,12 +1,12 @@
> // SPDX-License-Identifier: GPL-2.0
> /*
> - * base64.c - RFC4648-compliant base64 encoding
> + * base64.c - Base64 with support for multiple variants
> *
> * Copyright (c) 2020 Hannes Reinecke, SUSE
> *
> * Based on the base64url routines from fs/crypto/fname.c
> - * (which are using the URL-safe base64 encoding),
> - * modified to use the standard coding table from RFC4648 section 4.
> + * (which are using the URL-safe Base64 encoding),
> + * modified to support multiple Base64 variants.
> */
>
> #include <linux/kernel.h>
> @@ -15,26 +15,31 @@
> #include <linux/string.h>
> #include <linux/base64.h>
>
> -static const char base64_table[65] =
> - "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
> +static const char base64_tables[][65] = {
> + [BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
> + [BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
> + [BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,",
> +};
>
> /**
> - * base64_encode() - base64-encode some binary data
> + * base64_encode() - Base64-encode some binary data
> * @src: the binary data to encode
> * @srclen: the length of @src in bytes
> - * @dst: (output) the base64-encoded string. Not NUL-terminated.
> + * @dst: (output) the Base64-encoded string. Not NUL-terminated.
> + * @padding: whether to append '=' padding characters
> + * @variant: which base64 variant to use
> *
> - * Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
> - * by RFC 4648, including the '='-padding.
> + * Encodes data using the selected Base64 variant.
> *
> - * Return: the length of the resulting base64-encoded string in bytes.
> + * Return: the length of the resulting Base64-encoded string in bytes.
> */
> -int base64_encode(const u8 *src, int srclen, char *dst)
> +int base64_encode(const u8 *src, int srclen, char *dst, bool padding, enum base64_variant variant)
> {
> u32 ac = 0;
> int bits = 0;
> int i;
> char *cp = dst;
> + const char *base64_table = base64_tables[variant];
>
> for (i = 0; i < srclen; i++) {
> ac = (ac << 8) | src[i];
> @@ -48,44 +53,49 @@ int base64_encode(const u8 *src, int srclen, char *dst)
> *cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
> bits -= 6;
> }
> - while (bits < 0) {
> - *cp++ = '=';
> - bits += 2;
> + if (padding) {
> + while (bits < 0) {
> + *cp++ = '=';
> + bits += 2;
> + }
> }
> return cp - dst;
> }
> EXPORT_SYMBOL_GPL(base64_encode);
>
> /**
> - * base64_decode() - base64-decode a string
> + * base64_decode() - Base64-decode a string
> * @src: the string to decode. Doesn't need to be NUL-terminated.
> * @srclen: the length of @src in bytes
> * @dst: (output) the decoded binary data
> + * @padding: whether to append '=' padding characters
> + * @variant: which base64 variant to use
> *
> - * Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
> - * specified by RFC 4648, including the '='-padding.
> + * Decodes a string using the selected Base64 variant.
> *
> * This implementation hasn't been optimized for performance.
> *
> * Return: the length of the resulting decoded binary data in bytes,
> - * or -1 if the string isn't a valid base64 string.
> + * or -1 if the string isn't a valid Base64 string.
> */
> -int base64_decode(const char *src, int srclen, u8 *dst)
> +int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base64_variant variant)
> {
> u32 ac = 0;
> int bits = 0;
> int i;
> u8 *bp = dst;
> + const char *base64_table = base64_tables[variant];
>
> for (i = 0; i < srclen; i++) {
> const char *p = strchr(base64_table, src[i]);
> -
> - if (src[i] == '=') {
> - ac = (ac << 6);
> - bits += 6;
> - if (bits >= 8)
> - bits -= 8;
> - continue;
> + if (padding) {
> + if (src[i] == '=') {
> + ac = (ac << 6);
> + bits += 6;
> + if (bits >= 8)
> + bits -= 8;
> + continue;
> + }
> }
> if (p == NULL || src[i] == 0)
> return -1;